New Delhi: India-US Earth Overview Satellite, NASA-Israo Synthetic Aperture Radar (Nisar), is set to launch ISRO’s spaceport in Sriharikota riding on GSLV-F16 rocket on 30 July. But the real work of the mission begins after entering the orbit. In the next several weeks, the satellite will go through careful indexing functions before sending data. In all, Nisar will need at least 90 days to enter its “science phase”. How Nisar was madeBefore we launch what happens after the launch, it is mentioned how the satellite came together: Nisar is the result of almost a decade of cooperation between ISRO and NASA. In more than 8–10 years, the two agencies tested separately developed and tested major systems, which were later brought together to a observatory.The core radar was built in payload parts-Esro developed S-Band Synthetic Aperture radar (SAR), and NASA’s Jet Propulsion Laboratory (JPL) built the L-Band SAR. These were integrated into a shared structure called integrated radar instrument structure (IRIS).The assembly of Iris and other payload elements took place in JPL. The structure was then sent to ISRO, which developed the mainframe of the satellite at the Ur Rao Satellite Center (URSC) in Bengaluru. ISRO then tested the final assembly, integration and full satellite.And now that the satellite is ready for launch, let’s see what will happen in the initial Wednesday:Step 1: LaunchOn Wednesday (July 30), at 5.40 pm, the GSLV-F16 rocket 2.8-ton satellite will be placed in the Surya-Synchronous Polar Orbit. This means that the satellite will pass into the same part of the Earth at almost the same local solar time every day – ideal to monitor the surface changes.Step 2: Post-Lanch Days 10-18)Nisar is a large-scale 12-meter wide Aries refractor, which acts as a radar antenna. Since it is too large to launch it completely open, it will be twisted during launch and then deployed into space using a complex multistage boom system.This process begins on the 10th day from launch – “Mission Day 10” which becomes “posted day 1”. Here is how the purinjan comes out: On the deployment day 1 (DD -1), engineers start pre -finance checks and unlock six ‘launch restrictions’ that protect the system during the launch. Two more restrictions are issued, and the first hinge (called ‘wrist hurl’) is activated on DD -2. It starts the unfolding motion of the boom.On DD -3, the shoulder is extended, swinging the boom and outwards and on DD -4, the elbow opens opens, continues movement like hand. Route Kaj is deployed on DD -5, which brought the boom in full detail, and on DD -6, a stagnation is made in the schedule to allow for the analysis and verification of the earlier stages.And, DD-7 will have a buffer or ‘margin’ day if required to address any delays or issues. Once it occurs through DD -8, the satellite does a ‘Yava maneuver’ (rotation) to oriented properly, and then finally opens the circular radar reflector. This slow, deliberate sequence reveals delicate bounce and antenna without damage or misleading, and paves the way for the next step.Step 3: CommissioningAfter deployment and from launch to 90th day, all systems are checked and calibrated. This includes satellite mainframe, radar electronics and onboard instruments developed by both ISRO and JPL.Step 4: Science OpsOnce it is completely operational, Nisar will start capturing data in both L-Band and S-Band frequencies. Satellite ground movement, snow sheets, forest and land use – will feed data to researchers worldwide. Regular maneuvers will keep it in position, and a pre-concealed observation plan will guide its workload until the end of its mission life.
