THEY WERE ON each other’s radar, their wavelengths matched and it was a coming together like no other. No, romance was not in the air, but a rocket soon would be.
The rocket―the Indian Space Research Organisation’s Geosynchronous Satellite Launch Vehicle Mark II (GSLV-Mk II)―will carry the NASA-ISRO Synthetic Aperture Radar (NISAR). The launch date is set for early next year. The GSLV-Mk II will unload NISAR at an orbit 747km above Earth.
NISAR, to put it simply, will perhaps be the fanciest, high-tech version of a camera out there. Only, it will produce fine-resolution images of the Earth’s land and ice surfaces, helping measure the changing ecosystem and provide data about natural hazards, sea level rise and groundwater level. NISAR will be on a three-year mission, observing the planet every 12 days, morning and evening, come rain or shine. This is the first-ever collaboration between NASA and ISRO on an Earth-observing mission. And, NISAR is likely to be the most expensive satellite―$1.5 billion. That is probably because its payload will be the most advanced radar system ever launched.
A rocket’s payload can be a satellite, a space probe or a spacecraft carrying humans. NISAR’s payload is a satellite, consisting of two radar systems―the 24cm-wavelength L-band built by NASA’s Jet Propulsion Laboratory (JPL) in South California, and the 10cm-wavelength S-band built by ISRO. The S-band was shipped to JPL in March 2021. The two bands were integrated and tests were done to check if they work well together. And, on March 6 this year, the payload was flown in to ISRO’s U.R. Rao Satellite Centre in Bengaluru.
“The payload will undergo further integration with the satellite bus propulsion system,” said ISRO chairman S. Somanath. “After that, all the satellite parts will be integrated. It will then go through a lot of evaluation, vibration and antenna deployment. It should be completed by September 2023. If all goes well, we are planning to launch it (from the Satish Dhawan Space Centre in Sriharikota, Andhra Pradesh) by January-February 2024.”
But the NISAR dream has been more than a decade in the making. After several months of preliminary coordination at the agency level, JPL’s project scientist Paul Rosen was asked to travel to India in December 2011 to talk about NASA’s radar mission concept and to try and engage the scientists here. It turned out to be a trip to remember, and since then Rosen has travelled to India 28 times in 12 years (except the three pandemic years).“Travelling solo for the first time to India, arriving at 3am in Ahmedabad after 30 hours of travel, it was a surreal and new experience for me,” Rosen told THE WEEK in an exclusive interaction from the US. “The talk and subsequent discussions were successful and led to a preliminary agreement to work together, where NASA would provide the instrument, and ISRO would provide the spacecraft and launch vehicle. However, after my return, ISRO expressed a need to participate in the instrument development. I suggested that we add a second radar instrument at a different frequency. Due to the unique design of NISAR, this was possible using the basic design originally proposed. The agreement was then solidified, and the rest is history.”
Having two radars has its advantages. As Somanath, who is also secretary, department of space, explained, “They can give a deeper insight into various aspects, such as tectonic shifts, movements of ice, water bodies, agriculture, soil moisture and so on. The data will come from across the world.” According to aerospace and space expert Girish Linganna, S-band radars have become a vital tool for weather observation and their unique wavelength of 8-15cm and frequency of 2-4GHz make them less susceptible to attenuation, providing a reliable means of observation for both near- and far-range weather patterns. “The instrument structure of the S-band radar is also noteworthy, featuring a stationary antenna reflector constructed from gold-plated wire mesh,” said Linganna, director, ADD Engineering Components India Limited. “Measuring an impressive 39ft, this reflector works to concentrate the radar signals that are both emitted and received by the feed facing upwards. With this innovative technology, meteorologists and weather experts are better equipped than ever to track and predict weather patterns with greater accuracy.”
Rosen clarified that though there have been many airborne missions that use SAR technology similar to that of NISAR’s to collect the same kind of data, radars flown aboard airplanes cannot match the surface coverage of a space-borne instrument.
NISAR is expected to transmit 80 terabytes of data a day. “Initially, the data will be available only to NASA and ISRO,” said Somanath. “Later, the two space agencies will decide with whom the data can be shared. Although the mission is being termed very expensive, we are looking at the benefits it will give us and not the monetary aspect.”
Experts agree that undertaking a mission of the magnitude and intricacy of NISAR comes at a price. “The satellite will operate in a complex orbit and will require a large amount of ground support infrastructure, including antenna systems, data centres and processing facilities that are expensive to build and maintain,” said Srimathy Kesan, founder and CEO of Space Kidz India, which is into design, fabrication and launch of small satellites, spacecraft and ground systems. “The NISAR mission represents a significant investment in the future of Earth science research and will provide valuable insights that will benefit humanity for years to come.”
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So, how will those insights translate on ground? “One major benefit of the NISAR mission will be that it will help communities manage changes in land and other natural resources as well as infrastructure more effectively,” said Rosen. “The satellite will monitor soil moisture to help farmers use water more sustainably. NISAR will also monitor the expansion and shrinking of wetlands and forests, providing valuable information for their management. Its measurements of subsidence―the gradual sinking of land―will be used to improve the accuracy and consistency of groundwater usage estimates. NISAR’s data will also be able to reveal subtle movements of bridges, dams, levees, roads and buildings, potentially helping infrastructure managers identify structures that are at risk of failure.” That way it would make a great prediction and warning system, especially in places like Joshimath in Uttarakhand that started sinking this January. “In the case of hilly regions like Joshimath, the high-resolution mapping capabilities of NISAR can enable the identification of vulnerable slopes, geological structures and soil properties that may contribute to landslides,” said Rosen. “By monitoring these areas with NISAR’s all-weather imaging capability, researchers can detect subtle changes in surface deformation that may indicate the onset of a landslide, enabling early warning and evacuation of people living in disaster-prone areas. In the case of vanishing coastlines, NISAR’s mapping capabilities can enable the monitoring of coastal erosion and sea level rise.”
Besides NISAR, ISRO is gearing up for its third moon mission―Chandrayaan-3―set for a July launch. A follow-on mission following the Chandrayaan-2 debacle in 2019, Chadrayaan-3, too, will aim to perform a soft landing on the moon and demonstrate its ability to traverse its surface. The Chandrayan-3 landing station is a replica of the previous one, but its design has been modified to address the deficiencies of its predecessor. The hefty LVM Mark III, consisting of a flight module, lunar lander and a compact rover, will launch the satellite into the Earth’s orbit, where it will commence its journey to the Moon on its own.
Moreover, as per the Indian Space Policy 2023, published on April 20 after years of preparation, ISRO will move out from producing operational space systems and instead focus on research and development of advanced technologies. This is in line with the reforms it initiated in 2020 that opened up the space sector to private participation and foreign investors. “According to the new policy, ISRO must share technologies, products, processes and best practices with non-government entities (NGEs) and government enterprises,” said Linganna. “It will concentrate on cutting-edge research and development and long-term initiatives like Chandrayaan and Gaganyaan. At the same time, NGEs can engage in end-to-end activities in the space sector by establishing and operating space objects, ground-based assets and related services such as communication and remote sensing and navigation.”