Swift

Built to detect gamma-ray burstsgamma-ray burstA flash of gamma rays lasting milliseconds to minutes, followed by a fading afterglow at longer wavelengths. Long bursts come from collapsing massive stars; short ones from neutron-star mergers. with the Burst AlertalertA machine-readable notice that a source has appeared, changed or been detected, issued within seconds to days so other facilities can follow up. Optical alerts reach users through brokers; high-energy, neutrino and gravitational-wave alerts through GCN. Telescope (coded-maskcoded-mask imagingImaging hard X-rays and gamma rays, which cannot be focused, by placing a patterned mask above a position-sensitive detector. Each source casts a shifted shadow of the pattern; deconvolution recovers the sky over a wide field at modest resolution., 15–150 keVelectronvoltThe energy an electron gains across 1 volt, 1.602 × 10⁻¹⁹ J. High-energy astronomy labels photons by energy: optical light is about 1.7–3.1 eV, X-rays 0.1–100 keV, gamma rays from about 100 keV to beyond 100 TeV. A 1 keV photon has wavelength 1.24 nm., seeingseeingBlurring of starlight by turbulence in the atmosphere, usually quoted as the FWHM of a star's image in arcseconds. Good optical sites reach 0.5–0.8″, far worse than the diffraction limit of a large mirror. up to half the sky at once) and slew autonomously within 20–100 s to observe them with the X-ray Telescope (0.2–10 keV) and the 30 cm UV/Optical Telescope. From 2004 to 2026 it was the default rapid-response facility for transientstime-domain astronomyStudying how sources vary or appear over time: supernovae, tidal disruptions, flares, variable stars and moving objects. Needs wide fields, high cadence and fast data processing. across the high-energy sky.

Operator

NASA

Orbit

Low Earth orbit

Aperture

30 cm UV/optical telescope

BAT

15 keV – 150 keV

XRT

0.2 keV – 10 keV

UVOT

170 nm – 650 nm

Launch

20 November 2004

Final observation

20 October 2026