NASA's Upper Atmosphere Research Satellite, or UARS, is expected to re-enter Earth's atmosphere late Sept. 23 or early Sept. 24 Eastern Daylight Time, almost six years after the end of a productive scientific life. Although the spacecraft will break into pieces during re-entry, not all of it will burn up in the atmosphere.

The risk to public safety or property is extremely small, and safety is NASA’s top priority. 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. Nor is there a record of significant property damage resulting from a satellite re-entry.

As of 10:30 a.m. EDT on Sept. 23, 2011, the orbit of UARS was 100 miles by 105 miles (160 km by 170 km). Re-entry is expected late Friday, Sept. 23, or early Saturday, Sept. 24, Eastern Daylight Time. Solar activity is no longer the major factor in the satellite’s rate of descent. The satellite’s orientation or configuration apparently has changed, and that is now slowing its descent. 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. 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.Visit this page for updates on the satellite’s orbital track and predicted re-entry date.

› Re-Entry and Risk Assessment (498 KB PDF)
› Frequently Asked Questions: Orbital Debris

The updates posted here come from the Joint Space Operations Center of U.S. Strategic Command at Vandenberg Air Force Base, Calif., which works around the clock detecting, identifying and tracking all man-made objects in Earth orbit, including space junk.

The actual time of re-entry is difficult to predict because it depends on solar flux and the spacecraft’s orientation as its orbit decays. As re-entry draws closer, predictions on the date will become more reliable.

Because the satellite’s orbit is inclined 57 degrees to the equator, any surviving components of UARS will land within a zone between 57 degrees north latitude and 57 degrees south latitude. It is impossible to pinpoint just where in that zone the debris will land, but NASA estimates the debris footprint will be about 500 miles long.

If you find something you think may be a piece of UARS, do not touch it. Contact a local law enforcement official for assistance.

Source: NASA