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CIMR (Copernicus Imaging Microwave Radiometer) mission

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October 2018: Climate change resulting in ocean warming, sea level rise, and sea ice melting has consequences for the global economy, navigation, and security. The CIMR (Copernicus Imaging Microwave Radiometer) mission is a high priority candidate satellite mission within the European Copernicus Expansion program. It is designed to observe the ocean and sea ice and more particularly the Arctic environment. Sea surface temperature, ocean wind speed, sea surface salinity, and sea ice concentration are fundamental variables for understanding, monitoring, and predicting the state of the ocean and sea ice. Here we analyze the performances of this new satellite mission in terms of precision and spatial resolution on the sea surface temperature, sea surface salinity, and sea ice concentration and compare it with current missions. CIMR will provide sea surface temperature, sea surface salinity, and sea ice concentration with a spatial resolution of 15, 55, and 5 km and a precision of 0.2 K, 0.3 psu (practical salinity unit), and 5%, respectively. This satellite mission is currently in preparatory phase, and if selected, it is for a launch in the 2025 time frame. 1) 2)

On 27 April 2016, the European Commission and the High Representative of the Union for Foreign Affairs and Security Policy issued to the European Parliament and the Council, a joint communication that proposed 'An integrated Europe Union policy for the Arctic.' The Arctics fragile environment is also a direct and key indicator of the climate change, which requires specific mitigation and adaptation actions, as agreed with the global agreement reached during the United Nations Climate Change Conference, COP-21 (Conference of the Parties) held in Paris in December 2015. The integrated EU Arctic policy has identified and is addressing three priority areas:

1) Climate Change and Safeguarding the Arctic Environment (livelihoods of indigenous peoples and Arctic environment).

2) Sustainable Development in and around the Arctic (exploitation of natural resources, e.g., fish, minerals, oil, and gas), Blue economy and safe and reliable navigation (e.g., the Arctic Northern Sea Route).

3) International Cooperation on Arctic Issues (scientific research, EU and bilateral cooperation projects, fisheries management/ecosystems protection, and commercial fishing).

Continuously monitoring the vast and harsh Arctic environment with Earth observation, navigation, and communication satellites is considered essential. The European Commission has expressed user needs that recommends, as a first priority, an Imaging Microwave Radiometry Mission to address the Integrated EU Arctic Policy through the provision of operational ocean and sea-ice products with high spatial resolution, radiometric fidelity, and at least daily revisit in Polar regions. The Copernicus Imaging Microwave Radiometer (CIMR) mission is one of six High Priority Candidate Missions within the Copernicus Expansion program focused on new missions that have been identified by the European Commission as priorities for implementation in the coming years to provide additional capabilities in support of high priority user needs. The CIMR mission is currently in a phase A/B1 study expected to move into full implementation for a launch in the 2025+ time frame.

Sea surface temperature (SST), ocean wind speed, sea surface salinity (SSS), and sea ice concentration (SIC) are fundamental variables for understanding, monitoring, and predicting the state of the ocean and sea ice. CIMR is a conically scanning microwave radiometer imager that includes channels at 1.4, 6.9, 10.65, 18.7, and 36.5 GHz, in a Sun-synchronous polar orbit, to provide SST, ocean wind speed, SSS, and SIC with an increased accuracy and/or spatial resolution.


Figure 1: Example plots showing a simulation of the expected CIMR global coverage and over the Arctic highlighting the number of revisits each day with no hole at the pole. Daily coverage of the Copernicus Imaging Microwave Radiometer mission in the Arctic regions. The color map shows the number of revisit overpasses in a 24 hours period. The CIMR mission is specifically designed to ensure sub-daily coverage in all the Arctic region. Particularly, CIMR will achieve full sub-daily coverage of the Arctic region (i.e. "no hole at the pole" requirement). By symmetry, the coverage is also excellent in the Antarctic region. Over 95% of the globe will be covered on a daily basis (Lavergne, T., Pinol Sole, M. and Donlon, C.: Daily coverage of CIMR (Arctic, Antarctic, and Global views), figshare, doi:10.6084/m9.figshare.7749284.v1, 2019), image credit: ESA


Development status

• November 11, 2021: The Copernicus Imaging Microwave Radiometer (CIMR) satellite instrument is currently being implemented to observe the Polar Regions. It will measure different variables, including the temperature and salinity of the ocean surface, and the sea ice extension in the polar ice caps. To help design the instrument, the first instrument concept has been computer simulated. Together with simulations of the radiation emitted by the oceans, it allows reproducing what the instrument antennas will measure. This is followed by further computations that apply mathematical algorithms to the simulated measurements to estimate the values of the ocean and ice parameters of interest. Studying these simulated measurements is then used to see whether the CIMR instrument concept is suitable to achieve the mission goals, and how much better CIMR will measure compared with existing instruments already observing similar variables. Although more work is required to keep refining the instrument and its computer simulations, this study shows that CIMR can achieve its mission goals, measuring more accurately and with better spatial resolution than previous instruments, and greatly contributing to monitoring the rapid changes expected to take place in the Polar regions in the years to come. 3)

- The Copernicus Imaging Microwave Radiometer (CIMR) is a satellite system developed as part of the European Union Copernicus program expansion activities. CIMR is designed to monitor the rapid Earth system changes taking place in the Arctic in response to the Integrated European Policy for the Arctic. Prioritized user needs to be expressed by the European Commission Polar Expert Group.

- The aim of the mission is to provide high-spatial resolution microwave imaging radiometry measurements and derived products with global coverage and sub-daily revisit in the polar regions and adjacent seas to address Copernicus user needs. Its main challenges are (1) to provide high spatial resolution 5 km Ka/Ku band measurements of sea ice parameters that provide an enhanced capability compared to 89 GHz solutions that are challenged by atmospheric effects; (2) to provide high spatial resolution (15 km) C/X band measurements of global coverage sea surface temperature with quasi all-weather capability and rapid (1–2 days) revisit, and; (3) to maintain an L-band measurement capability to continue the legacy of sea surface salinity and soil moisture parameters from previous L-band missions.

- At the heart of the CIMR mission design is the need to measure fundamental quantities associated with large-scale ocean-cryosphere-atmosphere processes in the Arctic. Sea ice is part of the oceanographic "system" and the physics of eutectoid changes and the thermodynamically driven state of seawater is at the heart of the system. Level-2 products include Sea Ice Concentration (SIC), Sea Surface Temperature (SST), Sea Surface Salinity (SSS), Sea Ice Drift (SID), Sea Ice Thickness (SIT), Snow Depth on sea ice (SND), and Sea Ice Surface Temperature (SIST). As part of the mission design, which includes contiguous global coverage, CIMR will also have the capability to deliver a variety of additional parameters including ice-type, terrestrial snow extent, ice surface temperature, wind speed over the ocean, soil moisture, and vegetation indices. Data products are to be operationally available within 3 hr of sensing at the user point of pickup, with a capability to provide specific products within 1 hr of sensing in support of Arctic navigation safety.

- The CIMR instrument concept is based around a conically scanning multi-frequency microwave radiometer with a 55° incidence angle with the Earth surface. Its design partly inherits from previous studies conducted at ESA for the Multifrequency Imaging Microwave Radiometer (MIMR). CIMR measurements will be made using a forward scan arc followed ~260 s later by a second measurement of the same location using a backward scan arc. Channels in bands L, C, X, Ku, and Ka, centered at 1.414, 6.925, 10.65, 18.7, and 36.5 GHz, respectively, are included in the mission design. The measurements will be acquired in vertical (V) and horizontal (H) polarizations, with on board the spacecraft and on ground strategies put in place to mitigate Radio Frequency Interference (RFI) contamination. Modified Stokes parameters will be computed on-board the spacecraft. The spatial resolution of the real-aperture antenna for the C/X-band channel is at least 15 km, and 5 and 4 km, and for the Ku and Ka-band channels, respectively. The L-band channel will have a real-aperture resolution of at least 60 km, fundamentally limited by the size of the reflector and the focus of the L-band feed. However, all channels will be oversampled along and across-track by 20% allowing gridded products to be generated at better spatial resolutions. Channel Noise Equivalent Delta Temperature (NEΔT) is 0.2–0.7 K with total standard uncertainty at processing level L1B (instrument data processed to sensor units) better than 0.5 K (L,C,X), 0.6 K (Ku), and 0.7 K (Ka).

- CIMR will be flying in a dawn-dusk orbit deploying a wide-swath (>1,900 km), which will result in a 95% global coverage every day, better than daily coverage poleward of 55°N and 55°S, and no gap in coverage at the poles themselves. It is expected to operate in synergy with the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) MetOp-SG(B) mission so that collocated and contemporaneous measurements between CIMR and MetOp-SG(B) Microwave Imaging Radiometer (MWI), Ice Cloud Imager (ICI), and Scatterometer (SCA) measurements can be made available within ±10 min in the polar regions.

- Measuring SIC and SST are the two first mission objectives, and therefore critical to deriving the mission requirements. The impact of the CIMR channel selection for SST retrievals is discussed in Nielsen-Englyst et al. (2021), and sensitivity analysis of CIMR observations over the Arctic Ocean is presented in Kilic et al. (2021). The third main objective is to assure continuity of L-band, and, to illustrate the value of having the 1.4 GHz channel on board, the Sea Surface Salinity (SSS) retrieval performance is also studied. The main mission requirements for the measurements of SIC, SST, and SSS are summarized in Table 1.


Spatial resolution

Uncertainty a

Temporal sampling

Sea Ice Concentration (SIC)

5 km



Sea Surface Temperature (SST)

15 km

<0.3 K


Sea Surface Salinity (SSS)

5 km

<0.3 pss b


Table 1: Summary of the Requirements on the Sea Ice Concentration, Sea Surface Temperature, and Sea Surface Salinity Measurements for the Copernicus Imaging Microwave Radiometer Mission, in Terms of Spatial Resolution, Uncertainty, and Temporal Sampling

a: The value for SST is calculated for a theoretical retrieval as the mode value of daily global ocean average discrepancies assuming no uncertainty in the validation dataset, while for SIC and SSS it is a standard retrieval uncertainty.

b: Practical Salinity Scale 1978 (PSS-78) are used, following UNESCO guidelines (UNESCO, 1985). Although salinity measured using PSS-78 does not have units, the suffix "pss" is sometimes used in the text and figures to distinguish the values of salinity, rates, and variance.

• November 13, 2020: Today, ESA signed contracts with Thales Alenia Space in France and in Italy, and Airbus in Spain to build three of the new high-priority Copernicus satellite missions: CHIME, CIMR and LSTM, respectively. Each mission is set to help address different major environmental challenges such as sustainable agriculture management, food security, the monitoring of polar ice supporting the EU Integrated Policy for the Arctic, and all will be used to understand climate change. 4)

- ESA signed the contract for the development of the CIMR (Copernicus Imaging Microwave Radiometer) mission with Thales Alenia Space (TAS) Italy in the presence of the Under Secretary of the Council of Ministers of Italy, Riccardo Fraccaro. The contract is worth €495 million.

- Carrying a novel ‘conically-scanning' multi-frequency microwave radiometer, the mission will measure sea-surface temperature, sea-ice concentration and sea-surface salinity. It will also observe a wide range of other sea-ice parameters such as sea-ice thickness and sea-ice drift. CIMR is being developed in response to high-priority requirements from key Arctic user communities and will support the EU Integrated Policy for the Arctic. 5)

- Thales Alenia Space will serve as mission prime with main partners OHB Italia for the instrument and HPS (High Performance Space Structure System GmbH) for the Antenna Reflector. This mission is dedicated to provide observations of Sea-Surface Temperature (SST), Sea-Ice Concentration (SIC) and Sea-Surface Salinity (SSS). Uniquely, it would also observe a wide range of other sea-ice parameters as Sea Ice Thickness (SIT), Sea Ice Drift (SID), Ice Type/Stage, Snow Depth on Sea Ice or Ice Surface Temperature (IST). CIMR responds to high-priority requirements from key Arctic user communities and will improve continuity of missions monitoring the Polar Regions, notably in terms of spatial resolution (~5 km) temporal resolution (sub-daily) and geophysical accuracy. CIMR measurement performances are at worldwide state of art.


Figure 2: "Our strong expertise and heritage on both Copernicus programs and radar technologies will serve this mission which is considered essential to the successful implementation of the integrated EU Arctic Policy", declared Hervé Derrey, CEO of Thales Alenia Space (image credit: TAS)

- The CIMR system consists of up to 3 Satellites dedicated to day-and-night monitoring of land, ice and oceans flying in loose convoy with METOP SG satellite B. CIMR orbit is quasi-polar, near circular and sun-synchronous. In order to acquire measurements on a wide swath, the instrument rotates continuously about an axis parallel to the local spacecraft vertical. The antenna system view the Earth scene with a nearly constant incidence angle of about 55.5º.

- The CIMR satellites embark each a wide-swath conically-scanning multi-frequency microwave radiometer provided by OHB Italia and operating from L to ka band enabling radiometric measurements with unprecedented levels of accuracy. CIMR will be designed for a 7 years nominal lifetime with a sub-daily Arctic and Antarctic area coverage, it will be compatible with Vega-C and Ariane 6-2 launchers and will be fitted by a controlled reentry system.

- This program will take both advantage of Thales Alenia Space proven heritage in Copernicus missions, Earth observation satellites as well as the OHB Italia experience on rotating microwave imager, the platform is based on the new Thales Alenia Space Multi-Mission Platform product line (MILA),and the Large Deployable Reflector (LDRS) will be provided by the German company HPS.

1) Lise Kilic, Catherine Prigent, Filipe Aires, Jacqueline Boutin, Georg Heygster, Rasmus T. Tonboe, Hervé Roquet, Carlos Jimenez, Craig Donlon, "Expected Performances of the Copernicus Imaging Microwave Radiometer (CIMR) for an All‐Weather and High Spatial Resolution Estimation of Ocean and Sea Ice Parameters," JGR (Journal of Geophysical Research) Oceans, Vol. 123, pp: 7564–7580, Published online: 29 October 2018,, URL:

2) "Copernicus Imaging Microwave Radiometer (CIMR)Mission Requirements Document," ESA, 6 October 2020, URL:

3) Carlos Jiménez, Joseph Tenerelli, Catherine Prigent, Lise Kilic, Thomas Lavergne, Sotirios Skarpalezos, Jacob L. Høyer, Nicolas Reul, Craig Donlon, "Ocean and Sea Ice Retrievals From an End-To-End Simulation of the Copernicus Imaging Microwave Radiometer (CIMR) 1.4–36.5 GHz Measurements," JGR Oceans, Volume126, Issue12, December 2021, e2021JC017610, First published: 11 November 2021,, URL:

4) Contracts signed for three high-priority environmental missions," ESA Applications, 13 November 2020, URL:

5) "Thales Alenia Space to build Copernicus CIMR satellites," TAS Press Release, 13 November 2020, URL:


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 (

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