NISAR – Just 19 minutes to 747-km high orbit, but three months to become fully operational

It will take approximately 19 minutes for the NASA-ISRO Synthetic Aperture Radar (NISAR), an advanced imaging satellite, to be placed into orbit — 747 km above the earth — but about three months thereafter to become fully operational while floating in space to carry out its scientific missions.

NISAR is a joint project between the Indian Space Research Organisation (ISRO) and the US’ National Aeronautics and Space Administration (NASA). The satellite is scheduled to be launched on July 30 by ISRO’s geo-synchronous launch vehicle F16 into a polar sun-synchronous orbit.

According to information shared by ISRO, the NISAR mission phases can be broadly classified into four sections – launch phase, deployment phase, commissioning phase and science phase.

The launch phase will be the rocket’s lift-off part from ISRO’s Satish Dhawan Space Centre (SDSC), also referred to as the Sriharikota High Altitude Range (SHAR), located in Sriharikota on the southeast coast of the Indian peninsula in Andhra Pradesh.

In the deployment phase, a large reflector with a 12m diameter will be deployed in-orbit nine meters away from the satellite by a complex multistage deployable boom designed and developed by NASA’s Jet Propulsion Laboratory (JPL).

The commissioning phase will be spread over 90 days involving ‘in-orbit checkout”, to prepare the observatory for science operations. Commissioning is divided into sub-phases of initial checks and calibrations of mainframe elements followed by JPL engineering payload and instrument checkout.

After that, the science operations phase will commence, which will continue till the end of the spacecraft’s mission life of five years. During this phase, the science orbit will be maintained via regular manoeuvres, scheduled to avoid or minimise conflicts with science observations. Extensive calibration and validation activities will take place, ISRO said.

The observation plan for both L-band and S-band instruments, along with engineering activities like manoeuvres and parameter updates has been generated pre-launch through frequent coordination between JPL and ISRO.

The GSLV carrying the satellite has already been positioned on the launch pad at SHAR, where final pre-launch checks are being carried out. Lift-off is scheduled for 5.40 pm Indian Standard Time.

NISAR mission’s primary objectives are to study land and ice deformation, land ecosystems and oceanic regions in areas of common interest to the US and Indian science communities. The unique dual-band Synthetic Aperture Radar employs advanced and novel techniques which provides high resolution and large swath imagery.

According to NASA, NISAR has been designed to provide a detailed view of the earth to observe and measure some of the planet’s most complex processes, including ecosystem disturbances, ice-sheet collapse, natural hazards, sea level rise and groundwater issues.

Its radar, the first of its kind in space, will systematically map earth, measuring changes of our planet’s surface as small as a centimetre. It has a 240-km observable swath with 5-100m resolution and will collect and downlink about 26 terabits data per day. It will help scientists to understand the changes happening to the planet.

The spacecraft and the launch system have been built by ISRO. It carries two major payloads — the L-band and the S-band SAR. The S-band radar system, data handling and high-speed downlink system has been developed by ISRO, while the L-band radar system, high-speed downlink system, the solid-state recorder, GPS receiver and reflector have been provided by NASA. The 2,392kg satellite will be the first space platform to observe the earth with a dual frequency and detect changes in the planet’s surface down to “fractions of an inch”.

Further, ISRO will handle the satellite commanding and operations whereas NASA will provide the orbit manoeuvre plan and radar operations plan. The NISAR mission will be aided with ground station support of both ISRO and NASA for downloading of the acquired images, which after the necessary processing will be disseminated to the users.