CO3D Constellation

Quick facts

Overview

Summary

Mission Capabilities

Each CO3D satellite will carry a high resolution optical imager, providing imagery in red, green, blue and near infrared (NIR) bands. The constellation aims to create a worldwide digital surface model (DSM). These models will be applicable for both military and commercial purposes, in areas such as urban planning, terrain modelling and precision farming and forestry. 

Performance Specifications

The CO3D optical imager will have a spatial resolution of approximately 0.50 m, and a sensor footprint of 7 km x 5 km, with a wavelength range of 0.40 µm - 0.75 µm in its RGB bands, and a range of 0.75 µm - 1.3 µm in its NIR band. The instrument will collect data over approximately 123 Mkm2 of Earth’s surface within the first four years of operation.

Space and Hardware Components

The CO3D satellite buses will be identical, with each weighing approximately 300 kg and based off of the adapted electrical platform Astribus SE. The bus design will feature an electrical propulsion system and houses an S-band antenna for Telemetry, Tracking and Command (TT&C), supplied by Anywave, operating at a bandwidth of greater than 265 MHz.
 

Overview

The Optical Constellation in Three Dimensions (CO3D) mission is a French National Centre for Space Studies (CNES) high-resolution optical imaging and three-dimensional mapping constellation. The constellation will consist of four satellites, to rapidly collect imagery from different inclinations, and produce three dimensional (3D) digital surface models (DSMs). These models will be applicable for both military and commercial purposes, for purposes such as urban planning, terrain modelling, and precision farming and forestry. CO3D is expected to cover the entire globe within five years, an unprecedented collection rate for its high accuracy imagery, with zones of interest remodelled every few months. Airbus was awarded a contract for the construction of the CO3D satellites in July 2019, with launch expected in 2023. The constellation, while initially consisting of four satellites, could in future be expanded to include twenty. 3) 4) 7) 10)

Spacecraft

The CO3D satellite buses will be identical, with each weighing approximately 300 kg. Airbus, the satellites’ manufacturer, has based the bus design on the adapted electrical platform Astrobus SE, designed specifically for Low Earth Orbit (LEO) missions. The bus design is an evolution of the OneWeb commercial telecommunications satellite design, and will feature an electrical propulsion system. Each CO3D bus houses an S-band antenna for Telemetry, Tracking and Command (TT&C), supplied by Anywave, which will operate at a bandwidth of more than 265 MHz. 1) 7) 11) 12)

Launch

The launch of all four CO3D satellites is planned for 2023 aboard a Vega C rocket rideshare mission. The satellites will be inserted into an orbit with an altitude of 502 km. 9)

Mission Status

• June 23, 2021: Airbus announced that it would be equipping its CO3D satellites with S-band antenna from Anywave 1)
• December 9, 2020: Arianespace has been contracted to launch four CO3D satellites aboard its next-generation light-lifter rocket, Vega C. 9)
• July 8, 2019: It was announced that CNES will be awarding its contract for the development of the CO3D constellation fo Airbus. 2) 10)
• March 19, 2019: France’s CNES announced it would be progressing its planned CO3D constellation. 5)

Sensor Complement

Each CO3D satellite will carry a high resolution optical imager, with a spatial resolution of approximately 0.50 m, and a sensor footprint of 7 km x 5 km. Each of the satellites images in four bands, with wavelength and resolution detailed in Table 1.

These features will enable the generation of 2D image products at high resolution. However, CO3D is also able to make stereoscopic observations from the same orbit with a base to height ratio of 0.2 - 0.3 almost simultaneously, due to its two pairs of satellites each making simultaneous stereoscopic observations, a configuration that is shown in Figure 1. The constellation aims to produce a worldwide digital elevation model (DEM), with relative 3D accuracy of 1 m, as well as producing 2D Red, Blue and Green (RGB) imagery. The instrument will allow 123 Mkm2 of Earth surface to be covered within four years of data collection, to be commenced following an 18 month demonstration period with coverage of 27 Mkm2. 3) 4) 6) 7) 13)

Each of the satellites will provide images in red, green, and blue bands, with wavelengths of approximately 0.40 µm - 0.75 µm. A NIR (near-infrared) band will also be available with a resolution close to 1 m and wavelength of approximately 0.75 µm - 1.3 µm.

The 0.50 m spatial resolution will be achieved through Modulation Transfer Function (MTF) calibrations, which are especially important for image restoration and on-board refocusing, and enable higher accuracy than ground painted edge targets. These calibrations are applied to demosaiced images, reconstructed full colour images from incomplete RGB colour samples, such as those produced by the CO3D optical imager, and, as seen in Figure 2, make a significant improvement to image clarity. 8) 13)

The DEMs produced by the CO3D constellation will be highly applicable to a range of areas, such as infrastructure management, hydrology and flow-direction studies, as well as land use planning. They can also be used on larger spatial ranges for the contouring of topographic and relief maps, such as those for modelling water flow or mass movements.4)

Ground Segment

The CO3D satellites and their data will be handled by a ground segment including a control ground segment (CGS), operated by Airbus Defence and Space (ADS) Space Systems, as well as a User’s Service Segment (USS), which will be exploited by ADS and its partners. The CO3D ground segment is integrated within the multi-mission Geo-Digital Systems (GDS) of ADS, which already operates the ADS EO constellation, which consists of the SPOT 6, Pleiades and Pleiades Neo satellites. The ground segment infrastructure is shown in Figure 3. 7)

The processing of CO3D 2D and 3D imagery is the responsibility of CNES. These data products will consist of the Level 2A product of a native geometric model, simplified to correct the matrix distortion and rolling-shutter effects as well as the attitude disturbances and spectral band co-registrations of the optical imager. The projected Level 2B product will be the mean ground elevation value over a given area, while the Level 3 product will be a 3D, dated DSM with 1 m ground sample distance (GSD), and greater than 0.5°x 0.5° coverage. 6) 7)

References  

1. “Airbus equips CO 3D constellation with Anywaves.” SpaceWatch.Global, 23 June 2021, URL: https://spacewatch.global/2021/06/airbus-equips-co-3d-constellation-with-anywaves/.
2. “Airbus to develop CO3D Earth Observation programme for CNES.” Airbus Intelligence, 8 July 2019, URL: https://www.intelligence-airbusds.com/files/pmedia/public/r55079_9_en-airbus-sps-press-release-airbus-to-develop-co3d-earth-observation-programme-for-cnes.pdf
3. “CO3D.” CNES-CO3D, URL: https://co3d.cnes.fr/en/co3d-0
4. “CO3D, a Worldwide One One-Meter Accuracy dem for 2025.” NASA/ADS, URL: https://web.archive.org/web/20231211024233/https://ui.adsabs.harvard.edu/abs/2020ISPAr43B1..299L/abstract
5. “France's CNES Gives Go-Ahead To CO3D Earth Observ.” SpaceWatch.Global, 12 March 2019, URL: https://spacewatch.global/2019/03/frances-cnes-gives-go-ahead-to-co3d-earth-observation-programme/
6. Hagolle, Olivier. “CO3D: CNES Very High Resolution mission dedicated to 3D, to produce a global DSM by 2026 – Séries Temporelles.” Cesbio, URL: https://labo.obs-mip.fr/multitemp/co3d-the-very-high-resolution-mission-dedicated-to-3d/
7.  Lebègue, L. “CO3D, A WORLDWIDE ONE-METER ACCURACY DEM FOR 2025.” ISPRS - The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, URL: https://isprs-archives.copernicus.org/articles/XLIII-B1-2020/299/2020/isprs-archives-XLIII-B1-2020-299-2020.pdf
8. “MTF calibration method: Topics by WorldWideScience.org.” WorldWideScience, URL: https://worldwidescience.org/topicpages/m/mtf+calibration+method.html
9. Parsonson, Andrew. “Arianespace to launch four-satellite Airbus CO3D constellation aboard Vega C.” SpaceNews, 9 December 2020, URL: https://spacenews.com/arianespace-to-launch-four-satellite-airbus-co3d-constellation-aboard-vega-c/
10. Rocchi, Alexandre. “Contract award for CO3D Earth Observation satellites.” Air & Cosmos - International, 10 July 2019, URL: https://aircosmosinternational.com/article/contract-award-for-co3d-earth-observation-satellites-183
11. “S-Band TT&C Antenna.” Anywaves, URL: https://anywaves.eu/wp-content/uploads/2022/11/ANYWAVES-S-Band-TTC-Antenna-Test-Cap-compatible-version.pdf
12. “Small Mission to Mars –Architectural Study.” Airbus Defence and Space, 20 July 2021, URL: https://nebula.esa.int/sites/default/files/neb_study/2527/C4000133851ExS.pdf
13. Zerubia, Josiane, and Louis Hauseux. “Remote Sensing: Detecting and Tracking Vehicles on Satellite Images and Videos.” ERCIM News, 28 April 2023, URL: https://ercim-news.ercim.eu/en133/r-i/remote-sensing-detecting-and-tracking-vehicles-on-satellite-images-and-videos