Swift Observatory Tracker
NASA's Neil Gehrels Swift Observatory, launched 20 November 2004 aboard a Delta II from Cape Canaveral, re-entered the atmosphere on 4 November 2026. The most prolific gamma-ray burst hunter ever flown: its three co-aligned telescopes caught a burst somewhere on the sky every two to three days, then autonomously slewed within 90 seconds to point X-ray and UV/optical follow-up cameras. More than 2,000 GRBs detected in almost 22 years.
GRB 261017A: Long-Duration Burst in Leo
Swift's Burst Alert Telescope caught this gamma-ray burst at 16:05:05 UTC on 17 October 2026, the last burst on record before its re-entry. It lasted 89.36 seconds, a "long" GRB consistent with the collapse of a massive star into a black hole, and the X-ray Telescope pinned down its afterglow position.
The Most Prolific GRB Hunter Ever Flown
Swift was a rapid-response gamma-ray burst observatory. Its Burst Alert Telescope watched more than a tenth of the sky at once; when it caught a GRB, the spacecraft autonomously slewed the whole observatory within 90 seconds to point X-ray and UV/optical instruments at the burst location. In almost 22 years it detected more than 2,000 GRBs, and it was the first observatory built for this rapid response.
Three Co-Aligned Telescopes
Swift caught gamma-ray bursts with its wide-field BAT and followed up seconds later with two narrow-field telescopes that autonomously slewed to the burst location. The whole spacecraft was the pointing mount.
22 Years of Rapid Response
What Swift Actually Caught
Twenty-two years of hair-trigger autonomous response has redefined what we know about the most violent moments in the universe.
Swift vs Fermi, Chandra and XMM
Swift's speed was its superpower. Other X-ray and gamma-ray observatories had more area or higher resolution, but only Swift could autonomously slew to an unpredicted burst on the sky within 90 seconds.
| Telescope | Waveband | Mirror | Orbit | Launched |
|---|---|---|---|---|
| Swift | γ / X-ray / UV-Optical | 3 co-aligned (30 cm UVOT) | Re-entered 4 Nov 2026 | Nov 2004 |
| Fermi | Gamma-ray (30 MeV+) | LAT: 96 cm² area | LEO 550 km | Jun 2008 |
| Chandra | X-ray (0.1–10 keV) | 1.2 m Wolter grazing | HEO 14k–133k km | Jul 1999 |
| XMM-Newton | X-ray (0.1–12 keV) | 3 co-aligned mirrors | HEO 6k–100k km | Dec 1999 |
Why Swift Was Unique for 22 Years
Gamma-ray bursts fade in seconds. To follow up a burst you need a telescope that already sees a big fraction of the sky, that can autonomously decide something interesting has happened, that can slew the whole spacecraft in tens of seconds, and that carries the follow-up instruments already aligned. Every one of those is hard. Swift was the first observatory to do all four in one package.
Why the LEO orbit
Swift flew in low Earth orbit, easy to reach and clear of the outer Van Allen belts. The trade-off was drag: high solar activity swelled the upper atmosphere and pulled Swift down until it re-entered on 4 November 2026.
The commercial reboost
In September 2025 NASA contracted a commercial rendezvous-and-reboost mission to fly to Swift and raise its orbit. The rescue was called off in 2026, and Swift made an uncontrolled re-entry on 4 November 2026.
What it leaves behind
Swift's role in the multi-messenger astronomy network (following up gravitational-wave events, neutrino detections, and short-timescale transients) ended with the mission in 2026. Its observations of more than 2,000 bursts and their afterglows remain in the mission archive for researchers.
Swift Observatory, Frequently Asked
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