³Cat (Cube-cat)

Quick facts

Overview

Related Resources

Summary

Mission Capabilities

³Cat-1 is a 1U cube satellite with a seven-instrument payload: an eternal self-powered beacon demonstrator, CellSat Solar Cells, a Microelectromechanical Systems (MEMS), a Graphene Field Effect Transistor (GFET), an experimental Wireless Power Transfer (WPT) payload, a low-resolution CMOS camera and a neon-tube Geiger counter. ³Cat-2 hosts four instruments on board: a PYCARO, P(Y) and C/A ReflectOmeter, an experimental Mirabilis Star Tracker, an anisotropic magnetoresistance (AMR) evolved Laser Interferometer Space Antenna (eLISA), and a Fully Adaptive Prediction Error Coder (FAPEC).

³Cat-3 houses an optical camera for capturing images from 4-5 different bands in Visible and Near-Infrared (VNIR), using the data for testing the capability of small satellites to carry out multispectral imaging missions. ³Cat-4 carries an Automatic Identification Service (AIS) receiver, a Radio Frequency Interference detection and mitigation system, a radiometer and GNSS-R.

Performance Specifications

³Cat-1 was launched on 29th November 2018, onboard a PSLV C-42 from ISRO’s launch base in Sriharikota. The satellite sat in a 470 x 498 km orbit with a 97.48°inclination.

³Cat-2 was the first Catalan satellite and was launched on 15th August 2016 onboard an LM-2D (Long March) rocket from Jiuquan base in China by ISIS Space. Now inactive, the satellite operated in a 483 x 503 km orbit with a 97.4° inclination. The satellite passed over UPC’s North Campus twice daily.

³Cat-3’s orbit is expected to revisit locations every 7-10 days.

³Cat-4 was launched onboard ESA’s first Ariane 6 rocket from Europe’s Spaceport in French Guiana on 9th July, 2024. It orbits at about 550km altitude, with an inclination of 62.0°.

Space and Hardware Components

The ³Cat satellites each host a fully integrated single board, on-board computer (OBC) that handles the satellite’s four subsystems. Lithium-Ion batteries and laser-cut silicon cell solar panels power the spacecraft. Communication is handled by an Ultra High Frequency (UHF) receiver from Texas Instruments. The Attitude Determination and Control Subsystem (ADCS) uses a single-axis magnetorquer to carry out detumbling protocols. For power generation, storage, and distribution, ³Cat-2 has five surfaces covered with Triple Junction Gallium Arsenide solar cells from AzurSpace. ³Cat-3 plans include an on-board ARM Cortex. Uplink and downlink communications are to operate in UHF and a high-speed S-band downlink.

³Cat-4 has a single-board OBC equipped with a Real-Time Operating System (RTOS). A Nanopower P31u designed and developed by GomSpace is fitted with two Lithium-Ion batteries charged by five solar panels. A communication subsystem by NanoSat Lab allows UHF transmissions. The satellite is fitted with three sun sensors, a three-axis magnetometer and a three-axis gyroscope, alongside a 0.5-meter spring-like antenna.

Overview

The ³Cat (pronounced cube-cat) mission is a multi-nanosatellite constellation developed and operated by the Polytechnic University of Catalonia, Spain (UPC). The ³Cat Constellation is a series of nanosatellites designed to explore the capacity of the CubeSat standard across three main missions: education, technological demonstration and scientific experimentation.

Educationally, the satellites represent the work of graduate and undergraduate students who aided the development of novel subsystems and integrated payloads. Mission analysis, design and performance of technological tests were also primarily conducted by students, as a rare opportunity for hands-on industry experience. Several of ³Cat’s payloads demonstrate novel sustainability and push the boundaries of current technological capabilities of small-spacecraft systems. Lastly, ³Cat integrated various scientific payloads from research groups and different scientific inquests. 1)

³Cat-1 aims to develop capacity within current CubeSat standards. ³Cat-2 seeks to test a novel Global Navigation Satellite Systems Reflectometry (GNSS-R) payload alongside other experimental devices. ³Cat-3 is expected to analyse the feasibility of small-satellite multispectral imaging missions while lowering development time and cost. ³Cat-4 seeks to demonstrate nano-satellite capability, specifically 1-Unit standards for Earth Observation using GNSS-R.

For details about 3Cat-5A and -5B, see PhiSat-1 & -2.

Spacecraft

Each ³Cat platform differs in specifications, due to differing requirements and payloads.

³Cat-1

On-Board Computer and Flight Software

³Cat-1 uses a single-boarded device as its On-Board Computer (OBC) that interacts with the rest of the satellite subsystems through UART (Universal Asynchronous Receiver/Transmitter) and SPI (Serial Peripheral Interface)) communication protocol. On-board data handling also manages inter-device communication with microcontrollers and transceivers to generate data telemetry packets, configuration data, payload data and more. The OBC has an ATM91SAM9G20 Central Processing Unit (CPU) that runs at 400MHz and provides 64 MB of SDRAM (Synchronous dynamic random-access memory) storage. Using a Linux and Xenomai kernel, the software manages system functions such as energy management, system state control, task scheduling, running scientific experiments, communication, sensor monitoring, and housekeeping functions. 

Electric Power Subsystem (EPS)

The Nano-Sat Lab in-house designed and developed EPS autonomously deploys antennas and manages the satellite’s energy bank. A total of 1150 mAh energy can be stored on Lithium-Ion batteries that provide power when the satellite’s orbit is eclipsed by the Earth. With a centralised microcontroller, multiple DC/DC converters are located across the floors at each point of load, and protect payloads from overcurrent, allowing subsystem faults to be isolated.

A maximum power of 17 W governs the power bus, while Point-Of-Load converters can withstand 3.3-10 W of output power. ³Cat-1’s solar panels use laser-cut silicon cells, providing 18% efficiency, while the power conversion operates at 87.5% efficiency, leading to a 1.2 W maximum output. When not in a critical energy state, the EPS allows power management to be handled by the OBC from UART communication.

Communication Subsystem

Communications are handled by an amateur-band receiver. It operates in the Ultra High Frequency (UHF) band between 430-440 MHz and is based on a ready-made module from Texas Instruments. A radio-frequency power amplifier boosts communication signals up to 2 W, managing both uplink and downlink channels.

The cross-dipole antenna, deployed at start-up, has an omnidirectional pattern, allowing communication and direction of the satellite even when attitude control is disengaged. It also employs circular polarisation to allow transmissions to pass through the ionosphere without disturbance.

Attitude Determination and Control Subsystem (ADCS)

Given the onboard payload characteristics, accurate pointing is not required. Hence, the ADCS is grounded on passive control (permanent magnets and mu-metal strips) to perform de-tumbling and attitude stabilization. Additionally, ³Cat-1 has an active control system implemented with a single-axis magnetorquer which may be enabled when the spacecraft's attitude is stable. The attitude determination uses a commercial 6-degree-of-freedom IMU encompassing a triple-axis magnetometer and gyroscope.

³Cat-2

On-Board Computer and Flight Software

3Cat-2's On-Board Computer (OBC) manages satellite operations, controls subsystems, and processes data. It consists of a central microcontroller running at 40 MHz and uses 2MB of data storage, allowing the OBC to execute software tasks. It also holds a low-power 3-axis magnetometer for attitude determination, and a 2GB microSD card.

Electric Power Subsystem (EPS)

To manage power generation, storage, and distribution, ³Cat-2 has five surfaces covered with Triple Junction Gallium Arsenide solar cells from AzurSpace. With 30% efficiency in harvesting solar energy, a backup 7.4 V Lithium-Ion battery of 7000 mAh capacity ensures stable power supply for satellite operations.

Communication Subsystem

The communication system consists of UHF at 1200 bps uplink, very high frequency (VHF) downlink at 9600 bps and an S-band transceiver at 115 200 bps allows for transmission and reception of data between the satellite and ground stations.

The UHF-VHF system controls telemetry and command upload while the S-band downlink allows for users to access data files without an uplink command.

Additionally, the subsystem includes a VHF band beacon that periodically transmits open format telemetry data to Earth.

Attitude Determination and Control Subsystem (ADCS)

A set of three orthogonal-magnetic torquers with a magnetic moment of 0.24 act as actuators. They control spacecraft dynamics by generating torque via engaging a local dipole moment with the Earth’s magnetic field. The sensors are two 3-axis magnetometers that measure the Earth’s magnetic field. A MEMS gyroscope measures angular rate, while six photodiodes on each face of the satellite determine the Sun’s position. 4) 5) 

³Cat-3

³Cat-3 MOTS (Satellite Earth Observation Mission) has been commissioned for the Cartographic and Geologic Institute of Catalonia (ICGC). It will use power from batteries and solar cells. 6) 7)

On-Board Computer and Flight Software

³Cat-3 is planned to include an on-board ARM Cortex operating at 500MHz with embedded Linux and Xenomai kernels.

Communication Subsystem

A UHF half duplex of uplink and downlink at 9600 bps will allow for satellite telemetry and command data to be communicated. An additional high-speed S-band downlink with capacity for 4 Mbps and upward is to be employed.

³Cat-4

The satellite was selected by ESA Education's ‘Fly Your Satellite’ programme and was extensively developed and validated by students with careful final review from experts at ESA Education’s CubeSat Support Facility (CSF) in ESEC-Galaxia, Belgium.

On-Board Computer and Flight Software

A single-board OBC, NanoMind A3200 from GomSpace, provides processing capability to the satellite. The computer is capable of interacting with other systems through UART, SPI and I2C (inter-integrated circuit). On-board data handling (OBDH) software handles communication between the microcontrollers, transceivers and other devices, and generates data packages. A Real-Time Operating System (RTOS) executes commands for the OBDH, and prioritises the execution of a task based on the urgency. The flight software heightens system functionality, energy management, system control, task scheduling and execution of scientific experiments. Each subsystem is equipped with its own firmware to allow interaction with the main hardware. 9) 10)

Electric Power Subsystem (EPS)

A Nanopower P31u designed and developed by GomSpace acts as ³Cat-4’s EPS. With two Lithium-Ion batteries charged by five solar panels, they can store up to 2600 mAh and adaptively supply power between 3.3-5V. The subsystem oversees the satellite’s energy reservoir and is controlled by a centralised microcontroller through DC/DC converters. These power converters are located at each point of load in order to isolate and protect payloads from any subsystem failures.

The solar panels use AzurSpace 3G30A cells with Gallium Arsenide cells on top of a Germanium substrate. Power conversion efficiency is 30%, giving 2.4 W maximum power. When not in a critical energy state, EPS allows power management to be controlled by the OBC through I2C connection. 9) 10)

Communication Subsystem

Designed and fitted by NanoSat Lab, the communication subsystem involves an amateur-band transceiver operating in the UHF band at 437.35 MHz. For uplink and downlink, the transceiver is based on a commercial model from Texas Instruments. Mounted on a single board, a Radio Frequency power amplifier boosts signal up to 1 W (30dBm) and a Low Noise Amplifier (LNA) that gives up to 16 dB of gain in reception.

A monopole antenna deployed at system start allows for communication to flow with an omni-directional pattern, meaning the satellite may be commanded even when attitude control is disengaged.

The mission calls for the satellite to periodically transmit a beacon with the Instantaneous Telemetry (IT) containing all system status updates of the past 32 hours. 9) 10)

Attitude Determination and Control Subsystem (ADCS)

The payload of this satellite requires specific orientation to function. The spacecraft’s Z-axis must point to the centre point of the Earth (nadir). This is achieved using a Proportional-Integral-Derivative (PID) controller, which manages attitude through an Optimal REQUEST algorithm. With three sun sensors, a three-axis magnetometer and a three-axis gyroscope, orientation can be determined accurately. 9) 10)

Additionally, the spacecraft is set to launch from the International Space Station (ISS), which can disturb the required orientation with the large angular speed of ~ 30°/s. Thus, the ADCS kickstarts a B-dot algorithm to detumble the nanosat,bringing its angular speed below 0.5°/s. Once this is achieved and the spacecraft points to nadir, the three-axis magnetorquer can generate a magnetic field of 0.2 Am² (Ampere metre) for attitude adjustment. 9) 10)

Nadir Antenna and Deployment System (NADS)

3Cat-4 will test the feasibility and performance of a 0.5-meter spring-like antenna. Stowed away during launch, the antenna requires little room and will generate a gravity gradient. 11)

The subsystem is also responsible for deploying the L-Band antenna.

Flexible Microwave Payload (FMPL-1)

³Cat-4 integrates three instruments into a single board by leveraging a Software Defined Radio (SDR) module operating in various frequency bands; an Automatic Identification Service Receiver, a GNSS-R and an L-Band radiometer.

The FMPL-1 hosts a System On-Module (SOM) which functions as the processing unit for raw measurement data. With different radio-frequency chains, the quality of received signals from three antennas is amplified. 12)

Launches

Mission Status

• July 9, 2024: ³Cat-4 launches onboard ESA’s Ariane 6 in French Guiana.
• August 15, 2016: LM-2D launches ³Cat-2 from Jiuquan base, China.
• November 29, 2018: ³Cat-1 lifts off onboard a PSLV C-42 from ISRO’s launch base in Sriharikota.

Sensor Complement

³Cat-1

Eternal self-powered beacon demonstrator

Completely autonomous and unconnected to the satellite’s power or OBC, a small Peltier cell generates current that builds until enough power is generated to turn on a low-power microcontroller and RF stage. This sends a UHF signal to Earth, containing satellite identification and temperature data. 1)

CellSat Solar Cells

Pertaining to the technological development mission, an experimental solar cell developed by the university’s Micro- and Nano-Technologies group is fitted on one of the photovoltaic panels. The CellSat employs interdigitated back contact (IBC) techniques, offering up to 12% energy conversion efficiency. The purpose of the cell is to assess degradation and performance of solar cells in space by measuring output power correlated to irradiance and temperature of the cell group. 1)

Microelectromechanical Systems (MEMS) Monoatomic Oxygen Detector

Manufactured by UPC BarcelonaTECH, the MEMS device can detect monatomic oxygen through analysing resonant frequencies. 1)

Graphene Transistor

A Graphene Field Effect Transistor (GFET) is part of the experimentation regime and measures performance and degradation of graphene coated transistors in space, contributing to scientific innovation. 1)

Wireless Power Transfer (WPT) Plasma Study

Resonant Inductive Coupling (RIC) is a type of wireless power transfer (WPT), where two magnetically coupled coils in a resonant circuit operate at the same frequency. These systems are being developed as a means for satellites to exchange energy in Space, where plasma can affect system functions. Thus the WPT experiment will run an energy exchange experiment with a power meter to understand plasma effects on the circuits. 1)

Low-resolution CMOS camera

Integrated into the OBC interface, the payload captures images in the visible light spectrum at video graphics array resolution 640 x 490 pixels. 1)

Geiger counter

A neon-tube geiger counter collects ionised space radiation information and conducts radiation dosimetry. Its data is recorded on CPU hardware. 1)

³Cat-2

PYCARO GNSS-R

PYCARO, P(Y) and C/A ReflectOmeter, is based on a novel Global Navigation Satellite Systems Reflectometry (GNSS-R) correlation technique, which collects signals sent by GPS, Galileo, Glonass and BeiDou constellations. This is known as bistatic radar, meaning it does not emit and only captures signals from other systems.

The payload aims to generate altitude maps of Earth containing wind surface over sea, deforestation, soil moisture and other information. The technology holds dual polarisation capability, Right-hand and Left-hand Circular Polarisation (RHCP, LCHP), in the L1 and L2 bands of GPS. 21)

Mirabilis Star Tracker

Developed by the Department of Signal Theory and Communications and NanoSat Lab, Mirabilis is an experimental star tracker that is integrated as part of the experimental unit for attitude determination.

IEEC AMR eLISA magnetometer

From the Institut d'Estudis Espacials de Catalunya (IEEC), the anisotropic magnetoresistance (AMR) evolved Laser Interferometer Space Antenna (eLISA) will develop and validate a system for measuring magnetic fields at low-noise conditions of sub-millihertz frequencies. It serves as a pre-test for ESA’s LISA Pathfinder mission. 22)

FAPEC compression algorithm by DAPCOM

Fully Adaptive Prediction Error Coder (FAPEC) is a data compression algorithm by DAPCOM, a spinoff from UPC, that compresses scientific data packages generated by ³Cat-2’s payloads and sets a precedence as the first use of the algorithm aboard a space mission. 23)

³Cat-3

Optical Camera

The onboard optical camera captures images from 4-5 different bands in Visible and Near-Infrared (VNIR), imaging between 440-510 nm, 520-590 nm, 620-680 nm, 690-730 nm and 850-890 nm with a signal to noise ratio of 35-40 dB. The camera has a swath of 30-50 km and a ground sample distance between 5 – 10 m. A modulation transfer function (MTF) in the optic system gives resolution of 20 lp/mm (line pairs per millimetre) in each band, with a digitalisation of 12 bits/pixel. 6)

³Cat-4

Automatic Identification Service (AIS) receiver

The payload will validate an AIS receiver, tracking the trajectory of different vessels in remote areas without ground infrastructure, for example ships along intercontinental routes. The instrument includes a Radio Frequency Interference detection and mitigation system, generating RFI maps in L1, L2 frequencies and the band 1400-1427 MHz. 9)

Global Navigation Satellite System Reflectometer (GNSS-R)

A GNSS-R will provide details of surface roughness, ice coverage and more. The satellite will assess the relative sensitivity of the instrument when observing waveform peak amplitude and maximum derivative delay in different frequency bands (i.e. L1 and L2). The mission also aims to evaluate applications of GNSS-R over land surfaces, particularly for soil moisture and vegetation biomass, focusing on forests, since other missions are not able to due to Radio Frequency Interference (RFI). 9)

L-band microwave radiometer

A radiometer will collect soil moisture and biomass vegetation statistics in the 1-2 GHz frequency, while assessing the impact of ionospheric corrections on the delay of reflected signals. 9)

Ground Segment

³Cat-1

Telemetry data is broadcasted openly and can be decoded using a public repository supplied by the Universidad Politécnica de Cataluña (UPC). Its communication system is tuned to 437.250 MHz and transmits data at 9k6 bits per second (bps). 25)

³Cat-2

The spacecraft transmits periodically using an open VHF band beacon, transmitting telemetry data. The transmission time is every 20-40 seconds at frequency 145.97 MHz and using a BPSK modulation at 9k6 bps.

A groudstation in Barcelona uses a high gain VHF Yagi antenna with circular polarisation. It has a 144-146 MHz filter and 20 MHz bandwidth.

Ametur radio enthusiasts are encouraged to decode and access data from the satellite and can do so by following instructions on the UPC website. Data that can be accessed includes current satellite mode, battery voltage, power consumption, EPS temperature, status of ADCS system and control status of ADCS routine. 26)

³Cat-3

³Cat-3 can downlink data at high speeds in the S-band at greater than 4 Mbps. A UHF communication platform can also uplink and downlink at 9600 bps.

³Cat-4

³Cat-4 will communicate with a Ground Station in Montsec in the pre-Pyrenees of Catalonia. This new, remote ground station is ideal for large communications.

A Ground Station in Barcelona, also used in other ³Cat missions, will also be used for telecommunication. 27)

References

1) "3Cat-1," NanoSat Lab, Universitat Politècnica de Catalunya, URL: https://nanosatlab.upc.edu/en/missions-and-projects/3cat-1

2) "3Cat 1," Gunter’s Space Page, URL: https://space.skyrocket.de/doc_sdat/3cat-1.htm

3) "3Cat 2," Gunter’s Space Page, URL: https://space.skyrocket.de/doc_sdat/3cat-2.htm

4) "3Cat-2," NanoSat Lab, https://nanosatlab.upc.edu/en/missions-and-projects/3cat-2

5) "The first Catalan nanosatellite successfully launched with three experiments on board," phys.org, URL: https://phys.org/news/2016-12-catalan-nanosatellite-successfully-board.html

6) "3Cat-3," NanoSat Lab, Universitat Politècnica de Catalunya, URL: https://nanosatlab.upc.edu/en/missions-and-projects/cube-cat-3

7) "3Cat 3," Gunter’s Space Page, URL: https://space.skyrocket.de/doc_sdat/3cat-3.htm

8) "Meet the team: 3Cat-4," ESA, URL: https://www.esa.int/Education/CubeSats_-_Fly_Your_Satellite/Meet_the_team_3Cat-4

9) "3Cat-4," NanoSat Lab, Universitat Politècnica de Catalunya, URL: https://nanosatlab.upc.edu/en/missions-and-projects/3cat-4

10) "3Cat 4," Gunter’s Space Page, URL: https://space.skyrocket.de/doc_sdat/3cat-4.htm

11) "3Cat-4," ESA, URL: https://www.esa.int/ESA_Multimedia/Images/2024/05/3Cat-4

12) "Lift-off for 3Cat-4 and ISTSat-1," ESA Education, URL: https://www.esa.int/Education/CubeSats_-_Fly_Your_Satellite/Lift-off_for_3Cat-4_and_ISTSat-1

13) "FSSCAT A, B (3Cat 5A, 5B)," Gunter’s Space Page, URL: https://space.skyrocket.de/doc_sdat/fsscat.htm

14) "PhiSat-1 & -2 Nanosatellite Mission," eoPortal, URL: https://www.eoportal.org/satellite-missions/phisat-1

15) Giuffrida et al. "The Φ-Sat-1 Mission: The First On-Board Deep Neural Network Demonstrator for Satellite Earth Observation," IEEE Transactions on Geoscience and Remote Sensing, 2021, 60. 1-1. URL: https://doi.org/10.1016/j.asr.2024.03.053

16) "HyperScout-2," ESA InCubed, URL: https://incubed.esa.int/portfolio/hyperscout-2/

17) Nicolas, Longépé, Melega, Nicola, Marchese, Valentina, et al. "ΦSAT-2 MISSION OVERVIEW FOR THE #ORBITALAI CHALLENGE. February 15, 2023," URL: https://ai4eo.eu/wp-content/uploads/2023/02/Phisat-2_Mission_Overview_Web.pdf

18) Gentea A. "Successful 10th ISL launch," ISISPACE, August 16, 2016, URL: https://www.isispace.nl/news/successful-10th-isl-launch/

19) "FSSCat Overview," ESA Earth Online, URL: https://earth.esa.int/eogateway/missions/fsscat/description

20) "FSSCat," ESA Earth Online, URL: https://earth.esa.int/eogateway/missions/fsscat

21) Carreno-Luengo H, Camps A, Via P, et al. "3Cat-2—An Experimental Nanosatellite for GNSS-R Earth Observation: Mission Concept and Analysis," IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2016;9(10):4540-4551, DOI: 10.1109/JSTARS.2016.2574717

22) "Design and assessment of a low-frequency magnetic measurement system for eLISA," Universitat Politècnica de Catalunya, URL: https://core.ac.uk/reader/81576870

23) Portell J, Iudica R, García-Berro E, Villafranca AG, Artigues G. "FAPEC, a versatile and efficient data compressor for space missions. International Journal of Remote Sensing," 2018;39(7):2022-2042, DOI: 10.1080/01431161.2017.1399478

24) "FSSCat," NanoSat Lab, URL: https://nanosatlab.upc.edu/en/missions-and-projects/fsscat

25) "How to receive from 3Cat-1," NanoSat Lab, URL: https://nanosatlab.upc.edu/en/missions-and-projects/3cat-1/how-to-receive-from-3cat-1

26) "How to receive from 3Cat-2," NanoSat Lab, URL: https://nanosatlab.upc.edu/en/missions-and-projects/3cat-2/how-to-receive-from-3cat-2

27) "How to receive from 3Cat-4," NanoSat Lab, URL: https://nanosatlab.upc.edu/en/missions-and-projects/3cat-4/how-to-receive-from-3cat-1

28) "FSSCat products," ESA Earth Online, URL: https://earth.esa.int/eogateway/catalog/fsscat-products