NASA’s Earth Radiation Budget Satellite (ERBS) satellite, launched in 1984, will reenter on or around Jan. 8, NASA said, posing only a very small risk to people on the ground. Credit: NASA

Updated Jan. 9 7 a.m. Eastern with reentry.

WASHINGTON — A defunct NASA satellite, launched nearly four decades ago, reentered late Jan. 8 with a very small risk to people on the ground.

NASA said Jan. 6 that the Earth Radiation Budget Satellite (ERBS) satellite, launched in 1984 and shut down in 2005, will reenter Jan. 8. At the time, NASA estimated a reentry at 6:40 p.m. Eastern, plus or minus 17 hours, based on data from the U.S. Space Force.

The Space Force’s Space Track service updated that prediction late Jan. 6, with a new reentry time of 11:25 p.m. Eastern plus or minus 10 hours. The Aerospace Corporation’s Center for Orbital and Reentry Debris Studies estimated a reentry at 10:49 p.m. Eastern plus or minus 13 hours, based on data as of early Jan. 6.

Space Track provided a final estimated reentry time of 11:04 p.m. Eastern Jan. 8, off the coast of Alaska near the Aleutian Islands.

Most of the 2,450-kilogram satellite will burn up on reentry, NASA said in its statement, but some components will likely survive and reach the surface. The odds that debris would harm anyone on the ground is 1 in 9,400, the agency estimated.

ERBS launched on the space shuttle Challenger in October 1984 to study the balance between energy the Earth absorbed from the sun and energy it radiated away, as well as to monitor ozone in the stratosphere. Intended to operate for two years, ERBS was finally retired in 2005.

NASA launched ERBS before the agency’s first orbital debris mitigation guidelines in the 1990s. Current U.S. government orbital debris mitigation standard practices, last updated in 2019, call for satellites in low Earth orbit to be deorbited no more than 25 years after the end of their mission, which ERBS will meet. However, ERBS does not meet another aspect of the guidelines, limiting the risk of casualties from falling debris to no greater than 1 in 10,000.

There has been a long-running discussion about reducing the post-mission disposal lifetime limit from 25 years to as little as 5 years to minimize risks of collisions that could create debris. A National Orbital Debris Implementation Plan, published by the White House’s Office of Science and Technology Policy in July 2022, directed NASA and several other agencies to reevaluate existing mitigation guidelines, “specifically the potential benefits and cost in reducing the deorbit timelines.”

In September 2022, the Federal Communications Commission approved an order requiring commercial satellites that apply for FCC licenses or seek U.S. market access after September 2024 to deorbit their satellites no more than five years after the end of their missions. That rule applies that satellites that end their lives at altitudes of 2,000 kilometers or less.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...