The main terrestrial satellite for disaster tracking, the consequences of climate change

The concept of the artist. Credit: Jet Propulsion Laboratory

Designed to spot potential natural hazards and help researchers measure how melting land ice will affect sea level rise, the NISAR spacecraft represents a major step in how it is shaped.

The Earth’s SUV-sized satellite to be equipped with the largest reflector antenna NASA has ever launched is being formed in a clean room in the agency’s jet lab in Southern California. Named NISAR, a joint mission of NASA and the Indian Space Research Organization (ISRO) has big goals: By tracking subtle changes on the Earth’s surface, it will spot warning signs of imminent volcanic eruptions, help monitor groundwater supplies, monitor melting rate-related levels. seas must grow and notice shifts in the distribution of vegetation around the world. Tracking such changes on the planet’s surface on almost the entire globe has so far not been done with the high resolution in space and time that NISAR will deliver.

The spacecraft will use two types of synthetic aperture radar (SAR) to measure changes on the Earth’s surface, hence the name NISAR, which is short for NASA-ISRO SAR. The satellite will use a wired network radar reflector antenna with a diameter of almost 40 feet (12 meters) at the end of a 9-foot-long carrier to send and receive radar signals to and from the Earth’s surface. The concept is similar to the way weather radars bounce off raindrops to track storms.

NISAR will detect the movement of a surface of only 0.4 inches (centimeters) on the surfaces of approximately half of the tennis court. Launching in 2022 at the earliest, the satellite will scan the entire Earth every 12 days during its three-year primary mission, capturing the Earth’s landmass, ice sheets and sea ice in each orbit.

Activities such as pumping drinking water from an underground aquifer can leave marks on the surface: Take out too much water and the soil begins to sink. The movement of magma below the surface before a volcanic eruption can also cause soil movement. NISAR will provide radar images with high resolution time intervals of such shifts.







The SAR band, one of two types of radar in the NISAR mission, arrived at JPL on 19 March. The next day, technicians and engineers moved the S-SAR into the airlock into the clean room of the High Bay 1 spacecraft assembly facility. The equipment will be unpacked for a few days in a clean room. Credit: NASA / JPL-Caltech

All-weather satellite

On March 19, NISAR’s assembly, testing, and launch team at JPL received a key piece of equipment – the SAR SAR range – from its partner in India. Together with the L-band SAR provided by the JPL, the two radars serve as the main heart of the mission. “S” and “L” denote the wavelength of their signal, from “S” to about 10 centimeters (10 centimeters), and “L” to 25 centimeters (10 centimeters). Both can see through objects such as clouds and forest canopy leaves that interfere with other types of instruments, although L-band SARs can penetrate further into dense vegetation than the S-belt. This ability will allow the mission to monitor changes on the Earth’s surface day or night, rain or light.

“NISAR is an all-weather satellite that will give us an unprecedented ability to watch the Earth’s surface change,” said Paul Rosen, a scientist for the NISAR project from JPL. “It will be especially important for scientists who have been waiting for this kind of reliability and consistency of measurement to really understand what drives the Earth’s natural systems – and for people dealing with natural hazards and disasters like volcanoes or landslides.”

Both radars work by repelling microwave signals from the planet’s surface and recording how long the signals need to return to the satellite, as well as their power when they return. The larger the antenna that sends and receives signals, the higher the spatial resolution of the data. If researchers wanted to see something about 45 meters (45 meters) via a low-Earth satellite that controls L-band radar, they would need an antenna about 14,000 feet long (the equivalent of about 10 Empire State buildings stacked on top of each other. into space is simply not feasible.

Still, NISAR mission planners had the ambition to track surface changes at an even higher resolution – up to about 6 meters – requiring an even longer antenna. Therefore, SAR technology is used in the project. As the satellite orbits the Earth, engineers can take a series of radar measurements from a shorter antenna and combine them to simulate a much larger antenna, giving them the required resolution. And by using two wavelengths with complementary capabilities – S-SAR is more able to detect crop types and how rough the surface is, while L-SAR is more able to estimate the amount of vegetation in heavily forested areas – researchers can get a more detailed picture of the Earth’s surface.






This animation shows how the NISAR spacecraft will set up its radar reflector antenna after launch. Nearly 40 feet (12 meters) in diameter, the reflector will be located at the end of a 30-meter-long jib, sending and receiving radar signals to and from the Earth’s surface. Credit: NASA / JPL-Caltech

Testing, testing …

Thus the arrival of the S-band marked a great opportunity for a mission. The equipment was delivered to the clean High Bay 1 room of the JPL Space Assembly Facility – the same room where the probes used to explore the solar system, such as Galileo, Cassini and the twin Voyager spacecraft – were built – to unpack for days. “The team is very excited to get their hands on the SAR SAR range,” said Pamela Hoffman, NISAR’s Deputy Payload Manager at JPL. “We expected it to arrive in late spring or early summer last year, but COVID has influenced progress at both ISRO and NASA. We are eager to begin integrating ISRO’s S-SAR electronics with JPL’s L-SAR system. “

Engineers and technicians from JPL and ISRO will spend the next few weeks performing a health check on the radar before confirming that the L-band and S-band SARS are working together as planned. It will then integrate S-SAR into a part of the satellite structure. Another round of tests follows to make sure everything is working properly.

“NISAR will really open up a range of questions that researchers can answer and help resource managers monitor areas of concern,” Rosen said. “There’s a lot of excitement around NISAR and I can’t wait to see it fly.”


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Provided by the Jet Propulsion Laboratory

Citation: Major Earth Satellite Tracking Satellite, Climate Change Effects (2021, March 25) retrieved March 25, 2021 from https://phys.org/news/2021-03-major-earth-satellite-track-disasters.html

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