Anew radar satellite, launched last Wednesday, will track tiny shifts across almost all of Earth’s land and ice regions, measuring changes as slight as a centimetre. The satellite is a joint mission between Nasa and the Indian Space Research Organisation (Isro) and has been in the making for more than a decade.
The satellite lifted off from the Satish Dhawan Space Centre on India’s southeastern coast. About 20 minutes later, it was released into an orbit that passes close to the North and South poles at 747 kilometres above Earth’s surface.
The satellite is known as the Nasa-Isro Synthetic Aperture Radar mission, or Nisar. Nasa describes it as the most advanced radar system it has ever launched.
Because radar signals pass through clouds, they are ideal for monitoring Earth’s surface. “We can see through day or night, rain or shine,” said Paul Siqueira, a professor of electrical and computer engineering at the University of Massachusetts, Amherst, US, and the ecosystems lead for Nisar.
Deformations in Earth’s surface could provide early warning of impending natural disasters like volcanic eruptions and landslides. Measurements of ice sheets will reveal which areas are melting and which are growing through accumulated snowfall.
The data could also reveal flooded areas that would otherwise be hidden by bad weather, providing help to rescue teams.
The satellite could have helped after the earthquake off Russia’s Far East coast on July 30 and the subsequent tsunami.
The first 90 days will be devoted to deploying the spacecraft, including extending a 39-foot-wide gold-plated-mesh antenna reflector, which looks a bit like a giant beach umbrella, testing the instruments and performing initial observations. The primary mission is scheduled to last three years. If the spacecraft is still operational at that point, it will have enough propellant to continue for a couple more years.
The underlying technology, known as synthetic aperture radar, has been used in space
for decades.
What is different about Nisar is that it will bounce radar waves off almost all of Earth’s surface and will do so repeatedly — twice every 12 days. That will allow scientists to detect slight changes like slow-motion landslides and monitor places like Antarctica that are distant and inhospitable.
Nisar “will cover all of Antarctica for the first time,” said Eric Rignot, a glaciologist at Nasa’s Jet Propulsion Laboratory. “Conducting these measurements in the Antarctic would be nearly impossible for ground parties, because the continent is so vast.”
The Nisar data will track the motion of glaciers and ice sheets. “Scientists will be able to use this information in climate models to project what sea level would look like in the next few years, in the next decades, in the next century,” Rignot said.
Siqueira said Nisar could provide practical information closer to home, tracking the growth of crops. Microwaves bounce off water, so a field of healthy plants will appear brighter. “If a plant is desiccated, it’ll be more radar transparent,” Siqueira said.
The satellite includes two radar systems. One, built by Nasa, will transmit microwaves with a wavelength of 25 centimetres. The other, built by Isro, transmits 10-centimetre-long microwaves. For the study of vegetation, the shorter wavelengths will provide more detail about bushes and shrubs, while the longer wavelengths will provide a clearer picture of trees.
The amount of data will be almost overwhelming — terabytes every day. One challenge in designing the mission was figuring out how to send that much data to the ground and then how to process it.
Nasa’s share of the mission cost $1.2 billion (₹10,517.6 crore approximately), and Isro’s contribution was comparable.
NYTNS