17.08.2025
Giant Radar Antenna Reflector on NASA-ISRO Satellite in Full ‘Bloom’
The NISAR satellite uses a radar antenna reflector that’s 39 feet (12 meters) in diameter to gather information about Earth’s changing surface. The mission scans nearly all the planet’s land and ice surfaces twice every 12 days.
Credit: NASA/JPL-Caltech
Seventeen days after NISAR’s launch from southeastern India, an essential piece of science hardware has unfurled in orbit.
Spanning 39 feet (12 meters), the drum-shaped antenna reflector on the NISAR (NASA-ISRO Synthetic Aperture Radar) satellite mission from NASA and the Indian Space Research Organisation (ISRO) successfully unfurled in low Earth orbit. The reflector had been stowed, umbrella-like, until the 30-foot (9-meter) boom that supports it could be deployed and locked in place.
Launched by ISRO on July 30 from the Satish Dhawan Space Centre on India’s southeastern coast, NISAR will track the motion of ice sheets and glaciers, the deformation of land due to earthquakes, volcanoes, and landslides, and changes in forest and wetland ecosystems down to fractions of an inch. It also will aid decision-makers in fields as diverse as disaster response, infrastructure monitoring, and agriculture.
“The successful deployment of NISAR’s reflector marks a significant milestone in the capabilities of the satellite,” said Karen St. Germain, director, Earth Science Division at NASA Headquarters in Washington. “From innovative technology to research and modeling to delivering science to help inform decisions, the data NISAR is poised to gather will have a major impact on how global communities and stakeholders improve infrastructure, prepare for and recover from natural disasters, and maintain food security.”
The mission carries the most sophisticated radar systems ever launched as part of a NASA mission. In a first, the satellite combines two synthetic aperture radar (SAR) systems: an L-band system that can see through clouds and forest canopy, and an S-band system that can see through clouds as well but is more sensitive to light vegetation and moisture in snow. The reflector plays a key role for both systems, which is why the successful deployment of the hardware is such a significant milestone.
“This is the largest antenna reflector ever deployed for a NASA mission, and we were of course eager to see the deployment go well. It’s a critical part of the NISAR Earth science mission and has taken years to design, develop, and test to be ready for this big day,” said Phil Barela, NISAR project manager at NASA’s Jet Propulsion Laboratory in Southern California, which managed the U.S. portion of the mission and provided one of the two radar systems aboard NISAR. “Now that we’ve launched, we are focusing on fine-tuning it to begin delivering transformative science by late fall of this year.”
How Bloom Works
Weighing about 142 pounds (64 kilograms), the reflector features a cylindrical frame made of 123 composite struts and a gold-plated wire mesh. On Aug. 9, the satellite’s boom, which had been tucked close to its main body, started unfolding one joint at a time until it was fully extended about four days later. The reflector assembly is mounted at the end of the boom.
Then, on Aug. 15, small explosive bolts that held the reflector assembly in place were fired, enabling the antenna to begin a process called the “bloom” — its unfurling by the release of tension stored in its flexible frame while stowed like an umbrella. Subsequent activation of motors and cables then pulled the antenna into its final, locked position.
NISAR team members at JPL, along with colleagues at ISRO facilities in India, deployed the satellite’s radar antenna reflector. Depicted on the screen at right, the reflector unfurled from 2 feet (0.6 meters) across in its stowed configuration to its full size, 39 feet (12 meters), in 37 minutes.
Credit: NASA/JPL-Caltech
To image Earth’s surface down to pixels about 30 feet (10 meters) across, the reflector was designed with a diameter about as wide as a school bus is long. Using SAR processing, NISAR’s reflector simulates a traditional radar antenna that for the mission’s L-band instrument would have to be 12 miles (19 kilometers) long to achieve the same resolution.
“Synthetic aperture radar, in principle, works like the lens of a camera, which focuses light to make a sharp image. The size of the lens, called the aperture, determines the sharpness of the image,” said Paul Rosen, NISAR’s project scientist at JPL. “Without SAR, spaceborne radars could generate data, but the resolution would be too rough to be useful. With SAR, NISAR will be able to generate high-resolution imagery. Using special interferometric techniquesthat compare images over time, NISAR enables researchers and data users to create 3D movies of changes happening on Earth’s surface.”
The NISAR satellite is the culmination of decades of space-based radar development at JPL. Starting in the in the 1970s, JPL managed the first Earth-observing SAR satellite, Seasat, which launched in 1978, as well as Magellan, which used SAR to map the cloud-shrouded surface of Venus in the 1990s.
More About NISAR
The NISAR mission is a partnership between NASA and ISRO spanning years of technical and programmatic collaboration. The successful launch and deployment of NISAR builds upon a strong heritage of cooperation between the United States and India in space. The data produced by NISAR’s two radar systems, one provided by NASA and one by ISRO, will be a testament to what can be achieved when countries unite around a shared vision of innovation and discovery.
The ISRO Space Applications Centre provided the mission’s S-band SAR. The U R Rao Satellite Centre provided the spacecraft bus. Launch services were through Satish Dhawan Space Centre. After launch, key operations, including boom and radar antenna reflector deployment, are being executed and monitored by the ISRO Telemetry, Tracking and Command Network’s global system of ground stations.
Managed by Caltech in Pasadena, JPL leads the U.S. component of the project. In addition to the L-band SAR, reflector, and boom, JPL also provided the high-rate communication subsystem for science data, a solid-state data recorder, and payload data subsystem. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the Near Space Network, which receives NISAR’s L-band data.
Quelle: NASA
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Update: 30.08.2025
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NASA-ISRO Mission Aces Checkouts, on Track to Start Delivering Science
After launching July 30, the NISAR (NASA-ISRO Synthetic Aperture Radar) Earth-observing radar satellite mission, a joint effort between NASA and the Indian Space Research Organisation (ISRO), is on schedule to start science operations this fall.
Following the deployment of its 39-foot (12-meter) radar antenna reflector on Aug. 15, engineers powered on the satellite’s L-band and S-band synthetic aperture radar (SAR) systems, which, together, will track movement of Earth’s ice and land surfaces in unprecedented detail.
In addition, the spacecraft, including the radar payload, has passed all of the preliminary checks performed by NASA and ISRO mission teams to ensure they are operating normally. The mission began raising the satellite to its operational orbit, 464 miles (747 kilometers, mean altitude), on Aug. 26.
The mission team anticipates having science-quality radar images in the coming weeks. Full science operations have been scheduled to begin about 90 days after launch.
The NISAR mission is the first to carry two SAR systems. The L-band radar transmits and receives signals at a 10-inch (24-centimeter) wavelength, enabling it to penetrate forest canopies and measure soil moisture, forest biomass, and the motion of land and ice surfaces. The S-band radar, which uses a 4-inch (10-centimeter) wavelength, is more sensitive to small vegetation and observing certain types of agriculture, grassland ecosystems, and moisture in snow. Both systems can collect data through clouds and precipitation, day and night.
The satellite will monitor most of Earth’s land and ice surfaces twice every 12 days, tracking changes in the planet’s forests, frozen surfaces, major infrastructure, and crust down to fractions of an inch. The lattermost is a key measurement in understanding how the land surface moves before, during, and after earthquakes, volcanic eruptions, and landslides.
More About NISAR
The NISAR mission is a partnership between NASA and ISRO spanning years of technical and programmatic collaboration. The successful launch and deployment of NISAR builds upon a strong heritage of cooperation between the United States and India in space. The data produced by NISAR’s two radar systems, one provided by NASA and one by ISRO, will be a testament to what can be achieved when countries unite around a shared vision of innovation and discovery.
The ISRO Space Applications Centre provided the mission’s S-band SAR. The U R Rao Satellite Centre provided the spacecraft bus. Launch services were through Satish Dhawan Space Centre. After launch, key operations, including boom and radar antenna reflector deployment, are being executed and monitored by the ISRO Telemetry, Tracking and Command Network’s global system of ground stations.
Managed by Caltech in Pasadena, NASA’s Jet Propulsion Laboratory in Southern California leads the U.S. component of the project. In addition to the L-band SAR, reflector, and boom, JPL also provided the high-rate communication subsystem for science data, a solid-state data recorder, and payload data subsystem. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the Near Space Network, which receives NISAR’s L-band data.
Quelle: NASA