NEW DELHI :
Nasa chief Jim Bridenstine on Tuesday expressed concern on India’s anti-satellite test operation, calling it a “terrible thing" and saying debris from it endangered the International Space Station (ISS) and future space flights.
“It is a terrible, terrible thing to create an event that sends debris at an apogee that goes above the ISS. That kind of activity is not compatible with the future of human spaceflight," Jim Bridenstine, Nasa administrator, was quoted saying by AFP news agency.
“It’s unacceptable and Nasa needs to be very clear about what its impact to us is."
India’s 27 March test added enormous punch to the country’s offensive defence capability and established its credentials as a “space power." India is the fourth country after the US, Russia and China to demonstrate the capability to shoot down a satellite in space, but in the lower orbit.
A day after the test, the US State Department said it would “continue to pursue shared interests in space and scientific and technical cooperation including collaboration in safety and security in space"—while expressing concern over space debris.
In his comments, Bridenstine, who was speaking at a town hall meeting of the US space agency, said India’s A-SAT action had created 400 pieces of debris, posing a potential risk to astronauts aboard the ISS. Out of these 400 pieces of debris, 60 are being tracked and 24 of them are above the highest point of the ISS.
As per its estimate, the risk of a collision with ISS has increased by 44% over last the 10 days.
“The International Space Station is still safe. If we need to manoeuvre it, we will. The probability of that I think is low. But at the end of the day we have to be clear also that these activities are not sustainable or compatible with human spaceflight," he said.
There was no official reaction from any Indian government department, including the space agency Isro and the ministry of external affairs.
However, scientists agreed that space debris posed a danger to all satellites.
“Space debris is a big problem, not only for the ISS, but for all existing satellites and the ones to be sent in future. But, there is already so much space junk from various missions carried by countries all over the world, that India’s A-SAT test will be just a small addition to that," said Prof Nirupam Roy, Department of Physics, Indian Institute of Science (IISc), Bengaluru.
Scientists argued that India’s A-SAT test was not ‘unique’ in terms of the space junk it created, as the US, Russia and China had already tested their anti-satellite weapons in space.
As per Nasa data, there are already more than 20,000 pieces of debris larger than a softball orbiting the earth. There are 500,000 pieces the size of a marble or larger, of which nearly 3,000 were added in 2007, when China fired a missile to destroy and old weather satellite.
The satellite destroyed by the Defence Research and Development Organization (DRDO) on 27 March was a microsatellite, at an altitude of 300km, which is much lower than the orbit in which the ISS travels—an altitude of 321 and 402km.
DRDO maintains that debris left behind in space will get pulled down by earth’s gravity and burnt down by friction in the earth’s atmosphere. But this process could take weeks.
“If the ISS is moving at an orbital speed of 25,200km/hour and there is small space debris at 28,163km/hour, so the kinetic energy which it can impart to the ISS runs into thousand million times which is big enough to damage a satellite or a spacecraft. The momentum is huge," said Roy.
Another senior scientist, who did not want to be named said:
“Any satellite that even India intends to send into space will have to pass through this belt where space debris is moving around. Unlike a satellite, the trajectory of debris, which usually travels at a speed of at 28,163 km/hour is hard to predict. So one has to be careful about such missions."
As most of the information regarding the mission remains classified, it is difficult to ascertain how the target satellite was destroyed and how its pieces broke apart in different directions and their trajectory. How long it will take for the pieces to burn up would depend on the trajectory of the broken pieces, information which remains with DRDO.
India is gearing up for its most ambitious space mission as yet–Gaganyaan, where three Indians will travel into space aboard its biggest rocket, Geosynchronous Satellite Launch Vehicle Mark III (GSLV Mk III). The mission is set to take off by December, 2021.