In a significant step for global Earth observation, seventeen days after the launch of the NISAR satellite from southeastern India, key scientific hardware has successfully deployed in orbit. This is a giant antenna reflector, with an impressive diameter of 12 meters, which is part of the NISAR (NASA-ISRO Synthetic Aperture Radar) mission, a joint venture between the U.S. space agency NASA and the Indian Space Research Organisation (ISRO).

This drum-shaped reflector, which until now was carefully stowed like an umbrella, has successfully unfolded in low Earth orbit after the 9-meter support boom on which it is mounted was deployed and fixed. Launched on July 30 from India's Satish Dhawan Space Centre on the southeastern coast of India, the NISAR satellite represents a revolutionary tool for monitoring a range of vital geophysical and environmental changes on our planet. Its primary task includes the precise measurement of the movement of ice sheets and glaciers, land deformation caused by earthquakes, volcanic activity, and landslides, and changes in forest and wetland ecosystems, with an accuracy down to a fraction of a centimeter. The data it will collect will be of invaluable importance for decision-makers in various sectors, from natural disaster response and infrastructure monitoring to agriculture and resource management.

Karen St. Germain, director of the Earth Science Division at NASA Headquarters in Washington, highlighted the importance of this achievement. "The successful deployment of NISAR's reflector marks a significant milestone in the satellite's capabilities. From innovative technology to research and modeling, and to providing scientific data that helps in decision-making, the data that NISAR will collect will have a great impact on how global communities and stakeholders improve infrastructure, prepare for and recover from natural disasters, and maintain food security," said St. Germain.

A Technological Marvel in Orbit: How NISAR's Radar Works

The NISAR mission team at NASA's Jet Propulsion Laboratory (JPL), in collaboration with colleagues in India, performed the deployment of the satellite's radar antenna reflector on August 15, 2025. This reflector, about 12 meters in diameter, is crucial for directing microwave pulses from NISAR's two radars toward Earth and receiving the return signals. The mission carries the most sophisticated radar systems ever launched as part of a NASA mission, representing a significant leap forward in Earth observation technology.

For the first time, a satellite combines two synthetic aperture radar (SAR) systems: an L-band system and an S-band system. The L-band system, with its longer wavelengths, has the ability to penetrate clouds and dense forest canopy, making it ideal for monitoring changes in vegetation, forest biomass, and ice thickness. On the other hand, the S-band system, while also penetrating clouds, is more sensitive to light vegetation and moisture in snow, providing more detailed information about surface changes and soil moisture. The reflector plays a key role for both systems, which is why its successful deployment is such a significant milestone for the entire mission.

Phil Barela, NISAR project manager at NASA's Jet Propulsion Laboratory in Southern California, who managed the U.S. part of the mission and provided one of the two radar systems on NISAR, emphasized the complexity and importance of this achievement. "This is the largest antenna reflector ever deployed for a NASA mission, and of course, we were eagerly anticipating that the deployment would go well. It is a critical part of NISAR's Earth science mission and took years to design, develop, and test to be ready for this big day," said Barela. "Now that we have launched, we are focusing on fine-tuning it to start delivering transformative scientific data by late fall of this year."

The Antenna's "Blooming" Process: An Engineering Feat

The process of deploying the reflector, called "blooming," represented an exceptional engineering feat. The reflector, weighing about 64 kilograms, consists of a cylindrical frame made of 123 composite support rods and a gold-plated wire mesh. On August 9, the satellite's boom, which was tightly attached to the main body of the satellite, began to unfold joint by joint, until it was fully extended about four days later. The reflector assembly was mounted at the end of that boom.

Then, on August 15, small explosive bolts holding the reflector assembly in place were activated, allowing the antenna to begin the "blooming" process – its unfolding by releasing the tension stored in its flexible frame while it was stowed like an umbrella. Subsequent activation of motors and cables then pulled the antenna into its final, fixed position. The NISAR teams at JPL, along with colleagues at ISRO's facilities in India, monitored the entire process. The reflector unfolded from its initial 0.6 meters in its stowed configuration to its full size of 12 meters in just 37 minutes, a testament to the precision and reliability of the engineering design.

To image the Earth's surface with a pixel resolution of about 10 meters, the reflector was designed with a diameter roughly equal to the length of a school bus. Using SAR processing, the NISAR reflector simulates a traditional radar antenna that would need to be 19 kilometers long for the mission's L-band instrument to achieve the same resolution. This technique allows for achieving exceptionally high resolution with a relatively small physical antenna in space.

Synthetic Aperture Radar (SAR): A Window into Earth's Changes

Paul Rosen, NISAR project scientist at JPL, explained the principle of synthetic aperture radar. "Synthetic aperture radar, in principle, works like a camera lens, which focuses light to create a sharp image. The size of the lens, called the aperture, determines the sharpness of the image," Rosen said. "Without SAR, space radars could generate data, but the resolution would be too coarse to be useful. With SAR, NISAR will be able to generate high-resolution images. Using special interferometric techniques that compare images over time, NISAR allows researchers and data users to create 3D 'movies' of the changes happening on the Earth's surface."

This ability to track subtle changes in three dimensions is crucial for understanding complex geological processes. For example, NISAR will be able to detect millimeter-scale ground shifts before and after earthquakes, monitor the deformation of volcanic domes that may indicate upcoming eruptions, and map landslides and ground subsidence caused by groundwater extraction or permafrost thaw. Such data is invaluable for risk assessment and planning protective measures.

In addition to geological applications, NISAR will provide unprecedented insights into the global water and carbon cycles. By tracking changes in forest biomass, the satellite will help assess carbon storage and the impact of deforestation. By measuring soil moisture and changes in wetlands, it will contribute to a better understanding of hydrological processes and the impact of climate change on water resources. Its ability to penetrate clouds and vegetation ensures continuous data collection, regardless of weather conditions, which is crucial for monitoring dynamic processes.

Decades of Development and International Collaboration

The NISAR satellite represents the culmination of decades of development of space-based radar systems at JPL. Starting in the 1970s, JPL operated the first SAR satellite for Earth observation, Seasat, launched in 1978, as well as the Magellan mission, which used SAR to map the cloud-covered surface of Venus in the 1990s. This rich history and experience in developing radar technology in space laid the foundation for the ambitious NISAR mission.

The NISAR mission is a partnership between NASA and ISRO that encompasses years of technical and programmatic collaboration. The successful launch and deployment of NISAR builds on a strong legacy of cooperation between the United States and India in space. The data produced by NISAR's two radar systems, one provided by NASA and the other by ISRO, will be a testament to what can be achieved when countries unite around a common vision of innovation and discovery. This collaboration is not only technically impressive but also diplomatically significant, showing how scientific research can bridge borders and foster global cooperation for the benefit of all humanity.

ISRO's Space Applications Centre provided the mission's S-band SAR, while the U R Rao Satellite Centre provided the satellite bus. Launch services were provided through the Satish Dhawan Space Centre. After launch, key operations, including the deployment of the radar antenna boom and reflector, are performed and monitored through the global system of ground stations of ISRO's Telemetry, Tracking and Command Network.

JPL, which is managed by Caltech in Pasadena, leads the U.S. component of the project. In addition to the L-band SAR, reflector, and boom, JPL also provided a high-rate communication subsystem for science data, a solid-state data recorder, and a payload data subsystem. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the Near Space Network, which receives NISAR's L-band data. This division of responsibilities and expertise between the two leading space agencies ensures the robustness and success of the mission, promising an abundance of new data that will help us better understand and protect our planet.

NISAR's data is expected to have a wide range of applications. In the area of disasters, it will enable rapid damage assessment after earthquakes, floods, and volcanic eruptions, aiding humanitarian efforts and recovery planning. For infrastructure, it will be able to detect subtle subsidence of bridges, dams, and pipelines, allowing for preventive maintenance and disaster avoidance. In agriculture, data on soil moisture and crop health will help farmers optimize irrigation and fertilization, increasing yields and reducing resource waste. Finally, NISAR will be a key tool in global efforts to monitor and mitigate climate change, providing precise data on changes in glaciers, sea level, and ecosystems that are vital for modeling future scenarios and developing adaptation strategies.