The drum-shaped antenna reflector on the Indian Space Research Organization (ISRO) and NASA's NISAR (NASA-ISRO Synthetic Aperture Radar) satellite mission successfully unfurled in low Earth orbit, spanning 39 feet (12 meters). Until the 30-foot (9-meter) boom supporting it could be extended and secured, the reflector had been stored umbrella-like.
NISAR, which ISRO launched on July 30 from the Satish Dhawan Space Centre on the southeast coast of India, will monitor changes in forest and wetland ecosystems down to a fraction of an inch, the movement of ice sheets and glaciers, and land deformation from earthquakes, volcanoes, and landslides. Decision-makers in a variety of domains, including agriculture, infrastructure monitoring, and disaster response, will also benefit from it.
Karen St. Germain, director of the Earth Science Division at NASA Headquarters in Washington, stated, "The successful deployment of NISAR's reflector represents a significant milestone in the capabilities of the satellite." “The data NISAR is poised to collect will have a significant impact on how global communities and stakeholders improve infrastructure, prepare for and recover from natural disasters, and maintain food security, from cutting-edge technology to research and modeling to delivering science to help inform decisions.”
The most advanced radar systems ever launched as part of a NASA mission are carried by the mission. In the first, the satellite combines two synthetic aperture radar (SAR) systems: an S-band system that is more sensitive to light vegetation and moisture in snow, and an L-band system that can see through clouds and the forest canopy. The hardware's successful deployment is a major milestone because the reflector is essential to both systems.
Naturally, we wanted the deployment to go smoothly because this is the biggest antenna reflector ever used for a NASA mission. Phil Barela, NISAR project manager at NASA's Jet Propulsion Laboratory in Southern California, which oversaw the U.S. portion of the mission and supplied one of the two radar systems aboard NISAR, stated, "It's a crucial component of the NISAR Earth science mission and has taken years to design, develop, and test to be ready for this big day." "We are concentrating on optimizing it now that we have launched in order to start delivering transformative science by late fall of this year."
The reflector, which weighs roughly 142 pounds (64 kilograms), has a gold-plated wire mesh and a cylindrical frame composed of 123 composite struts. One joint at a time, the satellite's boom, which had been tucked near its main body, began to unfold on August 9 and was fully extended around four days later. At the end of the boom is the reflector assembly.
A procedure known as the "bloom"—the antenna's unfurling by the release of tension stored in its flexible frame while stowed like an umbrella—was then made possible on August 15 by the firing of tiny explosive bolts that held the reflector assembly in place. The antenna was subsequently drawn into its ultimate, locked position by the subsequent activation of motors and cables.
The reflector was made with a diameter roughly equal to the length of a school bus in order to picture the Earth's surface down to pixels that are about 30 feet (10 meters) square. NISAR's reflector uses SAR processing to mimic a conventional radar antenna, which would need to be 12 miles (19 kilometers) long for the mission's L-band instrument to have the same resolution.
In theory, synthetic aperture radar functions similarly to a camera's lens, which concentrates light to provide a crisp image. According to Paul Rosen, NISAR's project scientist at JPL, the aperture, or lens size, controls how crisp the image is. Spaceborne radars could produce data in the absence of SAR, but the resolution would be too imprecise to be of much use. NISAR will be able to produce high-resolution imagery using SAR. Researchers and data users can produce 3D movies of changes occurring on the Earth's surface by using NISAR's unique interferometric techniques, which compare images across time.
The result of decades of space-based radar work at JPL is the NISAR satellite. Beginning in the 1970s, JPL oversaw the launch of Seasat, the first Earth-observing SAR satellite, in 1978. In the 1990s, Magellan employed SAR to study Venus' cloud-covered surface.
NASA and ISRO have been working together on the NISAR mission for many years, both technically and programmatically. The United States and India have a long history of space collaboration, which is strengthened by the successful launch and deployment of NISAR. The information generated by NISAR's two radar systems—one supplied by ISRO and the other by NASA—will serve as evidence of what is possible when nations come together with a common goal of innovation and exploration.
The S-band SAR used in the flight was supplied by the ISRO Space Applications Centre. The spacecraft bus was donated by the U R Rao Satellite Centre. Satish Dhawan Space Centre provided the launch services. Following launch, the ISRO Telemetry, Tracking and Command Network's worldwide network of ground stations is carrying out and monitoring critical tasks, including as the deployment of boom and radar antenna reflectors.
JPL is in charge of the U.S. portion of the project, which is run by Caltech in Pasadena. JPL also supplied the payload data subsystem, a solid-state data recorder, and the high-rate communication subsystem for science data in addition to the L-band SAR, reflector, and boom. NISAR's L-band data is sent to the Near Space Network, which is run by NASA's Goddard Space Flight Center in Greenbelt, Maryland.
