Exclusive: NASA-ISRO satellite to capture 4,300 GB of Earth imagery daily

The NASA-ISRO Synthetic Aperture Radar (NISAR) satellite, jointly built by the American and Indian space agencies, will be capturing an unprecedented amount of Earth-imaging data as it circles 747 kms above the Earth’s surface. “NISAR would be capturing 4.37 Terabytes (over 4,300 GB) of data per day,” Dr. Sanghamitra Dutta, NISAR Program Executive, NASA Headquarters, told WION’s Sidharth M.P. For context, an average consumer laptop comes with 512 GB of storage space. Therefore, NISAR would capture enough imagery to fill up at least eight laptops in a single day.

Weighing nearly 2,400 kg, NISAR is meant to carry out high-resolution Earth imaging for at least three years. NISAR would generate a whopping 1569 Terabytes (over 1.5 million GB) of imaging data, considering its minimal operational life of three years. Over this period of three years, NISAR would generate enough data to fill up at least 2,900 laptops. The first-ever satellite to be built jointly by space agencies of India and the US, NISAR is meant to monitor Earth’s vital signs and help understand the impact of climate change and natural disasters, among others.

If everything goes according to plan, the GLSV-F16 rocket carrying the NISAR satellite will lift off from the Indian Spaceport Satish Dhawan Space Centre, Sriharikota, at around 5:40 pm Indian time, on 30th July, Wednesday. ISRO has officially announced the launch date and time for the mission.

24/7 Earth-monitoring for several years

Typically, an Earth-imaging satellite would have to only capture images when passing over its area of interest or region of study. When not flying over the area of interest, the imaging equipment can be turned off and put to rest. That’s where NISAR stands out—its job is to capture earth imaging data round-the-clock over its operational life of more than three years. NASA says NISAR will be capable of mapping the Earth’s land and ice-covered surface twice in a period of twelve days. While NISAR is expected to have a minimum mission life of three years, it is likely to perform its duties for five years or longer. Satellite life depends on how much fuel it carries on board, the design life of its electronic components, and other technical parameters.

NISAR is the first satellite mission to collect radar data in two microwave bandwidth regions, called the L-band and the S-band, to measure changes of our planet’s surface, including movements as small as a centimetre. This allows the mission to observe a wide range of Earth processes, from the flow rates of glaciers and ice sheets to the dynamics of earthquakes and volcanoes. NISAR will map the entire globe in 12 days.

How scientists would manage such vast amount of data from NISAR

Given how NISAR would generate over 4,300 GB of data daily, scientists face a major challenge in managing this vast trove of Earth-imaging information. Like all our gadgets, the Solid State Data recorder on the NISAR satellite has a limited capacity, which is why NASA and ISRO are working on quick methods to downlink the data (send the data from the satellite to Earth) as frequently as possible. Think of it like rapidly downloading all photos and videos from a camera’s memory card before deleting them to free up space for the next use.

NASA’s Dr. Dutta says that NISAR could generate the highest-ever amount of data from a single-satellite mission. “There has never been so much data coming from a mission on a daily basis, and we have prepared the downlink stations (Earth-based stations that receive data from satellites) for such high data rates. This would also help NASA in getting ready for future missions, when there would be a much higher volume of data transfers.” Notably, all of NISAR’s data would be archived and shared with the science community.

How a radar-imaging satellite works

Conventional Earth-imaging satellites click detailed colour photos of Earth, very similar to what a high-end camera does. In comparison, a radar-imaging satellite works in a totally different manner. Instead of giving an optics-based picture (like a photograph), radar satellites constantly beam radar waves onto the Earth. The features on Earth’s surface (buildings, trees, mountains, water bodies, roads, and glaciers) reflect these radar waves back to the satellite. By collecting and processing the reflected radar waves, radar-imaging satellites deliver imagery during day and night, during all weather conditions.

Typically, conventional satellites’ ability to deliver images is obstructed by clouds and weather-related phenomena. While conventional optical satellite images are in colour, radar satellite images are inherently black-and-white. However, these black-and-white radar satellite images can be processed to deliver false-colour images for analysis.

Is NISAR a spy satellite?

Synthetic Aperture Radar technology is widely used for military and strategic purposes, as it can delivery imagery during day and night conditions, even amid weather conditions that hinder traditional camera-based satellite imaging. During his time at the helm of ISRO, when asked if NISAR was a spy satellite, Dr. S. Somanath categorically stated, “NISAR is not a spy satellite.” He elaborated that the data generated by NISAR would be shared in a free and open manner with the entire scientific community. He said that it was purely a science mission and aimed at studying the Earth in high detail, which would help draw better conclusions on various phenomena that are affecting our planet.

Dr. Datta from NASA highlighted that the first civilian SAR satellite in history, called SEASAT, was launched by NASA in 1978. SEASAT led to a series of NASA space shuttle-based radar missions and inspired the development of spaceborne SAR systems worldwide. She added that Japan and Europe also have SAR satellites for Earth-imaging purposes.

All NISAR science data, L-band and S-band, will be freely available and open to the public, consistent with the long-standing NASA Earth Science open data policy. NASA has chosen the Alaska Satellite Facility Distributed Active Archive Center (DAAC) to host the mission’s data and products, said the American space agency.