Copernicus: Sentinel-2 — The Optical Imaging Mission for Land ServicesSpacecraft Launch Mission Status Sensor Complement Ground Segment References
Sentinel-2 is a multispectral operational imaging mission within the GMES (Global Monitoring for Environment and Security) program, jointly implemented by the EC (European Commission) and ESA (European Space Agency) for global land observation (data on vegetation, soil and water cover for land, inland waterways and coastal areas, and also provide atmospheric absorption and distortion data corrections) at high resolution with high revisit capability to provide enhanced continuity of data so far provided by SPOT-5 and Landsat-7. 1) 2) 3) 4) 5) 6) 7) 8)
Table 1: Copernicus is the new name of the former GMES program 9)
The overall GMES user requirements of the EU member states call for optical observation services in the areas of Global Climate Change (Kyoto Protocol and ensuing regulations), sustainable development, European environmental policies (e.g. spatial planning for Soil Thematic Strategy, Natura 2000 and Ramsar Convention, Water Framework Directive), European civil protection, common agricultural policy, development and humanitarian aid, and EU Common Foreign & Security Policy.
To meet the user needs, the Sentinel-2 satellite data will support the operational generation of the following high level products like:
• Generic land cover, land use and change detection maps (e.g. CORINE land cover maps update, soil sealing maps, forest area maps)
• Maps of geophysical variables (e.g. leaf area index, leaf chlorophyll content, leaf water content).
The mission is dedicated to the full and systematic coverage of land surface (including major islands) globally with the objective to provide cloud-free products typically every 15 to 30 days over Europe and Africa. To achieve this objective and to provide high mission availability, a constellation of two operational satellites is required, allowing to reach a 5-day geometric revisit time. The revisit time with only one operational satellite as it will be the case at the beginning of the deployment of the system is 10 days. - In comparison, Landsat-7 provides a 16-day geometric revisit time, while SPOT provides a 26-day revisit, and neither of them provides systematic coverage of the overall land surface.
The following list summarizes the top-level system design specifications derived from the user requirements:
• Sentinel-2 will provide continuity of data for services initiated within the GSE (GMES Service Element) projects. It will establish a key European source of data for the GMES Land Fast Track Monitoring Services and will also contribute to the GMES Risk Fast Track Services.
• The frequent revisit and high mission availability goals call for 2 satellites in orbit at a time, each with a 290 km wide swath using a single imaging instrument
• Continuous land + islands carpet mapping imaging within the latitude range of -56º to +83º (the selected orbit excludes imagery from Antarctica)
• 10 m, 20 m, and 60 m spatial resolution (in the VNIR to SWIR spectral range) to identify spatial details consistent with 1 ha MMU (Minimum Mapping Unit)
• An accurate geolocation (< 20 m) of the data is required (without GCPs) and shall be produced automatically to meet the timeliness requirements. The geolocation accuracy of Level 1 b imagery data w.r.t. WGS-84 (World Geodetic System - 1984) reference Earth ellipsoid of better than 20 m at 2σ confidence level without need of any ground control points is required.
• Very good radiometric image quality (combination of onboard absolute and on ground vicarious calibration).
• The mission lifetime is specified as 7.25 years and propellant is to be sized for 12 years, including provision for de-orbiting maneuvers at end-of-life.
• 2 weeks of satellite autonomy and maximum decoupling between flight operations and mission exploitation
Table 2: Sentinel-2 fast track service compliance to land user requirements
To provide operational services over a long period (at least 15 years following the launch of the first satellites), it is foreseen to develop a series of four satellites, with nominally two satellites in operation in orbit and a third one stored on ground as back-up.
In partnership: The Sentinel-2 mission has been made possible thanks to the close collaboration between ESA, the European Commission, industry, service providers and data users. Demonstrating Europe’s technological excellence, its development has involved around 60 companies, led by Airbus Defence and Space in Germany for the satellites and Airbus Defence and Space in France for the multispectral instruments. 10)
The mission has been supported in kind by the French space agency CNES to provide expertise in image processing and calibration, and by the German Aerospace Center DLR that provides the optical communication payload, developed by Tesat Spacecom GmbH.
This piece of technology allows the Sentinel-2 satellites to transmit data via laser to satellites in geostationary orbit carrying the European Data Relay System (EDRS). This new space data highway allows large volumes of data to be relayed very quickly so that information can be even more readily available for users.
Seven years in the making, this novel mission has been built to operate for more than 20 years. Ensuring that it will meet users’ exacting requirements has been a challenging task. Developing Sentinel-2 has involved a number of technical challenges, from early specification in 2007 to qualification and acceptance in 2015.
The satellite requires excellent pointing accuracy and stability and, therefore, high-end orbit and attitude control sensors and actuators. The multispectral imager is the most advanced of its kind, integrating two large visible near-infrared and shortwave infrared focal planes, each equipped with 12 detectors and integrating 450,000 pixels.
Pixels that may fail in the course of the mission can be replaced by redundant pixels. Two kinds of detectors integrate high-quality filters to isolate the spectral bands perfectly. The instrument’s optomechanical stability must be extremely high, which has meant the use of silicon carbide ceramic for its three mirrors and focal plane, and for the telescope structure itself.
The geometric performance requires strong uniformity across the focal planes to avoid image distortion. The radiometric performance excluded any compromise regarding stray light, dictating a tight geometry and arrangement of all the optical and mechanical elements. The instrument is equipped with a calibration and shutter mechanism that integrates a large spectralon sunlight diffuser.
Each satellite has a high level of autonomy, so that they can operate without any intervention from the ground for periods of up to 15 days. This requires sophisticated autonomous failure analysis, detection and correction on board.
The ‘carpet mapping’ imaging plan requires acquisition, storage and transmission of 1.6 TB per orbit. This massive data blast results from the combination of the 290 km swath with 13 spectral channels at a spatial resolution as high as 10 m.
In addition, the optical communication payload using the EDRS data link is a new technology that will improve the amount and speed of data delivery to the users. This was very recently demonstrated by Sentinel-1A, which also carries an optical communication payload.
Land in focus: Ensuring that land is used sustainably, while meeting the food and wood demands of a growing global population – a projected eight billion by 2020 – is one of today’s biggest challenges. The Copernicus land service provides information to help respond to global issues such as this as well as focusing on local matters, or ‘hotspots’, that are prone to specific challenges.
However, this service relies on very fast revisit times, timely and accurate satellite data in order to make meaningful information available to users – hence, the role of Sentinel-2. Through the service, users will have access to information about the health of our vegetation so that informed decisions can be made – whether about addressing climate change or how much water and fertilizer are needed for a maximum harvest.
Sentinel-2 is able to distinguish between different crop types and will deliver timely data on numerous plant indices, such as leaf area index, leaf chlorophyll content and leaf water content – all of which are essential to accurately monitor plant growth. This kind of information is essential for precision farming: helping farmers decide how best to nurture their crops and predict their yield.
While this has obvious economic benefits, this kind of information is also important for developing countries where food security is an issue. The mission’s fast geometric revisit of just five days, when both satellites are operational, and only 10 days with Sentinel-2A alone, along with the mission’s range of spectral bands means that changes in plant health and growth status can be easily monitored.
Sentinel-2 will also provide information about changes in land cover so that areas that have been damaged or destroyed by fire, for example, or affected by deforestation, can be monitored. Urban growth also can be tracked.
The Copernicus services are managed by the European Commission. The five ‘pan-European’ themes covering 39 countries are addressed by the land service, including sealed soil (imperviousness), tree cover density, forest type, and grasslands. There is currently insufficient cloud-free satellite data in high resolution with all the necessary spectral bands that cover Europe fast enough to monitor vegetation when it is growing rapidly in the summer. Sentinel-2 will fill this gap.
This multi-talented mission will also provide information on pollution in lakes and coastal waters at high spatial resolution and with frequent coverage. Frequent coverage is also key to monitoring floods, volcanic eruptions and landslides. This means that Sentinel-2 can contribute to disaster mapping and support humanitarian aid work.
Leading edge: The span of 13 spectral bands, from the visible and the near-infrared to the shortwave infrared at different spatial resolutions ranging from 10 to 60 m on the ground, takes global land monitoring to an unprecedented level.
The four bands at 10 m resolution ensure continuity with missions such as SPOT-5 or Landsat-8 and address user requirements, in particular, for basic land-cover classification. The six bands at 20 m resolution satisfy requirements for enhanced land-cover classification and for the retrieval of geophysical parameters. Bands at 60 m are dedicated mainly to atmospheric corrections and cirrus-cloud screening.
In addition, Sentinel-2 is the first civil optical Earth observation mission of its kind to include three bands in the ‘red edge’, which provide key information on the vegetation state.
Thanks to its high temporal and spatial resolution and to its three red edge bands, Sentinel-2 will be able to see very early changes in plant health. This is particularly useful for the end users and policy makers to detect early signs of food shortages in developing countries (Ref. 10).
Table 3: Facts and figures
In April 2008, ESA awarded the prime contract to Airbus Defence and Space (former EADS-Astrium GmbH) of Friedrichshafen, Germany to provide the first Sentinel-2A Earth observation satellite. In the Sentinel-2 mission program, Astrium is responsible for the satellite’s system design and platform, as well as for satellite integration and testing. Astrium Toulouse will supply the MSI (MultiSpectral Instrument), and Astrium Spain is in charge of the satellite’s structure pre-integrated with its thermal equipment and harness. The industrial core team also comprises Jena Optronik (Germany), Boostec (France), Sener and GMV (Spain). 11) 12) 13) 14)
Sentinel-2 uses the AstroBus-L of EADS Astrium, a standard modular ECSS (European Cooperation for Space Standards) compatible satellite platform compatible with an in-orbit lifetime of up to 10 years, with consumables sizeable according to the mission needs. The platform design is one-failure tolerant and the standard equipment selection is based on minimum Class 2 EEE parts, with compatibility to Class 1 in most cases. The AstroBus-L platform is designed for direct injection into LEO (Low Earth Orbit). Depending on the selection of standard design options, AstroBus-L can operate in a variety of LEOs at different heights and with different inclinations. An essential feature of AstroBus-L is the robust standard FDIR (Failure Detection, Isolation and Recovery) concept, which is hierarchically structured and can easily be adapted to specific mission needs.
Figure 1: Artist's rendition of the Sentinel-2 spacecraft (image credit: ESA, Airbus DS)
The satellite is controlled in 3-axes via high-rate multi-head star trackers, mounted on the camera structure for better pointing accuracy and stability, and gyroscopes and a GNSS receiver assembly. The AOCS (Attitude and Orbit Control Subsystem) comprises the following elements: 18)
• A dual frequency GPS receiver (L1/L2 code) for position and time information
• A STR (Star Tracker) assembly for precise attitude information (use of 3 STRs)
• A RMU (Rate Measurement Unit) for rate damping and yaw acquisition purposes
• A redundant precision IMU (Inertial Measurement Unit) for high-accuracy attitude determination
• Magnetometers (MAG) for Earth magnetic field information
• CESS (Coarse Earth Sun Sensors) for coarse Earth and Sun direction determination
• 4 RW (Reaction Wheels) and 3 MTQ (Magnetic Torquers)
• RCS (Reaction Control System) a monopropellant propulsion system for orbit maintenance with 1 N thrusters
The different tasks of the AOCS are defined the following modes:
• Initial Acquisition and Save Mode (rate damping, Earth acquisition, yaw acquisition, steady-state)
• Normal Mode (nominal and extended observation)
• Orbit Control Mode (in- and out-of-plane ΔV maneuvers).
Figure 2: Overview of the AOCS architecture (image credit: EADS Astrium)
The geolocation accuracy requirements of < 20 m for the imagery translate into the following AOCS performance requirements as stated in Table 4.
Table 4: AOCS performance requirements in normal mode
For Sentinel-2 it was decided to mount both the IMU and the star trackers on the thermally controlled sensor plate on the MSI. So the impact of time-variant IMU/STR misalignment on the attitude performance can be decreased to an absolute minimum. Furthermore, the consideration of the time-correlated star tracker noises by covariance tuning was decided.
Figure 3: Sentinel-2 spacecraft architecture (image credit: Astrium GmbH)
Figure 4: Block diagram of the Sentinel-2 spacecraft (image credit: EADS Astrium)
The EPS (Electric Power Subsystem) consists of:
• Solar Array (one deployable and rotatable single wing with three panels). Total array area of 7.1 m2. Use of 2016 triple junction GaAs solar cells with integrated diode. Total power of 2300 W (BOL) and 1730 W (EOL). The mass is < 40 kg.
• SADM (Solar Array Drive Mechanism) for array articulation. Use of a two phase stepper motor with µ-stepping to minimize parasitic distortions during MSI operation, motor step angle 1.5º. Mass of < 3.2 kg.
• PCDU (Power Control and Distribution Unit). PCDU with one unregulated 28 V ±4 V main power bus. Mass of < 21.6 kg; the in-orbit life is 12.25 years.
• Li-ion batteries with 8 cells in series. Total capacity of 102 Ah @ EOL. Mass = 51 kg.
Figure 5: Block diagram of the electrical power subsystem (image credit: EADS Astrium)
The OBC is based on the ERC32 PM (Processor Module) architecture. The PLDHS (Payload Data Handling System) provides source data compression from 1.3 Gbit/s to 450 Mbit/s [state-of-the-art lossy compression (wavelet transform)].
The spacecraft mass is ~ 1200 kg, including 275 kg for the MSI instrument, 35 kg for the IR payload (optional) and 80 kg propellant (hydrazine). The S/C power is 1250 W max, including 170 W for the MSI and < 100 W for the IR payload. The spacecraft is designed for a design life of 7.25 years with propellant for 12 years of operations, including deorbiting at EOL (End of Life).
Table 5: Overview of some spacecraft parameters
Figure 6: Schematic view of the deployed Sentinel-2 spacecraft (image credit: EADS Astrium)
Figure 7: The Sentinel-2 spacecraft in launch configuration (image credit: ESA)
Payload data are being stored in NAND flash memory technology SSR (Solid State Recorder) based on integrated CoReCi (Compression Recording and Ciphering) units of Airbus DS, available at various capacities. The CoReCi is an integrated image compressor, mass memory and data ciphering unit designed to process, store and format multi-spectral video instrument data for the satellite downlink. The mass memory utilizes high performance commercial Flash components, ESA qualified and up-screened for their use in space equipment. This new Flash technology allows mass and surface area used in the memory to be reduced by a factor of nearly 20 when compared with the former SD-RAM (Synchronous Dynamic Random Access Memory) based equipment. The first CoReCi unit has been successfully operating on SPOT-6 since September 2012. Sentinel-2A is carrying a CoReCi unit. 19) 20)
The MRCPB (Multi-Résolution par Codage de Plans Binaires) compression algorithm used is a wavelet transform with bit plane coding (similiar to JPEG 2000). This complex algorithm is implemented in a dedicated ASIC, with speeds of up to 25 Mpixel/s. Alternatively this unit can be supplied with a CCSDS compression algorithm using a new ASIC developed with ESA support. The ciphering is based on the AES algorithm with 128 bit keys. The modularity of the design allows the memory capacity and data rate to be adapted by adjusting the number of compressor and memory boards used.
• August 9, 2021: Engineers at Airbus Defence and Space in Friedrichshafen, Germany, have spent the last 4 months completing the build-up of the Sentinel-2C satellite by integrating its all-important multispectral imager instrument, and have now transported it to IABG’s facilities in Ottobrunn for a series of exhaustive tests that will run until the end of 2021. The program includes a range of mechanical tests that simulate the noise and vibrations of liftoff, tests that check that the satellite deploys its solar wing correctly, other tests that place the satellite under the extreme temperature swings it will experience in space, and electromagnetic compatibility tests to measure radio frequency radiation levels generated by the satellite and to verify the correct operation of the satellite equipment under this environment. 21)
- Copernicus Sentinel-2 is designed to provide images that can be used to distinguish between different crop types as well as data on numerous plant indices, such as leaf area index, leaf chlorophyll content and leaf water content – all of which are essential to accurately monitor plant growth.
Figure 8: The Sentinel-2C satellite is pictured here in its transport container just after arrival at IABG (image credit: IABG)
• July 29, 2021: Airbus has finished the integration of the Copernicus Sentinel-2C satellite. It is the third of its kind and will now be shipped to Munich to undergo extensive environmental tests to prove its readiness for space. The test campaign will last until March 2022. 22)
- The data gathered by Sentinel-2 satellites are used for monitoring land use and changes, soil sealing, land management, agriculture, forestry, natural disasters (floods, forest fires, landslides and erosion) and to assist humanitarian aid missions. Environmental observation in coastal areas likewise forms part of these activities, as does glacier, ice and snow monitoring.
- Offering "color vision" for the Copernicus program, Sentinel-2C – like its precursor satellites Sentinel-2A and -2B – will deliver optical images from the visible to short-wave infrared range of the electromagnetic spectrum. From an altitude of 786 km, the 1.1 ton “C” satellite will enable continuation of imaging in 13 spectral bands with a resolution of 10, 20 or 60 m and a uniquely large swath width of 290 km.
- The telescope structure and the mirrors are made of silicon carbide, first pioneered by Airbus to provide very high optical stability and minimize thermo-elastic deformation, resulting in an excellent geometric image quality. This is unprecedented in this category of optical imagers. Each Sentinel-2 satellite collects 1.5 TB/day, after on-board compression. The data is formatted at high speed and temporarily stored on board in the highest capacity Mass Memory and Formatting unit currently flying in space. Data recording and laser-enabled downlink can take place simultaneously at high speed via the EDRS SpaceDataHighway, in addition to the direct X-band link to the ground stations.
- The current Sentinel-2-mission is based on a constellation of two identical satellites, Sentinel-2A (launched 2015) and Sentinel-2B (launched 2017), flying in the same orbit but 180° apart for optimal coverage and revisit time. The satellites orbit the Earth every 100 minutes covering all Earth’s land surfaces, large islands, inland and coastal waters every five days.
- The Sentinel-2 satellites are currently sensing systematically all land and water areas, producing excellent results. Last year, the Sentinel-2 mission remained the top European mission in terms of peer-reviewed scientific publications (1200 during 2020) and data volume distributed to users.
- The Sentinel-2 mission has been made possible thanks to the close collaboration between ESA, the European Commission, industry, service providers and data users. Its development has involved around 60 companies, led by Airbus Defence and Space in Germany for the satellites and Airbus Defence and Space in France for the multispectral instruments, while Airbus Defence and Space in Spain is responsible for the mechanical satellite structure.
- Copernicus, Europe’s environmental monitoring program, is led by the European Commission (EC) in partnership with the European Space Agency (ESA). The Copernicus Sentinels supply remote sensing data of the Earth, delivering key operational services related to environment and security.
Figure 9: Photo of the Copernicus Sentinel-2C satellite. The climate satellite will now undergo extensive testing (image credit: Airbus)
• February 27, 2017: The ninth Vega light-lift launcher is now complete at the Spaceport, with its Sentinel-2B Earth observation satellite installed atop the four-stage vehicle in preparation for a March 6 mission from French Guiana. 23)
• January 12, 2017: Sentinel-2B arrived at Europe’s spaceport in Kourou, French Guiana on 6 January 2017 to be prepared for launch. After being moved to the cleanroom and left for a couple of days to acclimatise, cranes were used to open the container and unveil the satellite. Over the next seven weeks the satellite will be tested and prepared for liftoff on a Vega rocket. 24)
• November 15, 2016: Sentinel-2B has successfully finished its test program at ESA/ESTEC in Noordwijk, The Netherlands. The second Sentinel-2 Airbus built satellite will now be readied for shipment to the Kourou spaceport in French Guiana begin January 2017. It is scheduled for an early March 2017 lift-off on Vega. 25)
- Offering "color vision" for the Copernicus program, Sentinel-2B like its twin satellite Sentinel-2A will deliver optical images from the visible to short-wave infrared range of the electromagnetic spectrum. From an altitude of 786 km, the 1.1 ton satellite will deliver images in 13 spectral bands with a resolution of 10, 20 or 60 m and a uniquely large swath width of 290 km.
• June 15, 2016: Airbus DS completed the manufacture of the Sentinel-2B optical satellite; the spacecraft is ready for environmental testing at ESA/ESTEC. The Sentinel-2 mission, designed and built by a consortium of around 60 companies led by Airbus Defence and Space, is based on a constellation of two identical satellites flying in the same orbit, 180° apart for optimal coverage and data delivery. Together they image all Earth’s land surfaces, large islands, inland and coastal waters every five days at the equator. Sentinel-2A was launched on 23 June 2015, its twin, Sentinel-2B, will follow early next year. 26)
- The Sentinel-1 and -2 satellites are equipped with the Tesat-Spacecom’s LCT (Laser Communication Terminal). The SpaceDataHighway is being implemented within a Public-Private Partnership between ESA and Airbus Defence and Space.
Figure 10: Sentinel-2B being loaded at Airbus Defence and Space’s satellite integration center in Friedrichshafen, Germany (image credit: Airbus DS, A. Ruttloff)
• April 27, 2015: The Sentinel-2A satellite on Arianespace’s next Vega mission is being readied for pre-launch checkout at the Spaceport, which will enable this European Earth observation platform to be orbited in June from French Guiana. — During activity in the Spaceport’s S5 payload processing facility, Sentinel-2A was removed from the shipping container that protected this 1,140 kg class spacecraft during its airlift from Europe to the South American launch site. With Sentinel-2A now connected to its ground support equipment and successfully switched on, the satellite will undergo verifications and final preparations for a scheduled June 11 liftoff. 27)
Figure 11: Sentinel-2A is positioned in the Spaceport’s S5 payload processing facility for preparation ahead of its scheduled June launch on Vega (image credit: Arianespace)
• April 23, 2015: The Sentinel-2A satellite has arrived safe and sound in French Guiana for launch in June. The huge Antonov cargo aircraft that carried the Sentinel-2A from Germany, touched down at Cayenne airport in the early morning of 21 April. 28)
• April 8, 2015: The Sentinel-2A satellite is now being carefully packed away in a special container that will keep it safe during its journey to the launch site in French Guiana. The satellite will have one final test, a ‘leak test’, in the container to ensure the propulsion system is tight. Bound for Europe’s Spaceport in French Guiana, Sentinel-2A will leave Munich aboard an Antonov cargo plane on 20 April. Once unloaded and unpacked, it will spend the following weeks being prepared for liftoff on a Vega rocket. 29)
• February 24, 2015: Sentinel-2A is fully integrated at IABG’s facilities in Ottobrunn, Germany before being packed up and shipped to French Guiana for a scheduled launch in June 2015. 30)
Figure 12: Photo of the Sentinel-2A spacecraft in the thermal vacuum chamber testing at IAGB's facilities (image credit: ESA, IABG, 2015)
• In August 2014, Airbus Defence and Space delivered the Sentinel-2A environmental monitoring satellite for testing . In the coming months, the Sentinel-2A satellite will undergo a series of environmental tests at IABG, Ottobrunn, Germany, to determine its suitability for use in space. 31) 32)
Figure 13: Sentinel-2A solar array deployment test at IABG (Airbus Defence & Space), image credit: ESA 33)
- Sentinel-2A is scheduled to launch in June 2015; Sentinel-2B, which is identical in design, is set to follow in March 2017. Together, these two satellites will be able to capture images of our planet’s entire land surface in just five days in a systematic manner.
Figure 14: Photo of the Sentinel-2A spacecraft at the satellite integration center in Friedrichshafen, Germany (image credit: Airbus DS, A. Ruttloff)
RF communications: The payload data handling is based on a 2.4 Tbit solid state mass memory and the payload data downlink is performed at a data rate of 560 Mbit/s in X-band with 8 PSK modulation and an isoflux antenna, compliant with the spectrum bandwidth allocated by the ITU (international Telecommunication Union).
Command and control of the spacecraft (TT&C) is performed with omnidirectional S-band antenna coverage using a helix and a patch antenna. The TT&C S-band link provides 64 kbit/s in uplink (with authenticated/encrypted commands) and 2 Mbit/s in downlink..
The requirements call for 4 core X-band ground stations for full mission data recovery by the GMES PDS (Payload Data System).
In parallel to the RF communications, an optical LEO-GEO communications link using the LCT (Laser Communication Terminal) of Tesat-Spacecom (Backnang, Germany) will be provided on the Sentinel-2 spacecraft. The LCT is based on a heritage design (TerraSAR-X) with a transmit power of 2.2 W and a telescope of 135 mm aperture to meet the requirement of the larger link distance. The GEO LCT will be accommodated on AlphaSat of ESA/industry (launch 2012) and later on the EDRS (European Data Relay Satellite) system of ESA. The GEO relay consists of an optical 2.8 Gbit/s (1.8 Gbit/s user data) communication link from the LEO to the GEO satellite and of a 600 Mbit/s Ka-band communication link from the GEO satellite to the ground. 36)
To meet the user requirements of fast data delivery, DLR (German Aerospace Center) is funding the OCP (Optical Communication Payload), i.e. the LCT of Tesat, – a new capability to download large volumes of data from the Sentinel-2 and Sentinel-1 Earth observation satellites - via a data relay satellite directly to the ground. A contract to this effect was signed in October 2010 between ESA and DLR. 37)
Since the Ka-band downlink is the bottleneck for the whole GEO relay system, an optical ground station for a 5.625 Gbit/s LEO-to-ground and a 2.8 Gbit/s GEO-to-ground communication link is under development.
Orbit: Sun-synchronous orbit, altitude = 786 km, inclination = 98.5º, (14+3/10 revolutions/day) with 10:30 hours LTDN (Local Time at Descending Node). This local time has been selected as the best compromise between cloud cover minimization and sun illumination.
The orbit is fully consistent with SPOT and very close to the Landsat local time, allowing seamless combination of Sentinel-2 data with historical data from legacy missions to build long-term temporal series. The two Sentinel-2 satellites will be equally spaced (180º phasing) in the same orbital plane for a 5 day revisit cycle at the equator.
The Sentinel-2 satellites will systematically acquire observations over land and coastal areas from -56° to 84° latitude including islands larger 100 km2, EU islands, all other islands less than 20 km from the coastline, the whole Mediterranean Sea, all inland water bodies and closed seas. Over specific calibration sites, for example DOME-C in Antarctica, additional observations will be made. The two satellites will work on opposite sides of the orbit (Figure 15).
Figure 15: Twin observation configuration of the Sentinel-2 spacecraft constellation (image credit: ESA)
• The first stage separated 1 min 55 seconds after liftoff, followed by the second stage and fairing at 3 min 39 seconds and 3 min 56 seconds, respectively, and the third stage at 6 min 32 seconds.
• After two more ignitions, Vega’s upper stage delivered Sentinel-2B into the targeted Sun-synchronous orbit. The satellite separated from the stage 57 min 57 seconds into the flight.
• Telemetry links and attitude control were then established by controllers at ESOC in Darmstadt, Germany, allowing activation of Sentinel’s systems to begin. The satellite’s solar panel has already been deployed.
• After this first ‘launch and early orbit’ phase, which typically lasts three days, controllers will begin checking and calibrating the instruments to commission the satellite. The mission is expected to begin operations in three to four months.
Sentinel-2B will join its sister satellite Sentinel-2A and the other Sentinels part of the Copernicus program, the most ambitious Earth observation program to date. Sentinel-2A and -2B will be supplying ‘color vision’ for Copernicus and together they can cover all land surfaces once every five days thus optimizing global coverage and the data delivery for numerous applications. The data provided by these Sentinel-2 satellites is particularly suited for agricultural purposes, such as managing administration and precision farming.
With two satellites in orbit it will take only five days to produce an image of the entire Earth between the latitudes of 56º south and 84º north, thereby optimizing the global coverage zone and data transmission for numerous applications.
To ensure data continuity two further optical satellites, Sentinel-2C and -2D, are being constructed in the cleanrooms of Airbus and will be ready for launch as of 2020/2021.
Figure 16: Illustration of the Sentinel-2B spacecraft in orbit (image credit: Airbus DS, Ref. 40)
Figure 17: This technical view of the Sentinel-2 satellite shows all the inner components that make up this state-of-the-art high-resolution multispectral mission (video credit: ESA/ATG medialab)
Note: As of 01 April 2021, the Sentinel-2 file has been split into a total of six files. — As of May 2019, the previously single large Sentinel-2 file has been split into two additional files, to make the file handling manageable for all parties concerned, in particular for the user community.
• This article covers the Sentinel-2 mission and its imagery in the period 2022
Mission status and some imagery of 2022
• June 17, 2022: Part of the Glacier Bay National Park and Preserve, which lies along the coast of southeast Alaska, is featured in this image captured by the Copernicus Sentinel-2 mission. 42)
- Covering over 13,000 km2 of rugged, snow-capped mountains, freshwater lakes, glaciers and deep fjords, Glacier Bay National Park and Preserve is one of the highlights of Alaska’s Inside Passage. As marine waters make up almost one-fifth of the park, Glacier Bay is rich with marine life, including humpback whales, orcas and sea otters. It’s also home to a large population of bears, moose, wolves and mountain goats.
- The bay contains some of the world’s most impressive glaciers that descend from the ice-covered St. Elias Range in the east and the Fairweather Range in the west, with a few notable tidewater glaciers extending all the way to the sea.
- John Hopkins Glacier, visible in the far left of the image, is the largest tidewater glacier in the region. Muir Glacier, formerly the most famous of the tidewater glaciers, once rose around 80 m above water and was nearly 3 km wide but has now shrunk and receded and no longer reaches the sea.
- Glacier Bay is just one of the many areas suffering from the effects of global warming. The bay is expected to become warmer and drier over the next century, with widespread effects including the further shrinking glaciers, reduced sea ice and shoreline erosion.
- Monitoring glaciers is often a challenge considering their sheer size, remoteness and rugged terrain they occupy. Satellites, including ESA’s CryoSat mission, with its elite spaceborne sensor – the radar altimeter – allows for the mapping of glaciers in fine detail. In a study published last year in the Cryosphere, scientists utilised data from the CryoSat mission to show how much ice had been lost from mountain glaciers in the Gulf of Alaska.
- Today marks the opening of the ‘Earth’s Memory - glaciers witnesses to the climate crisis’ exhibition, that follows the scientific and photographic journey of glaciers around the world, premiering the results of the ‘On the trail of the glaciers’ project directed by Italian photographer Fabiano Ventura. The exhibition, which is being held in the Forte di Bard Museum, Aosta Valley, Italy, offers its visitors the opportunity to witness the effects of global warming through the power of both photography and ESA satellite imagery.
Figure 18: In this week's edition of the Earth from Space programme, we explore part of the Glacier Bay National Park and Preserve, Alaska, with Copernicus Sentinel-2. This image is also featured on the Earth from Space video programme (image credit: ESA)
- The exhibition focuses on the world’s largest mountain glaciers with 90 photographic comparisons displayed alongside scientific data collected during the team’s expedition to the world’s largest mountain glaciers. It runs until 18 November 2022 and includes images such as the one featured on this week’s Earth from Space programme. More information on the exhibition, which is part of a scientific collaboration between ESA and is sponsored by UNESCO, can be found here.
• June 9, 2022: A team of scientists have used satellite data to detect methane plumes from an offshore platform in the Gulf of Mexico. This is the first time that individual methane plumes from offshore platforms are mapped from space. 43)
- Methane is the second most abundant anthropogenic greenhouse gas after carbon dioxide yet is more than 25 times as potent as carbon dioxide at trapping heat in the atmosphere, within a 100-year time period. The mitigation of methane emissions from fossil fuel extraction, processing and transport is one of the most effective ways to slow global warming.
- Satellite-based methods have proved instrumental for the detection and quantification of these type of emissions. However, despite the rapid development of satellite-based methane plume detection methods over land, there is still an important observational gap regarding emissions coming from offshore oil and gas operations – which accounts for roughly 30% of global production.
- This is mostly due to the low reflection of water in the shortwave infrared wavelengths used for methane remote sensing. This limits the amount of light reaching the sensor which, subsequently, makes it difficult to distinguish methane emissions.
- In a recent study published in Environmental Science and Technology Letters, a team, led by scientists from Universitat Politècnica de València (UPV), used data from Maxar’s WorldView-3 satellite, obtained through ESA’s Third Party Missions Programme, and US Landsat 8 mission to detect and quantify strong methane plumes from an offshore oil and gas production platform near the coast of Campeche – in one of Mexico's major oil producing fields.
- These results are part of a study led by Christian Retscher, Atmosphere Scientist at ESA’s Directorate of Earth Observation Programmes. The study received funding from the EO Science for Society component of ESA’s FutureEO Programme and the ESA Living Planet Fellowship.
- The team found that the platform released high volumes of methane during a 17-day ultra-emission event which amounted to approximately 40,000 tonnes of methane released into the atmosphere in December 2021.
- These emissions are equivalent to around 3% of Mexico’s annual oil and gas emissions and this single event would have a similar magnitude to the entire regional annual emissions from Mexico’s offshore region.
Figure 19: This Copernicus Sentinel-2 image, captured on 28 December 2021, shows the location of the Zaap-C offshore platform with many other offshore platforms visible flaring in the area. - Please note that the water vapour columns are very typical on days when flaring is active. It is not the case for the days when the methane fluxes occur (on these days, there is neither flaring nor water vapour), image credit: ESA the image contains modified Copernicus Sentinel data (2021), processed by ESA, CC BY-SA 3.0 IGO, CC BY-SA 3.0 IGO
- The team then analysed a longer time-series of flaring activity at the site. The results from this analysis showed that this ultra-emitting event, likely related to abnormal process conditions, was a one-time incident with the longest duration since flaring activity began at this platform.
Figure 20: This image shows a methane plume from an offshore platform as detected by the WorldView-3 satellite on 18 December 2021 [image credit: ESA (Data: WorldView-3)]
Figure 21: This map shows the oil and gas extraction areas in and around the Gulf of Mexico. Data has been extracted from the Global Energy Monitor [image credit: ESA (Data: Global Oil and Gas Extraction Tracker, Global Energy Monitor, January 2022)]
- Luis Guanter, from the Valencia Polytechnic University, commented, “The results here demonstrate how satellites can detect methane plumes from offshore infrastructure. This represents a breakthrough in the monitoring of industrial methane emissions from space, as it opens the door to systematic monitoring of emissions from individual offshore platforms.”
- Itziar Irakulis-Loitxate, scientist at UPV and lead author of the study, added, “In fact, we are currently expanding this work to other offshore oil and gas production regions in the world with both Copernicus Sentinel-2 and Landsat, with the first results extremely promising.”
- Christian Retscher commented, “The study demonstrates the growing capabilities to detect methane emissions from space at a very high spatial resolution.”
- Yasjka Meijer, Mission Scientist of ESA’s upcoming Copernicus Carbon Dioxide Monitoring mission, added, “Observations from satellites are instrumental for the detection and quantification of these human-made emissions.”
• June 3, 2022: Puglia (Apulia), the heel of the boot-shaped country, has the longest coastline of any Italian mainland region. Covering almost 20,000 km2, it is Italy’s seventh largest region and its coastline, dotted with some of Italy’s finest sandy beaches and azure seas, runs for around 800 km. With a population of around four million, Puglia borders the Adriatic Sea to the east and the Ionian Sea to the west. 44)
- Puglia is the least mountainous region of Italy, consisting of broad plains and low-lying hills. It is home to two national parks, the Alta Murgia National Park and Gargano National Park. The area is one of the largest and most productive plains in Italy where a significant amount of both wine and olive oil is produced.
- Puglia’s chief town is Bari (not visible in the image), which is the largest urban and metropolitan area on the Adriatic. Major cities in the image include Brindisi, easily identifiable as a major port town on the Adriatic coast, and Lecce, an urban sprawl straddling both the Adriatic and Ionian coasts. Lecce has a large historical centre that includes the famous Piazza del Duomo square and many Baroque-style buildings dating from the 16th century—including the Basilica di Santa Croce.
- Another historical seaside town and port is Otranto, visible about 40 km from Lecce on the Adriatic Sea. On a clear day, it's possible to see Albania over the Otranto Strait.
- The seaside town of Gallipoli can be seen on the Ionian coast, in the bottom of the image. The old town centre sits on a tiny island connected to the mainland by a 17th century bridge.
- As well as providing detailed information about Earth’s vegetation, the Copernicus Sentinel-2 mission is designed to play a key role in mapping differences in land cover to understand the landscape, map how it is used and monitor changes over time.
Figure 22: This image, captured on 19 January 2022, the Copernicus Sentinel-2 mission takes us over part of Puglia, a region in southern Italy. The image is also featured on ESA’s Earth from Space video programme, (image credit: ESA)
• May 24, 2022: We live in uncertain times. The detrimental impacts of climate change are being felt around the world and threatening our future, we are emerging from the global COVID pandemic that halted life as we know it for more than two years, and now the Ukraine crisis is not only a tragedy for those directly affected but its rippling effects are jeopardising energy and food security far and wide. Some nations are able to weather these storms better than others, but a number of countries in Africa, for example, are already on the back foot, particularly when it comes to food security. 45)
- Today, at ESA’s Living Planet Symposium, much of the focus was on furthering the uptake of Earth observation and advancing the digital transformation in Africa to address societal challenges.
- Europe and Africa have been working together in the field of Earth observation for a number of years now, particularly thanks to the EU’s Copernicus programme – the biggest environmental monitoring programme in the world. Through Copernicus, satellite data from the family of Copernicus Sentinels, developed and built by ESA, are made available through key services.
- The free and open access to data and services has allowed African institutions to develop applications to monitor water quality in lakes, prepare adaptation measures for agriculture and to monitor biodiversity, for example. The GMES & Africa Initiative lead by the African Union Commission has been instrumental to establish Earth observation services across the African continent.
- ESA’s Science for Society programme works with the African Union Commission on many research and development projects based on satellite data to develop innovative, open-source applications adapted to African-specific challenges.
- A recent common call resulted in the award of 15 new projects lead by a tandem of African–European scientists. These projects focus largely on food and water security, including projects to monitor crop stress in arid and drought-prone regions to forecast crop yield, and to manage precious water resources, for example.
- The Global Development Assistance programme is collaborating with international finance institutes, such as the World Bank and the African Development Bank, for more uptake of these innovative Earth observation applications.
Figure 23: This view of Africa and more has been compiled with optical images from the Copernicus Sentinel-2 mission. The contrast between dry arid regions and those covered by vegetation is clear to see. The Copernicus Sentinel-2 mission is designed to provide images that can be used to distinguish between different crop types as well as data on numerous plant indices, such as leaf area, leaf chlorophyll and leaf water – all essential to monitor plant growth accurately. Information from the mission is used to monitor crop stress in arid and drought-prone regions to forecast crop yield, and to manage precious water resources, for example (image credit: ESA, the image contains modified Copernicus Sentinel data, processed by ESA)
- ESA’s Climate Change Initiative projects and datasets on Essential Climate Variables are also of huge value in mapping change over the African continent.
- For example, satellite data showing burned ground not only reveal damage from wildfires, but also where slash and burn practices have taken place.
- Optical data from the Copernicus Sentinel-2 mission have shown that the area of land across the whole continent affected by fire is 80% bigger than previously thought.
- In short, Europe and Africa are already working together to exploit Earth observation to the benefit of African citizens, and to address challenges of specific importance laid out in the African Union Agenda 2063 – the blueprint and master plan for transforming Africa into the global powerhouse of the future.
- At the Living Planet Symposium, Tidiane Ouattara from the African Union Commission, said, “Earth observation in Africa is a very dynamic sector that can be even more accelerated through an effective collaboration with its European partners such as the European Commission, ESA and Eumetsat.”
Figure 24: Fire burned areas in August 2019. The image shows areas that have been burned by fire. The southern part of Africa is particularly affected. Satellite data showing burned ground not only reveal damage from wildfires, but also where slash and burn practices have taken place. For example, optical data from the Copernicus Sentinel-2 mission have shown that the area of land across the whole continent affected by fire is 80% bigger than previously thought (image credit: ESA/CCI Fire Project)
- The Living Planet Symposium being held in Bonn, Germany, has allowed parties to come together to review and discuss progress made so far but, importantly, to focus on the roadmap for the future, particularly taking account of outcomes from the European Union–African Union Summit, which was held in February, and the Europe–Africa Space Earth Observation High-Level Forum, last year in Lisbon.
- The Lisbon declaration, for example, recommended the closer integration of observations from space with data from other sectors, along with full socio-economic value chains re-enforcing links with the private sector, including New Space initiatives.
Figure 25: Burn scars near Cape Town. This Copernicus Sentinel-2 image from 26 January 2019 shows fire-scarred land near the Betty’s Bay area of Cape Town in South Africa. This false-colour image has been processed to show burned areas in dark greys and browns, and areas covered with vegetation are shown in red (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
- ESA’s Benjamin Koetz, concluded, “Challenges such as the recent global food crisis, which is connecting and affecting both the African and European continents, make the uptake of Earth observation even more pressing. Something that can only be achieved through closer partnerships exchanging expertise, data and insights from both sides.
• May 20, 2022: Bonn, one of the oldest cities in Germany, can be seen straddling the Rhine River in the lower half of the image, around 24 km south of Cologne. 46)
- ESA’s Living Planet Symposium – one of the largest Earth observation conferences in the world – is being held on 23–27 May in Bonn, Germany. Held every three years, the symposium brings together scientists and researchers, as well as industry and users of Earth observation data, from all over the world to present and discuss the latest findings on Earth science.
- Bonn is in the south of the Rhine-Ruhr region, Germany’s largest metropolitan area with over 11 million inhabitants.
- The city has a total area of 141 km2 and 330 000 inhabitants. As the birthplace of Ludwig van Beethoven, Bonn is devoted to the promotion of musical arts with the Beethovenhalle concert hall, a centre of the city’s musical life. Socially, Bonn is a very active city with many art galleries, gardens and a buzzing nightlife to offer.
- Bonn is one of Germany’s top-ranked conference cities and is home to numerous international organisations and several United Nations institutions including the United Nations Framework Convention on Climate Change (UNFCCC).
- The 1233 km-long Rhine River flows from the Swiss Alps to the North Sea through Switzerland, Liechtenstein, Austria, France, Germany, and the Netherlands. In the image, it flows from bottom-right to top-left. Along the river lies one of the most modern congress centres in Europe: the World Conference Center Bonn. It is here where ESA’s Living Planet Symposium 2022 will take place.
- Organised with the support of the German Aerospace Center, the week-long event focuses on how Earth observation contributes to both science and society. With over 240 scientific sessions on Earth observation science and satellite missions, there will also be a wide range of sessions focusing on advances in artificial intelligence, digital twins of Earth, commercial opportunities thanks to the space industry, the upcoming ESA Ministerial Council in 2022, and much more.
Figure 26: This image, also featured on the Earth from Space video programme, was captured by the Copernicus Sentinel-2 mission. With its high-resolution optical camera, it can image up to 10 m ground resolution (image credit: ESA)
• May 6, 2022: The Rhine River, the longest river in Germany, is featured in this colourful image captured by the Copernicus Sentinel-2 mission. Along this river lies the city of Bonn: the host of this year’s Living Planet Symposium – one of the largest Earth observation conferences in the world – taking place on 23–27 May 2022. 47)
- The picturesque Rhine Valley has many forested hills topped with castles and includes vineyards, quaint towns and villages along the route of the river. One particular stretch that extends from Bingen in the south to Koblenz, known as the Rhine Gorge, has been declared a UNESCO World Heritage Site (not visible). Cologne is visible at the top of the image.
Figure 27: This composite image was created by combining three separate Normalised Difference Vegetation Index (NDVI) layers from the Copernicus Sentinel-2 mission. The NDVI is widely used in remote sensing as it gives scientists an accurate measure of health and status of plant growth. Each colour in this week’s image represents the average NDVI value of an entire season between 2018 and 2021. Shades of red depict peak vegetation growth in April and May, green shows changes in June and July, while blue shows August and September. The image is also featured on the Earth from Space video programme (image credit: ESA)
- Each colour in this week’s image represents the average NDVI value of an entire season between 2018 and 2021. Shades of red depict peak vegetation growth in April and May, green shows changes in June and July, while blue shows August and September.
- Colourful squares, particularly visible in the left of the image, show different crop types. The nearby white areas are forested areas and appear white as they retain high NDVI values through most of the growing season, unlike crops which are planted and harvested at set time frames. Light pink areas are grasslands, while the dark areas (which have a low NDVI) are built-up areas and water bodies.
- Along the Rhine River lies the World Conference Center Bonn. It is here where ESA’s Living Planet Symposium 2022 will take place.
- Organised with the support of the German Aerospace Center (DLR), the Living Planet Symposium will bring together scientists and researchers, as well as industry and users of Earth observation data, from all over the world to present and discuss the latest findings on Earth science.
- The week-long event, taking place on 23–27 May 2022, focuses on how Earth observation contributes to science and society, and how disruptive technologies and actors are changing the traditional Earth observation landscape, which is also creating new opportunities for public and private sector interactions.
- The Living Planet Symposium will be held in-person offering you the chance to network with the most eminent scientists in the industry, learn about novel Earth observing techniques and explore innovative concepts such as New Space, the digital transformation and commercialisation.
• May 05, 2022: The global trade in agricultural commodities provides food, fuel and fibre to consumers around the world. Commodity production, however, is also linked with negative environmental impacts, including the loss and degradation of forested land. 48)
- Approximately 90% of global deforestation is driven by agricultural expansion – a phenomenon which has roots in the global demand for products such as palm oil, soy and beef. New research reveals how satellites can be used to map and monitor forest-cover changes and help implement effective zero deforestation commitments.
- The Intergovernmental Panel on Climate Change (IPCC) estimates that 23% of total human driven greenhouse gas emissions result from agriculture, forestry and other land uses. Therefore, protecting forests is essential to meet the objectives of the Paris Agreement and the 2030 Agenda for Sustainable Development.
- At the 2021 United Nations Climate Change Conference, 10 of the world’s largest commodity traders published a ‘shared commitment’ to halting forest loss, and the European Union published proposed legislation imposing a legal responsibility for trading companies to ensure their sourcing is not linked to deforestation.
- While many companies recognise the central role forest ecosystems play in the fight against climate change and biodiversity loss and have made zero-deforestation commitments, progress in implementing deforestation-free supply chains remains slow.
- In a new study published in Science Advances, a team of scientists from Europe and the US, combined detailed shipping data from Trase with corporate disclosures, farm-level production and remote sensing data to better understand how commodity traders source products on the ground, and how this affects the implementation of corporate zero-deforestation commitments. 49)
- They focused on commodity trading companies handling the top 60% of exports of four focus commodities: soy from South America, cocoa from the Ivory Coast, palm oil from Indonesia, and live cattle exports from Brazil.
Figure 28: Oil palm plantations distribution. This global map shows the potential and detected distribution of oil palm plantations using data from the GOPM (Global Oil Palm Map), image credit: ESA
- The team found that traders commonly source commodities ‘indirectly’ via local intermediaries (aggregators, cooperatives and other middlemen). The leading traders each sourced 12-44% for soy, 15-90% of palm oil, 94-99% of live cattle and essentially 100% of cocoa indirectly.
- This distinction between direct and indirect sourcing is significant as it’s inevitably more challenging for traders to identify the source of its products – and check for deforestation or other sustainability risks – when the trader is (at least) one-tier removed from the product’s origin.
- Erasmus zu Ermgassen, lead author of the paper and scientist at UC-Louvain, commented, “Indirect sourcing is a major blind spot for sustainable procurement efforts. Indirect sourcing is ignored by many sustainable procurement efforts across the cattle, soy, cocoa, and oil palm sectors.
- “Efforts to trace commodities from farm to fork should be enabled by producer government policies which prioritise transparency and unlock data on supply chains. In order to deliver on promises to eliminate deforestation sectoral sustainability initiatives, we need to acknowledge, monitor, and report on indirect sourcing – and ultimately ensure it doesn't remain a barrier to delivering on sustainability goals.”
Figure 29: Taï National Park in the Ivory Coast surrounded by plantations. Taï National Park is a national park in the Ivory Coast that contains one of the last areas of primary rainforest in West Africa. In recent years, the cultivation of cocoa has led to the loss of vast tracts of forested areas in Ivory Coast and Ghana – the largest producers of cocoa in the world (image credit: ESA, the image contains modified Copernicus Sentinel-2 data (2020), processed by ESA, CC BY-SA 3.0 IGO)
Spotlight on cocoa plantations
- In recent years, the cultivation of cocoa has led to the loss of vast tracts of forested areas in Ivory Coast and Ghana – the largest producers of cocoa in the world. As noted above, indirect sourcing accounts for essentially 100% of cocoa, and thus, the mapping and monitoring of such plantations is essential, not only for the zero-deforestation commitments and biodiversity loss, but also for production, quality, and sustainability of cocoa in both countries.
Figure 30: Cacao tree (image credit: Pixabay/Falco)
- Findings to support this article partially come from a recently published study in Science Direct, where the authors identified cocoa plantations in both Ivory Coast and Ghana using satellite data from the Copernicus programme. The team were able to detect cocoa plantations thanks to Sentinel-1’s radar data combined with Sentinel-2’s optical imagery in a big data cloud-computing environment. 50)
- It was reported there that cocoa farms largely encroach intro protected areas, with 20% of the detected cocoa plantation areas located in protected areas.
- Zoltan explains: “Thanks to the satellite data, we found a successful method to map cocoa farms at a national level and show its potential to be upscaled on a wider scale. Earth observation satellites are instrumental in providing comprehensive information on the full extent and rate of cocoa-driven deforestation. The findings highlight the urgent need for governments and cocoa buyers to address the causes of cocoa-related deforestation.”
Join us at ESA’s Living Planet Symposium in Bonn
- Being held on 23–27 May 2022 in Bonn, Germany, ESA’s prestigious Living Planet Symposium offers attendees the unique opportunity to hear first-hand about the most recent developments in the field of Earth observation.
- Attendees will be able to hear about the latest scientific findings on our planet and how observing Earth from space supports environmental research and action to combat the climate crisis, learn about novel space technologies and about the new opportunities emerging in the rapidly changing sector of Earth observation.
- An ‘agora’ session will be dedicated to the topic of sustainability along industrial value chains in delivering Green Deal and EU sustainability objectives. The ‘Sustainable products and supply chain due diligence – how to enhance the use of Copernicus and big data session’ will take place on Tuesday 24 May from 10:20-11:20.
• April 29, 2022: Mount Aso, the largest active volcano in Japan, is featured in this image captured by the Copernicus Sentinel-2 mission. 51)
Figure 31: Located in the Kumamoto Prefecture on the nation’s southernmost major island of Kyushu, Mount Aso rises to an elevation of 1592 m. The Aso Caldera is one of the largest calderas in the world, measuring around 120 km in circumference, 25 km from north to south and 18 km from east to west. This image is also featured on the Earth from Space video programme (image credit: ESA)
- The caldera was formed during four major explosive eruptions from approximately 90,000 to 270,000 years ago. These produced voluminous pyroclastic flows and volcanic ash that covered much of Kyushu region and even extended to the nearby Yamaguchi Prefecture.
- The caldera is surrounded by five peaks known collectively as Aso Gogaku: Nekodake, Takadake, Nakadake, Eboshidake, Kishimadake. Nakadake is the only active volcano at the centre of Mount Aso and is the main attraction in the region. The volcano goes through cycles of activity. At its calmest, the crater fills with a lime green lake which gently steams, but as activity increases, the lake boils off and disappears. The volcano has been erupting sporadically for decades, most recently in 2021, which has led to the number of visitors drop in recent years.
- Not far from the crater lies Kusasenri: a vast grassland inside the mega crater of Eboshidake. Active just over 20,000 years ago, the crater has been filled with volcanic pumice from other eruptions, with magma still brewing a few kilometres below. Rainwater often accumulates on the plain forming temporary lakes. The pastures are used for cattle raising, dairy farming and horse riding.
- One of the nearest populated cities is Aso, visible around 8 km north from the volcano, and has a population of around 26,000 people.
- There are 110 active volcanoes in Japan, of which 47 are monitored closely as they have erupted recently or shown worrying signs including seismic activity, ground deformation or emissions of large amounts of smoke.
- Satellite data can be used to detect the slight signs of change that may foretell an eruption. Once an eruption begins, optical and radar instruments can capture the various phenomena associated with it, including lava flows, mudslides, ground fissures and earthquakes. Atmospheric sensors on satellites can also identify the gases and aerosols released by the eruption, as well as quantify their wider environmental impact.
• April 11, 2022: After decades of drought, water levels in Lake Powell, the second-largest humanmade reservoir in the United States, have shrunk to its lowest level since it was created more than 50 years ago, threatening millions of people who rely on its water supply. Satellite images allow us to take a closer look at the dwindling water levels of the lake amidst the climate crisis. 52)
- Straddling the border of southeast Utah and northeast Arizona, Lake Powell is an important reservoir in the Colorado River Basin. The Colorado River, which Lake Powell flows through, was dammed at Glen Canyon in the early 1960s. The lake provides water to approximately 40 million people, irrigates over 2.2 million hectares of land and has the capacity to generate more than 4200 megawatts of hydropower electricity.
- In mid-March 2022, Lake Powell’s elevation dropped to an astonishing 1074 m above sea level – the lowest the lake has been since it was filled in 1980. This drastic drop in water levels is documented in natural-colour images captured by the Copernicus Sentinel-2 mission.
Figure 32: This Copernicus Sentinel-2 image allows us a wider view of Lake Powell and its dwindling water levels amidst the climate crisis. After decades of drought, water levels in Lake Powell, the second-largest humanmade reservoir in the United States, have shrunk to its lowest level since it was created more than 50 years ago, threatening millions of people who rely on its water supply (image credit: ESA, the image contains modified Copernicus Sentinel data (2022), processed by ESA, CC BY-SA 3.0 IGO)
Figure 33: Surface area changes of Lake Powell. This animation shows the surface area changes of the reservoir near Bullfrog Marina, approximately 155 km (~90 miles) north from Glen Canyon Dam, between March 2018 and March 2022. Dry conditions and falling water levels are unmistakable in the image captured on 18 March 2022, compared to the 2018 shoreline outlined in the image in yellow (image credit: ESA, the image contains modified Copernicus Sentinel data (2018-22), processed by ESA, CC BY-SA 3.0 IGO)
- The drop in water levels comes as hotter temperatures and falling water levels left a smaller amount of water flowing through the Colorado River. The peak inflow to Lake Powell occurs in mid-to-late spring, as the winter snow in the Rocky Mountains melts.
Figure 34: Lake Powell elevation. The line graph shows the drastic drop in average water levels in March since 2000, when Lake Powell was at around 1120 m elevation. The current elevation is just a few meters from what is considered the ‘minimum power pool’ – the level at which Glen Canyon Dam is able to generate hydroelectric power. If Lake Powell drops even more, it could soon hit a ‘deadpool’ where water will likely fail to flow through the dam and onto the nearby Lake Mead [chart: ESA, Source: USBR (US Bureau of Reclamation), created with Datawrapper]
- According to a report compiled by the US Geological Survey (USGS) in cooperation with the Bureau of Reclamation, Lake Powell’s storage capacity has lost nearly 7% of its potential storage capacity from 1963 to 2018, when the diversion tunnels of Glen Canyon Dam closed and the reservoir began to fill.
- The capacity of the reservoir is said to be shrinking because of sediments transported by the Colorado and San Juan Rivers. These sediments settle at the bottom of the reservoir and decrease the total amount of water the reservoir can hold.
- Climate change is expected to make droughts more severe in the future. According to the National Oceanic and Atmospheric Administration (NOAA) Spring Outlook for the US, nearly 60% of the continental US is experiencing drought.
- These conditions are likely to continue across more than half of the continental United States through at least June, straining water supplies and increasing the risk of wildfires. While these conditions are not new, the agency expects them to potentially worsen in the coming months.
• April 8, 2022: The Copernicus Sentinel-2 mission takes us over part of Sindh – the third-largest province of Pakistan. 53)
- Sindh stretches around 580 km from north to south in southern Pakistan, covering an area of around 141,000 km2. It is bounded by the Thar Desert to the east, the Kirthar mountains to the west and the Arabian Sea to the south. In the centre of the province is a fertile plain around the Indus River.
- Agricultural fields dominate this weeks’ Earth from Space image, creating a colourful patchwork of geometric shapes. Agriculture is key to Sindh’s economy with cotton, wheat, rice, sugarcane and maize being the major crops produced in the province. Livestock raising is also important, with cattle, buffalo, sheep and goats being the main animals kept.
- The colourful image was created by combining three separate images from the near-infrared channel from the Copernicus Sentinel-2 mission.
Figure 35: The first image, captured on 15 October 2021, is assigned to the red channel; the second from 24 November 2021, represents green, and the third from 13 January 2022 covers the blue part of the spectrum. All other colours visible in the image are different mixtures of red, green and blue, and vary according to the stage of vegetation growth over the four-month period. This image is also featured on the Earth from Space video programme (image credit: ESA, the image contains modified Copernicus Sentinel data (2021-22), processed by ESA, CC BY-SA 3.0 IGO)
- The city of Badin is visible in the centre-right of the image and is often referred to as ‘Sugar State’ owing to its production of sugar. Small lakes, artificial water bodies and some flooded fields can be spotted in dark blue and black in the image.
- Thanks to their unique perspective from space, Earth observing satellites are key in mapping and monitoring croplands. The Copernicus Sentinel-2 mission is specifically designed to provide images that can be used to distinguish between crop types as well as data on numerous plant indices, such as leaf area index, leaf chlorophyll content and leaf water content – all of which are essential to accurately monitor plant growth.
• April 01, 2022: Barranquilla, the capital of the Atlántico department in northwest Colombia, is featured in this image taken by the Copernicus Sentinel-2 mission. 54)
- Barranquilla, visible in grey at the top of the image, covers an area of around 155 sq km and is the fourth-most populous city in Colombia after Bogotá, Medellín and Cali. The city of Barranquilla serves as a major trade centre for Colombia, housing the largest port along the Caribbean Sea. Thanks to this famous port, Barranquilla earned itself the nickname ‘Colombia's Golden Gate’ (or La Puerta de Oro de Colombia in Spanish).
- The city lies strategically next to the delta of the Magdalena River, one of the main rivers in Colombia, flowing northwards for around 1500 km through the west half of the country before emptying into the Caribbean Sea.
- The urban area of Barranquilla, with airport runways visible south of the city, contrasts with the Ciénaga Grande de Santa Marta swampy marshes to the east visible in dark green. Selected as a Ramsar Site of International Importance, the site is important for its mangrove ecosystem, which is the largest on the Caribbean coast of Colombia. It also serves as habitat and winter breeding ground for several bird species.
- Other notable features in the image include the El Guajaro Reservoir, around 50 km southwest of Barranquilla. The reservoir was created by the union of seven smaller swamps in the area to supply water for agricultural irrigation. In addition to sewage discharges, the reservoir receives agricultural runoff, particularly during the rainy season, which leads to states of eutrophication in the water that are accompanied by blooms of harmful microorganisms, otherwise known as cyanobacteria.
- These types of algae, which are commonly present in freshwater and saline ecosystems, are most likely why the lake appears in emerald green in today’s image. Satellite data from the Copernicus Sentinel-2 mission can track the growth and spread of harmful algae blooms in order to alert and mitigate against damaging impacts for tourism and fishing industries.
Figure 36: Barranquilla, Colombia. Owing to large quantities of sediment, as seen by the extensive sediment plume at its mouth and the brownish colour of its waters, the Magdalena requires frequent dredging of its main channel to allow access to Barranquilla’s port for oceangoing vessels. This image, captured with Sentinel-2 in March 2021, was taken just before the onset of the rainy season, which starts in April. The image is also featured on the Earth from Space video programme (image credit: ESA, the image contains modified Copernicus Sentinel data (2021), processed by ESA)
• March 30, 2022: Spotted by the Copernicus Sentinel-2 mission, the Conger ice shelf collapsed in East Antarctica around 15 March. 55)
Figure 37: The region has experienced unusual high temperatures, with the Concordia station reaching a record of -11.8ºC on 18 March; the average high temperatures in March are around -48ºC. While the cause of the collapse of the ice shelf is not clear, global warming is likely a contributing factor (image credit: ESA, the image contains modified Copernicus Sentinel data (2022), processed by ESA, CC BY-SA 3.0 IGO)
• March 25, 2022: The Copernicus Sentinel-2 mission takes us over Carrara – an Italian city known especially for its world-famous marble. 56)
- Carrara lies along the Carrione River, in northern Tuscany, around 130 km from Florence. It can be seen just above the centre of the image, stretching into the mountains.
- The city is famous for its white or blue-grey marble, called Carrara, taken from nearby quarries in the Apuan Alps, a mountain range that stretches for approximately 55 km and reaching around 2000 m high. What appears as snow cover on the rugged mountains is actually bright white marble, contrasting with Tuscany’s lush green vegetation.
- Carrara marble is one of the most prestigious marbles in the world, with its quarries producing more marble than any other place on Earth. The unique stone was formed by calcite-rich shells left behind by marine organisms when they die. When water bodies evaporate, the deposited remains form limestone, and when buried under multi-tonne layers of rock, the intense heat and pressure cause the limestone to metamorphose into marble.
- The special quality of the Carrara marble has made it a popular resource for many famous sculptures, including Michelangelo’s Pietà, and has been used for some of the most remarkable buildings in Ancient Rome, including the Pantheon and Trajan’s Column.
- Also featured in this summery image from Sentinel-2 are the towns of Forte dei Marmi, Pietrasanta, Lido di Camaiore and Viareggio. Marina di Carrara, southwest of the city, is a beach resort on the Ligurian Sea, with port facilities for transporting and shipping marble. The most popular resorts and beaches nearby are those at Marina di Carrara and Marina di Massa, both of which become very crowded during the summer, especially with Italian holidaymakers. La Spezia, a major naval base and the second largest city in the Liguria region, is visible in the top-left of the image.
Figure 38: Sentinel-2 image of the Carrara in the Ligurian Sea region of Italy. This image is also featured on the Earth from Space video programme (image credit: ESA, the image contains modified Copernicus Sentinel data (2021), processed by ESA, CC BY-SA 3.0 IGO)
• March 18, 2022: Lake Nasser, visible in the lower-right in black, is a vast lake and reservoir located in southern Egypt and northern Sudan. The lake was created as a result of the construction of the Aswan High Dam across the waters of the Nile in the late-1960s. This ambitious project was designed to provide irrigation to new agricultural developments and attract people to the region. 57)
- The dam is located around 200 km northeast of the area pictured here and cannot be seen. The dam impounds floodwaters from the Nile, releasing them when needed to maximise their utility on irrigated land, to water hundreds of thousands of hectares of land downstream, but also in the nearby area. The dam also helps improve navigation through Aswān and generates an enormous amount of hydroelectric power. The lake covers a total surface area of 5250 km2, yet is relatively shallow with an average depth of 25 m.
- The ancient Egyptian temple of Abu Simbel laid in the path of the rising waters produced by the dam, resulting in the relocation of the temple complex. In the 1960s, the historical site was taken apart piece by piece and reassembled in a new location to avoid submersion. Although the resolution of the image doesn’t allow us to see the temple in detail, the town of Abu Simbel and its airport can be spotted at the bottom of the image, close to several plantations seen in red.
- Part of the Toshka Lakes, natural depressions that are filled by overflow from Lake Nasser, can be seen in the top-left of the image. These endorheic lakes were created in the 1980s and 1990s by the diversion of water from Lake Nasser through the manmade canal visible in green in the image.
- The rise and fall of the lakes depend on multi-year fluctuations in water flow from the Nile. From 2012 to 2018, the lakes had shrunk significantly, leaving only small remnants of water in the basins. Summer rainfall in Sudan in 2019 and record-breaking floods in 2020, resulted in the rapid filling of the lake’s waters. The lakes are relatively salty, with visible signs of eutrophication and algae formation.
Figure 39: Part of Lake Nasser, one of the largest artificial lakes in the world, is featured in this false-colour image captured by the Copernicus Sentinel-2 mission. This image was created by utilising the near-infrared channel from Copernicus Sentinel-2 to emphasise the scarce vegetation in the area. This helps identify the presence of pivot irrigation fields, visible as circular shapes in the image, with the largest having a diameter of around 750 m. The image is also featured on the Earth from Space video programme (image credit: ESA)
- Pivot irrigation systems work where watering equipment rotates around a fixed water supply point and crops are watered with sprinklers. This type of irrigation helps farmers manage their watering demands and helps conserve their water sources.
• March 4, 2022: Today, the Copernicus Sentinel-2 mission takes us over the Pyrenees Mountains in southwest Europe. The mountain range forms a natural border between France and Spain with the small, landlocked country of Andorra sandwiched in between. 58)
- Located in the Spanish province of Huesca in the Posets-Maladeta Natural Park lies Pico de Aneto, the highest mountain peak in the Pyrenees. It rises to an elevation of 3404 m and is also the third-highest mountain in Spain. Click on the circle in the image to take a closer look at Pico de Aneto.
- Geological studies have revealed that the Pyrenees Mountains have been around for longer than the Alps, with their sediments first deposited in coastal basins during the Paleozoic and Mesozoic eras. The entire mountain range formed due to the upwelling of large sedimentary rocks by the collision of the Iberian and the Eurasian plate around 100 to 150 million years ago, followed by intense erosion from ice and water.
- Snow covers many of the peaks year-round, especially those in the centre-section of the chain. The western Pyrenees typically receive greater precipitation than the eastern Pyrenees owing to moisture blowing in from the Atlantic Ocean. The mountain range is also home to several small glaciers, as well as many mountain lakes and some of the highest waterfalls in Europe including Gavarnie Falls which, at 422 m, is France’s highest waterfall.
- Few people live at the Pyrenees’ highest elevations; however, Andorra is nestled among peaks near the eastern end of the chain (not visible in the image). With an area of around 468 km2, Andorra is the sixth smallest country in Europe.
- The Copernicus Sentinel-2 mission is designed to play a key role in mapping differences in land cover to understand the landscape, map how it is used and monitor changes over time. As well as providing detailed information about Earth’s vegetation, it can also systematically map different classes of cover such as forest, grassland, water surfaces and artificial cover like roads and buildings.
Figure 40: Earth from Space: Snowy Pyrenees. Stretching from the shores of the Mediterranean Sea on the east to the Bay of Biscay (Atlantic Ocean) on the west, this international mountain range is 430 km long. The area pictured in this image, captured on 30 January 2022, spans around 120 km from the village of Escallare in the east to Panticosa to the west. This image is also featured on the Earth from Space video programme (image credit: ESA, the image contains modified Copernicus Sentinel data (2022), processed by ESA, CC BY-SA 3.0 IGO)
• February 18, 2022: The Copernicus Sentinel-2 mission takes us over Tenerife – the largest of Spain’s Canary Islands. 59)
- Located in the Atlantic Ocean, opposite the northwest coast of Africa, the Canary Islands consist of eight main islands including Gran Canaria, Lanzarote and La Palma, as well as many small islands and islets.
- Teide National Park, located in the centre of the island, is a UNESCO World Heritage Site and includes Mount Teide which dominates the island. Standing at around 3718 m, its summit is the highest point on Spanish soil. However, much of the volcano’s height is hidden. If measured from the ocean floor, its height of 7500 m makes Teide the third-highest volcano in the world.
- Teide is an active volcano: its most recent eruption occurred in 1909 when a lava flow buried much of the town and harbour of Garachico on the northern coast.
- Owing to the island’s diverse topography and unique climatic factors, Tenerife has multiple microclimates, which means that the weather can vary drastically from one part of the island to the other. Weather and climate are heavily influenced by the trade winds blowing from the northeast for most of the year, bringing humidity and precipitation to the north of the island, as well as to the northern slopes of Mount Teide. This effect can be clearly seen in the dark green colours in the image showing vegetation cover. This band of green generally follows the boundary of Corona Forestal Natural Park, which covers a total area of 46,000 hectares.
- Most of Tenerife’s inhabitants live on the lower slopes, within a few kilometres of the sea. Around half the population is in or near the cosmopolitan capital of Santa Cruz de Tenerife, on the narrower northeast part of the island, and San Cristóbal de la Laguna, the former capital. Other inhabitants live on the intensively cultivated slopes near the northern coast, where the chief towns are La Orotava, Los Realejos, and Puerto de la Cruz. The south is a popular destination where holidaymakers enjoy time on the beautiful beaches of Costa Adeje.
Figure 41: This image, captured on 31 December 2021, is also featured on the Earth from Space video programme (image credit: ESA)
- Tenerife is home to Teide Observatory, located around 10 km from Santa Cruz de Tenerife on the Izaña mountain, which is home to ESA’s IZN-1 laser ranging station – the first laser ranging station to be made commercially available. It is here where lasers are aimed into Earth’s skies, seeking out satellites and soon pieces of space rubbish, as well as measuring their positions and trajectories to prevent catastrophic collisions.
- The station, telescope and laser have recently undergone months of testing and commissioning and have passed their final tests with flying colours.
• February 11, 2022: Hereford, which is the county seat of Deaf Smith County in Texas, is widely known for its agriculture industry. Known as the beef capital of the world owing to its large number of cattle fed, Hereford can be spotted in the centre-bottom of the image. The area is known for its semiarid climate, with heavy farming and ranching sustained by irrigation from the Ogallala Aquifer – a massive underground reservoir spanning eight landlocked states. 60)
- A variety of crops are grown in the area including corn, wheat, maize, soybeans and onions. Circular shapes in the image are an example of centre-pivot irrigation systems, where equipment rotates around a central pivot and crops are watered with sprinklers. This type of irrigation helps farmers manage their watering demands as well as help conserve their precious water sources.
Figure 42: Hereford, and its surrounding colourful patchwork of agricultural fields, is featured in this Copernicus Sentinel-2 image. This composite image over the High Plains in Texas was created by combining three separate Normalised Difference Vegetation Index (NDVI) images from the Copernicus Sentinel-2 mission spanning from 17 March to 21 April 2019. This image is also featured on the Earth from Space video programme (image credit: ESA)
- Shades of red, yellow and green depict changes in vegetation growth at the beginning of the season. Black patches of land indicate very low vegetation for the season, while white signifies a high level of vegetation during these dates. The Normalised Difference Vegetation Index is widely used in remote sensing as it gives scientists an accurate measure of health and status of plant growth.
- The US Route 60 can be seen cutting across the bottom-right of the image. The motorway is a major east-west US route, which runs over 4200 km from southwest Arizona to the Atlantic Ocean coast in Virginia.
• February 4, 2022: New eruption at Krakatoa Volcano. 61)
Figure 43: A new eruption started at the Anak Krakatoa, or Krakatau, volcano on Rakata Island in Indonesia on 3 February 2022, as seen in this image captured by the Copernicus Sentinel-2 mission. The eruption prompted the Anak Krakatau Volcano Observatory to raise the aviation colour code to orange. The eruption started at around 16:15 local time, with a thick column of gas, with possible volcanic ash content, rising to around 200 m above the crater (image credit: ESA, the image contains modified Copernicus Sentinel data (2022), processed by ESA, CC BY-SA 3.0 IGO)
• February 4, 2022: The Copernicus Sentinel-2 mission takes us over Batura Glacier – one of the largest and longest glaciers in the world, outside of the polar regions. 62)
- Located in the upper Hunza Valley, in the Gilgit-Baltistan region of Pakistan, the Batura Glacier is visible in the centre of the image and is approximately 57 km long. It flows from west to east and feeds the Hunza River in north Pakistan, then joins the Gilgit and Naltar Rivers before it flows into the Indus River.
- The lower portions of the Batura Glacier feature a grey sea of rocks and gravelly moraine (an accumulation of rocks and sediment carried down by the glacier often caused by avalanches). The glacier has a mean ice thickness of around 150 m, with the lower parts of the glacier holding most of its mass.
Figure 44: This false-colour composite image uses the near-infrared channel of the Copernicus Sentinel-2 mission to highlight vegetation, which appears in red. Batura is bordered by several villages and pastures with herds of sheep, goats and cows where roses and juniper trees are quite common. In the upper-right of the image, pockets of cultivated vegetation alongside the Gilgit and Hunza rivers can be spotted. This image, captured on 13 August 2021, is also featured on the Earth from Space video programme (image credit: ESA)
- The Batura Glacier is located just north of the Batura Muztagh, a sub-range of the Karakoram mountain range, which includes the massifs of the Batura Sar, the 25th highest mountain on Earth standing at 7795 m, and Passu Sar at 7478 m.
- Glacier shrinkage is a prominent sign of ongoing climate change. However, unlike many glaciers around the world, the glaciers residing in the mountain ranges in Karakoram are not responding to global warming. Their retreating is less than the global average, and in some cases, are either stable or growing. This anomalous behaviour of the region’s glaciers has been coined the ‘Karakoram Anomaly’.
- Scientists typically measure the motions of glaciers with ground-based measurements. Because of the rugged terrain and challenges involved in field studies, long-term ground observational data on Karakoram is sparse. Satellites can help monitor changes in glacier mass, extents, trace area and length of glacier changes through time and derive surface velocity. Learn more about how Copernicus Sentinel-2 can help enhance glacier monitoring.
• January 28, 2022: The Copernicus Sentinel-2 mission takes us over northwest Lesotho – a small, land-locked country surrounded entirely by South Africa. 63)
- Known for its tall mountains and narrow valleys, Lesotho is the only nation in the world that lies completely above 1000 m in elevation. Lesotho has an area of just 30,000 km2, around the same size as Belgium, and has a population of around two million.
- Around 80% of the country’s population lives in rural areas and more than three quarters of these people are engaged in agriculture – mostly traditional, rainfed cereal production and extensive animal grazing. The country’s agricultural system faces a growing number of issues, including a small portion of the land deemed arable, as well as other climate-related vulnerabilities such as drought, floods and extreme temperatures occurring more frequently.
Figure 45: This composite image was created by combining three separate images from the near-infrared channel from the Copernicus Sentinel-2 mission over a period of nine months. The first image, captured on 27 November 2020, is assigned to the red channel and represents the onset of the wet summer season; the second from 12 March 2021, represents green, and was captured towards the end of the wet season; and the third from 19 August 2021 covers the blue part of the spectrum, captured during the short, dry season (image credit: This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2020-21), processed by ESA, CC BY-SA 3.0 IGO)
- All other colours visible in the image are different mixtures of red, green and blue, and vary according to the stage of vegetation growth. A distinct pattern emerges due to topographical differences in this mountainous landscape, such as altitude and slope, which influence local water availability.
- Maseru, the capital and largest urban centre of Lesotho, lies directly on the Lesotho— South Africa border. The city is located on the left bank of the Caledon River, also known as the Mohokare River, visible in black.
- The Copernicus Sentinel-2 mission is designed to provide images that can be used to distinguish between different crop types as well as data on numerous plant indices, such as leaf area, leaf chlorophyll and leaf water. The mission’s revisit time of just five days, along with the mission’s range of spectral bands, mean that changes in plant health and growth can be more easily monitored.
• January 26, 2022: An unusual snowstorm has blanketed parts of Turkey and Greece, causing power cuts and chaos on the roads and flight cancellations. These two satellite images, from the Copernicus Sentinel-2 mission, show Athens: the image of Figure 46 was captured on 25 January and the image of Figure 47 is from 20 January. Just five days apart, the difference that this severe Mediterranean snowstorm has made to the Greek capital is clear to see. Heavy snow fell here for more than 12 hours on 24 January, leaving thousands of motorists stranded on the Attiki Odos motorway, with those not rescued having to cope with temperatures as low as –14°C as night fell. The Greek government declared a two-day public holiday after the snowstorm. 64)
- The storm has also caused similar chaos in Turkey. And, remarkably beaches in Antalya have seen snow for the first time in 29 years.
- Copernicus Sentinel-2 is a two-satellite mission. Each satellite carries a high-resolution camera that images Earth’s surface in 13 spectral bands. Together they cover all Earth’s land surfaces, large islands, inland and coastal waters every five days at the equator.
Figure 46: The Sentinel-2 mission captured this image of Athens under snow on 25 January 2022 (image credit: ESA, the image contains modified Copernicus Sentinel data (2022), processed by ESA, CC BY-SA 3.0 IGO)
Figure 47: The Sentinel-2 mission captured this image of Athens on 20 January 2022 (image credit: ESA, the image contains modified Copernicus Sentinel data (2022), processed by ESA, CC BY-SA 3.0 IGO)
• January 21, 2022: Part of Mecklenburg–West Pomerania, also known as Mecklenburg-Vorpommern, a state in northeast Germany is featured in this image captured by the Copernicus Sentinel-2 mission. A portion of the northwest coast of Poland can be seen in the right of the image. 65)
- Mecklenburg–West Pomerania extends along the Baltic Sea coastal plain with the region’s landscape largely shaped by glacial forces – which deposited materials that produced the coastal lowlands that are today filled with wetlands, streams and lakes.
- Mecklenburg–West Pomerania is one of Germany’s least populated states. Nearly two-thirds is covered by farmland with the main crops being rye, wheat, barley and hay. The green areas present in this image are most likely winter wheat and winter rapeseed. The region’s pastures typically support sheep, horses and cattle.
- On the state’s coastline on the Baltic Sea lie many holiday resorts, unspoilt nature and the islands of Rügen (partly visible in the top left) and Usedom (in the centre of the image), as well as many others. The most populous island in the Baltic Sea, the 445 sq km island of Usedom is mostly flat and is partly covered by marshes.
- The Baltic Sea is no stranger to algae blooms, with two annual blooms taking place each year (the spring bloom and the cyanobacterial bloom in late spring.) Given this image was captured in February, it is most likely an onset of a spring bloom.
- Although algal blooms are a natural and essential part of life in the sea, human activity is also said to increase the number of annual blooms. Agricultural and industrial run-off pours fertilisers into the sea, providing additional nutrients algae need to form large blooms.
Figure 48: The icy Szczecin Lagoon, or Szczeciński Lagoon, dominates this week’s image, which was captured on 22 February 2021. An extension of the Oder estuary, the lagoon is shared between Germany and Poland, and is drained (via the Świna, Peene, and Dziwna rivers) into Pomeranian Bay of the Baltic Sea, between Usedom and Wolin. - From the south, it is fed by several arms of the Oder River, Poland’s second-longest river, and several smaller rivers. The distinct line across the lagoon depicts the shipping waterway that connects the port cities of Świnoujście and Szczecin. Several emerald-green algae blooms can be seen in the image, with the most visible near Peenestrom, an arm of the Baltic Sea, in the left of the image. Peenestrom separates the island of Usedom from the mainland and is an important habitat for waterfowl, especially because of its fish population, such as white-tailed eagles and herons. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2021), processed by ESA, CC BY-SA 3.0 IGO)
Sensor complement: (MSI)
MSI (Multispectral Imager):
The instrument is based on the pushbroom observation concept. The telescope features a TMA (Three Mirror Anastigmat) design with a pupil diameter of 150 mm, providing a very good imaging quality all across its wide FOV (Field of View). The equivalent swath width is 290 km. The telescope structure and the mirrors are made of silicon carbide (SiC) which allows to minimize thermoelastic deformations. The VNIR focal plane is based on monolithic CMOS (Complementary Metal Oxide Semiconductor) detectors while the SWIR focal plane is based on a MCT (Mercury Cadmium Telluride) detector hybridized on a CMOS read-out circuit. A dichroic beamsplitter provides the spectral separation of VNIR and SWIR channels. 66) 67) 68) 69) 70) 71) 72)
Airbus DS (former EADS Astrium SAS) of Toulouse is prime for the MSI instrument. The industrial core team also comprises Jena Optronik (Germany), Boostec (Bazet, France), Sener and GMV (Spain), and AMOS, Belgium. The VNIR detectors are built by Airbus DS-ISAE-e2v, while the French company Sofradir received a contract to provide the SWIR detectors for MSI.
Calibration: A combination of partial on-board calibration with a sun diffuser and vicarious calibration with ground targets is foreseen to guarantee a high quality radiometric performance. State-of-the-art lossy compression based on wavelet transform is applied to reduce the data volume. The compression ratio will be fine tuned for each spectral band to ensure that there is no significant impact on image quality.
The observation data are digitized on 12 bit. A shutter mechanism is implemented to prevent the instrument from direct viewing of the sun in orbit and from contamination during launch. The average observation time per orbit is 16.3 minutes, while the peak value is 31 minutes (duty cycle of about 16-31%).
Figure 49: MSI instrument architecture (image credit: ESA)
Table 6: MSI instrument parameters
Copernicus: Sentinel-2 continued
Spectral bands: MSI features 13 spectral bands spanning from the VNIR (Visible and Near Infrared) to the SWIR (Short-Wave Infrared), featuring 4 spectral bands at 10 m, 6 bands at 20 m and 3 bands at 60 m spatial sampling distance (SSD), as shown in Figure 52.
Table 7: Specification of VNIR and SWIR FPAs 73)
Figure 50: The MSI instrument (left) and the associated VNIR focal plane (right), image credit: Airbus DS-ISAE-e2v
Figure 51: Left: VNIR FPA (image credit: Airbus DS-F, ev2); right: SWIR FPA (image credit: Airbus DS-F, Sofradir)
Figure 52: MSI spatial resolution versus waveleng: Sentinel-2’s span of 13 spectral bands, from the visible and the near-infrared to the shortwave infrared at different spatial resolutions ranging from 10 to 60 m on the ground, takes land monitoring to an unprecedented level(image credit: ESA)
Table 8: MSI spectral band specification
The filter-based pushbroom MSI instrument features a unique mirror silicon carbide off-axis telescope (TMA) with a 150 mm pupil feeding two focal planes spectrally separated by a dichroic filter. The telescope comprises three aspheric mirrors: M2 mirror is a simple conic surface, whereas the other mirrors need more aspherization terms. The spectral filtering onto the different VNIR and SWIR spectral bands is ensured by slit filters mounted on top of the detectors. These filters provide the required spectral isolation.
CMOS and hybrid HgCdTe (MCT) detectors are selected to cover the VNIR and SWIR bands. The MSI instrument includes a sun CSM (Calibration and Shutter Mechanism). The 1.4 Tbit image video stream, once acquired and digitized is compressed inside the instrument.
The instrument carries one external sensor assembly that provides the attitude and pointing reference (star tracker assembly) to ensure a 20 m pointing accuracy on the ground before image correction.
The detectors are built by Airbus Defence and Space-ISAE-e2v: they are made of a CMOS die, using 0.35µm CMOS process, integrated in a ceramic package (Figure 53). The VNIR detector has ten spectral bands, two of them featuring an adjacent physical line allowing TDI operating mode, with digital summation performed at VCU (Video and Compression Unit) level. On-chip analog CDS (Correlated Double Sampling) allows to reach a readout noise of the order of 130 µV rms. For each detector, the ten bands are read through 3 outputs at a sample rate of 4.8MHz. The detector sensitivity has been adjusted for each band through CVF (Charge to Voltage conversion Factor) in view of meeting SNR specifications for a reference flux, while avoiding saturation for maximum flux. A black coating deposition on the non-photosensitive area of the CMOS die is implemented to provide high straylight rejection.
Figure 54: MSI electrical architecture (image credit: Astrium SAS, Ref. 69)
The filter assemblies are procured from Jena Optronik (JOP) in Germany. A filter assembly is made of filter stripes (one for each spectral band) mounted in a Titanium frame. The aims of the filter assembly are: i) to separate VNIR spectral domain into the ten bands B1 to B9, ii) to prevent stray light effects. This stray light limitation is very efficient since it is made very close to the focal plane. Each filter stripe, corresponding to each spectral band, is aligned and glued in a mechanical mount. A front face frame mechanically clamps the assembly together.
The FEE (Front End Electronics) are procured from CRISA in Spain. Each FEE unit provides electrical interfaces to 3 detectors (power supply, bias voltages, clock and video signals) plus video signal filtering and amplification.
Video and Compression Unit (VCU) is manufactured by JOP and aims i) at processing the video signals delivered by the FEEs : digitization on 12 bits, numerical processing, compression and image CCSDS packet generation, ii) interfacing with the platform (power supply, MIL-BUS, PPS), iii) providing the nominal thermal control of the MSI.
Figure 55: Internal configuration of MSI (image credit: EADS Astrium)
Figure 56: Mechanical configuration of the telescope (image credit: EADS Astrium)
The mechanical structure of MSI instrument holds the 3 mirrors, the beam splitter device, the 2 focal planes and 3 stellar sensors. It is furthermore mounted on the satellite through 3 bolted bipods. This main structure (Figure 56) has a size of 1.47 m long x 0.93 m wide x 0.62 m high with a mass of only 44 kg.
The optical face of these mirror blanks have been grounded by Boostec before and after CVD coating (i.e. before polishing), with a shape defect of few tens of a µm. M1 and M2 are designed to be bolted directly on the main SiC structure. M3 is mounted on the same structure through glued bipods. 74)
Table 9: MSI mirror characteristics
Mirror manufacturing: The mirror optomechanical design was performed by EADS-Astrium on the basis of the SiC-100 sintered silicon carbide from Boostec who produced the mirror blanks and delivered them to AMOS (Advanced Mechanical and Optical Systems), Liege, Belgium. AMOS is in charge of the deposition of a small layer of CVD-SiC (Chemical Vapor Deposition-Silicon Carbide) on the mirror. The purpose is to generate a non-porous cladding on the mirror surface which allows the polishing process reaching a microroughness state, compatible with the system requirements regarding straylight. 75)
Figure 57: Optical elements and schematic layout of the MSI telescope (image credit: EADS Astrium)
VNIR and SWIR focal plane assemblies: Both focal planes accommodate 12 elementary detectors in two staggered rows to get the required swath. The SWIR focal plane operates at -80ºC whereas the VNIR focal plane operates at 20ºC. Both focal planes are passively cooled. A monolithic SiC structure provides support to the detectors, the filters and their adjustment devices and offers a direct thermal link to the radiator.
Figure 58: Focal plane configuration (image credit: EADS Astrium)
Filters and detectors: Dedicated strip filters,mounted on top of each VNIR or SWIR detector, provide the required spectral templates for each spectral band. The VNIR detector is made of a CMOS die, using the 0.35 µm CMOS technology, integrated in a ceramic package. The detector architecture enables “correlated double.”
The so-called VNIR Filter Assembly contains 10 VNIR bands (from 443 nm to 945 nm) and the so-called SWIR Filter Assembly includes 3 SWIR bands (from 1375 nm to 2190 nm). The sophisticated development of the filter assemblies is caused by the specified spectral performance parameters and the high stray light requirements due to the topology of the spectral bands. 76)
Sampling for the 10 VNIR spectral bands along with TDI (Time Delay IntegrationI) mode for the 10 m bands. Black coating on the die eliminates scattering.
Figure 59: Photo of the VNIR (top) and SWIR spectral filter assemblies (image credit: Jena Optronik)
Figure 60: Photo of a CMOS detector with black coating (image credit: EADS Astrium)
The SWIR detector is made of an HgCdTe photosensitive material hybridized to a silicon readout circuit (ROIC) and integrated into a dedicated hermetic package. The SWIR detector has three spectral bands for which the spectral efficiency has been optimized. The B11 and B12 bands are being operated in (TDI) mode.
Figure 61: Photo of the EM model of the SWIR detector at hybridization stage (image credit: Sofradir)
CSM (Calibration and Shutter Mechanism): In MSI, the two functions of calibration and shutter are gathered in one single mechanism to reduce mass, cost and quantity of mechanisms of the instrument, increasing its reliability at the same time. The CSM is located at the entrance of MSI, a rectangular device of ~ 80 cm x 30 cm, mounted on the frame of the secondary structure. The design and development of the CSM is provided by Sener Ingenieria y Sistemas, S.A., Spain. 77)
Figure 62: Photo of the CSM (Calibration and Shutter Mechanism) mechanical configuration (image credit: Sener)
Requirements and design drivers:
• During launch the CSM has to protect the instrument from sun illumination and contamination by covering the instrument entrance with a rectangular plate (named the door). This is the close position, which has to be maintained under the action of the launch loads.
• Once in orbit, the following functions are required from the CSM:
- To allow Earth observation to the instrument (MSI) the door needs to rotate from the close position 63º inwards the instrument and maintain it stable without power. This is the open position.
- From time to time, in calibration mode of the MSI, the CSM inserts a sun diffuser in front of the primary mirror and the sun diffuser is illuminated by direct solar flux. This mode corresponds to a door position located 55º from the close position outward the instrument. This position must be also stable without any power supply.
Figure 63: Sentinel-2A/MSI sun diffuser. Size: 700 x 250 mm2 ensuring calibration of each pixel into the FOV (image credit: Airbus DS-F)
- In case of emergency, the CSM has to rotate the door to the close position from any initial position to prevent the sun light to heat sensible components of the instrument. Similarly to the previous positions, the close position shall be stable without power supply.
Figure 64: View of the CSM in calibration position (image credit: Sener)
A face to face ball bearing as rotation axis hinge in the opposite side of the actuator is used supported by means of an axially flexible support. Apart from that the pinpuller mounted on a flexible support, holds the door during launch by means of a cylindrical contact with respect to the door bushing. This design is the result of the optimization made in order to reach a stiff and robust but light and hyper-statically low constrained mechanism to make it compatible under possible thermal environments.
The pinpuller provides a reliable launch locking device and allows after pin retraction the mechanism to rotate in both senses.
The MSI instrument design represents state-of-the-art technology on many levels that is being introduced for next generation European land-surface imagers. Obviously, its performance will set new standards for future spaceborne multispectral imagers.
Storage technology introduction:
MMFU (Mass Memory and Formatting Unit):
The introduction of MMFU by EADS Astrium GmbH and IDA (Institut für Datentechnik und Kommunikationsnetze) at TU Braunschweig represents a new spaceborne storage technology based on SLC (Single Level Cell) NAND-Flash memory devices.
Note: NAND (Not And) is a Boolean logic operation that is true if any single input is false. Two-input NAND gates are often used as the sole logic element on gate array chips, because all Boolean operations can be created from NAND gates.
The NAND storage technology is not only an established technology in commercial applications but represents also a real and effective alternative for mass memory systems in space. The main advantages of the NAND-Flash technology are: a) the non-volatile data storage capability and b) the substantially higher storage density.
In the commercial world the NAND technology has become the preferred solution for storing larger quantities of data on devices such as SSDs (Solid State Drives), USB (Universal Serial Bus) Flash memory sticks, digital cameras, mobile phones and MP3-Players. In the space business, this technology has been used in some experiments only, but not in the frame of large scale mass memory systems. This is now going to be changed. 78) 79) 80)
Astrium and IDA have continuously worked for over seven years on the subject “NAND-Flash Technology for Space”. In the frame of an ESA study dubbed SGDR (Safe Guard Data Recorder) this NAND-Flash technology has been introduced and intensively evaluated.
As a result of this extensive testing, the radiation effects of this technology are well known meanwhile and appropriate error handling mechanisms to cope with the observed effects have been developed. For the S2 (Sentinel-2) mission, a complete qualification program has been performed including radiation tests, assembly qualification, construction analysis, electrical characterization, reliability tests like burn-in, destructive physical analysis, stress and life tests.
All these investments led to the final conclusion that the selected SLC NAND-Flash is an adequate technology for high capacity memory systems for space, even for systems with very high data integrity requirements.
Table 10 lists some main requirements and provides in parallel the related figures of two Astrium MMFU implementations. The first implementation is based on SLC NAND-Flash devices and will be launched with the Sentinel 2 satellite. The second option uses SDR-SDRAM devices, which was the initially required baseline technology for this mission.
Table 10: Sentinel-2 MMFU requirements and resulting implementations
The related simplified architectural block diagram of the Astrium Sentinel-2 MMFU is shown in Figure 65. The MMFU receives two parallel data streams either from the nominal or redundant VCU (Video Compression Unit). The interfaces are cross-strapped with redundant PDICs (Payload Data Interface Controllers). After reception and adaptation to internal data formats of the received source packets, the data is stored in memory modules. FMM (Flash Memory Module) and respectively SMM for the SDR-SDRAM memory module. For replay, the data is read out from two parallel operated memory modules and routed via two active TFGs (Transfer Frame Generators) providing interfaces for downlink and test. The system is controlled by a Memory System Supervisor, which is based on an ERC32 processor. The required supply voltages are provided by a power converter.
Figure 65: Architecture of the MMFU system (image credit: Astrium)
Each function is implemented by nominal and redundant hardware components. The functions and boards are summarized in Table 11:
Table 11: Number of functions and boards
Storage capacity: Astrium uses for all boards a standard format. Therefore the maximum number of memory and other devices which can be assembled on one board is limited by this form factor. Both types of memory modules are nearly identical in form, fit and function and because they can be mutually replaced; this represents a good basis for comparison.
The selected NAND-Flash device provides a capacity of 32 Gbit plus some spare. It is realized by means of four 8 Gbit dies encapsulated in a standard TSOP1 package. In total, the FMM (Flash Memory Module) includes 76 devices. The devices are arranged in four partitions which can be independently powered. A partition represents also the lowest level for reconfiguration. Each partition contains sixteen devices to store user data and three devices that are used to store parity information. This configuration enables single symbol error correction and double symbol error detection.
The SDRAM based memory module has a similar organization. There are also four partitions and each devices for single symbol error correction. A device is represented by a stack which contains eight SDRAM chips with a capacity of 512 Mbit each. From this follows the user storage capacity per memory module and some other parameters as listed in Table 12.
The number of FMM modules is determined by the total data rate and the operational concept, which requires the operation of two independent data streams. Therefore there are two memory modules operated in parallel. The third one is provided for redundancy.
The number of SMM modules is mainly determined by the required capacity. Also here two modules are operated in parallel and one SMM is included for reliability reasons.
Table 12: Performance characteristics of Astrium Sentinel 2 MMFU memory modules
The much higher storage density of the NAND-Flash devices (factor of 8) leads to a massive reduction in the number of required memory modules. For a mass memory system this becomes especially evident, if there is a requirement for a large user capacity as in case of the Sentinel-2 MMFU. Further positive aspects evolve with reduction of the number of modules. The complete system design from electrical and mechanical point of view is greatly relaxed.
Mass and volume: With reduction of the number of memory modules, it is obvious that directly related physical budgets like mass and volume, decline accordingly. Mass is always a critical issue for space missions which can be reduced by using NAND-Flash technology; but also the complete system design of a satellite, in terms of mass, power, thermal and other aspects, can be positively influenced by applying NAND-Flash based memory systems. In case of the Sentinel-2 MMFU, indeed 14 Kg (about 50%) can be saved.
Power: The power consumption is also reduced by more than 50% (Table 10). This is mainly caused by the number of memory modules operated in parallel. In case of Flash, there are only two active memory modules. In case of the SDRAM technology, 10 memory modules are operated in parallel: up to four modules for data access, two modules for read, two modules for write, and all other modules in data retention mode. Data retention means that the modules store user data and the SDRAM chips have to be refreshed and scrubbed for error detection and correction.
In contrast, a Flash-based memory module can be completely switched off without loss of data in the data retention mode. For a minimum, the partitions can be switched off and the power consumption of the controller part of the module is reduced due to low activity.
It is not obvious, that, in all cases, NAND-Flash consumes less power than SDR-SDRAM based systems. The power consumption depends on several factors like required storage capacity, data rates and operations. Generally it can be said, that as long as the required storage capacity determines the number of memory devices, Flash might be the better choice. If the number of memory devices is determined by the required data rate, SDRAM based systems may have a better performance from a power consumption point of view.
Data rates: Table 13 shows that SDR-SDRAM devices provide a much better performance from data rate point of view. The overall performance of a memory module depends on further characteristics like type of interfaces, memory controller performance, and maximum power consumption and others. Generally an SDRAM based memory module has advantages in terms of access speed.
Table 13: Performance characteristics of the memory devices
The lower performance of NAND-Flash is determined by three characteristics. During writing the NAND-Flash devices need to be programmed and this takes a time of about 700 µs per 4 kbyte data (one device page). Additionally the so-called blocks of a NAND-Flash device have to be erased before programming. This consumes another 2 ms per block (64 pages). Last but not least, the selected NAND-Flash devices use an eight bit interface for serial commanding, addressing and data transfer with a maximum operating frequency of 40 MHz.
This lack in performance can be mitigated by mainly two measures. The first straight forward measure is parallel operation of NAND-Flash devices. The second measure is interleaved access to several NAND-Flash devices. Interleaving uses the programming time of a NAND-Flash device to write in parallel the next device. These methods allow increasing the write access performance.
Life time and reliability: NAND-Flash devices provide a limited endurance. This is caused by an inherent wear out mechanism of the Flash memory cells which limits the number of erase and write cycles to about 105 cycles. To mitigate the endurance limitation, most Flash memory systems are equipped with an address management system, which distributes the write accesses rather uniformly over the address space. This technique is called Wear Leveling.
Furthermore the very high device capacity of NAND-Flash devices offers the opportunity to implement a physical address space, which exceeds the required logical user address space by a factor of n. This enhances the wear out limit of the logical addresses by the factor of n too. Hence there are two methods to keep the total count of write accesses to the same physical address below the wear out limit.
Radiation and error rates: In general, sensitivity of electronic devices to space radiation is a major topic and is also shortly discussed here through a comparison of NAND-Flash and SDR-SDRAM devices.
The mass memory system based on NAND-Flash shows clear advantages and fits well to the high storage capacity and moderate data rates of the Sentinel-2 application. The very high storage density of the NAND-Flash devices leads to a reduced number of memory modules with advantages in terms of power consumption, mass and volume. Furthermore this feature improves the reliability and eases the system design from mechanical and electrical points of view.
Figure 66: Photo of the EQM (Engineering Qualification Model), Sentinel-2 MMFU (image credit: Astrium)
Table 14: Parameters of the Sentinel-2 MMFU 81)
For Copernicus operations, ESA has defined the concept and architecture for the Copernicus Core ground segment, consisting of a Flight Operations System (FOS) and a Payload Data Ground Segment (PDGS). Whereas the flight operations and the mission control of Sentinel-1 and -2 is performed by ESOC (ESAs European Space Operations Center in Darmstadt, Germany), the operations of Sentinel-3 and the Sentinel-4/-5 attached payloads to meteorological satellites is performed by EUMETSAT.
The ground segment includes the following elements:
• Flight Operations Segment (FOS): The FOS is responsible for all flight operations of the Sentinel-2 spacecraft including monitoring and control, execution of all platform activities and commanding of the payload schedules. It is based at ESOC, Darmstadt in Germany and comprises the Ground Station and Communications Network, the Flight Operations Control Centre and the General Purpose Communication Network.
• Payload Data Ground Segment (PDGS): The PDGS is responsible for payload and downlink planning, data acquisition, processing, archiving and downstream distribution of the Sentinel-2 satellite data, while contributing to the overall monitoring of the payload and platform in coordination with the FOS.
The Service Segment, geographically decentralized, will utilize the satellite data in combination with other data to deliver customized information services to the final users.
The baseline ground station network will include four core X-band ground stations for payload observation data downlink and one S-band station for Telemetry, Tracking and Control (TT&C). To a limited extent, the system can also accommodate some direct receiving local user ground stations for Near-Real Time applications.
The systematic activities of the PDGS include the coordinated planning of the mission subsystems and all processes cascading from the data acquired from the Sentinel-2 constellation, mainly:
1) The automated and recurrent planning of the satellite observations and transmission to a network of distributed X-band ground stations
2) The systematic acquisition and safeguarding of all spacecraft acquired data, and its processing into higher level products ensuring quality and timeliness targets
3) The recurrent calibration of the instrument as triggered by the quality control processes
4) The automated product circulation across PDGS distributed archives to ensure the required availability and reliability of the data towards users
5) The long-term archiving of all mission data with embedded redundancy over the mission lifetime and beyond.
Figure 67: PGDS context in Sentinel-2 system (image credit: ESA)
Figure 68: The Sentinel-2 ground segment (image credit: ESA)
Figure 69: Physical layout of the PGDS ground stations (image credit: ESA) 82)
• CGS (Core Ground Stations: Matera (Italy), Maspalomas (Spain), Svalbard (Norway), Alaska (USA).
• PAC (Processing/Archiving Center): Farnborough (UK), Madrid (Spain)
• MPC (Mission Performance Center): TBD
• PDMC (Payload Data Management Center): ESA/ESRIN, Frascati, Italy.
Table 15: Sentinel-2 level-1 and level-2 products
Copernicus / Sentinels EDRS system operations:
EDRS (European Data Relay Satellite) will provide a data relay service to Sentinel-1 and -2 and initially is required to support 4 Sentinels simultaneously. Each Sentinel will communicate with a geostationary EDRS satellite via an optical laser link. The EDRS GEO satellite will relay the data to the ground via a Ka-band link. Optionally, the Ka-band downlink is planned to be encrypted, e.g. in support to security relevant applications. Two EDRS geo-stationary satellites are currently planned, providing in-orbit redundancy to the Sentinels. 83)
EDRS will provide the same data at the ground station interface as is available at the input to the OCP (Optical Communications Payload) on-board the satellites, using the same interface as the X-band downlink. The EDRS transparently adapts the Sentinels data rate and format to the internal EDRS rate and formats, e.g. EDRS operates at bit rates of 600 Mbit/s and higher.
With EDRS, instrument data is directly down-linked via data relay to processing and archiving centers, while other data continues to be received at X-band ground stations. The allocation of the data to downlink via X-band or EDRS is handled as part of the Sentinel mission planning system and will take into account the visibility zones of the X-band station network and requirements such as timeliness of data.
Figure 70: Sentinel missions - EDRS interfaces (image credit: ESA)
Copernicus / Sentinel data policy:
The principles of the Sentinel data policy, jointly established by EC and ESA, are based on a full and open access to the data:
• anybody can access acquired Sentinel data; in particular, no difference is made between public, commercial and scientific use and in between European or non-European users (on a best effort basis, taking into consideration technical and financial constraints);
• the licenses for the Sentinel data itself are free of charge;
• the Sentinel data will be made available to the users via a "generic" online access mode, free of charge. "Generic" online access is subject to a user registration process and to the acceptation of generic terms and conditions;
• additional access modes and the delivery of additional products will be tailored to specific user needs, and therefore subject to tailored conditions;
• in the event security restrictions apply to specific Sentinel data affecting data availability or timeliness, specific operational procedures will be activated.
Sen2Coral (SEOM S24Sci Land and Water: Coral Reefs)
The objective of ESA’s SEOM (Scientific Exploration of Operational Missions) Program Sen2Coral is the preparation of the exploitation of the Sentinel-2 mission for coral reefs by developing and validating appropriate, open source algorithm available for the community. The project objectives are the scientific exploitation and validation of the Sentinel-2 MSI (Multispectral Instrument) for mapping (habitat, bathymetry, and water quality) and detection change for coral reef health assessment and monitoring, and algorithm development dedicated to Sentinel-2 capabilities to satisfying these objectives. 89)
To address the extremely interesting and challenging questions posed by this project a consortium of contractors with appropriate background knowledge and skills has been assembled. The consortium comprises:
• ARGANS Limited, UK
• CNR-IREA, Italy
• CS-SI, France
The consortium is complimented by a science team of consultants and partners who are recognized international scientists in the field.
• A critical analysis of feedback from scientists and institutions collected through consultations in ESA and Third Party workshops, symposia and conferences.
• Proposal of potential observation scenarii for Sentinel-2 in terms of required spatial coverage and repeat cycle considering user requirements, existing observation initiatives and synergy with other sensors (Landsat, SPOT sensor families).
• Identifying scientific priority areas and providing guidance for future scientific data exploitation projects. 90)
Tropical coral reefs are globally important environments both in terms of preservation of biodiversity and for the substantial economic value their ecosystem services provide to human communities. Managing and monitoring reefs under current environmental threats requires information on their composition and condition, i.e. the spatial and temporal distribution of benthos and substrates within the reef area. Determining the relative abundance of biotic types such as coral and macroalgae is the key for detecting and monitoring important biotic changes such as phase or regime shifts due to changes in environmental conditions. Coral bleaching events, where stressed corals expel their symbiotic algae and turn white in color, can provide indications of anthropogenic stressors and climate change impacts, while subsequent coral mortality may be a key determinant of future reef state. In addition to monitoring of current status, maps of benthos have the potential to inform management decisions such as the placement of marine protected areas and could in the future be used to seed models to predict ecosystem dynamics.
Figure 71: Image of the North Palau Reef (Western Pacific), acquired with Sentinel-2A on Feb. 10, 2016 (image credit: ESA, Sen2Coral consortium)
Figure 72: Image of Fatu Huku (Pacific) acquired with Sentinel-2A on Feb. 11, 2016 (image credit: ESA, Sen2Coral consortium)
Figure 73: Image of Heron Island, Great Barrier Reef, acquired with Sentinel-2A on Jan. 31, 2016 (image credit: ESA, Sen2Coral consortium)
Background: The degradation of coral reefs is a fact, with 55% of reefs being affected by overfishing and destructive fishing methods, which as the most pervasive threats, whereas 25% of reefs are affected by coastal development and pollution from land, including nutrients from farming and sewage, while one tenth suffer from marine-based pollution (local pressures are most severe in South-East Asia, where nearly 95 per cent of coral reefs are threatened).
In addition the coral reefs’ ecosystems appear to be the first to respond to global climate changes, such as increased sea surface temperature (SST), ultraviolet radiation (UV) and acidification of seawater that results from higher levels of atmospheric CO2 concentration.
Sentinel-2 MSI Data Acquisition:
The MSI (Multispectral Instrument) of the Sentinel-2A mission offers several potential technical advantages in the remote sensing of coral reefs due to:
• 10 meter spatial resolution allowing improvement in visual interpretation of reef features, classification accuracy and bathymetry.
• Additional water penetrating optical band improving consistency under varying water conditions, reducing uncertainty in bottom type and bathymetric mapping, deeper bathymetric accuracy and ability to determine water optical properties.
• Additional NIR/SWIR bands enabling more consistent and accurate determination of atmospheric and surface glint correction.
• Short re-visit time enabling the use of image series to determine fundamental uncertainties for change detection.
• Addresses the current limited remote sensing acquisition plan covering the coast areas.
Figure 74: Overview of processing steps (image credit: Sen2Coral consortium)
Algorithm Development & Data Processing:
The objective “to develop and validate new algorithms relevant for coral reef monitoring based on Sentinel-2 observations” will be addressed by parameterizing existing models for processing hyper-spectral & multi-spectral data and developing pre-processors for these models to build Sentinel-2 data processing algorithms for the retrieval of coral reefs’ static and dynamic characteristics. The code developed will be made available open source.
Validation and uncertainty analysis will involve both comparing Sentinel MSI performance versus Landsat-8 on coral reef mapping objectives and comparing coral reef monitoring products against in situ data from reef sites representative of different composition and structure.
To design, verify and validate three coral reef monitoring products making the best use of Sentinel-2 MSI mission characteristics:
• Habitat mapping of coral reefs
• Coral reef change detection
• Bathymetry over coral reefs.
A 6 day field campaign around the South Pacific island of Fatu Huku was undertaken by French scientist Antoine Collin to collect in-situ data to test and validate the capabilities of the Sentinel-2 satellite to monitor coral reef bleaching.
Fatu Huku Island in French Polynesia was chosen as the survey site because of the presence of developed coral reefs and it is an area water temperatures are high as a result of the current El Niño event. During the survey, water temperature exceeding 30°C were recorded and coral bleaching, the expulsion of the symbiotic algae that provide energy from sunlight to the coral, was observed to be taking place.
Data collected from this field campaign complements archives of in-situ data collected over previous years from coral reef sites across the globe such as at Heron Island and Lizard Island, in Australia, and reefs around Palau, in the western Pacific Ocean.
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The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (email@example.com).
Spacecraft Launch Mission Status Sensor Complement Ground Segment References Back to top
The Sentinel series:
Provides data continuity for: