A NASA satellite, the Van Allen Probe A, is undergoing an uncontrolled reentry into Earth's atmosphere. While most of the spacecraft will burn up, some debris is expected to reach the surface, posing a slightly higher public risk than standard US government guidelines allow.
The risk of harm to anyone on Earth is approximately 1 in 4,200, which exceeds the typical 1 in 10,000 standard. NASA granted a waiver for this non-compliance, citing the mission's scientific benefits and the overall low risk.
The main topics covered are the satellite's uncontrolled reentry, the associated risk assessment, and NASA's regulatory waiver.
A NASA satellite that spent more than a decade coursing through the Van Allen radiation belts encircling Earth is about to fall back into the atmosphere.
Most of the spacecraft will burn up during reentry, but a fraction of the material making up the 1,323-pound (600-kilogram) satellite will likely reach Earth’s surface without vaporizing in the atmosphere. Uncontrolled reentries of satellites with comparable mass happen quite regularly—multiple times per month, according to one recent study—but most of them are older spacecraft or spent rocket bodies.
This reentry is notable because it poses a higher risk to the public than the US government typically allows. The risk of harm coming to anyone on Earth is still low, approximately 1 in 4,200, but it exceeds the government standard of a 1 in 10,000 chance of an uncontrolled reentry causing a casualty.
“Due to late-stage design changes, the potential risk of uncontrolled reentry increased,” a NASA spokesperson told Ars. “After taking into account the mission’s scientific benefits and the low risk of harm to anyone on Earth, NASA granted a waiver to address the non-compliance with the US Government Orbital Debris Mitigation Standard Practices. Consistent with national policy, NASA notified the US Department of State about the exception.”
Plus or minus 10
The spacecraft, called Van Allen Probe A, launched in 2012 as part of a two-satellite mission to study Earth’s radiation belts. The belts are a collection of charged particles trapped by Earth’s magnetic field, and they help protect our planet from cosmic radiation and solar storms.
It is difficult to predict satellite reentries. The density of the upper atmosphere varies, and the latest prediction from the US Space Force showed Van Allen Probe A will reenter the atmosphere early this week, with the reentry window open from late Monday through late Wednesday.
Meridiano
