NASA's Swift Space Telescope Could Fall to Earth Within Hours

NASA's Neil Gehrels Swift Observatory, a space telescope that has been falling steadily out of orbit, could re-enter Earth's atmosphere as early as tonight, the agency says. Live Science reported that NASA's latest estimate, shared Nov. 2, points to about 3:30 a.m. EST on Nov. 4, give or take 11 hours.

The risk to people is small. Most of the roughly 3,200-pound (1,450 kilograms) spacecraft is expected to burn up on the way down, according to NASA.

When will the Swift telescope come down?

NASA's estimate is a window rather than a single moment. With an uncertainty of plus or minus 11 hours, the spacecraft could drop out of the sky as early as this evening, Live Science reported.

An independent analysis from the Aerospace Corporation, a private nonprofit that tracks thousands of objects in orbit, lands close by. It estimates reentry at 5:12 a.m. EST on Nov. 4, give or take eight hours. NASA says it will keep updating its predictions as the window narrows.

Where could pieces land?

Any fragments that survive the fiery descent are likely to fall somewhere between 20.6 degrees south latitude and 20.6 degrees north latitude, according to NASA. That band covers parts of Mexico, the Caribbean, Central and South America, the Arabian Peninsula, India, Africa and Oceania, as well as a great deal of open ocean.

Because the exact timing is still uncertain, the landing area cannot yet be narrowed further.

How big is the danger?

NASA puts the chance that Swift debris falls over a populated area at about 1 in 2,100. For comparison, the National Weather Service puts the odds of a person being struck by lightning over a lifetime at 1 in 15,300, Live Science noted.

What does this mean for people on the ground?

For nearly everyone, very little. The agency describes the risk to humans as minimal, as it is for all spacecraft reentries. Most of the observatory should vaporize in the atmosphere, and the zone where pieces could reach the surface includes large stretches of ocean.

The bigger loss is scientific. Swift gave astronomers a steady view of some of the most violent events in the universe, and its retirement ends a long run of observations.

What was Swift, and why is it coming down?

Swift is a multiwavelength telescope that observes in optical, ultraviolet and X-ray light. It launched in November 2004 to study the most powerful explosions in space. It was designed for a two-year primary mission but ended up working for more than 10 times that long, hunting supernovas, gamma-ray bursts and eruptions linked to black holes.

The spacecraft has been losing altitude for more than a year, after intense solar activity increased the drag on it, Live Science reported. In August, a costly attempt to raise Swift's orbit using a private spacecraft failed shortly after launch, which removed the last realistic way to keep it aloft.

Engineers shut down the observatory's science operations on Oct. 20, after it dropped too low in orbit to keep making steady observations of the sky.

What does Swift leave behind?

According to NASA, Swift's data have contributed to more than 7,000 scientific papers so far. That number is expected to grow as the telescope's final observations are processed.

Around Prague, based on reporting by Live Science