'A terrible, terrible thing:' NASA said India's satellite destruction created so much space junk it now threatens the safety of the International Space Station

• NASA said that India has threatened the International Space Station and the astronauts on board by shooting down a satellite with a missile.
• NASA Administrator Jim Bridenstine said the satellite shattered into small pieces of space junk that pose an "unacceptable" threat to astronauts and called it a "terrible, terrible thing."
• India said it deliberately chose to destroy a satellite in low orbit so the debris would not harm the station and other satellites, and said the debris would fall back to earth.
• But Bridenstine said that pieces were moving above the station, and "that kind of activity is not compatible with the future of human spaceflight."

NASA called India's destruction of a satellite last week a "terrible, terrible thing" and said the space debris created by the explosion should now be considered a threat to the International Space Station, and the astronauts on board.

India intentionally destroyed one of its own satellites with a missile last week, a move that Prime Minister Narendra Modi welcomed as one that established India "as a space power."

But NASA Administrator Jim Bridenstine told employees on Monday that it poses an "unacceptable" threat to astronauts on board the ISS.

Read more: India's anti-satellite missile test just moved humanity closer to a space-junk nightmare scenario

He said that the satellite shattered into pieces, with many of those pieces large enough to pose a danger to the space station but not large enough to track. It is unclear exactly how many pieces of debris the satellite created.

"What we are tracking right now, objects big enough to track - we're talking about 10cm (four inches) or bigger -about 60 pieces have been tracked," he said.

He said that 24 of those pieces were going above the ISS, even though the satellite had been orbiting 185 miles above the earth, lower than the station, which orbits roughly 250 miles above the earth.

"That is a terrible, terrible thing to create an event that sends debris at an apogee that goes above the International Space Station," Bridenstine added.

"That kind of activity is not compatible with the future of human spaceflight."

Read more: India's anti-satellite missile test may have created 6,500 pieces of space junk larger than a pencil eraser, according to a new simulation

He said that the risk of ISS collision with debris has increased by 44% in 10 days as a result of the Indian missile.

"It's unacceptable and NASA needs to be very clear about what its impact to us is," he said.

There are currently six crew members living on board the ISS.

A software-engineering company called Analytical Graphics Inc. (AGI) made a simulation of the debris created by the anti-satellite test, which it posted on YouTube.

"We modeled 6,500 fragments, basically those that were larger than half a centimeter," Tom Johnson, the vice president of engineering for Analytical Graphics Inc., said.

India downplayed the risk of debris after its missile launch, with its top scientists saying last week that it expects the debris to burn out in less than 45 days.

Read more: India says space debris from its anti-satellite test will 'vanish in no time'

G. Satheesh Reddy, the chief of India's Defence Research and Development Organisation, said a low-altitude military satellite was picked to reduce the risk of debris.

"That's why we did it at lower altitude, it will vanish in no time," he told Reuters. "The debris is moving right now. How much debris, we are trying to work out, but our calculations are it should be dying down within 45 days."

Acting US defence secretary Patrick Shanahan warned a day after India's test that the event could create a "mess" in space.