The head of NASA classified the destruction of one of its satellites by India as a "terrible thing" that created 400 orbital fragments and led to new dangers for astronauts aboard the International Space Station (ISS).
Jim Bridenstine addressed officials five days after India knocked down a low-orbit satellite on a missile test to prove it was among the world's advanced space powers.
Not all parts were large enough to track, Bridenstine explained. "What we're trawling now, objects large enough to track – we're talking about 10 centimeters (six inches) or larger – about 60 pieces were tracked."
The Indian satellite was destroyed at a relatively low altitude of 300 km, well below the ISS and most satellites in orbit.
But 24 of the pieces were above the apogee of the ISS, Bridenstine said. "This is terrible, a terrible thing to create an event that sends debris into a heyday that goes beyond the International Space Station," he said, adding, "This kind of activity is not compatible with the future of human spaceflight."
"It's unacceptable and NASA needs to be very clear about the impact it has on us."
The US military tracks objects in space to predict the risk of collision for ISS and satellites. They are currently tracking 23,000 objects larger than 10cm.
This includes about 10,000 pieces of space debris, of which about 3,000 were created by a single event: a Chinese anti-satellite test in 2007, 530 miles above the surface.
As a result of the Indian test, the risk of collision with the ISS increased by 44% in 10 days, Bridenstine said. But the risk will dissipate over time, as more of the debris will burn as it enters the atmosphere.