On November 15, 2021, the International Space Station (ISS) Flight Control team was notified of indications of a satellite breakup that may create sufficient debris to pose a collision threat to the station. NASA's Administrator, Bill Nelson, released the following statement.

"Earlier today, due to the debris generated by the destructive Russian Anti-Satellite (ASAT) test, ISS astronauts and cosmonauts undertook emergency procedures for safety.

"Like Secretary Blinken, I'm outraged by this irresponsible and destabilizing action. 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. Their actions are reckless and dangerous, threatening as well the Chinese space station and the taikonauts on board.

"All nations have a responsibility to prevent the purposeful creation of space debris from ASATs and to foster a safe, sustainable space environment.

"NASA will continue monitoring the debris in the coming days and beyond to ensure the safety of our crew in orbit."

Safety precautions were immediately taken. The crew was awakened and ordered to close hatches to radial modules while leaving access between U.S. and Russian segments open. This was followed with the precautionary sheltering of the crew for approximately two hours in reentry capsules. The space station passed through or near the debris cloud every 90 minutes, but the crew was required to shelter for only the second and third passages.

This event emphasized the fact that space debris is a serious problem. Larger pieces of at least 5 cm in size are detectable and trackable, but with poor ephemeris prediction accuracy. Smaller debris objects, down to about 1 mm still pose major threats. Add to this the fact that all low-orbiting objects are traveling at speeds in excess of 26,000 km/hr.

This translates to possible head-on collision speeds in excess of 52,000 km/hr (32,500 mph). At speeds well below these, a 1 cm diameter metal object encountering a satellite could pass right through the structure, probably causing catastrophic damage. For example, just four months ago a small debris object struck one of the ISS's robotic arms and left a half-cm diameter hole clean through a part of the arm.

Noting that the ISS is flying at an altitude of about 410 km, the debris threat created by last week's Russian ASAT test will not last beyond a few weeks, because this debris will decay and de-orbit into the atmosphere rather quickly. In general, orbiting debris below about 600 km altitude tend to decay rather rapidly due to the upper end of the Earth's atmosphere inducing drag on these items. Once you get above 600 km, there isn't enough atmosphere to cause rapid decay and reentry of debris.

Thus, the permanent debris threat applies mainly to satellite constellations in orbits above 600 km. Unfortunately, most uncrewed Earth-orbiting satellites are in orbits at altitudes between 700 km and 1,100 km, where debris tend to persist for many decades and longer. To further exacerbate the debris threat, not only is every object in these orbits traveling at over 26,000 km/hr in all directions, most of these satellites pass over the Earth's polar regions twice per orbit.

The physics of orbital mechanics forces dangerous congestions to occur near these polar regions. Finally, to make the risks even higher, new satellites are being added to these orbits with an expected 40,000+ more to be launched in the next few years.

This situation will, one day soon, have to be dealt with, possibly leading to a whole new space infrastructure architecture that will enable permanent management of space traffic. In other words, the sustainability of a safe space environment may well require a permanent space traffic management and debris control infrastructure that has yet to be properly addressed.

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When debris disaster strikes
Paris (ESA) Nov 19, 2021
In 2021 so far, some 2467 new objects large enough to be tracked have been added to world catalogues of orbital objects, out of which 1493 are new satellites and the rest are debris. While new objects are added, others are dragged down to Earth by the atmosphere where they safely burn up, resulting in a net increase of at least 1387 trackable objects between 2020 and 2021. In addition, an estimated 1500 new objects - an increase of about 5% with respect to the total population - were added just th ... read more

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