September 24, 2011

UARS Falls Back to Earth Over Pacific Ocean


The decommissioned Upper Atmosphere Research Satellite (UARS) fell back to Earth overnight, penetrating the atmosphere somewhere over the Pacific Ocean, NASA officials reported early Saturday morning.

In an advisory posted to the UARS mission page, officials from the Joint Space Operations Center at Vandenberg Air Force Base in California said that the satellite re-entered the planet's atmosphere sometime between 11:23 p.m. EDT Friday night and 1:09 a.m. EDT Saturday morning.

The exact time and place of re-entry was not known as of 3:46 a.m. EDT on September 24.

Irene Klotz of Reuters reported that UARS "plunged through the atmosphere early on Saturday, breaking up and possibly scattering debris in Canada, NASA said“¦ There were reports on Twitter of debris falling over Okotoks, a town south of Calgary in western Canada" -- debris believed that have originated from the satellite, which had been in orbit for two decades.

According to the Associated Press (AP), it is the largest NASA spacecraft to fall out of orbit and plummet, uncontrolled, back to the surface in more than three decades.

The re-entry was originally expected to occur sometime in late September or early October, but last week NASA altered their predictions to September 23, plus or minus one day, due to a "sharp increase in solar activity."

Early Friday morning, NASA had reported that UARS would re-enter Earth's atmosphere that afternoon. As a result, it was believed that it would most likely miss North America, as it would not be passing over the continent during at that time.

However, at 10:30 a.m. EDT, they posted an update to the UARS mission page, stating that "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," officials from the U.S. space agency added. "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."

NASA later updated the satellite's status once again, noting that as of 7:00 p.m. EDT, UARS's orbit was 90 miles by 95 miles, and that re-entry was expected to occur between 11 p.m. Friday evening and 3 a.m. Saturday morning. The agency noted that the satellite would be passing over Canada, Africa, Australia, and the Pacific, Atlantic, and Indian Oceans during that time frame.

As previously reported on RedOrbit, NASA officials believed that the odds of a piece of debris from the UARS satellite would hit a person were approximately 1-in-3,200, and that the odds of any particular individual would be struck were 1-in-21 trillion.

Scientists had previously predicted that 26 pieces of debris, weighing a total of 1,100 pounds, would survive the planet's atmosphere. It had been anticipated that the remainder of the 13,000 pound satellite would burn up during the re-entry process.

The $750 million UARS satellite was launched in September 1991 to help measure the ozone layer, wind and temperature.  Its mission was initially scheduled to last for a period of three years. The satellite was officially decommissioned in December 2005 after being struck by a small piece of debris and damaged.

While NASA officials had confirmed that there were no hazardous materials remaining onboard the satellite, they nonetheless advise, "If you find something you think may be a piece of UARS, do not touch it. Contact a local law enforcement official for assistance."


Image Caption: This conceptual image shows the Upper Atmosphere Research Satellite, launched on Sept. 15, 1991, by the space shuttle Discovery. Originally designed for a three-year mission, UARS measured chemical compounds found in the ozone layer, wind and temperature in the stratosphere, as well as the energy input from the sun. Together, these measurements helped define the role of Earth´s upper atmosphere in climate and climate variability. The 35-foot-long, 15-foot-diameter UARS was decommissioned on Dec. 14, 2005. (Credit: NASA)