NASA ends Swift, its gamma-ray burst hunter since 2004
· BehindLines newsroom
NASA has brought the science mission of the Neil Gehrels Swift Observatory to a close, retiring one of its main tools for watching the most violent explosions in the Universe. In a post dated 23 October, the agency said the telescope made its final observation on 20 October. It is due to fall back into the atmosphere and break up within a few weeks; SpaceNews points to a re-entry in November, a date that remains an estimate.
The cause is physical. Swift now circles less than 275 kilometres above the ground. At that height, drag from the upper atmosphere stops it from staying steadily pointed at its targets. Recent solar activity, which puffs up the atmosphere, sped up the descent. The satellite has no engine able to raise its orbit. A rescue attempt by a commercial vehicle, Katalyst Space's LINK, was called off: according to SpaceNews, the craft could neither latch on nor push the observatory because of persistent attitude-control problems.
Launched on 20 November 2004 for a primary mission planned to last two years, Swift operated for more than two decades. Its job was to spot gamma-ray bursts, very brief flashes linked to the collapse of massive stars or the merger of neutron stars, then swing within tens of seconds towards the source to study it in X-ray and ultraviolet light. According to NASA's review of the mission, it observed more than 2,000 gamma-ray bursts and over 1,400 supernovae, and its data fed into about 7,000 scientific papers. It bears the name of its former principal investigator, Neil Gehrels.
What it changes: Swift acted as a lookout for the whole field. When a gravitational-wave or neutrino detector flagged an event, its quick alerts let large ground-based telescopes get into position. Its loss leaves a gap in so-called multi-messenger astronomy, which combines several kinds of signals. NASA says it will look for other ways to respond quickly to cosmic events and will lean on its current missions to partly make up for the loss.
For the public, the risk from the re-entry is considered low, as it is for most satellites of this size, but the exact date and area will only be known at the last moment. Swift's archives remain open to researchers around the world.