NASA-ISRO's NISAR satellite deploys largest space radar, advances Earth observation

Seventeen days after the NASA-ISRO Synthetic Aperture Radar (NISAR) was placed in orbit, the advanced earth imaging satellite had fully deployed its massive 39-foot wide radar antenna, a key step in its schedule for commissioning.

NISAR, a joint project by the Indian Space Research Organisation (ISRO) and the US National Aeronautics and Space Administration (NASA) was launched from ISRO’s Satish Dhawan Space Centre on the southeastern coast on July 30.

“Giant Radar Antenna Reflector on NASA-ISRO Satellite in Full Bloom,” NASA said on its website, adding that an essential piece of science hardware has unfurled in orbit. The largest and the most sophisticated radar systems ever sent to space, the drum-shaped antenna had been stowed like an umbrella until the 30-foot (9-meter) boom that supports it could be deployed and locked in place.

“NISAR is one big step closer to beginning its mission to study Earth’s changing surfaces,” NASA’s Jet Propulsion Laboratory said on its X handle in the wee hours of August 16, India time.

“Today, the satellite successfully unfurled its 39-foot-wide (12-meter-wide) antenna reflector. It’s the largest reflector NASA has ever deployed in space!” the post added.

NISAR will track the motion of ice sheets and glaciers, the deformation of land due to earthquakes, volcanoes, and landslides, and changes in forest and wetland ecosystems down to fractions of an inch. It also will aid decision-makers in fields as diverse as disaster response, infrastructure monitoring, and agriculture.

“The successful deployment of NISAR’s reflector marks a significant milestone in the capabilities of the satellite,” said Karen St Germain, Director, Earth Science Division at NASA Headquarters according to a statement posted by NASA.

“From innovative technology to research and modeling to delivering science to help inform decisions, the data NISAR is poised to gather will have a major impact on how global communities and stakeholders improve infrastructure, prepare for and recover from natural disasters, and maintain food security.”

Weighing about 64 kg, the reflector features a cylindrical frame made of 123 composite struts and a gold-plated wire mesh. On August 9, the satellite’s boom, which had been tucked close to its main body, started unfolding one joint at a time until it was fully extended about four days later.

Then, on August 15, small explosive bolts that held the reflector assembly in place were fired, enabling the antenna to begin a process called the “bloom” — its unfurling by the release of tension stored in its flexible frame while stowed like an umbrella, according to information shared by NASA. Subsequent activation of motors and cables then pulled the antenna into its final, locked position.

The commissioning of the NISAR, launched by ISRO’s GSLV F-16 rocket into a 747 km high polar orbit, is expected to take another two-and-a-half months, after which the scientific operations for which it has been designed will commence. Till then In-orbit checks and calibrations will be carried out.

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 2,392 kg 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.