STS-75 Tether Incident

STS-75 was a Space Shuttle Columbia mission that launched from Kennedy Space Center on February 22, 1996, and landed there on March 9. Its crew of seven, led by commander Andrew Allen and including European Space Agency astronauts from Switzerland and Italy and Italian payload specialist Umberto Guidoni, flew the Tethered Satellite System Reflight, a U.S.-Italian experiment that reeled a satellite out on a long conducting tether to study electrodynamics in the ionosphere. On the evening of February 25 (01:29 GMT on February 26), with 19.7 kilometers of tether deployed and the satellite approaching its planned 20.7-kilometer station, the tether snapped inside the deployer boom and the satellite sped away from the orbiter. No one was hurt.

NASA's investigation board reported on May 31, 1996, that the tether had burned through. A breach in its insulation, which the board attributed most probably to foreign-object penetration or damage during manufacture or handling, let the conductor's roughly 3,500 volts arc intermittently to the orbiter's ground for about nine seconds until the normal load pulled the weakened tether apart. The board noted that no video showed the break itself, although cameras recorded the tether afterward. NASA said the experiment still returned useful data, including currents at least three times higher than predicted.

The mission's place in UFO history comes from that later video of the drifting tether. Against the dark sky the bright line is surrounded by dozens of glowing, disc-shaped spots, many sharing the same notched or ring-like shape, moving at different speeds. Promoters say some reverse direction or pass behind the tether, which would make them enormous; a 2025 analysis on the UAP Files Substack cited estimates of up to a mile across, and a 2026 Reddit post repeated an unnamed scientist's figure of more than two miles. The sequence has circulated for years among the shuttle downlink recordings associated with Martyn Stubbs, a Canadian television producer who taped NASA's live feeds in the 1990s.

NASA attributed the objects to debris and ice particles lit by sunlight. James Oberg, a former Mission Control engineer who has written for decades about shuttle video, has described the strangest STS-75 sequence as a cloud of ice crystals. Skeptics argue that the uniform notched discs are small particles near the shuttle seen far out of focus, so that their shape comes from the camera's aperture rather than the objects, an explanation the UAP Files analysis called contested. Debunkers add that objects as large as claimed would have been clearly visible from the ground.

The clip found a new audience in 2026. When the White House and the Department of War began releasing government UFO files in May, the X account Interstellar reposted it, describing a swarm of "pulsating orbs" around the broken tether. On June 10 the account High Strangeness billed the footage as "David Grusch's Sentient Plasmoids" in a post that journalist Ross Coulthart reposted, although it quoted no statement by David Grusch about the mission. As with the STS-80 downlink clips, the engineering record of STS-75 is detailed and settled, while the UFO reading depends on how far away, and therefore how large, the lights in the video really were.