The Infra-Red Calibration Balloon (S73-7) satellite, launched in 1974 by the US Air Force Space Test Program, disappeared from radar twice, once in the 1970s and again in the 1990s. According to astrophysicist Jonathan McDowell, tracking objects in orbit is challenging due to the large number of objects currently in orbit. With over 20,000 objects already in space, ground-based radar and optical sensors help track space junk but identifying each object remains difficult.
Engineers can monitor a satellite’s progress based on its original path and altitude, but deviations from the plan or drifts can make finding it again a challenge. The rediscovery of S73-7 is a success in tracking lost satellites and space junk. However, with more satellites being launched every day, understanding what is in orbit around Earth will become increasingly difficult. As McDowell explains, missing even a few objects may not pose a significant risk, but our goal is to do the best possible job of tracking objects in space. The discovery of lost satellites like S73-7 is a step towards improving our knowledge of what is in orbit around Earth.
