NASA has switched off the Swift telescope after 22 years, and it is expected to fall to Earth within weeks

NASA has ended the science mission of its Neil Gehrels Swift Observatory after nearly 22 years in orbit. The spacecraft made its last observation on Oct. 20 and now circles less than 171 miles (275 kilometers) above Earth, low enough that the thin air still present at that height is dragging it down. NASA expects the telescope to re-enter the atmosphere within the next few weeks.

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Swift was designed for a two-year primary mission and ran for more than ten times that long. Shawn Domagal-Goldman, director of the Astrophysics Division at NASA Headquarters in Washington, put the record in exactly those terms, describing a spacecraft that was productive for more than 10 times as long as planned. The ending is a quiet one: NASA’s account describes no dramatic failure on the last day, just an orbit that sank until steady pointing at a target was no longer possible, after nearly 22 years of catching light from the most violent events astronomers know.

Atmospheric drag below 171 miles ended the observing

NASA’s mission-end post, written by Francis Reddy of Goddard Space Flight Center and dated Oct. 23, 2026, gives the mechanism plainly. At the lower altitude, greater atmospheric drag keeps Swift’s telescopes from observing their astronomical targets steadily, so the science stopped even though the spacecraft is still intact. The NASA release does not give a failure of any onboard system as the reason for the shutdown.

Swift did not start out that low. According to the observatory’s reference history, it was launched on Nov. 20, 2004, on a Delta II rocket from Cape Canaveral into a near-circular orbit roughly 585 by 604 kilometers up. That account attributes the long descent mostly to increased solar activity, which heats and expands the upper atmosphere and raises drag, and says a contracted servicing spacecraft meant to lift Swift’s orbit could not rendezvous with it because of attitude-control problems. Those details come from that secondary history, not from NASA’s release.

The re-entry forecast carries real uncertainty, and the physics of atmospheric entry explains why: a spacecraft this size does not fall in one clean arc but spirals inward as each orbit meets slightly denser air than the last. NASA’s wording is an expectation, not a schedule: the spacecraft is expected to come down in the next few weeks, and the release names no date. How quickly a satellite sheds altitude depends on conditions in the upper atmosphere that are hard to predict far ahead, which is why NASA frames the timing as a window rather than a day.

Burst Alert Telescope, X-ray Telescope and the one-minute response

Swift carried three instruments working together. The Burst Alert Telescope, a gamma-ray detector with a coded-aperture mask, finds a burst and estimates where it sits in the sky. The X-ray Telescope then images the afterglow and refines the position, and the Ultraviolet/Optical Telescope looks for the fading light at visible and ultraviolet wavelengths. NASA’s release describes the observatory as a multiwavelength facility with co-aligned optical and ultraviolet and X-ray telescopes.

S. Bradley Cenko, the mission’s principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, explained what the design was for. Swift was built to study gamma-ray bursts, and it typically took about a minute to detect one, alert other observatories and turn its telescopes to image the burst before the afterglow faded. That speed let ground-based telescopes around the world join within minutes of an explosion that may have happened billions of years ago.

The ability to retarget on command mattered as much as the speed of the first response. Astronomers could request target-of-opportunity observations that were commanded from the ground within minutes, and the schedule could carry up to 75 independent targets per day. John Nousek, the mission’s operations director and a professor at Penn State’s Eberly College of Science, credited the fast hardware response and the teamwork of the operations and science staff for putting Swift at the center of emerging research areas.

2,000 bursts, 1,400 supernovae and a 12-terabyte archive

The totals are large. Swift observed more than 2,000 gamma-ray bursts, the most powerful explosions in the cosmos, and studied more than 1,400 supernova explosions. Its data fed about 7,000 published scientific papers. It also watched stars being shredded by black holes, monitored active galaxies, carried out an all-sky X-ray survey and observed asteroids and comets, work far removed from the burst-chasing that defined its early years, and a reminder of how a flexible, fast-slewing telescope gets used once the community learns what it can do.

One early result changed a long-running argument. In May 2005, Swift detected GRB 050509B, a burst that lasted only 0.03 seconds. Swift caught 11 X-ray photons from it, making it the first short burst with a detected afterglow, and NASA says those observations supported models in which short bursts come from the merger of two neutron stars.

The data stay behind. NASA says the archive holds nearly 22 years of brightness measurements, multiwavelength spectra and more than 1.5 million images from the Ultraviolet/Optical Telescope, and that the public dataset runs to about 12 terabytes. The mission also carries the name of its first principal investigator: NASA renamed it in 2018 for Neil Gehrels after his death.

Domagal-Goldman said NASA is exploring how its existing space telescopes, including fast-to-orbit commercial capabilities and new missions, can respond rapidly to cosmic events once Swift is gone. The release says NASA will keep prioritizing new ways to react to transient events and will use current missions to fill the gap in the meantime. No replacement with Swift’s one-minute reflexes has been announced.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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