Space Force Found a Satellite Lost in Space for 25 Years

The short NBC News documentary Battlefield Space took viewers inside Space Force, the newest branch of the United States military, for a look at its efforts to safeguard the final frontier. The organization’s stated mission is both broad and vague: to secure the interests of the U.S. and deter aggression in, from, and to space.

While that might conjure images of space soldiers piloting tactical spacecraft in orbital dogfights, it mostly amounts to keeping an eye on the skies. The many duties of Space Force include but are not limited to Space Domain Awareness, which mostly amounts to detection, identification, tracking, and cataloging of satellites and space debris.

For More on Space Debris:
A Florida Home May Have Been Hit by Debris from Space
How Scientists Are Mapping and Attempting to Clean Up Some 100 Million Pieces of Space Debris
The Atmosphere Is Polluted with Pieces of Burnt Up Spacecrafts

Space Force Analysts Spotted a Lost Satellite, Note Seen for 25 Years

"Space Junk" is seen floating above the earth. Photo: NASA

That’s no easy task, NASA estimates there are 6,000 tons of space debris in low-Earth orbit, leftover from the last several decades of space operations. All of that mass, the equivalent of 1,000 male African elephants, is broken up into more than 170 million pieces. Of those, 29,000 are larger than 10 centimeters, the sort of thing which might be a lost satellite.

Part of the Space Force mission is understanding where those pieces are and how they are moving. With that information scientists can calculate when objects will de-orbit and when or if they’ll pose a threat to future space operations. Recently, the eagle-eyed analysts at the 18th Space Defense Squadron spotted a 50-year-old satellite that’s been lost in space for the last 25 years. The sighting was reported by astronomer Jonathan McDowell, in a post on X (previously Twitter).

The S73-7 Infra-Red Calibration Balloon (IRCB) launched April 10, 1974, from inside of a larger payload called the KH-9 Hexagon. It rode inside the hexagon to an orbit of 500 miles before being released, and that’s when things went wrong. The inflatable sphere was intended to be an infrared calibration target for remote sensing, but it failed to fully inflate. Instead, it drifted off into space and was lost. There was a brief sighting in the ‘90s, before the satellite was lost again, and it hasn’t been seen for 25 years, until now.

Unlike some more advanced modern satellites, S73-7 wasn’t equipped with any communications systems. There was no way for us to ping it and it couldn’t call home, so once it slipped into the darkness it became almost impossible to find again. With no way to seek out a satellite, you have to rely on fortuitous sightings, and that’s apparently what’s finally happened.

Analysis of the satellite’s current trajectory reveals that it has only lost about 9 miles of altitude since its launch in 1974. At that rate, it will be a long time yet before it descends enough to get pulled down by the atmosphere and burn up. McDowell also noted that additional sightings of S73-7 might be hiding in historical data as unidentified debris. Now that we know where it is, analysts might be able to trace its path backward to fill in some of the gaps in its history. With any luck, we won’t lose it again.

Get a look inside Space Force in Battlefield Space, streaming now on Peacock.