All you need to know about NISAR's Radar Reflector Antenna, which arrived from NASA

The NASA-ISRO Synthetic Aperture Radar (NISAR) mission has reached a significant milestone with the recent arrival of its radar antenna reflector at the Indian Space Research Organisation's (ISRO) facility in Bengaluru. This crucial component, measuring approximately 39 feet (12 meters) in diameter, is designed to enhance the satellite's capabilities in monitoring Earth's vital signs, including ice mass changes, wetland health, and land deformation due to natural disasters.

As a collaborative effort between two of the world's leading space agencies, NISAR promises to revolutionize our understanding of the planet. After arriving in Bengaluru from NASA on a C-130 cargo jet, the reflector was sent to the ISRO's Spacecraft Integration and Test Establishment for reintegration with the NISAR spacecraft in preparation for further testing.

The NISAR reflector is shaped like a drum and is one of NASA’s contributions to this joint project. By helping focus the transmitted and received microwave signals to and from Earth’s surface, the reflector allows NISAR to scan almost all of the land and ice surfaces twice every 12 days, to gather scientific data. Before being flown to India, the reflector was at a specialised facility in California, where engineers applied reflective tape and took other precautionary measures to mitigate temperature increases that could have hampered the reflector’s deployment from its stowed (folded) configuration prior to beginning science operations.

“NISAR observations will assist civilization by allowing researchers across the world to better comprehend changes in our planet’s surface, including ice sheets, glaciers and sea ice. It will also record changes in its forest and wetland ecosystems, as well as movement and deformation of our planet’s crust from earthquakes, landslides and volcanic activity. NISAR’s global and rapid coverage will provide new chances for disaster response, generating data to aid in damage mitigation and assessment, as well as observations before and after disasters in short time frames,” explained space and aerospace expert Girish Linganna.

NISAR has two Synthetic Aperture Radars (SARs) on board: an L-band (L-SAR) and an S-band (S-SAR). It will be the first satellite to use two separate radar frequencies. The SAR technique can pierce clouds and work in darkness, allowing continuous surveillance regardless of weather conditions. As a result, the L-SAR will be utilized to monitor landscape topography and densely forested areas. Higher S-band frequencies will be utilized to monitor soil moisture, especially in the polar regions, because they are less affected by the ionosphere.

Both devices will cover a distance of 242 km. L-SAR can handle 1.25 GHz frequencies with a spatial resolution of 3 - 48 metres, whereas S-SAR can handle 3.2 GHz frequencies with a resolution of 3 - 24 metres. NISAR will be in a sun-synchronous orbit at 747 km altitude and 98.4° inclination. It will last 100 minutes and repeat every 12 days.

“NISAR employs a customised version of ISRO’s I3K spacecraft bus, which connects to a 9-metre-long radar antenna boom (a lengthy structure that holds and places the antenna away from the main satellite body), which supports a 12-metre-wide radar antenna reflector. Simply put, the spacecraft bus serves as the primary structure or ‘body’ that transports all of the mission equipment. The boom keeps the radar reflector properly positioned to scan wide portions of Earth’s surface from space, allowing the satellite to collect comprehensive data for scientific research,” said Linganna.

NASA is providing the L-Band SAR payload, while ISRO is contributing the S-Band SAR payload. Both radar systems will share a large, foldable antenna that opens up to about 12 metres in diameter. Along with this, NASA will also supply key engineering equipment for the mission. This includes a system to manage and store data, a high-speed data transmission setup, GPS receivers for navigation and a solid-state recorder to store information.

“NISAR will provide insights into how climate change impacts ecosystems and ice sheets, particularly in regions like Antarctica and Greenland. The satellite's advanced radar technology will allow scientists to monitor changes in ice thickness and movement, providing invaluable data for climate models. The satellite's rapid coverage capabilities will aid in assessing and mitigating damage from natural disasters like earthquakes, landslides, and flooding. By providing timely data on ground deformation and land use changes, NISAR can help emergency responders make informed decisions during crises,” observed Srimathy Kesan, founder and CEO of Space Kidz India, which is into design, fabrication and launch of small satellites, spacecraft and ground systems.

In addition to this, NISAR will monitor forest and wetland ecosystems, contributing valuable data for biodiversity conservation efforts.

Understanding the health of these ecosystems is essential for sustainable development and resource management. NISAR will also measure changes in groundwater levels, which is crucial for agricultural planning and water resource management in India and beyond.

The integration of NISAR's radar reflector at ISRO's Bengaluru facility not only signifies a technological advancement but also presents substantial economic benefits for India.

“The project has already generated employment opportunities within ISRO and related sectors. As the mission progresses towards launch in early 2025, further job creation is expected in engineering, research, and operational roles. The collaboration is likely to involve thousands of professionals across various disciplines, from software development to satellite operations. Collaborating with NASA provides Indian scientists and engineers exposure to advanced technologies and methodologies, enhancing their skill sets and fostering innovation. Training programmes associated with the mission will equip local talent with cutting-edge skills that can be applied across multiple sectors,” added Kesan.

Successfully executing such a high-profile international mission elevates India's status in global space exploration and Earth observation initiatives. It positions India as a key player in addressing global challenges related to climate change and environmental monitoring. The technological advancements derived from this mission could lead to innovations that benefit various industries, including agriculture, urban planning, and disaster management. By leveraging satellite data for better decision-making, India can boost its economic resilience against climate-related challenges.

“In addition to its scientific and economic implications, the NISAR mission also offers educational opportunities for students in both countries. NASA Administrator Nelson plans to engage with students during his visit to discuss science, technology, engineering, and mathematics (STEM) education. This interaction aims to inspire the next generation of scientists and engineers who will play crucial roles in tackling global challenges related to climate change and sustainability,” remarked Kesan.