Russia tested an anti-satellite missile on Monday, the State Department and the Pentagon said, creating a large cloud of debris that, according to NASA, endangered the International Space Station, its crew and could go on to threaten other satellites.

Why it matters: Weapon tests in space can generate thousands of pieces of debris that may stay in orbit and pose a risk for space-based technologies and people for years, and even decades.

Roscosmos, Russia's state-run space agency, said the seven-member crew, including three cosmonauts, currently aboard the ISS took shelter early Monday due to an undefined passing "object."

• NASA administrator Bill Nelson said in a statement Monday night that the crew undertook emergency procedures for safety directly in response to debris generated by the test.
• "I'm outraged by this irresponsible and destabilizing action," Nelson said. "With its long and storied history in human spaceflight, it is unthinkable that Russia would endanger not only the American and international partner astronauts on the ISS, but also their own cosmonauts."

The other side: Russia's Defense Ministry confirmed the missile test but denied having endangering the ISS, claiming the U.S. "knows for certain that the resulting fragments, in terms of test time and orbital parameters, did not and will not pose a threat to orbital stations, spacecraft and space activities," according to TASS, a Russian state news agency.

• It called the accusations by U.S. officials “hypocritical," though the U.S. was not the only entity to conclude that the fragments threatened the space station.
• Independent astronomers and satellite trackers also concluded that the emergency sheltering procedure aboard the ISS was initiated in response to the destructive test.

What they're saying: "Earlier today, the Russian Federation recklessly conducted a destructive satellite test of a direct-ascent anti-satellite missile against one of its own satellites," State Department spokesperson Ned Price said.

• "The test has so far generated over 1,500 pieces of trackable orbital debris and hundreds of thousands of pieces of smaller orbital debris that now threaten the interests of all nations," Price added.
• "In addition, this test will significantly increase the risk to astronauts and cosmonauts on the International Space Station, as well as to other human spaceflight activities."

Context: Russia has tested similar anti-satellite weapons before, but it had not previously intercepted another object in orbit during these trials.

• Russia tested anti-satellite weapons at least three times in 2020.
• Two of those tests included non-destructive direct-ascent missiles, while another involved a space-based kinetic weapon aboard a satellite that injected a new object into orbit.
• The in-space test was also nondestructive, but the object was released in proximity to another Russian satellite ⁠— signifying that the object could destroy other space-based technologies.

The big picture: Militaries have increasingly focused on developing and testing anti-satellite weapons in recent years, and more competition in space may pressure additional countries to pursue such technologies.

• China tested a direct-ascent kinetic weapon in 2007 that spawned a cloud of more than 3,000 pieces of space debris. The ISS was forced last week to maneuver itself out of the trajectory of debris caused by that weapon test.
• India successfully tested an anti-satellite weapon in March 2019. That test too created hundreds of pieces of debris, though the Indian government took steps to limit the amount of time those fragments would remain in orbit.
• Security experts have doubted the effectiveness of such weapons because the aftermath can be a danger to any nation or company with satellites.

Go deeper: Tensions on Earth reflected in orbit

Editor's note: This post has been updated with comments from NASA administrator Bill Nelson and Russia's Defense Ministry.

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