BENGALURU: India and the United States have cleared a major milestone in their joint Earth-observation effort, with the Nasa-Isro Synthetic Aperture Radar (Nisar) mission completing antenna deployment, early calibration, and the full commissioning run. The mission has now moved into its science phase, with Isro releasing the first set of S-band radar images on Friday, the 100th day of the satellite in orbit.After the successful launch of Nasa-Isro Synthetic Aperture Radar (Nisar) satellite onboard GSLV – F16 on July 30, the 12m diameter Antenna reflector has been successfully deployed. The 12-meter diameter antenna reflector plays a key role for both Isro’s S-Band and Nasa’s L-Band Synthetic Aperture Radar (SAR) payload. The antenna was launched in a stowed condition on a 9m long boom, which was tucked to the satellite. The antenna and the 9m boom was developed by Nasa.The unfolding of the joints of the boom commenced on Aug 9, and was carried out over a period of five days (Wrist, Shoulder, Elbow and Root deployments). The reflector assembly mounted on the end of the boom was deployed successfully on Aug 15 and the performance of the antenna systems are satisfactory. The entire operations were carried out from the Isro Telemetry Tracking and Command Network (Istrac) with the support of Nasa’s Jet Propulsion Laboratory (JPL).Commissioning Phase“Since the first acquisition on Aug 19, Nisar S-Band SAR is regularly imaging over Indian landmass and global calibration-validation sites in various payload operating configurations. Reference targets such as Corner reflectors were deployed around Ahmedabad, Gujarat and a few more locations in India for calibration of the images,” Isro said. Data acquired over Amazon rainforests were also used for calibration of spacecraft pointing and images. Based on this, payload data acquisition parameters were fine-tuned resulting in high quality images. Initial analysis by scientists and engineers revealed the potential of S-Band SAR data for various targeted science and application areas like agriculture, forestry, geo-sciences, hydrology, Polar/Himalayan ice/snow and oceanic studies. “The first image of S-band SAR acquired on Aug 19 captures the fertile Godavari River Delta in Andhra Pradesh, India. Various vegetation classes like mangroves, agriculture, arecanut plantations, aquaculture fields, etc are clearly seen in the image. The image highlights Nisar’s S-Band SAR ability to map river deltas and agricultural landscapes with precision,” Isro said.“On the 100th day of Nisar in-orbit, the S-SAR images are released to the public… the science phase has now commenced,” Isro added.
