ERS-1 | ERS-2
European Space Agency (ESA)
Commissioned: 04/1992 - 02/2001
European Remote Sensing (ERS) satellites 1 and 2, launched in July 1991 and April 1995 respectively, represented the first European satellite-mounted SAR instruments, and have provided a comprehensive archive of imagery for use in interferometric ground movement detection.
ERS-1 failed in March 2001, having far exceeded its life expectancy. Upon losing functionality of onboard gyroscopes, ERS-2 acquired its last usable image for InSAR purposes in February 2001. The ERS archive is a useful tool for retrospectively monitoring ground movement and has a wide coverage over Europe.
Further Information: ESA
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Envisat
European Space Agency (ESA)
Commissioned: 03/2002 - 10/2010
Envisat was launched in March 2002 with an on-board hydrazine capacity designed to last 5 years. Careful management of satellite orbital maneuvers allowed hydrazine to be saved, extending Envisat’s operative life by an additional 3.5 years.
Image acquisition continued regularly until Envisat was de-orbited in October 2010. The satellite obit was lowered to conserve fuel and prolong acquisition life, but at the cost of InSAR processing. Although Envisat continues to acquire, it can no longer be considered reliable for ground movement detection (due to large baselines). Envisat is hence not suggested for long-term monitoring projects, but as a retrospective tool for historical ground movement.
Further Information: ESA
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Radarsat-1
Canadian Space Agency (CSA)
Commissioned: 11/1995 - date
Radarsat-1, launched in November 1995, is currently the oldest SAR platform still in operation today. Amongst other instrumentation, it mounts a C-band SAR sensor and offers a number of different acquisition modes.
In over 15 years of services, Radarsat-1 has long outlived its design lifetime. Due to the failure of an on-board tape recorder, Radarsat-1 cannot be used for future monitoring projects in the Middle East as there is currently no ground station equipped to receive acquired data. Radarsat-1 has acquired data worldwide, creating a large dataset for retrospective ground movement detection, but is not recommended for future monitoring projects.
Further Information: CSA
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Radarsat-2
Canadian Space Agency (CSA)
Commissioned: 04/2008 - date
Radarsat-2, the sister to Radarsat-1, was launched in 2007 mounting an advanced C-band SAR system and is capable of acquiring higher resolution images than Radarsat-1. The sensor also performs polarimetric acquisitions, suitable for ground target characterization purposes.
Radarsat-2 is suitable for use as a long-term monitoring satellite.
Further Information: CSA
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Cosmo-SkyMed
Italian Space Agency (ASI), Telespazio
Commissioned: 06/2007 - date
COSMO-SkyMed is a constellation of four satellites for both civilian and military use, the first of which was launched in June 2007. The fourth and final satellite became operational at the end of 2010, allowing rapid repeat passes to be acquired (one image every 4 days). This significantly reduced the time between two sequential acquisitions compared to other satellite systems, whilst also reducing the time required to create a minimum baseline of images for InSAR processing and creating data redundancy.
The satellite mounts an X-band SAR sensor, capable of acquiring high resolution images. Cosmo-SkyMed is recommended for long-term monitoring projects.
Further information: ASI | Telespazio
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TerraSAR-X | TanDEM-X
German Aerospace Center (DLR), Astrium
Commissioned: 06/2007 - date
TerraSAR-X, launched June 2007, is a satellite operated by both the German Space Agency DLR) and Astrium (Infoterra) and is available for commercial purposes. TanDEM-X, a twin to TerraSAR-X, was successfully launched in June 2010. The baseline between the two satellites is maintained between 250-500m.
Both TerraSAR-X and TanDEM-X are X-band high resolution sensors, with 11-day repeat cycles, and are recommended for long-term monitoring projects.
Further Information: DLR | Astrium
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ALOS
Japanese Aerospace Exploration Agency (JAXA)
Commissioned: 01/2006 - 04/2011
ALOS was launched in January 2006, the scope of the mission being to precisely measuring land coverage. An L-band sensor mounted aboard the ALOS satellite acquires SAR data that can be used to detect ground displacement by InSAR processing. The satellite stopped acquiring in April 2011, due to a power failure.
L-band data has a longer wavelength than C-band or X-band sensors, which means it acquires data at a lower ground resolution. This is however advantageous for monitoring ground movement in areas of low vegetation, due to its vegetation-penetrating capabilities.
Further information: JAXA
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