Military Tracks Errant Satellite for NASA

WASHINGTON, Sept. 22, 2011 — As a 6.5-ton NASA satel­lite makes its way back to Earth lat­er this week, an Air Force space oper­a­tions team in Cal­i­for­nia is track­ing its every move to pre­dict when — and pos­si­bly where — it will re-enter the atmos­phere.

The Joint Space Oper­a­tions Cen­ter, part of the Joint Func­tion­al Com­po­nent Com­mand for Space at Van­den­berg Air Force Base, is respon­si­ble for track­ing the 22,000 objects — most­ly space junk — that orbit Earth. The cen­ter, which reports to U.S. Strate­gic Com­mand, also main­tains “space sit­u­a­tion­al aware­ness” in sup­port of nation­al secu­ri­ty, said Jere­my Eggers, pub­lic affairs direc­tor for the oper­a­tions cen­ter.

As part of that mis­sion, the cen­ter is gath­er­ing track­ing data to help NASA offi­cials ana­lyze the satel­lite and its move­ments. NASA launched the upper-atmos­phere research satel­lite in the ear­ly 1990s, but decom­mis­sioned it in 2005.

The pro­ject­ed re-entry is tomor­row after­noon, but many fac­tors can affect the actu­al time, Eggers said. For exam­ple, a solar storm altered the first pro­ject­ed re-entry date, Sept. 26.

“The oper­a­tions cen­ter has a lot of sen­sors look­ing at the …satel­lite,” he said. “As it re-enters the Earth’s atmos­phere, the data will become more and more refined.”

If the satel­lite doesn’t incin­er­ate when it enters Earth’s atmos­phere, NASA offi­cials expect to see 25 or 26 pieces of debris from the craft. The biggest piece is esti­mat­ed to weigh 300 pounds.

No mod­el exists to ana­lyze or pre­dict where the debris will fall, because there’s no way to pre­dict how the object will break up upon re-entry, Eggers said.

So to get the best pos­si­ble assess­ment, the Joint Space Oper­a­tions Cen­ter start­ed issu­ing reports to NASA four days before the expect­ed re-entry, report­ing more reg­u­lar­ly as the satel­lite gets clos­er to Earth.

“The cen­ter will advise NASA when the satel­lite is two hours out from re-enter­ing the Earth’s atmos­phere, give or take 15 min­utes,” said Air Force Maj. Michael Dun­can, deputy chief of space sit­u­a­tion­al aware­ness at the cen­ter.

“That 15 min­utes,” he added, “could mean the dif­fer­ence of 7,000 miles [in dis­tance] and where it pen­e­trates the Earth’s atmos­phere.”

As of yes­ter­day, Dun­can said, the satel­lite was orbit­ing the Earth every 90 min­utes at more than 17,000 miles per hour. It was hov­er­ing “at 120 miles away, and drop­ping,” he said.

Satel­lites re-enter the Earth’s atmos­phere rou­tine­ly, Dun­can said, but this craft gar­nered world­wide atten­tion because it’s described as the size of a bus.

“Some­thing of this size hap­pens about once every year,” he said. “But about once a week we have an object that’s usu­al­ly a rock­et body or some­thing larg­er that’s re-enter­ing the Earth.”

It’s high­ly unlike­ly that the satel­lite will cause per­son­al injury, Eggers said.

“It’s impor­tant to note that 70 per­cent of the Earth is cov­ered with water, and of the land on Earth, only about 70 per­cent of that is inhab­it­ed,” he said. He not­ed that in 50 years of the U.S. space pro­gram, there is no doc­u­men­ta­tion of debris falling from space strik­ing any­one or caus­ing any sig­nif­i­cant dam­age.

After the re-entry is com­plete, the oper­a­tions cen­ter will con­tin­ue its mis­sion of track­ing and observ­ing the 22,000 objects in space, Eggers said. “The space sit­u­a­tion­al aware­ness plays an impor­tant role in pro­tect­ing U.S. space-based assets,” he said.

U.S. Depart­ment of Defense
Office of the Assis­tant Sec­re­tary of Defense (Pub­lic Affairs)