The Indian Space Research Organisation (Isro) will on Monday put in orbit its first radar imaging satellite (Risat), which can watch'
the earth under all-weather conditions, day and night.

Isro's workhorse PSLV (C-12) will take off at 6.45am from the Satish Dhawan Space Centre at Sriharikota, an island by the sea 100km north of Chennai. About 17 minutes later, the 300-kg Risat will be put in an orbit 550km from the earth. Riding piggyback on Risat will be a microsatellite called Anusat, developed by Anna University, Chennai.

"The countdown will start 48 hours before take-off (Saturday morning). As of now, everything is going on fine. Risat, which can penetrate clouds and observe earth under all climatic conditions, will be extremely useful in disaster management," Isro spokesperson S Satish told TOI. Unlike Isro's previous remote sensing satellites that used optical imaging, Risat uses synthetic aperture radar (SAR) that has several antennas
to receive signals that will be processed into high-resolution pictures.

While its applications in mapping and managing natural disasters such as floods and landslides are spoken about, Risat will come in handy for defence applications as well. Isro had started work on a 1,780-kg Risat, but shelved its launch to advance the launch of the present 300-kg variant. Defence sources confide that the lighter Risat version was assembled on a war footing in the wake of terrorist attacks. "Risat has been put together with inputs from the Israeli Space Agency (ISA), but the satellite images
will be used solely for Indian purposes," Satish said.

Also in the PSLV-C12 payload will be Anusat, the first satellite to be assembled by an Indian university. "Scores of students and faculty members from different streams have been working on Anusat for six years," said Anusat project director P V Ramakrishna. Anusat will be a store-and-forward communication satellite that will enable transfer of confidential academic material like exam question papers, to get rid of leakages.

PSLV-C11 had, on October 22, 2008, carried the lunar probe as part of Chandrayaan-I. Ever since it launched the first satellite Aryabhatta on April 1, 1975, Isro has launched more than a dozen satellites, including the INSAT (Indian National Satellites) series for communication, broadcasting and meteorology and IRS (Indian Remote Sensing Satellites) for resources monitoring and management.