September 8, 2011
NASA Prepares For Satellite Re-entry
NASA on Wednesday said that a 20-year-old satellite is due to re-enter Earth´s atmosphere sometime in the next six weeks, burn up, and rain debris over a wide area.
The defunct 7-ton Upper Atmosphere Research Satellite (UARS) should plunge to Earth sometime in late September or early October, but the agency cannot determine exactly when that re-entry will occur and what geographic area may be affected. However, NASA is keeping a close eye on the satellite and will keep the public informed of the track and re-entry date as soon as they know for sure.
“Although the spacecraft will break into pieces during re-entry, not all of it will burn up in the atmosphere,” NASA said.
It is too early to set an exact date on when and where it will make its final plunge, but Russian news reports suggested that Moscow was “in the zone of risk.” However, that projection was based on the inclination of UARS´ orbit.
NASA spokeswoman Beth Dickey said the track and re-entry location are going to be “more refined as the days pass.”
Even though the satellite is not expected to entirely burn up in re-entry, NASA said there should be no cause for alarm as the risk to public safety 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,” said NASA.
NASA is cautioning the public not to touch anything that they believe might be from UARS. Instead the public should immediately contact local law enforcement.
UARS´ current orbit is 155 by 174 miles, with an inclination of 57 degrees. That means the satellite would have to descend into the atmosphere somewhere between 57 degrees north latitude and 57 degrees south, the agency said. NASA said possible debris would stretch out about 500 miles.
“The actual date 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,” NASA said.
UARS was launched on September 12, 1991, aboard the shuttle Discovery (STS-48) and was deployed into orbit 3 days later.
The $750 million mission measured the concentrations and distribution of gases important to ozone depletion, climate change and other atmospheric phenomena. NASA said reading from UARS provided conclusive evidence that chlorine in the atmosphere, originating from human-produced chlorofluorocarbons, is at the root of the polar ozone hole.
The satellite also provided key data on the amount of light that comes from the Sun at ultraviolet and visible wavelengths. UARS´ productive life came to an end in 2005. “They had put it in a disposal orbit at that point, and that disposal orbit reduced its orbital lifetime by about 20 years,” said Dickey.
NASA will post weekly updates about the satellite´s re-entry. Daily updates will be posted four days before re-entry, and then will be posted more frequently within 24 hours of re-entry. The re-entry process is being tracked by the Joint Space Operations Center of US Strategic Command at Vandenberg Air Force Base in California, which works to detect, identify and track all man-made objects orbiting the Earth.
NASA will host a media teleconference at 11 a.m. EDT on Friday, September 9, to discuss the anticipated re-entry of the decommissioned UARS.
Participants at the teleconference are expected to include Paul Hertz, chief scientist, NASA's Science Mission Directorate, Washington; Nick Johnson, chief scientist, NASA's Orbital Debris Program, Johnson Space Center, Houston; and U.S. Air Force Major Michael W. Duncan, deputy chief, space situational awareness, U.S. Strategic Command, Vandenberg Air Force Base.
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
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