WASHINGTON/ NEW DELHI: Indian space and missile experts have rubbished the claims of Nasa 's chief, who on Monday called India's anti-satellite (A-Sat) test a "terrible, terrible thing" and said debris from the test could endanger astronauts aboard the International Space Station (ISS).

In arguments reminiscent of the American reaction to India's nuclear test, the US space agency bore down on India with a vehemence not reflected in the more measured response from the Trump administration. "That is a terrible, terrible thing to create an event that sends debris at an apogee that goes above the International Space Station," Nasa administrator Jim Bridenstine said at a townhall meeting of the agency's employees.

Former DRDO director general V K Saraswat said the statement was a typical American response to India's progress. "Pieces of debris from the missile-satellite collision do not have enough velocity to survive in space for long. The debris, generated at an altitude of 300km, will ultimately fall and burn out in Earth's atmosphere," Saraswat told TOI.

Saraswat slammed Nasa for singling out India's A-Sat test on the question of space debris .

"Lakhs and lakhs of space debris are already orbiting in space. Aren't they posing a danger to ISS? Every year, 190 satellites of varying sizes are launched into the low-earth orbit and this number is only going to grow. Each satellite launch creates a lot of debris. So talking about a little debris from India's test is meaningless," he said.

Bridenstine claimed that Nasa's analysis showed that the threat to ISS from possible collisions had increased by 44%, without explaining how he came up with the number.

"We are learning more and more every hour about orbital debris created from this anti-satellite test. Where we were last week, from an assessment that comes from Nasa experts... was that the risk to ISS was increased by 44%. The risk, and I am talking about small debris impact to the ISS, went up 44% over a period of 10 days," he said.

"We have identified 400 pieces of orbital debris from that one event (the Indian test)," Bridenstine explained gravely. "Now, all of it cannot be tracked. What we are tracking right now, objects big enough to track... 10cm or bigger... about 60 pieces have been tracked. They have got tracking number... Out of those 60, we know that 24 of them are going above the apogee of ISS."

India has questioned how 400 pieces of orbital debris generated by the test posed a greater hazard than the tens of thousands of fragments produced by US, Chinese and Russian tests.

Bridenstine, however, also acknowledged that the debris from the Indian test was much smaller compared to that created by a similar test by China in 2007, which generated thousands of pieces, and that no harm was likely to be done to the ISS or the astronauts.

"While the risk went up 44%, our astronauts are still safe. The ISS is still safe. If we need to manoeuvre it, we will. But the probability of that, I think, is low," he said, adding, "The good thing is that it is low enough and over time this will all dissipate. You go back in time, 2007, (the) direct ascent anti-satellite test by the Chinese, a lot of the debris is still in orbit."

The ISS orbits Earth at an orbit between 330 and 435km, mostly well above the 300km altitude at which India conducted the A-Sat test on March 27.

"Such comments by the Nasa head are discriminatory and irresponsible. It's more of propaganda," former DRDO scientist Ravi Gupta told TOI.

"There is remote possibility of debris moving upwards. Even if some pieces do move up, these will lose energy after some time and fall. Nasa is blaming us now but the US itself had conducted a lot of A-Sat tests in the past which generated thousands and thousands of large-size debris that continue to pose a danger to all space assets, including ours. Likewise, Russia and China too had conducted A-Sat tests that had generated a lot of debris," Gupta said.

According to an estimate by the European Space Agency , there are over 34,000 pieces of space debris larger than 10cm, close to a million pieces between 1cm and 10cm, and 128 million pieces of debris less than a centimetre in size.



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