COSMO-SkyMed is an Earth-observation satellitespace-based radar system funded by the Italian Ministry of Research and Ministry of Defence and conducted by the Italian Space Agency, intended for both military and civilian use. The prime contractor for the spacecrafts was Alenia Spazio. The space segment of the system includes four identical medium-sized satellites called COSMO-SkyMed1, 2, 3, 4, equipped with synthetic aperture radar sensors with global coverage of the planet. Observations of an area of interest can be repeated several times a day in all-weather conditions. The imagery will be applied to defense and security assurance in Italy and other countries, seismic hazard analysis, environmental disaster monitoring, and agricultural mapping.
Space segment
The four satellites are in sun-synchronous polar orbits with a 97.9° inclination at a nominal altitude of 619 km and an orbital period of 97.2 minutes. The local time ascending node at the equator is 06:00. The expected operating life of each satellite is estimated to be 5 years. Each satellite repeats the same ground track every 16 days, and all of the satellites follow the same ground track. They cross the equator at 06:00 and 18:00 local-time each day. The satellites are phased in the same orbital plane, with COSMO-SkyMed's 1, 2 and 4 at 90° to each other and COSMO-SkyMed 3 at 67.5° from COSMO-SkyMed 2. This results in varied intervals between the satellites along the same ground track of between 1 and 15 days. The sun-synchronous orbit is used to keep the solar cells illuminated at all times. The satellites' main components are:
The radar antenna is a phased array that is 1.4 m wide x 5.7 m long. The system is capable of both single- and dual-polarization collection. The center frequency is 9.6 GHz with a maximum radar bandwidth of 400 MHz.
Launch
provided launch services for the satellites with their Delta II 7420-10C rockets from Vandenberg AFB. Satellite processing for the first two satellites was handled by the Astrotech Space Operations subsidiary of SPACEHAB. The first satellite COSMO-1 was launched at 02:34 GMT on 8 June 2007. COSMO-2 was launched at 02:31:42 GMT on 9 December 2007, the launch having been delayed from 6 December due to bad weather, and problems with the rocket's cork insulation. COSMO-3 launched at 02:28 GMT on 25 October 2008. COSMO-4 launched on 6 November 2010 02:20 UTC.
The Argentinian and the French governments are involved respectively in the civil and military segments of the system.
SAR capabilities
The COSMO-SkyMed satellites have three basic types of imaging modes:
Spotlight, a high-resolution mode collected over a small area by steering the radar beam slightly fore-to-aft during the collection period.
Stripmap, a medium-resolution mode collected over long, continuous swaths in which the beam is pointed broadside to the satellite track.
ScanSAR, a low-resolution mode that creates extra-wide swaths by collecting short segments at different ranges and then mosaicking them together.
There are two Spotlight modes:
SPOTLIGHT1, which is a military-only mode, and
SPOTLIGHT2, which provides a resolution of 1 m over a 10 km x 10 km area. Spotlight polarization is limited to either HH or VV
There are two Stripmap modes:
HIMAGE, which provides a resolution of between 3 and 5 m over a swath of 40 km, and
PINGPONG, which collects dual-polarization data at 15 m resolution over a swath of 30 km. The dual-polarization data can consist of any two polarizations, and it is non-coherent, as it is collected in "pulse groups" that alternate from one polarization to the other.
There are two ScanSAR modes:
WIDEREGION, which provides 30 m resolution data over a swath of 100 km, and
HUGEREGION, which provides 100 m resolution data over a swath of 200 km.
The system is sized to collect up to 450 images per satellite per day.
Commercialization
, a joint venture between European spaceflight services company Telespazio and the Italian Space Agency, has the exclusive worldwide commercial rights to sell COSMO-SkyMed data and products.
Flares
The COSMO-SkyMed satellites are lesser-known deliverers of satellite flares, sometimes approaching magnitude −3. Flares come mainly from SAR-panels of the satellites. Although overshadowed by the Iridium satellites, the flares are often long-lasting, with the satellites traversing much of the sky at brighter-than-average magnitudes.
COSMO-SkyMed second generation, CSG
To replace the first COSMO-SkyMed constellation, the Italian Space Agency is developing the COSMo-SkyMed 2nd generation constellation. The 2nd generation constellation has the same function of radar-based Earth observation with particular focus on the Mediterranean area as the 1st generation. The main difference from 1st generation is that the 2nd generation consists of only 2 satellites, CSG 1 and 2. The satellites are improved versions of the 1st generation satellites. Also the radar payload CSG-SAR is an improved version of the 1st generation X-band SAR payload. Furthermore, the 2nd generation satellites will operate in the same orbit as the 1st generation satellites. The 2nd generation satellites slightly outweigh the first generation satellites at 2230kg mass. The contract for building the satellites was signed in September 2015. The satellites are built by Thales Alenia Space. They have a planned lifetime of 7 years. CSG 1 was launched 18 December 2019 by Soyuz ST-A from Guiana Space Centre. As of November 2019, CSG 2 satellite targets launch for 2020.
