Currently, existing Synthetic Aperture Radar (SAR) satellites orbiting in space and accessible to CSTARS are the Canadian Space Agency’s (CSA) RadarSat-1, the European Space Agency’s (ESA) ERS-2 and ENVISAT ASAR. ENVISAT and ERS-2 are in the same orbits and follow each other within 30 minutes. The main difference is that ERS-2 has only one beam mode at a nominal incidence angle of 23 degrees which coincides with ENVISAT’s beam mode I2.

RadarSat-1 is a C-Band Synthetic Aperture Radar (SAR) that penetrates clouds and can image day and night and in all weather conditions. Launched in November 1995, RadarSat-1 is operated by MDA GeospatialServices of Richmond, Canada.

ENVISAT ASAR is a C-band Advanced Synthetic Aperture Radar instrument onboard the European Space Agency’s ENVISAT satellite, and is capable of penetrating clouds and can image day and night and in all weather conditions. Launched in March 2002, ENVISAT-1 is operated by the European Space Agency.

ERS-2 is a C-band Synthetic Aperture Radar instrument following its predecessor ERS-1 satellite, and is capable of penetrating clouds and can image day and night and in all weather conditions. Launched in April 1995, ERS-2 is one of the longest operational SARs in space and continues to be operated by the European Space Agency.

Recently several new SAR satellites were launched into space. The Japanese Space Agency’s (JAXA) L-band PALSAR sensor onboard the ALOS satellite is a follow on sensor to the JERS-1 SAR launched in the mid-1990’s. While L-band is much better suited for detection of ocean surface features such as eddies and internal waves, the high-resolution data of PALSAR is not available in near-real time due to complicated downlink restrictions. Only medium resolution data is available from the Alaska Satellite Facility (ASF) and soon from CSTARS.

PALSAR is a Phased Array type L-band Synthetic Aperture Radar instrument on ALOS and is capable of penetrating clouds and can image day and night and in all weather conditions. Launched in January 2006, PALSAR is operated by the Japanese Space Agency.

TerraSAR-X is the first commercially available radar satellite to offer one-meter resolution imagery products.  TerraSAR-X was launched in June 2007 and is operated in a German public, private partnership (PPP) program between the German Aerospace Center (DLR) an d Astrium.  Astrium's subsidiary Infoterra GmbH is responsible for the commercial exploitation of the TerraSAR-X data. The technologies of the active phased array X-band SAR utliizes in-depth experience by the PPP partners in spaceborne synthetic aperture radar (SAR) systems, e.g. from airborne remote sensing or the shuttle missions SIR-C/X-SAR and SRTM.  TerraSAR-X is an excellent complement to optical systems such as Quickbird, IKONOS, FormoSat-2 and SPOT 5 with its high resolution SAR capability. The precise attitude and orbit determination of TerraSAR-X allows an orthorectification without ground control point achieving an image pixel location accuracy of up to 1m depending on relief, incidence angle and available DEM.

Cosmo-SkyMed (COnstellation of small Satellites for Mediterranean basin Observation) is an Italian X-band SAR for earth observation and its first satellite was launched June 2007. The COSMO constellation will consist of four Low Earth Orbit (LEO) mid-sized satellites, each equipped with a multi-mode high-resolution Synthetic Aperture Radar (SAR) operating at X-band and fitted with particularly flexible and innovative data acquisition and transmission equipment. COSMO-SkyMed will be operated by the Italian Space Agency (ASI) and will provide an earth observation asset characterized by full global coverage, all weather, day/night acquisition capability, higher resolution, higher accuracy (geo-location, radiometry, etc.), superior image quality, fast revisit/response time, interferometric/polarimetric capabilities and quicker-and-easier ordering and delivery of data, products and services.