Lost satellite rediscovered after 25 years in space

The Infra-Red Calibration Balloon (S73-7), an experimental satellite launched by the United States Air Force in 1974, has been rediscovered after being undetected in orbit for 25 years. The satellite, part of the Air Force's Space Test Program, was designed to inflate and serve as a calibration target for remote sensing equipment, but it failed to do so upon deployment. Its rediscovery was achieved using ground-based radar and optical sensors, with data provided by the U.S. Space Force.

The satellite, which was also known as part of "The Hexagon System," had previously eluded radar detection twice, first in the 1970s and again in the 1990s. Despite its initial loss and subsequent rediscovery, the satellite now adds to the tens of thousands of known objects orbiting Earth, presenting both a victory for space debris tracking efforts and a growing challenge as more objects accumulate in orbit. The identification of S73-7 underscores the importance of monitoring space debris for the safety of ongoing and future space missions.