Arbitrage Sunday: The Sky is Falling... Well Kinda

A 2.7-ton defunct satellite came down over the Bering Sea on January 8 near the Aleutian Islands, and while most of it burned up in the atmosphere, NASA says it's likely that some pieces reached the surface. NASA says its Earth Radiation Budget Satellite (ERBS) made its reentry at 11:04 p.m. ET on Sunday, January 8, with Space Force's Space Track confirming a reentry near the Aleutian Islands, as reported in SpaceNews. The 5,400-pound research satellite had spent the last 38 years in low Earth orbit, having been delivered to space on October 5, 1984 by the Space Shuttle Challenger. The ERBS mission was only supposed to last for two years, but it eked out a 21-year career, having been retired in 2005.

The satellite got a special sendoff from Challenger. America's first woman in space, Sally Ride, released the satellite into orbit using the shuttle's robot arm. That same mission also featured the first spacewalk by a U.S. woman: Kathryn Sullivan. It was the first time two female astronauts flew in space together. It was the second and final spaceflight for Ride, who died in 2012.

While it was in operation, ERBS gathered data on Earth's energy budget, that is, the balance between the amount of solar energy that our planet receives and the amount it radiates back to space. Three instruments aboard the spacecraft were used to measure stratospheric concentrations of water vapor, ozone, nitrogen dioxide, and various aerosols. ERBS boosted our understanding of climate and ozone layer health, and it contributed directly to the adoption of the 1987 Montreal Protocol Agreement limiting the use of damaging chlorofluorocarbons (CFS), according to NASA.

NASA "expected most of the satellite to burn up as it traveled through the atmosphere, but for some components to survive the reentry," as the space agency explained in its statement. An earlier version of its post assessed the odds of potentially harmful debris reaching the ground at 1 in 9,400. There are no reports of injury or damage as a result of the falling debris.

This latest satellite reentry represents the old way of doing things, both in terms of the time it took the satellite to deorbit after retirement and the risk it posed to people on the ground. In September 2022, the U.S. Federal Communications Commission adopted a new five-year rule for the deorbiting of defunct satellites, a move designed to decrease the amount of space junk and minimize chances of in-space collisions. In addition, a 2019 update to U.S. government orbital debris mitigation standard practices states that the "risk of human casualty from surviving components" should be less than 1 in 10,000.

ERBS violates both of these rules, but obviously these policies weren't in place when ERBS launched to space in 1984; these sorts of things are to be expected for legacy spacecraft, though on a decreasing basis. Or at least, for satellite and launch providers who adhere to these guidelines, whether they be domestic or international. Indeed, China designed its Long March 5B rocket such that it cannot perform a controlled reentry - a decision that has now threatened human life and property on four different occasions, the most recent in November 2022.