NASA's Swift Telescope Is About to Fall Back to Earth After 22 Years

Keypoints:

• NASA's Swift Observatory is expected to reenter Earth's atmosphere on or around Friday
• It has studied the universe's most powerful explosions since its launch in November 2004
• A commercial rescue mission failed to raise its orbit
• Most of the 1.5 ton spacecraft will burn up, but dense parts like tungsten pieces may survive
• Any debris will most likely land in the ocean, and the risk to people is very low

A famous space telescope is coming home, and not in a gentle way. NASA's Neil Gehrels Swift Observatory, which has watched cosmic explosions for more than two decades, is expected to fall back through Earth's atmosphere on or around Friday, according to the US Space Force. Tracking dates can shift by a few days.

Swift launched in November 2004 and became one of astronomy's best alert systems. Its special talent was swiveling quickly toward sudden events like gamma-ray bursts, which are some of the most powerful explosions in the universe. Then Hubble, Webb and other telescopes would follow its alerts for a closer look. NASA considered it a first responder for the rest of the fleet.

So what went wrong? Swift was built without an engine to keep its orbit. As the Sun became more active, it puffed up Earth's upper atmosphere, creating extra drag that slowly dragged the telescope down from its original 600 kilometer orbit. NASA hired a company called Katalyst Space to try a rescue with a robotic spacecraft named Link, which launched in July. 

Link got within about 12 to 15 kilometers of Swift but could not reach it. Link itself fell back to Earth in September. Swift's science work stopped in late October, when it dropped too low to point steadily, and NASA officially ended operations on October 23.

Now the question is what survives. Most of the spacecraft will burn up. But mission chief scientist Brad Cenko says some parts made of tungsten, a metal denser than lead, along with some mirror pieces, could make it to the surface. Scientists expect any debris to fall into the ocean. The possible reentry zone does include parts of Africa, Australia, India, Southeast Asia and Central and South America, but the risk to people is considered extremely low.

Cenko summed it up simply. Swift's team has known this day would come since before launch, because anything in low Earth orbit eventually comes back down. For astronomers, it is the end of a long and productive career.