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COSMO-SkyMed (Constellation of Small Satellites for Mediterranean basin Observation) is a 4-spacecraft constellation, conceived by ASI (Agenzia Spaziale Italiana), and funded by the Italian Ministry ... of Research (MUR) and the Italian Ministry of Defense (MOD), Rome, Italy. The program is managed in cooperation by ASI and MOD. Each of the four satellites is equipped with a SAR (Synthetic Aperture Radar) instrument and is capable of operating in all visibility conditions at high resolution and in real time.
The overall objective of this program is global Earth observation and the relevant data exploitation for the needs of the military community as well as for the civil (institutional, commercial) community.
Sample applications of COSMO-SkyMed data are seen the following fields:
• Defense and security applications: Surveillance, intelligence, mapping, damage assessment, vulnerability assessment, target detection/localization
• Risk management applications: Floods, droughts, landslides, volcanic/seismic, forest fire, industrial hazards, water pollution
• Other applications: Marine and coastal environments, agriculture, forestry, cartography, environment, geology and exploration, telecommunication, utilities and planning
• Provision of commercial imaging services
• The high revisit frequency offered by the four X-band SAR spacecraft is also expected to provide a unique potential to the operational meteorological user community through provision of ancillary data and/or data on meteo-correlated phenomena, in particular as regards sea ice monitoring and study of ocean wave patterns.
Background: In 1996 the Italian Government provided initial funding for the realization of a national Earth observation program. In 1997 the general guidelines for the 1998-2002 Italian National Space Plan (PSN) were approved including the activities on Earth observation. The strategic element in this plan is the COSMO-SkyMed dual-use program of ASI. 1) 2)
In the summer of 2001, the Italian Ministry of Defense became a partner in the COSMO-SkyMed program (a welcome funding partner for the Italian Ministry of Research). However, the dual-use nature of the COSMO-SkyMed program, i. e. civil (research and commercial) and military use of its data products, resulted in a virtually classified program. A great disadvantage of the new arrangement is that rather sparse technical information of the mission can only be made available to the public.
Although the first constellation satellite SAR instruments (SAR-2000) will observe in X-band (9.6 GHz with a wavelength of 3.1 cm), multi-mode scenarios (X-, C- L- and P-band) are planned for the future.
The overall system architecture is composed of a space segment, a constellation of SAR satellites, and a ground segment including full featured user services. The requirements call for the following general performance characteristics: 3)
• Full global observation coverage with all weather, day/night acquisition capability
• Collection capability of large areas within a single pass, with along-track stereo imaging during a single pass
• High image quality, to allow a robust image interpretability at the requested scale of analysis (data sets are characterized by adequate spatial and spectral resolution suitable to perform analyses at different scales of detail)
• Ground track repeatability: the satellites of the SAR constellation shall have a ground track repeatability of better than 1 km
• Fast response times (from the data/service user request up to the data/service delivery to that requiring user).
The SABRINA project was started in 2004/5.
The COSMO-SkyMed space segment is composed of a constellation of four SAR satellites. The PRIMA \[Piattaforma Riconfigurabile Italiana Multi-Applicativa (Reconfigurable Italian Platform for Multiple Applications)\] bus of Alcatel Alenia Space is being employed. Alcatel Alenia Space is also the prime contractor of the space segment \[funding by ASI and I-AD (Ministry of Defense)\]. - Note: As of April 10, 2007, the EC approved the transfer to Thales of Alcatel-Lucent's shareholdings in the two space sector joint venture companies Alcatel Alenia Space and Telespazio. Hence, Alcatel Alenia Space was renamed to Thales Alenia Space.
The S/C is three-axis stabilized, it consists of the main body (bus), two deployable solar arrays, and a SAR antenna. The bus provides all support functions like: AOCS, electrical power (power generation, storage and distribution), data handling, thermal control, RF communications, and on-orbit propulsion for orbit injection and maintenance. The platform mechanical configuration consists of two elements or modules, namely:
• SVM (Service Module) at the bottom of the bus which contains all bus subsystems including the propulsion module
• PLM (Payload Module) at the top, dedicated to the payload complement, the PDHT (Payload Data Handing and Transmission) subsystem, and the AOCS (Attitude and Orbit Control Subsystem) with star trackers gyros actuators.
The bus structure material is CFRP (Carbon Fiber Reinforced Plastic) while SVM and PLM consist of aluminum alloys. The interfaces of the SAR antenna, star trackers and gyros are mounted on the CFRP structure for pointing precision and stability (a star tracker is being used as well as a high-quality GPS receiver). The SSTI (Satellite-to-Satellite Tracking Instrument) is the LAGRANGE GPS receiver of Laben SpA. The SAR antenna bore sight is pointing with an incidence angle about 38º to the right side of the S/C ground track. AOCS provides an antenna steering capability of ±2º in yaw as well as for a re-pointing capability to the left side of the ground track. Each S/C in the constellation features a RCT (Reaction Control Thruster) system for orbit maintenance.
The mass of each spacecraft is about 1700 kg. The design life is 5 years. The S/C provides an onboard operational autonomy for a period of 24 hours.
Launch: The launch of the first COSMO spacecraft in the constellation took place on June 8, 2007 (UTC). The launch was provided by the Boeing Company on a Delta-2 (7420-10 configuration) vehicle from VAFB, CA. This represented the first commercial Delta-2 launch since the formation of the United Launch Alliance (ULA) in December 2006.
Circular sun-synchronous dawn-dusk orbit, nominal altitude = 619.6 km, inclination = 97.86º, period = 97.1 min, with LTAN (Local Time of Ascending Node) at 6:00 AM, 14.8125 rev./day (or 14 13/16). All spacecraft of the SAR constellation will be positioned in the same orbital plane with a phasing outlined in Table 2. The nominal repeat cycle is 16 days; however, each single satellite will have a near revisit time of 5 days.
Information obtained from http://www.eoportal.org/
Vandenberg Air Force Base, USA
Italian Ministry of Defense (MOD)
Agenzia Spaziale Italiana (ASI), Italy