NASA’s Swift observatory is due to fall back to Earth on Nov. 4, nearly 22 years after launch

A 3,200-pound NASA astronomy satellite is on course to drop out of orbit on Wednesday, Nov. 4, and the agency’s forecast leaves a window of 22 hours around its best estimate. The Neil Gehrels Swift Observatory was launched on Nov. 20, 2004, which puts the end of its flight just under 22 years after liftoff. The U.S. Space Force predicted reentry at about 3:30 a.m. EST, give or take 11 hours.

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The satellite has no propulsion, so its descent is uncontrolled and the exact location of any debris will not be known until after the fact.

Reentry window and the Space Force prediction

NASA’s reentry notice on the Swift blog, posted Nov. 2, says the U.S. Space Force expected the observatory to come down at about 3:30 a.m. EST on Nov. 4 as of Monday, with an uncertainty of 11 hours. That span runs from the late afternoon of Nov. 3 to the early afternoon of Nov. 4, which is why the date can still shift even though NASA names Nov. 4 as the day. Both NASA and the Space Force said they would keep monitoring and update predictions. Readers reaching the story after the window has opened should check the Swift blog for the confirmed time, since a forecast of this kind is revised as the orbit decays.

Independent trackers pointed the same way. Leonid Space, cited by IFLScience, estimated a fall on Nov. 4 with a small chance of up to two days earlier.

Burn-up, surviving parts and the 1-in-2,100 figure

NASA says most of the spacecraft will burn up as it moves through the atmosphere, though some components may survive to the ground. IFLScience reported that the likeliest survivors are the six reaction wheels and tougher parts such as lenses and mirrors, and quoted Dean Sladen of Accu Components saying most of the spacecraft will melt and vaporize. The agency puts the risk of harm to anyone on Earth at about 1 in 2,100 and calls harm unlikely. Because Swift flew a low-inclination orbit, any surviving fragments could land only between 20.6 degrees south and 20.6 degrees north latitude, a band that covers the tropics, much of open ocean and several densely populated countries. NASA adds that landing sites depend on the reentry time and can differ between hemispheres.

The 1-in-2,100 figure is NASA’s estimate for harm to anyone on Earth, taken as a whole, and the agency’s notice says nothing about property damage. A figure of that size is a little under five hundredths of one percent, which is low but not negligible for a single reentry, and the last prediction before the event is the one that matters most for anyone living inside the 20.6-degree band.

How a 2004 gamma-ray burst hunter lost its altitude

Swift was designed for a two-year prime mission and kept working far beyond it. Its team at Penn State ran operations, and NASA’s mission page lists the Ultraviolet/Optical Telescope and the X-ray Telescope among its instruments; the latter underpinned a 2022 black hole result in which a distant hole repeatedly fed on a Sun-like star. IFLScience credits the mission with more than 2,000 gamma-ray bursts and over 1,400 supernovae, and roughly 7,000 published papers. Shawn Domagal-Goldman, director of NASA’s Astrophysics Division, said Swift delivered an incredible, lasting return on investment for the nation.

The end came from drag. NASA’s Oct. 23 post on the end of the mission says increased solar activity thickened the upper atmosphere and the spacecraft began sinking rapidly. A servicing mission in August did not attempt a boost, and science observations resumed, but the added drag brought another quick descent. On Oct. 20, at 171 miles up, Swift could no longer offset the drag and entered safe mode, and the Penn State operations team then sent a command that effectively ended operations to prepare it for reentry.

The failed rescue and the science left behind

IFLScience reports that NASA gave a private company, Katalyst, the chance to lift Swift with a robotic craft. Katalyst’s LINK spacecraft launched on July 3 but failed itself, so no rescue was attempted. After the August servicing window passed, the team made the best of the final weeks with observations of hundreds of targets, including remnants of stellar explosions, active supermassive black holes in distant galaxies and comets in the solar system. The Swift blog carries the running updates.

The open question is where, if anywhere, the six reaction wheels come down. The Space Force prediction carries 11 hours of uncertainty, and each hour of orbit covers thousands of miles of ground track, so the location will probably be known only once the observatory is gone. NASA has not said whether it will publish a debris assessment afterward, or whether the Space Force will release a final track, and those two records would settle where the pieces landed.

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

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