From UPSC perspective, the following things are important :
Prelims level : RISAT Constellation
Mains level : Utility of the all weather imaging satellite
- The PSLV-C46 is set to launch RISAT-2B from Satish Dhawan Space Centre in Sriharikota.
- RISAT-2B, short for “Radar Imaging Satellite-2B”, is the second in a series of satellites used to observe weather conditions on Earth using radar imagery.
- RISAT-2 was the first satellite in the series, launched for the purpose of surveillance. RISAT-1 was launched later, to become India’s first all-weather radar imaging satellite.
- RISAT-2B is to be followed by RISAT-2BR1, 2BR2, RISAT-1A, 1B, 2A and so on.
- ISRO orbited its first two radar satellites in 2009 & 2012 and it plans to deploy four or five of them in 2019 alone.
- A constellation of such space-based radars means a comprehensive vigil over the country.
- Once operational, the satellite will be capable of monitoring weather day and night, in all weather conditions.
- The PSLV-C46 mission is ISRO’s 48 PSLV launch, and the 14th PSLV Core-Alone (CA) mission.
- The PSLV was the first of ISRO’s rockets to be equipped with liquid rocket stages.
- In the PSLV-CA version, the rocket doesn’t have the six strap-on boosters that larger rockets do, and only uses the four core stages of the PSLV to launch its payload.
Utility of this constellation
- When it is cloudy or dark, ‘regular’ remote-sensing or optical imaging satellites — which work like a light-dependent camera — cannot perceive hidden or surreptitious objects on the ground.
- Satellites that are equipped with an active sensor, the synthetic aperture radar (SAR), can sense or ‘observe’ Earth in a special way from space day and night, rain or cloud.
- This all-weather seeing feature is what makes them special for security forces and disaster relief agencies.
- In India we also use radar imaging for crop estimation because our main crop growing season of kharif is in May-September when it rains and gets cloudy.
- We have used this data extensively for forestry, soil, land use, geology and during floods and cyclone.
- Radar imaging satellites pick up structures, new bunkers very well, and sometimes help to count them, too.