Ritu Jha-
When NASA decided to build a cutting-edge radar imaging satellite to map the world, its experts recommended collaborating with the Indian Space Research Organisation (ISRO), given the latter’s ability to provide quality material while working with a tight budget. That led to the NASA ISRO Synthetic Aperture Radar (NISAR).
Wendy Edelstein of the Jet Propulsion Laboratory (JPL), who visited India 17 times while working on the project, told indica she was really impressed with how the ISRO team built everything from scratch.
Sanghamitra Dutta, a NASA program executive who was at the Feb. 3 coconut-peanut ceremony at JPL in Pasadena, California, told indica, “This is an excellent project between India and the US. I have been in this project from the very beginning – in 2013.”
She said that while considering which group was good in what area, they went for JPL, the radar house of NASA, and ISRO’s strong Space Applications Centre (SAC).
NISAR orbit is 747 km (464 miles) above the Earth altitude orbit. Over 12 days it is to make 173 orbits that cover the globe.
Since January 2012 when the initial idea of using two bands of radio, L- and S-band SAR, to map the Earth, , JPL and ISRO teams have worked to refine the science and its implications for the mission.
“It [India]was at the right place at the right time,” Dutta told indica, describing how it joined the NISAR project. Word was out in the scientific community that ISRO was interested in building the SAR at that time.
In September 2013, ISRO received the Indian government’s approval to work on the mission with NASA. A technical assistance agreement (TAA) was signed between ISRO and California Institute of Technology/JPL was enacted on September 30, 2013. NASA Administrator Charles Bolden and ISRO Chairman K. Radhakrishnan met in Canada, where they signed the NISAR Implementing Arrangement (IA) on September 30, 2014.
COVID slowed down the project, which was to start in 2022, with the launch set for some time in 2024. The NISAR observatory is to be transported on an ISRO geosynchronous satellite launch vehicle (GSLV) Mark II from the Satish Dhawan Space Center (SDSC) in Sriharikota, India.
Dutta told indica, “We normally don’t talk about the money but … we did not exchange funds. We just decided who is going to build what. We did not give any money and they did not give any money. It is based on mutual interest.”
The ISRO Telemetry Tracking and Command Network (ISTRAC) center in Bangalore is to do day-to-day observatory operations. ISTRAC is to monitor and control the spacecraft, sending spacecraft telemetry to a local archive from which JPL can access the data. All science data is to be processed and archived first in the JPL Science Data System, and then at a location from where ISRO can access the data. In addition, some L-band and S-band data (as specified by SAC) will go to India (at an NRSC ground station).
Gerald W Bawden, a program scientist involved in geodetic imaging at the Earth Science Division at NASA headquarters in Washington, D.C., told indica that while he has been responsible for the NISAR project since 2017, he has been involved in work on it since its inception.
Describing the road to NISAR, he described how NASA, which relies on 10-year surveys from the National Academy of Science, recommended a mission called DESDynI (Deformation, Ecosystem Structure, and Dynamics of Ice) to continue the spaceborne observation program.
DESDynI was intended to address the needs of three disciplines – solid earth, ecosystems, and cryospheric sciences – and provide data important for many applications.
“Bowden said the project cost NASA a billion dollars; he did not know India’s budget. But that country is building the satellite, the spacecraft, and the rockets, while the US is providing a huge radar balloon.
Bawden said there were numerous challenges because this is an international project.
“We have to learn to work with each other, and there was a global pandemic that delayed NISAR,” he said.
In the clean room where NISAR is undergoing final tests, Wendy Edelstein, the deputy project manager for NISAR, showed indica NISAR’s radar payload unit, a drum-like object covered in gold foil with wires snaking out of it to dozens of machines.
“What you see here is the result of the last two-and-a-half years of testing building the L-band system and India S-band,” she said. “In 2021, the S-band was delivered, and we have been testing it together for the last six to nine months.”
She pointed to a metal container and said it contained the reflector antenna, packed to be shipped to India.
The 12-meter antenna was built by Northrop Grumman’s Astro Astro Aerospace in Santa Barbara. Boeing built the transmit-receive model.
Edelstein said 200 people are working on the project at JPL, adding that at its peak, the project relied on an even larger team.
Over India, L and S band data will be collected only to study agriculture, but the L band will be also used across the globe. Scientists can track surface changes from earthquakes, landslides, volcanic activity, and ice sheets.
To reduce heat damage, most surfaces are reflective to bounce light off.
“They[ISRO] have a robust space program and we took advantage of all spacecraft bus components,” Edelstein said. “They have GSLV II, a very large launch vehicle more than sufficient for our needs. And both JPL and ISRO have radar capability.”
She added that she was impressed that the JPL team had decided to build the radar with already existing technology and parts, but the Indians had built their own custom device.
Susan Owen, a deputy project scientist at JPL, who has been hosting weekly calls with their Indian counterparts, told indica the satellite will generate 80 terabytes of data every day for experts everywhere.
“We will be providing data on natural hazards, for people studying how ice sheets are changing, how the forests are changing,” she said. “We are also going to read soil moisture and help the agriculture community in groundwater management as well as fire management. So 80 terabytes of data is going to be very useful for a wide variety of communities.”
[Photo courtesy: indica and https://nisar.jpl.nasa.gov/]
