Article Posted on : - Sep 20, 2011

An artistic illustration of Upper Atmosphere Research Satellite.

WASHINGTON (PTI): A six-and-a-half tonne defunct climate satellite that has been circling the Earth for the past 20 years will make a fiery death plunge this week, NASA officials have warned.

According to NASA’s latest projections, the bus-size Upper Atmosphere Research Satellite (UARS) will likely plummet down to Earth sometime around Friday (September 23).

But there is a one-in-3,200 chance that its debris could hit any person, the US space agency officials said.

“Re-entry is expected September 23, plus or minus a day,” they said, adding that at least 26 large pieces of the dead satellite will hit the ground on Earth surviving the scorching temperatures of atmospheric re-entry, LiveScience reported.

Though it’s still uncertain exactly where the debris will fall, NASA officials indicated that the drop zone for UARS satellite debris could be anywhere between the latitudes of northern Canada and southern South America, an area that includes much of the planet.

The USD 750-million satellite, which was launched in 1991 to study the ozone layer and Earth’s upper atmosphere to better understand their role in the planet’s climate, should re-enter over a 804km track, the experts have predicted.

Since 75 per cent of Earth is covered with ocean, there is a high likelihood that the satellite will re-enter over the sea or a remote, uninhabited stretch of land, said Victoria Samson, the Washington Office Director of the Secure World Foundation.

The UARS was designed for a three-year mission, but it lasted for 14 years until newer satellites made it obsolete.

It was decommissioned in December 2005 with NASA experts commanding the spacecraft to fire its thrusters one last time to use all its remaining fuel to place it on a years-long path toward disposal in Earth’s atmosphere.

If the satellite does fall while flying over a populated region of Earth, sky watchers could see a “dazzling light show if they have clear weather,” Nick Johnson, chief scientist of NASA’s Orbital Debris Program in Houston, said.

As of Sunday, the UARS was flying in an orbit that reached a high point of about 149 miles (240 km) above Earth.

That is down from an orbit that peaked at an altitude of 171 miles (275 km) on September 8.

The huge satellite, which is 35 feet long and 15 feet wide, and has been falling faster than anticipated (initial re-entry estimates pegged its plunge to somewhere between late September and early October) due to increased solar activity last week.

Solar activity can cause Earth’s atmosphere to heat and expand, increasing drag on low-flying spacecraft, the researchers said.

The US Strategic Command at Vandenberg Air Force Base, California, and NASA are keeping a close eye on the falling UARS spacecraft, but have said that they will only be able to pinpoint the satellite’s point of impact to within about 6,000 miles (10,000 km) about two hours before re-entry due to its unpredictable nature.