A "lost" satellite was found after many years of being lost in space A "lost" satellite was found after many years of being lost in space

A "lost" satellite was found after many years of being lost in space

A "lost" satellite was found after many years of being lost in space

Scientists were able to find the small satellite called S73-7, which had been missing since the 1990s, after nearly 25 years.

Scientists found the experimental satellite using tracking data from the US Space Force's 18th Space Defense Squadron (18 SDS), after the satellite went off radar twice, once in the 1970s, then again in the 1990s.

The rediscovery of the satellite was announced by Jonathan McDowell, an astrophysicist from the Harvard-Smithsonian Center for Astrophysics, through a post on the “X” platform showing a graph of the satellite’s positions since 1975.

The graphic shows two main periods of missing data: between the 1990s and early 2000s and between approximately 2002 and today.

It appears that the satellite appears to be gradually losing altitude from its initial height of about 805 km (500 miles) to about 790 km (491 miles) today.

The S73-7 satellite was launched in 1974 as a payload aboard the larger KH-9 Hexagon System satellite. It was called the "Infrared Calibration Balloon" and was launched on April 10, 1974, as part of the US Air Force's Space Test Program.

As part of this mission, the S73-7 was planned to be ejected from the KH-9 and enter low Earth orbit (LEO).

Once deployed in space, the 66 cm wide satellite will head into low Earth orbit so that it can orbit the Earth continuously from a distance of 800 km.

Once there, the satellite was to help calibrate remote sensing equipment on Earth, helping set up space instruments.

However, this failed to materialize during deployment. Since then, the probe has disappeared twice: first in the 1970s, then again in the 1990s, joining the graveyard of unwanted space junk until it was discovered again in April.

Questions have been raised about how this satellite disappeared from the radar for so long.

Jonathan McDowell pointed out in an interview with Gizmodo that the failure to deploy the satellite properly made it not appear well on radar.

Satellite tracking involves using a global network of sensors to track an orbiting object and match its path to the flight path of a circular satellite. This data is then sent to an updated satellite guide, which McDowell describes as similar to air traffic control.

Although the surveillance system may seem foolproof, it is difficult for the Department of Defense's global space surveillance network to track more than 20,000 objects.

This is especially true because many objects in orbit do not transmit their identities. It is understood that this poses a major challenge to network oversight.

If an object in the crowded region of space has not been observed for a while, matching its orbit can be difficult, similar to finding a needle in an intergalactic haystack, as in the case of S73-7.

When an object orbits directly above the equator, without radar coverage, it may be difficult to track because it is effectively in a blind spot.

As a result, any unexpected maneuver in this region would force engineers to locate the satellite misplaced in Earth's orbit.


  1. Scientists recently rediscovered the S73-7 satellite, which had been missing since the 1990s. This experimental satellite, launched in 1974 as part of the US Air Force's Space Test Program, was initially lost from radar twice.

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