The ERS-2/Envisat tandem observation campaign is split in two phases: the first one ran from September 2007 until February 2008, while the second campaign ran from November 2008 until April 2009. For both campaigns the principle was that one satellite follows the other 30 minutes apart in precisely controlled orbital loops, with the second satellite’s ground track offset from that of the first by 2 km.
Both satellites are equipped with synthetic aperture radar (SAR) instruments (able to generate highly accurate radar images) and the combining of SAR images taken by one satellite of the same site permits to detect slight changes that may have occurred between acquisitions. This technique is known as SAR interferometry, or InSAR, and has proven to be very useful for applications such as glacier monitoring, surface deformation detection and creating digital elevation models (DEMs).
On 29 April 2009 ESA announced that Envisat and ERS-2, considered also as ESA’s old EO missions, have completed the second tandem campaign. The later consisted in involving the fly of the two satellites in precisely coordinated orbits, which generate new radar data relevant for modelling Arctic terrain. The new data will also help to identify natural carbon sources and wetlands in permafrost regions.
Finally the two ERS-2/Envisat tandem campaigns contributed to enhance EO by helping scientists measure fast-moving glaciers, detect land-ice motion and develop new elevation models over flat terrain. As a consequence, both campaigns have successfully completed their missions.
More information at ESA