The text-book launch of India’s latest Earth observation satellite RISAT-2B (Radar Imaging Satellite) early on Wednesday morning would substantially enhance the country’s surveillance capabilities as it would be able to effectively monitor the country’s borders round-the-clock and in all weather conditions. Weighing 615 kilograms, RISAT-2B has an estimated mission life of 5 years.
The satellite will be used for border surveillance, to deter insurgent infiltration and for anti-terrorist operations. Unlike conventional remote-sensing satellites, which gather images of ground features in visible light but are ineffective at night and under cloudy conditions, RISAT 2B is a radar imaging satellite, equipped with an active sensor called the synthetic aperture radar, which can sense or ‘observe’ Earth in a special way using radar beams from space, day and night and also under cloudy conditions. The X-band synthetic aperture radar of RISAT-2B can give added details such as size of objects on ground, structures, movement and change.
Apart from RISAT-2B, the Polar Satellite Launch Vehicle (PSLV-C46) carried two important piggyback payloads–an indigenously developed low-cost, Vikram processor and a low-cost Inertial Navigation System, which, the Indian Space Research Organization (ISRO)Chairman, Dr. K Sivan said is going to revolutionise our future launch vehicle missions. The Vikram processor developed at the Semiconductor Complex in Chandigarh will control future ISRO launch vehicles.
The RISAT series satellites are the first all-weather earth observation satellites from ISRO. Previous Indian observation satellites relied primarily on optical and spectral sensors which were hampered by darkness and cloud cover. This all-weather viewing feature is what makes the radar imaging satellites special for security forces and disaster relief agencies. RISAT-2B can pick up structures, new bunkers very well, and sometimes help to count them, too. Such data are useful for agencies that need ground imageries during cloud, rain and in the dark.
In India, radar imaging is also being used for crop estimation because our main crop growing season of ‘kharif’ is from May to September when it rains and is generally cloudy. RISAT data is also being used extensively for forestry, soil, land use, geology and during floods and cyclone.
RISAT-2B is the third Indian radar imaging satellite in ten years. While work on the initial RISATs was going on, the launch plan of the satellites was modified in the wake of the November 2008 Mumbai attacks and ISRO decided to launch RISAT-2 before RISAT-1, since the indigenous C-band synthetic aperture radar to be used for RISAT-1 was not ready. RISAT-2 used an Israel Aerospace Industries X-band sensor. So, RISAT-2 was launched in 2009 and RISAT-1 in 2012. Both the satellites have reached the end of their lives. RISAT-2B would replace the RISAT-2.
ISRO has planned a series of radar imaging satellites in the coming months to enhance its space-based observation of Earth and the Indian region. ISRO has plans to deploy four or five of them in 2019 alone.
Incidentally, the latest successful launch has once again demonstrated the extreme reliability of the PSLV rocket, which has become the workhorse of ISRO. The PSLV-C46 was the 14th flight of the PSLV in its core-alone configuration without the use of the solid strap-on motors. Out of 48 launches till date, the rocket has encountered only two failures so far – its maiden developmental flight ended unsuccessful way back in 1993. In September 2017, the PSLV performed perfectly and the flight went off without any hitch, but the navigation satellite IRNSS-1H could not be released into orbit after the PSLV-C39’s heat shield failed to open on reaching the orbit. The PSLV has also been used to launch Chandrayaan-1, India’s first mission to Moon in 2008 and India’s first interplanetary mission to Mars in 2013.
India’s next mission to Moon, Chandrayaan-2 is scheduled for launch in July. It is going to be a landmark mission aimed at landing a rover near the Moon’s South Pole.
Script: Biman Basu, Senior Science Commentator