Cosmo-SkyMed Credit - ASI

COSMO-SkyMed (Constellation of Small Satellites for Mediterranean basin Observation) was planned as a constellation of four Synthetic Aperture Radar satellites for primarily military surveillance, but with products made available to civilian users as well.

The system was funded by the Agenzia Spaziale Italiana and the Italian Ministry of Defense. Italy began initial work in 1996 on a national Earth observation program. In 2001 the Ministry of Defense became a partner in the COSMO-SkyMed program, which led to subsequent details becoming classified.

The first satellite used an X-band radar; later satellites were to be equipped with more sophisticated multi-mode X-, C- L- and P-band instruments. The constellation and associated ground segment were to provide global, all-weather, day-night surveillance coverage of the earth's surface. Stereo imaging would be possible in a single pass, and ground track repeatability was to be better than 1 km.

The spacecraft were three-axis stabilized. The Carbon Fiber Reinforced Plastic bus was equipped with two deployable solar arrays and the SAR antenna. A star tracker and a high-quality GPS receiver provided the necessary positional and pointing accuracy. The SAR antenna pointed 38º to the right of the satellite ground track. Momentum wheels and a liquid propellant reaction control system positioned the spacecraft.

The satellites were deployed in sun-synchronous dawn-dusk orbits, all spacecraft in the same orbital plane. The full constellation would achieve a revisit time of a few hours on a global scale. The COSMO-Skymed constellation could be operated in a nominal stand-alone configuration or pairs could be operated in an interferometric configuration. The interferometric configuration allowed acquisition of 3D SAR imagery by combining radar measurements from two satellites of the same target from slightly different incidence angles. It required control of the baseline distance between the two satellites with an accuracy of tens of meters.

The SAR-2000 radar was built by Alcatel Alenia Space. A swath width of between 10 and 200 km was available, depending on mode, with any target within 650 km left or right of the ground target being observable. Acquisition modes were:

• Spotlight / Frame: Spot observation area: 10 km x 10 km, resolution under 1 m
• HIMAGE / Stripmap: Swath width: 40 km, resolution 3-15 m
• WideRegion / ScanSAR: Swath width: 100 km, resolution 30 m
• HugeRegion / ScanSAR: Swath width: 200 km, resolution 100 m
• Ping Pong / Stripmap: Swath width: 30 km, resolution: 15 m

Design Life: 5 years. Typical orbit: 619.6 km, 97.86 deg. Mass: 1,700 kg (3,700 lb). Electrical System: 2 solar panels, 18.3 m2 total, 17.8 kW peak. Electric System: 3.60 average kW. Battery: 336.00 Ah.

• 2007 June 8 - Cosmo-SkyMed 1 - Launch Site: Vandenberg. Launch Complex: SLC2W. Launch Vehicle: Delta. Mass: 1,700 kg (3,700 lb). Perigee: 622 km (386 mi). Apogee: 626 km (388 mi). Inclination: 97.90 deg. Period: 97.20 min.
  The first of four Constellation of Small Satellites for Mediterranean basin Observation, Synthetic Aperture Radar satellites for primarily Italian military surveillance, but with products made available to civilian users as well.

• 2007 December 9 - Cosmo-SkyMed 2 - Launch Site: Vandenberg. Launch Complex: SLC2W. Launch Vehicle: Delta. Mass: 1,700 kg (3,700 lb). Perigee: 621 km (385 mi). Apogee: 624 km (387 mi). Inclination: 97.90 deg. Period: 97.20 min.
  Second Italian military radar satellite in the Cosmo-Skymed system.