NASA’s Swift telescope is expected to reenter Earth in the coming days - Space and astronomy

The Neil Gehrels Swift Observatory will make an uncontrolled reentry after its orbit decayed and a rescue mission failed to raise it. Experts say most of the spacecraft should burn up, although the exact timing and location remain uncertain.

NASA’s Neil Gehrels Swift Observatory is expected to reenter Earth’s atmosphere in the next few days, following the failure of a robotic mission intended to move the telescope into a higher orbit. The reentry will be uncontrolled, and researchers have not yet determined exactly when or where it will occur.

Launched in November 2004, Swift spent more than two decades studying gamma-ray bursts and other cosmic phenomena. It used three instruments: the Burst Alert Telescope, the X-Ray Telescope and the Ultraviolet/Optical Telescope.

NASA reported on Oct. 20 that Swift’s orbit had fallen to about 171 miles (275 kilometers) above Earth. At roughly 3,300 pounds (1,500 kilograms), the observatory could no longer counter the increasing atmospheric drag. The spacecraft entered safe mode, and its operations team at Pennsylvania State University sent a command that ended its mission ahead of the reentry.

The spacecraft is expected to break apart and largely burn up in the atmosphere. Darren McKnight, a senior technical fellow at LeoLabs, said Swift is unlikely to create a significant ground casualty hazard, although some internal components from its X-ray and optical telescope could survive.

Aerospace engineer Dean Sladen said the main breakup would likely occur after Swift drops to around 78 kilometers (48 miles) in altitude. Solar panels and antennas would probably detach first, while most of the aluminum, wiring and electronics would melt or vaporize.

Potential survivors could include dense, heat-resistant components such as the spacecraft’s six reaction wheels and parts of its telescopes, including lenses and mirrors. Sladen said only a small number of scorched fragments would be expected to reach the surface, rather than anything recognizable as a complete telescope.

Swift’s orbit passes over a region extending to about 21 degrees north and south of the equator. That area is mostly ocean, but it also includes populated parts of Africa, South and Southeast Asia, and Latin America. The precise landing location of any surviving debris is not yet known.

Experts cited in the report described the risk to people on the ground as very small. They also noted that uncontrolled reentries are becoming more common as the number of objects in low Earth orbit increases, highlighting the growing importance of designing spacecraft to burn up completely or steer themselves into remote ocean areas at the end of their missions.

Sources: Space.com.