NASA's Van Allen Probe A satellite, launched in 2012 to study Earth's radiation belts, is set to reenter the atmosphere early this week after running out of fuel in 2019. The agency has approved a safety waiver due to the reentry's risk exceeding government standards, though the chance of harm remains low at 1 in 4,200. Most of the 1,323-pound spacecraft will burn up, with some debris potentially reaching the surface.
The Van Allen Probe A, part of a two-satellite mission built by the Johns Hopkins University Applied Physics Lab, was deployed in 2012 to investigate the Van Allen radiation belts—regions of charged particles trapped by Earth's magnetic field that shield the planet from cosmic radiation and solar storms. Originally planned for two years, the mission extended to seven years until the probes depleted their fuel in 2019, at which point they could no longer orient toward the sun for power.
NASA initially projected the satellite's reentry for 2034, but heightened solar activity during the current solar maximum expanded the atmosphere, increasing drag and accelerating its descent. The US Space Force predicts reentry early this week, with a window from late Monday through late Wednesday, centered around 7:45 p.m. ET on Tuesday, though predictions can vary by up to 24 hours due to atmospheric density fluctuations.
This uncontrolled reentry poses a risk of 1 in 4,200 for casualties, surpassing the US government's 1 in 10,000 threshold. "Due to late-stage design changes, the potential risk of uncontrolled reentry increased," a NASA spokesperson told Ars Technica. The agency granted a waiver for non-compliance with the US Government Orbital Debris Mitigation Standard Practices, notifying the US Department of State as required.
The spacecraft's elliptical orbits, inclined 10 degrees to the equator and reaching up to 20,000 miles at apogee, limit potential impact to tropical regions. No human injuries from space debris have been recorded, though past incidents have caused property damage. The mission yielded key discoveries, including evidence of a transient third radiation belt during intense solar activity. Data from the probes continues to inform predictions of space weather effects on communications, navigation, power grids, and astronauts. Van Allen Probe B is expected to reenter no earlier than 2030, with comparable risks.
Similar waivers have been issued before, such as for the Rossi X-ray Timing Explorer in 2018, which had a 1-in-1,000 risk but caused no harm. Globally, uncontrolled reentries occur multiple times monthly, with larger risks from other nations' rocket stages, like China's Long March 5B cores, which dropped wreckage on land without injuries.
