NASA Anticipates UARS Debris Will Survive Reentry

NASA anticipates that pieces of its Upper Atmosphere Research Satellite (UARS) will survive the trip through Earth’s atmosphere when the satellite reenters later this month or in early October.

A set of slides on NASA’s UARS website show that 56 “potentially hazardous objects [are] expected to survive,” with a total mass of 532 kilograms. The “estimated human casualty risk” is approximately 1 in 3,200.

The satellite was launched in 1991 and completed its mission in 2005. The slides point out that at the time UARS was designed, built, and launch, “no NASA or [U.S. Government] human casualty risk limits existed.”

The satellite is in an orbit inclined 57 degrees to the equator, which means that it could reenter anywhere on the globe between 57 degrees north and 57 degrees south latitude, which is most of the populated region of Earth. The Earth’s surface, however, is 70 percent water, so the risk to human health and safety is less than what one might initially infer. In the 54 year history of the Space Age, there have been no confirmed reports of injuries to humans from falling space debris, although pieces have been recovered. NASA urges anyone who finds anything that might be a piece of UARS debris to not touch it, but to contact local law enforcement for assistance.

When UARS will reenter is uncertain, since it is dependent on variables such as solar activity. NASA plans to post weekly updates at the UARS website until four days before reentry and then more frequently.

Although NASA cannot predict exactly where the debris will reenter, it says that the debris footprint will be 500 miles long.

The Joint Space Operations Center (JPSoC) of U.S. Strategic Command is the official government agency responsible for reentry predictions of uncontrolled space objects, although NASA has its own orbital debris office at Johnson Space Center.