The successful launch of RISAT- 2B, an indigenously developed radar imaging earth observation satellite, comes as yet another feather in the cap of the Indian Space Research Organisation (Isro). It will enhance India’s all-weather capabilities in agriculture, forestry and disaster management and its data will be vital for the Armed Forces, agriculture forecasters and disaster relief agencies. With Isro drawing up plans to launch four more such radar imaging satellites this year, the country’s ability to monitor crops and floods as well as engage in military surveillance will be hugely enhanced. The launch marked the resumption of a vital ring of Indian all-seeing radar imaging satellites after seven years. World over, the radar imaging satellites are at a premium in the Earth observation scene. India has almost kept pace with the advanced space-faring nations in terms of developing radar satellites. The RISAT-2B satellite uses X-band synthetic aperture radar for the first time; the synthetic aperture radar was developed indigenously. Unlike the C-band that was used by RISAT-1, the shorter wavelength of the X-band allows for higher resolution imagery for target identification and discrimination. Since it has high resolution, the satellite will be able to detect objects with dimensions of as little as a metre. This capacity to study small objects and also movement could be useful for surveillance. The satellite could be used for civil and strategic purposes. RISAT-2B will have an inclined orbit of 37 degrees, which will allow more frequent observations over the Indian subcontinent.
This is the third Indian RISAT in 10 years, and follows the Israeli-built RISAT-2 in 2009 and the Isro-built RISAT-1 in 2012. The older RISATs have reached the end of their lives. When it is cloudy or dark, the 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 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. The RISAT-2B will enhance India’s capability in crop monitoring during the monsoon season, forestry mapping for forest fires and deforestation, and flood mapping as part of the national disaster management programme. Much like the RISAT-1 satellite, RISAT-2B will also use microwave radiation. Unlike visible light, microwaves have a longer wavelength and so will not be susceptible to atmospheric scattering. Microwave radiation can thus easily pass through the cloud cover, haze and dust, and image the ground. Hence, RISAT-2B satellite will be able to image under almost all weather and environmental conditions.