New phase: On the NISAR mission

The GSLV-F16 mission lifted off from Sriharikota on July 30, placing the NASA ISRO Synthetic Aperture Radar (NISAR) satellite into a sun synchronous orbit. The ascent capped a decade-long bilateral effort and opened a new phase in global earth observation cooperation. NISAR is a 2.8-tonne observatory that combines a NASA-built L-band radar with an ISRO-made S-band radar — also a first. They allow NISAR to detect surface changes measuring only a few centimetres, even through clouds and vegetation. NISAR will supply freely accessible data on ground deformation, glacier flow, biomass, land use changes, and sea ice dynamics. As its dawn-dusk orbit repeats every 12 days, its radars will be able to revisit the same point under nearly identical lighting conditions. This geometry, coupled with a duty cycle exceeding 50% in the L-band, has been designed to yield closely spaced time series observations that can quantify geological processes. Indeed, its various engineering firsts lead up to NISAR’s unusually broad science agenda: map mangrove extent, urban subsidence, crop-soil interactions, and calving rates in polar ice shelves in a single orbital cycle. Its data could help support the Sendai Framework on reducing disaster risk and refine IPCC models.

For ISRO, flying a flagship payload on the GSLV Mk II rocket is notable for a vehicle once dubbed “naughty boy” for its early-career setbacks. The ISRO-NASA partnership would also have eased technology transfer between the two countries. Developing the S-band radar would have demanded tighter tolerances in radiofrequency electronics, thermal stability, and data throughput than previous Indian satellites. From a diplomatic standpoint, the launch confirms that India can be trusted with high-value hardware and demanding integration schedules, although it is still learning to shape joint missions on equal terms. The 12-metre reflector, the Ka band downlink, and much of the flight software stack were imported, and the key design reviews were led by NASA. Achieving parity will require larger domestic investments in advanced materials, deep-space communications, and systems engineering plus earlier Indian involvement in framing the scientific agenda of future multilateral missions. NISAR’s data downlink rate also presents a challenge. ISRO must expand its Ka-band ground network, automate cloud-based processing, and release analysis-ready products within hours if state agencies are to make timely use of the data. Sustaining the time-wise data will also depend on authorising follow-on SAR spacecraft before 2030 and finalising data-sharing rules that encourage private analytics while protecting sensitive scenes. Addressing these gaps will determine how fully NISAR’s potential is realised in India.