US, India launch powerful Earth-monitoring satellite

WASHINGTON – A formidable new radar satellite jointly developed by the United States and India was launched on July 30, designed to track subtle changes in Earth’s land and ice surfaces and help predict both natural and human-caused hazards.

Dubbed Nisar – Nasa-Isro Synthetic Aperture Radar – the pickup truck-sized spacecraft blasted off at around 5.40pm local time (8.10pm Singapore time) from the Satish Dhawan Space Centre on India’s south-eastern coast, riding an Indian Space Research Organisation (Isro) Geosynchronous Satellite Launch Vehicle rocket.

Live streaming of the event showed excited schoolchildren brought to watch the launch and mission teams erupting in cheers and hugging.

Highly anticipated by scientists, the mission has also been hailed by US President Donald Trump and Indian Prime Minister Narendra Modi as a milestone in growing cooperation between the two countries.

“Congratulations, India!” Dr Jitendra Singh, India’s Science and Technology Minister, wrote on X, calling the mission a “game changer”.

“Our planet surface undergoes constant and meaningful change,” Dr Karen St Germain, director of US space agency Nasa’s earth science division, told reporters ahead of the launch.

“Some change happens slowly. Some happen abruptly. Some changes are large, while some are subtle.”

By picking up on tiny shifts in the vertical movement of the Earth’s surface – as little as 1cm – scientists will be able to detect the precursors to natural and human-caused disasters, from earthquakes, landsides and volcanoes to ageing infrastructure like dams and bridges.

“We’ll see land substance and swelling, movement, deformation and melting of mountain glaciers and ice sheets covering both Greenland and Antarctica, and of course, we’ll see wildfires,” added Dr St Germain, calling Nisar “the most sophisticated radar we’ve ever built”.

India in particular is interested in studying its coastal and nearby ocean areas by tracking yearly changes in the shape of the sea floor near river deltas and how shorelines are growing or shrinking.

Data will also be used to help guide agricultural policy by mapping crop growth, tracking plant health and monitoring soil moisture.

In the coming weeks, the spacecraft will begin an approximately 90-day commissioning phase, during which it will unfurl its 12m-wide radar antenna reflector.

Once operational, Nisar will record nearly all of Earth’s land and ice twice every 12 days from an altitude of 747km, circling the planet near the Poles rather than around the Equator.

Microwave frequencies

As it orbits, the satellite will continuously transmit microwaves and receive echoes from the surface.

Because the spacecraft is moving, the returning signals are distorted, but computer processing will reassemble them to produce detailed, high-resolution images.

Achieving similar results with traditional radar would require an impractically large 19km-wide dish.

Nisar will operate on two radar frequencies: L-band and S-band. The L-band is ideal for sensing taller vegetation like trees, while the S-band enables more accurate readings of shorter plants such as bushes and shrubs.

Nasa’s Jet Propulsion Laboratory and India’s Isro shared the workload, each building components on opposite sides of the planet before integrating and testing the spacecraft at Isro’s Satellite Integration and Testing Establishment in the southern Indian city of Bengaluru.

Nasa’s contribution came to just under US$1.2 billion (S$1.6 billion), while Isro’s costs were around US$90 million.

India’s space programme has made major strides in recent years, including placing a probe in Mars’ orbit in 2014 and landing a robot and rover on the Moon in 2023.

Mr Shubhanshu Shukla, a test pilot with the Indian Air Force, recently became the second Indian to travel to space and the first to reach the International Space Station – a key step towards India’s own indigenous crewed mission planned for 2027 under the Gaganyaan (“Sky craft”) programme. AFP