Rediscovering Lost Spacecraft: The Importance of Tracking Space Junk

The Infrared Calibration Balloon satellite, S73-7, was launched on April 10, 1974 by the US Air Force Space Test Program with a width of 66 cm. Originally intended as a calibration target for remote sensing equipment, the mission failed and the satellite became space junk until its recent rediscovery. According to astrophysicist Jonathan McDowell, S73-7 disappeared from radar twice, first in the 1970s and then in the 1990s. Tracking objects in orbit is challenging due to the large number of objects currently in orbit over 20,000. Ground-based radar and optical sensors help track space junk but identifying each object remains difficult.

Engineers monitor a satellite’s progress based on its original path and altitude; however, deviations from the plan or drifts can make finding it again challenging. The rediscovery of S73-7 is a success in tracking lost satellites and space junk; however, with more satellites being launched understanding what is in orbit and potential threats will become increasingly difficult. McDowell explains that missing a few objects may not pose a significant risk but tracking objects accurately is critical to ensuring safe operations in space. The discovery of lost satellites like S73-7 is an important step towards improving our knowledge of what is in orbit around Earth.