Exclusive | NASA + ISRO + One Vision: Project Director Chaitra Rao Tells The NISAR Story

Bengaluru: NASA–ISRO Synthetic Aperture Radar (NISAR), a joint Earth observation mission of the US space agency NASA and the Indian space agency ISRO, launched on July 30, 2025, at 5:40 PM IST aboard ISRO’s GSLV-F16 from Sriharikota. Equipped with the world’s first dual-frequency SAR—the L-band radar from NASA and the S-band radar from ISRO, this advanced satellite can capture all-weather, day-and-night high-resolution images with centimetre-level precision, mapping nearly all of Earth's land and ice-covered regions every 12 days. Its data will play a vital role in monitoring climate change, natural disasters, and agriculture.

Chaitra Rao, the project director of the NISAR mission, aided in developing the entire satellite and led its configuration, building, integration, testing, and launch operations in collaboration with NASA. Talking to ETV Bharat, she shared her experience and said that one of her most memorable moments was the successful launch, marking the beginning of NISAR’s journey in space.

NISAR mission significance and dual-band radars

Following the launch, Rao confirmed the successful deployment of the solar panel and NISAR’s transition into the commissioning phase. Chaitra Rao said, "The most challenging milestone was achieved on August 15th with the deployment of the multi-stage 9m boom and 12m reflector."

When asked about the NISAR mission and its significance, Rao said that NISAR is a truly collaborative mission jointly developed by NASA and ISRO. Its uniqueness lies in carrying both dual-frequency Synthetic Aperture Radars—NASA-JPL’s (Jet Propulsion Laboratory) L-band and ISRO’s S-band—on a single satellite platform, a complex integration effort that took over a decade of development and testing.

The two radars were developed independently—the L-band radar at Pasadena, California, and the S-band radar at the Space Applications Centre, Ahmedabad. Their development was carried out in different phases, covering design, fabrication, and testing. Eventually, both radars were brought together for integration onto a common structure, where they now share a 12-meter deployable reflector to capture wide-area imaging, she explained.

NISAR showcases Indian space engineering on a global stage

"From the launch of Aryabhata in 1975 to the 50-year completion milestone we celebrated in April 2025, India’s space program has come a long way," Rao said. "Over the years, technology has advanced by leaps and bounds, marking significant progress and growth.”

She stated that NISAR showcases Indian space engineering on a global stage by incorporating cutting-edge technologies such as a high-data-rate Ka-band transmitter and advanced radar systems. The satellite is expected to generate nearly 80 terabytes of data each day, which demands a powerful downlink system. To meet this challenge, a Ka-band data link capable of transmitting at an impressive almost 3 gigabytes per second was incorporated.

NISAR also integrates some of the finest and most advanced subsystems to ensure top-quality performance, Rao said, adding that the first-time used sweep SAR technique will capture a 240 km-wide swath with unprecedented detail. Typically, high resolution comes at the cost of coverage, and a wide swath reduces resolution, but NISAR overcomes this trade-off, delivering both large-area coverage and high-resolution imagery simultaneously, she explained.

NISAR's crucial role in addressing calamities

Rao said that India’s diverse topography and tropical location make it vulnerable to natural disasters like floods and droughts. NISAR will play a crucial role in addressing these calamities by providing valuable data to study climate change, track soil moisture variations over time, identify drought-prone regions, and monitor carbon footprints, as well as deforestation patterns.

A 5 Year Mission with more than 200 Imaging Modes

Talking to ETV Bharat, Chaitra Rao revealed that the NASA-ISRO joint science teams have laid out a three-and-a-half-year pre-defined imaging plan, which is tailored for different terrains and scientific needs, with the radars operating either collaboratively or independently.

In picture: NISAR project director Chaitra Rao (ETV Bharat)

"The S-band, with lower penetration, is suited for surface-level studies such as crop and canopy assessment, forest mapping, and deforestation monitoring," she explained. "The L-band, with deeper penetration, provides insights into vegetation, subsurface layers, land deformation, and subsidence. Combining data from both radars offers a more comprehensive picture."

NISAR and real-time monitoring

When asked if NISAR data can be used for real-time disaster monitoring, such as earthquakes, landslides or floods, Rao mentioned that while NISAR can aid in real-time disaster monitoring, its 12-day repeat cycle makes it challenging for immediate responses. The satellite captures a swath of 240 km at a time, so it can record a disaster only if it is passing over the affected area. However, its data is highly valuable for disaster assessment—such as mapping flooded regions, identifying impacted vegetation, and guiding evacuation efforts. The goal is to cover the entire globe in 12 days, but coverage of a specific disaster depends on its timing and location.

Mission challenges

Continuing on the challenges, Rao noted that the major hurdles during the mission were finalising technical interfaces and managing cultural differences between the organisations.

Rao said ISRO and JPL followed a parallel development approach, each building its onboard computer to simplify interface finalisation. Later, challenges arose in handling faults—how one system would communicate if the other failed. To address this, both teams incorporated fault detection, isolation, and recovery features. Secondly, engineers from ISRO travelled to the US to support radar integration, while NASA-JPL teams came to India when the integrated system was brought back for satellite assembly.

Unlike typical ISRO projects that take 5–6 months of integration and testing, NISAR’s satellite integration alone stretched to 10–11 months, with nearly another year devoted to IRIS integration. By 2023, however, the teams had completed all phases and were ready for launch.

Speaking about the NASA–ISRO collaboration, Rao noted that while the two agencies bring different cultural perspectives and problem-solving approaches, the shared mission goals helped align their efforts. Despite initial differences in thought, the common objective brought both teams together, ensuring smooth progress toward the mission’s success.

She also highlighted the challenges of coordinating work across different continents and time zones with NASA, noting that meetings were often scheduled in the early mornings or late evenings to accommodate the 12-hour time difference. Over the past 5–6 years, the team worked tirelessly, day and night, to meet the timelines.

NISAR Data: A global resource for science, collaboration, and humanity

Chaitra Rao emphasised the importance of the joint mission's unique capabilities and urged the science community to utilise and build upon the data generated, making it freely available for further applications. The data will greatly benefit humanity in the coming years by providing new insights. As a collaborative effort, the mission also sets the stage for greater inclusivity. With a 12-day repeat cycle, even minor changes in any region can be clearly tracked.

Data availability: NISAR's data on Earth’s ecosystems and ice masses will be publicly available on ISRO’s Bhoonidhi and NASA cloud platforms.