RISAT-1

Template:Infobox Spacecraft RISAT-1 (short for Radar Imaging Satellite - 1) is the first of the RISAT series of Indian remote sensing satellites built by the Indian Space Research Organisation (ISRO). It uses a C-band Synthetic Aperture Radar (SAR) for all-weather earth observation.

According to ISRO officials, RISAT-1 at 1,850 kilograms (4,080 lb) is the heaviest microwave satellite to be launched by India. While the RISAT-1 is the first in the RISAT serice of remote sensing satellites of the RISAT series, it is the second to be launched.PSLV, the workhorse launch vehicle of Indian Space Research Organisation, achieved its 20th consecutive successful flight when it launched RISAT-1, the heaviest satellite ever lifted by it, in a mission described as a “grand success” by the space agency chief K Radhakrishanan.

RISAT-1, culmination of nearly 10 years of effort by ISRO, has the capability to take images of Earth during day and night, as well as in cloudy conditions.

The previous Indian remote sensing satellites relied mainly on optical and infrared sensors & India heavily depended on images from a Canadian satellite as existing domestic remote sensing spacecraft could not take pictures of Earth during cloud cover. RISAT-1 uses an indigenously developed C-band SAR, operating in multi-polarisation, multi-resolution modes.

The fabrication and launch of RISAT-1 was postponed in the aftermath of the 2008 Mumbai attacks in order to prioritize the launch of RISAT-2 with its X-band SAR of Israeli origin.

SPECIAL FEATURES OF RISAT-1

Remote sensing satellites send back pictures and other data for use. India has the largest constellation of remote sensing satellites in the world providing imagery in a variety of spatial resolutions, from more than a metre ranging up to 500 metres, and is a major player in vending such data in the global market.With 11 remote sensing/earth observation satellites orbiting in the space, India is a world leader in the remote sensing data market. The 11 satellites are TES, Resourcesat-1, Cartosat-1, 2, 2A and 2B, IMS-1, Risat-2, Oceansat-2, Resourcesat-2 and Megha-Tropiques. Risat-1's synthetic aperture radar (SAR) can acquire data in C-band and would orbit the earth 14 times a day. In 2009, ISRO had launched 300 kg Risat-2 with an Israeli built SAR enabling earth observation in all weather, day and night conditions. With Thursday's launch the PSLV rocket has launched successfully 53 satellites out of 54 it carried - majorly remote sensing/earth observation satellites both Indian and foreign - and has been a major revenue earner for ISRO. The one failure happened in 1993 when the satellite was not able reach the orbit. The rocket that delivered Risat-1 in the space is ISRO's four stage PSLV's upgraded variant called PSLV-XL. The letters XL stand for extra large as the six strap-on motors hugging the rocket at the bottom can carry 12 tonnes of solid fuel as against the base version that has a fuel capacity of nine tonnes. The PSLV's four stages are fuelled with solid and liquid propellants. The first and third stages are fuelled by solid fuel, while the second and fourth stages are powered by liquid fuel. ISRO had used the PSLV-XL variant for its Chandrayaan-1 moon mission in 2008 and for launching the GSAT-12 communications satellite in 2011. The features of RISAT include:

• 160 x 4 Mbps data handling system
• 50 Newton-meter-second reaction wheels
• SAR antenna deployment mechanism
• Phased array antenna with dual polarisation

RISAT-1 has a resolution of 3m-50m. It also supports a spotlight mode for prolonged focus on a given geographical area at a resolution of 1m. Most of the design and the installation of basic instrument subsystems for the satellite was done in 2010.

Approximate cost of the mission was ₹4.9 billion (US$59 million). The satellite cost ₹3.78 billion (US$45 million) to develop, while the launch vehicle cost was ₹1.1 billion (US$13 million).

Applications

RISAT 1 is India's first radar imaging satellite and uses microwaves instead of light to see. Just like a camera fires a flash of light, RISAT-1 fires microwaves, which the ground reflects back. A radar inside the satellite uses those reflections to make pictures so clear, that from six hundred kilometers above, the satellite can tell all of the ground activities. Because it doesn't need light, RISAT works both by day and night, in cloudy conditions and crucially, they can see even if somebody hiding under trees, in forests. That makes them useful for the military.The SAR sensor will enable RISAT-1 to collect data during both day and night and in all weather conditions. The satellite would be used for natural resources management, primarily agriculture planning and forestry surveys, as well as to predict and prevent flooding. It will be used for monitoring paddy plantation and yields in the kharif season and to assist India's food security planning.officially, pictures from RISAT-1 will be used to estimate the number of hectares being farmed in India, to assess crop health and predict total yield.They can also be used to identify wreckage from airplanes that go down in forested areas. RISAT-1 was not designed as a surveillance satellite, given its reliance on the C-band.

Launch

RISAT-1 was successfully launched on 26th April 2012 at exactly 5.47 a.m IST by Polar Satellite Launch Vehicle C19 (PSLV-C19) (XL variant) from Sriharikota, Andhra Pradesh.The perfect launch of the satellite catapulted India into a select band of countries having indigenous radar imaging technology.According to PS Veeraraghavan, Director, Vikram Sarabhai Space Centre “Only the US, Canada, Japan and the European consortium have the technology so far,” PS Veeraraghavan, Director, Vikram Sarabhai Space Centre . N. Valarmathi was the project director for the RISAT launch.She is only the second woman in Indian history to launch a satellite into space.Valarmathi said , "I beleive everyone is equally capable. Take enough pains and anyone can succeed."

Reactions after the launch

The Prime Minister, Dr. Manmohan Singh, has congratulated the scientists of the Indian Space Research Organization (ISRO), for the successful launch of PSLV-C19 carrying the Radar Imaging Satellite RISAT-1. Following is the text of the Prime Minister’s message:

"I would like to warmly congratulate all scientists of the Indian Space Research Organization (ISRO) for the successful launch today of the Polar Satellite Launch Vehicle (PSLV)-C19 carrying the Radar Imaging Satellite-1 (RISAT-1), the heaviest satellite launched till date using PSLV. The twentieth consecutive successful launch of the PSLV is an important milestone in our space programme and is testimony to ISRO’s mastery of the complex launch vehicle technology. I have no doubt that RISAT-1’s all weather, day-night imaging ability will significantly contribute to the nation’s remote sensing capabilities. The country is proud of ISRO’s achievements and I wish the organization all success in its future endeavours." ISRO Chairman K Radhakrishnan described the launch "a grand success".A beaming Radhakrishnan said "I am extremely happy to announce that the PSLV C-19 mission is a grand success. This is the 20th successive successful flight of our PSLV. It injected precisely India's first radar imaging satellite into the desired orbit,"

New Missions After RISAT-1 Success

Buoyed by the successful launch of all-weather radar imaging satellite RISAT-1, ISRO has announced it would launch two GSLVs and a PSLV this fiscal and the second Indian moon mission of Chandrayaan 2 in 2014 on board a GSLV.P S Veeraraghavan, Director, Vikram Sarabhai Space Centre, who was present, said ISRO will launch a low cost communication satellite GSAT-14 on board GSLV D5 in September/October 2012.PSLV C-20 with Indo French satellite SARAL and four small satellites would be launched in October, 2012 and PSLV C-21 with a commercial payload SPOT, a French satellite on earth observation in August 2012, he said.