Seventeen days after NISAR’s launch from southeastern India, an essential piece of science hardware has unfurled in orbit.
Spanning 12 metres, 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 9-metre 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,” says Karen St Germain, director: Earth Science Division at NASA Headquarters. “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.”
NISAR mission team members at NASA JPL, working with colleagues in India, executed the deployment of the satellite’s radar antenna reflector on 15 August 2025. About 12 metres in diameter, the reflector directs microwave pulses from NISAR’s two radars toward Earth and receives the return signals.
Credit: NASA/JPL-Caltech
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,” says Phil Barela, NISAR project manager at NASA’s Jet Propulsion Laboratory in Southern California, which managed the US 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 64kg, the reflector features a cylindrical frame made of 123 composite struts and a gold-plated wire mesh. On 9 August, 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 15 August, 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 0,6 metres across in its stowed configuration to its full size, 12 metres, in 37 minutes.
NASA/JPL-Caltech
To image Earth’s surface down to pixels about 10 metres 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 19km 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,” says 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 techniques that 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.
Featured image: The NISAR satellite uses a radar antenna reflector that’s 12 metres 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.
NASA/JPL-Caltech