RISAT – is a series of Indian radio imaging satellites built by Indian Space Research Organisation (ISRO). These satellites are designed to afford services in the field of agriculture, forestry, defence and disaster management. Being a radar (Radio detection and ranging) based observation system RISAT satellites are capable of taking Earth images day-night and even through clouds.
The latest in the series is RISAT -2B, launched by ISRO on May 22, 2019. It is the successor to RISAT 2 launched in 2009. Another one in the series is RISAT -1, launched in 2012.
How they image?
The real tech behind imaging is Synthetic-aperture Radar (SAR). SAR usually mounted on a moving platform like satellite or an aircraft uses the motion of antenna over the target to create images.
Unlike conventional beam-scanning radars, SAR produce images with exceptional spatial resolution. As satellite moves, the location of SAR relative to the target (landscape) changes so that the position of the antenna. With multiple antenna positions, a synthetic aperture is formed resulting in higher resolution images.
Synthetic aperture is a larger aperture, synthetically created due to the relative movement of antenna and target. Signal processing plays a significant role in combining multiple radio echos received from the target.
Other indigenous techs on board
Weighs about 615 Kg, RISAT-2B also packs in multiple indigenous technologies. Vikram Processor developed by Semi-Conductor Labouratory, Chandigarh and the Inertial Navigation System (INS) developed by ISRO Inertial Systems Unit, Thiruvananthapuram being the notable ones. ISRO also successfully deployed the Radial Rib Antenna technology in RISAT -2B.
PSLV – C46, the launch vehicle of RISAT-2D marks its 50 tonnes of total payloads to space. Stay tunned to Sciteum to read about the upcoming story on PSLV.
Written by M R Raghul