CHENNAI: A 27.5-hour countdown for GSLV F-16/ Nisar- Nasa Isro Synthetic Aperture Radar- Mission commenced at 2.40pm on Tuesday. The launch is scheduled for 5.40pm on Wednesday at Satish Dhawan Space Centre in Sriharikota.NISAR is the first of its kind mission, jointly developed by Isro and NASA. It will have an L and S-band, global, microwave imaging mission, with capability to acquire fully polarimetric and interferometric data.The unique dual-band Synthetic Aperture Radar of NISAR employs advanced, novel SweepSAR technique, which provides high resolution and large swath imagery. NISAR will image the global land and ice-covered surfaces, including islands, sea-ice and selected oceans every 12 days.NISAR mission’s primary objectives are to study land & ice deformation, land ecosystems, and oceanic regions in areas of common interest to the US and Indian science communities.