New Delhi: From natural disasters like landslides, floods and forest fires to more gradual changes, like those in glaciers, sea ice and agricultural land, the Earth observation NISAR satellite to be launched on 30 July will be able to capture everything.
NISAR is the first-ever space collaboration between India and the US, developed through a rare 50-50 partnership between ISRO and the US’s National Aeronautics and Space Administration (NASA).
More than a decade in the making, NISAR will finally lift off from Sriharikota on 30 July at 5.40 am. It was built jointly by ISRO and NASA’s Jet Propulsion Laboratory, and assembled in India.
The NISAR satellite weighs about 2,392 kg and is one-of-a-kind because of the Earth observation technology it hosts.
While both NASA and ISRO have launched Earth observation satellites independently before, NISAR will help both countries with 3-D images of land and ice to see how the Earth “changes over time”.
It is the first Earth observation satellite in the world to be equipped with both L-band and S-band radar frequencies, and is expected to scan the entire globe every 12 days.
“NISAR is a model for next-generation earth observation satellites, and is an international collaboration that is built on open science capabilities,” Karen St Germain, Director of Earth Science Division, NASA, told a press conference.
According to NASA, 180 organisations, both public and private, have already lined up to use the data that will be generated by NISAR.
These “early adopters”, as NASA called them, will use NISAR’s data for disaster responses, mapping forest cover, and monitoring wetlands and coastal vegetation.
“Remote-sensing missions like NISAR are storytellers about how the Earth and humans interact, and how we connect with the planet,” Paul Rosen, project scientist, NISAR, said at the press conference. “NISAR is a truly unique storyteller.”
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What is NISAR?
NISAR stands for NASA-ISRO Synthetic Aperture Radar, a technology used in most Earth observation satellites.
Synthetic Aperture Radar (SAR) technology is based on microwave pulses that are sent to the ground by the satellite and bounced back by the Earth. These pulse echoes are used to construct a two-dimensional image of the Earth.
“Because of the size of our antenna, we have a very large footprint on the ground,” said Rosen. “And because we’re sending like a thousand pulses per second, we’re going to get a very fine resolution of images of the Earth,” he added.
The unique thing about the NISAR satellite is that it will send out microwave pulses in two different frequencies—L-band and S-band.
Most other Earth observation satellites that use SAR technology have only one frequency, but NISAR is the first satellite to use dual frequency.
While the L-band frequency developed by NASA is good for detecting subtle land changes and seeing through thick vegetation, the S-band frequency developed by ISRO is better for large surface detail and seeing through clouds. Together, they offer a view of the Earth that will be more detailed than any other earth observation satellite.
According to ISRO’s website, NISAR is expected to detect even the slightest changes like ground deformation or ice sheet changes, and even changes in soil moisture, which is important both for agriculture and landslide monitoring.
NISAR is also one of the costliest Earth observation satellites. Initial estimates pegged the total cost at $1.5 billion. However, NASA Monday said it had independently spent $1.2 billion on the mission.
While it did not disclose ISRO’s expenditure, the mission is a 50-50 partnership, suggesting a comparable investment by the Indian space agency.
Work on NISAR began in the early 2000s, when NASA was searching for international collaborators for its new and advanced Earth observation mission for cryoscience, ecosystem science and Earth science.
“We had then approached Germany, Canada, Argentina, until in 2011 I was sent to India to tell them about the mission,” recalled Rosen, who has been working on this idea since the beginning. “There, ISRO told us this is exactly the kind of thing we want to do next.”
While the initial launch of the satellite was scheduled for March 2024, testing and other issues pushed the mission back a few times before 30 July was finally announced as the date.
According to NASA, all equipment—including the antenna, the solar arrays and the reflector—is ready and in place at ISRO’s Satish Dhawan Space Centre in Sriharikota.
The NISAR satellite will fly aboard ISRO’s GSLV-F16 launch vehicle, and will be placed in Low-Earth Orbit or a distance of 2,000 km or less from the Earth.
Since the satellite has solar arrays too, it will be in a sun-synchronous orbit, meaning it will be placed at an angle to always be able to interact with the Sun Given the size of the bowl-shaped antenna, it will be folded up during launch and will be deployed only 10 days after the launch.
The satellite will begin collecting data 90 days after being in orbit, with all information, including raw data, to be made publicly available both on the ISRO and NASA websites.
“Each image is about 240×240 km and is available in the raw format, but we’re also providing some inferred products like maps and graphs that show displacement and change easily,” said Rosen. “We have an unprecedented data set for NISAR as compared to any other SAR mission,” he added.
Challenges of working together
The NASA press conference also spoke about the challenges of working with an international partner that was “9,000 miles away”.
“I think the biggest challenge was the time zone difference and just the amount of travel we did with our scientists going to India and theirs coming to California,” Wendy Edelstein, the deputy project manager of NISAR, said at the press conference.
“ISRO and NASA had very different ways of doing things, but we learnt to work alongside each other.”
In response to a question about why there was no ISRO presence at the press conference despite the mission being a 50-50 partnership, the NASA team said that it was mainly due to the time zone difference.
“You know we’ve learnt to work across the world; even if we’re not physically together, we have worked over the phone. It’s because both teams are extremely committed to the mission,” said Edelstein.
(Edited by Sugita Katyal)
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