US space agency NASA estimates a six-tonne decommissioned satellite will break up and fall to Earth late today or tomorrow, but says the risk to public safety or property is extremely small.
The space shuttle Discovery launched the Upper Atmosphere Research Satellite, or UARS, in September 1991. UARS’ job, as the first multi-instrumented satellite, was to observe chemical constituents of the atmosphere to better understand atmospheric photochemistry and transport.
Now, in its latest update, NASA says the unpowered spacecraft’s orientation has changed, slowing its descent. It is expected to break into 26 pieces during re-entry into the Earth’s atmosphere, though not all the pieces will burn up.
"There is a low probability any debris that survives re-entry will land in the United States, but the possibility cannot be discounted because of this changing rate of descent," NASA said. "It is still too early to predict the time and location of re-entry with any certainty, but predictions will become more refined in the next 12 to 18 hours."
Since the beginning of the Space Age in the late 1950s, there have been no confirmed reports of an injury resulting from re-entering space objects, NASA says. Nor is there a record of significant property damage resulting from a satellite re-entry.
NASA is also warning the public to keep their hands off any pieces of UARS they may think they have come across after the debris hits the Earth. Instead, they should call law enforcement officials for help.