The countdown for the NISAR satellite mission started at 2.10 p.m. on Tuesday (July 29, 2025). The Geosynchronous Satellite Launch Vehicle (GSLV) with the 2,392-kg satellite is scheduled to lift off from the second launch pad of the Satish Dhawan Space Centre in Sriharikota at 5.40 p.m. on Wednesday (July 30, 2025).

About 19 minutes after lift-off, the GSLV-F16 rocket will inject the NISAR satellite into a 743-km sun-synchronous orbit. The NISAR satellite — NASA-ISRO Synthetic Aperture Radar satellite — will scan the Earth and provide all-weather, day-and-night data at 12-day intervals, and enable a wide range of applications.

It is the first joint satellite of the Indian Space Research Organisation (ISRO) and National Aeronautics and Space Administration (NASA).

Senior NASA officials said that working with the ISRO on the mission has strengthened their relationship.

The Director of Earth Science, NASA Headquarters, Karen St. Germain said, “Building a satellite on opposite sides of the world during a global pandemic was really hard, but it strengthened our relationship with ISRO. The collaboration, the cooperation, information sharing, and, frankly, joint learning between our two agencies is a foundation that we look forward to continuing to build upon.”

She added that NISAR is a model for the next generation of Earth observation capability.

“India built the spacecraft bus and the S-band radar and is providing the launch vehicle, launch services, and satellite mission operations. NASA’s Jet Propulsion Laboratory (JPL) built the L-band radar and the mission’s radar reflector and boom. NASA is also providing a high-rated communications subsystem for science data, GPS receivers, a solid-state recorder, and the payload data subsystem,” she added.

Phil Barela, NISAR project manager, JPL, said that the two space agencies learnt a lot from each other in the last decade.

“We have been at this for over a decade with our partner, ISRO, and it has been a phenomenal journey. The amount that we have learned from each other during this period has just been phenomenal,” Mr. Barela said.

He added that during the height of COVID-19 pandemic, around 65 ISRO engineers visited JPL to work on the integration and conduct tests.

“Over the last two-and-a-half years, NASA has sent out over 175 engineers to ISRO’s facilities to keep the integration and tests going and get us ready for where we stand today and ready for launch. It has been a wonderful journey. I’m anticipating a lot of very happy people, not only in the U.S., but also in India,” he added.

The NISAR mission, a collaborative effort between ISRO and NASA, will demonstrate Indian space engineering capabilities for Earth observation on a global scale, a top scientist has said.

The NISAR (NASA-ISRO Synthetic Aperture Radar) is a global mission, and its data will be accessible for download worldwide by users, said Radha Krishna Kavuluru, former Ground Segment Engineer and Ex-Project Manager of NISAR.

ISRO is set to launch the NISAR satellite aboard the GSLV-Mk II rocket from Sriharikota, Andhra Pradesh, on July 30 at 5:40 p.m. The GSLV-F16 marks the 18th flight of India’s Geosynchronous Satellite Launch Vehicle and the 9th operational flight with an indigenous cryogenic stage.

The countdown is expected to commence later on Tuesday (July 29, 2025), ISRO sources said.

This mission is the first GSLV launch to achieve a Sun-Synchronous Polar Orbit. The 51.7-meter-tall, three-stage rocket will lift off from the second launch pad, approximately 135 km east of Chennai. About 19 minutes after launch, the satellite is expected to be placed into its designated orbit.

Explained | What are ISRO and NASA aiming to achieve with the NISAR satellite?

Elaborating on the mission, Mr. Kavuluru explained that NASA provides the L-Band, while ISRO contributes the S-Band for the Synthetic Aperture Radar, enabling the collection of vast amounts of data.

“The satellite will transmit extensive data covering the Earth, including Antarctica, the North Pole, and oceans,” he told PTI.

Highlighting the mission’s significance, Mr. Kavuluru noted that unlike earlier ISRO observation satellites such as the Resourcesat and RISAT series, which could capture images globally but were operationally focused on India and surrounding regions, NISAR will collect data across the entire globe for operational use.

“This data will be extensively utilised by governments and commercial entities worldwide,” he said.

“NISAR is one of the key missions that will garner large-scale operational user feedback from across the globe,” Mr. Kavuluru emphasised.

“All countries will leverage NISAR data for various applications, showcasing the strength of Indian space engineering. This is the core importance of the mission,” he added.

Mr. Kavuluru underscored the mission’s importance as ISRO’s first major partnership with NASA for an Earth observation satellite. “This collaboration fosters significant technical exchange, with ISRO and NASA sharing insights into their respective planning and execution processes,” he said.

Mr. Kavuluru added that ISRO will process and make most of the data available as open-source, accessible to users globally. The satellite, which will cover the entire Earth every 12 days, will provide approximately 2.5 coverages per month and 10 coverages in 120 days.

“This will enable us to monitor seasonal changes, including forest dynamics, mountain shifts, and glacier movements in regions like the Himalayas and Antarctica,” he explained.

“This is a highly significant, high-value, and ambitious mission for ISRO,” Mr. Kavuluru remarked. The GSLV-F16/NISAR mission is designed for a lifespan of five years.

Ahead of the launch of the NASA-ISRO Synthetic Aperture Radar (NISAR) satellite scheduled for July 30, 2025, the ISRO on Monday (July 28, 2025) announced that the satellite had been mounted on a geosynchronous satellite launch vehicle (GSLV), and all systems of the rocket had been checked.

After lifting off from the second launch pad of the Satish Dhawan Space Centre in Sriharikota at 5.40 p.m. on July 30, 2025, the GSLV-F16 rocket will inject the NISAR satellite into a 743-km sun-synchronous orbit.

Explained | What are ISRO and NASA aiming to achieve with the NISAR satellite?

The NISAR satellite, weighing 2,392 kg, is a unique Earth observation satellite. It will be the first satellite to observe the Earth with a dual-frequency Synthetic Aperture Radar (SAR) — NASA’s L-band and ISRO’s S-band — both using NASA’s 12-metre unfurlable mesh reflector antenna, integrated with ISRO’s modified I3K satellite bus.

With a mission life of five years, NISAR will observe earth with a swathe of 242 km and high spatial resolution, using SweepSAR technology for the first time.

Day-and-night data

“The satellite will scan the entire globe and provide all-weather, day-and-night data at 12-day intervals, and enable a wide range of applications. NISAR can detect even small changes in the earth’s surface, such as ground deformation, ice sheet movement, and vegetation dynamics. Further applications include sea ice classification, ship detection, shoreline monitoring, storm characterisation, changes in soil moisture, mapping and monitoring of surface water resources, and disaster response,” the ISRO said.

The NISAR mission is broadly classified into different phases – launch, deployment, commissioning and science phases.

In the launch phase, the satellite will be launched by the GSLV-F16 launch vehicle, while in the deployment phase, a 12-metre reflector antenna will be deployed in orbit nine metres away from the satellite by a complex multistage deployable boom. This will be followed by the commissioning phase.

“The first 90 days after launch will be dedicated to commissioning, or in-orbit checkout, the objective of which is to prepare the observatory for science operations. Commissioning is divided into sub-phases of initial checks and calibrations of mainframe elements followed by JPL engineering payload and instrument checkout,” ISRO said.

The final science operations phase begins at the end of commissioning and extends till the end of NISAR’s five-year mission life.

“During this phase, the science orbit will be maintained via regular manoeuvres, scheduled to avoid or minimise conflicts with science observations. Extensive calibration and validation activities will take place,” ISRO said.