After a remarkable 25 years of stealthy orbiting, the Infra-Red Calibration Balloon (S73-7), a Cold War-era experimental spy satellite launched by the United States Air Force’s Space Test Program on April 10, 1974, has been detected once again on April 25.
“The S73-7 satellite has been rediscovered after being untracked for 25 years,” announced astrophysicist Jonathan McDowell, citing the critical role of U.S. Space Force data in the satellite’s detection. McDowell’s revelation sent ripples through space communities, igniting discussions about space debris management and the intricacies of satellite tracking.
Initially purposed as a calibration target for remote sensing equipment, the S73-7 satellite was designed to inflate post-launch, a plan that misfired. Twice it slipped the radar’s gaze, first in the 1970s and again during the 1990s when the satellite joined the vast and growing graveyard of space junk.
But what led to the satellite’s disappearance and why did it reemerge only now? According to McDowell, “The problem is that it possibly has a very low radar cross section… And maybe the thing that they’re tracking is a dispenser or a piece of the balloon that didn’t deploy right, so it’s not metal and doesn’t show up well on radar.” This explanation sheds light on the challenges faced in tracking the over 20,000 man-made objects in Earth’s orbit.
The task of monitoring these objects is daunting. Ground-based radars and optical sensors catalogue space junk, yet confirming the identities of these objects is a complex puzzle. “If you’ve got a recent orbital data set, and there’s not too many things that are similar orbit, it’s probably an easy match,” McDowell explained. However, he noted that if an object hadn’t been seen for a while, or if it’s in a crowded part of space, matching it up becomes challenging.
Relevant articles:
– ‘Lost’ spy satellite orbited Earth undetected for 25 years—until now, scientists say, Phys.org
– ‘Lost’ satellite found after orbiting undetected for 25 years, Space.com
– ‘Lost’ satellite orbited Earth undetected for 25 years — until now, scientists say, Yahoo News
– ‘Lost’ satellite finally found after orbiting undetected for 25 years, Live Science