NASA's Swift telescope is about to fall out of orbit, and the Sun is the reason. It lost 0.7 km of altitude in all of 2019. This year it lost 185 km.

Swift has been catching gamma-ray bursts since 2004. Those are the brightest explosions in the universe, from collapsing stars and colliding neutron stars. Swift was built to spot one and swing its telescopes onto it within about a minute. It has found well over a thousand.

It never had an engine to hold its orbit, so it was always going to come down eventually. The Sun set the timing. When the Sun is active, it heats Earth's upper atmosphere and makes it swell upward. The air thickens at the height where satellites fly. During the quiet years around 2019, Swift barely moved. Then the current solar cycle ramped up, and the fall began. Each drop put it into denser air, which made it fall faster still. By our model, the air at its height today is about 1,400 times denser than what it flew through in 2019.

NASA tried to save it. A company called Katalyst launched a small spacecraft in July to grab Swift and push it higher. That spacecraft went into a spin, and the rescue was called off in August.

The U.S. Space Force forecast puts reentry around November 4, give or take about 14 hours. Most of Swift will burn up. Whatever survives will come down somewhere in the tropics, most likely over ocean.

— u/oldschoolscreenname