Out-of-control satellite slows rate of descent as it closes in on Earth

WASHINGTON, D.C. (BNO NEWS) -- An out-of-control U.S. satellite slowed its rate of descent on Friday as it neared the Earth's atmosphere where it will partly burn up before crashing somewhere on the planet, NASA said. Impact is expected late Friday or early Saturday.

NASA's Upper Atmosphere Research Satellite (UARS) is expected to re-enter Earth's atmosphere on late Friday evening or early Saturday morning U.S. time, almost six years after the end of its productive scientific life. Although the spacecraft will break into pieces during re-entry, not all of it will burn up in the atmosphere.

As of 7 p.m. EDT on Friday, the orbit of UARS was 90 miles by 95 miles (145 kilometers by 150 kilometers). Its rate of descent had slowed earlier on Friday, according to NASA, which said the satellite's orientation or configuration had apparently changed.

"During that time period (when it re-enters the atmosphere), the satellite will be passing over Canada, Africa and Australia, as well as vast areas of the Pacific, Atlantic and Indian oceans," NASA said in a Friday update. "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."

Earlier this week, NASA repeatedly said the satellite's debris was not expected to impact North America, but the changed rate of descent forced the agency to retract those statements. The U.S. Federal Aviation Administration later issued a warning to pilots.

"Aircraft are advised that a potential hazard may occur due to reentry of satellite UARS into the Earth's atmosphere," a special Notice To Airmen (NOTAM) said. "FAA is working with the Department of Defense and NASA to ensure the most current re-entry information is provided to operators as quickly as possible. Further NOTAMs will be issued if specific information becomes available indicating a United States airspace impact."

It added: "In the interest of flight safety, it is critical that all pilots/flight crew members report any observed falling space debris to the appropriate ATC (Air Traffic Control) facility and include position, altitude, time, and direction of debris observed."

Earlier on Friday, a Chinese expert said a debris tracker will be able to give a fairly accurate prediction where debris will fall about two hours before it hits Earth, giving any residents some time to evacuate. Pang Zhihao, a researcher from the Chinese Research Institute of Space Technology, said it is most likely that the debris will fall into the ocean or unpopulated areas.

NASA previously said the risk to public safety or property is extremely small, but a small chance remains that debris could impact a populated area. It is estimated some 26 pieces, the heaviest weighing around 350 pounds (158 kilograms), will survive the re-entry and fall to Earth.

"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 (804 kilometers) long," the agency said earlier. It added that, 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.

One of the reasons why it is unknown where the debris will crash is because the satellite can skip and skitter on the Earth's atmosphere, making it difficult to predict a time of re-entry. The debris will also roll and rotate as it goes down due to pieces sticking out, making it harder to project a precise course.

Saturday, September 24th, 2011

Source: WireUpdate.
Link: http://wireupdate.com/news/out-of-control-satellite-slows-rate-of-descent-as-it-closes-in-on-earth.html.