WASHINGTON —
The U.S. Air Force will deactivate the Pentagon's Orbital Express satellites the
week of July 2, eliminating any chance of NASA using the experimental
spacecraft to test robotic techniques applicable to future Mars sample return
missions.
Orbital
Express is a roughly $300 million satellite-refueling demonstration led by the
U.S. Defense Advanced Research Projects Agency (DARPA). It consists of a pair
of unmanned spacecraft that were launched in March aboard an Atlas 5 rocket to
conduct a series of experiments over a planned 90-day period. NASA contributed about $25 million to the project back in 2001 and engineers at the space agency's Marshall Space Flight Center helped develop the spacecraft's automated guidance system.
Sources
familiar with the situation said NASA and DARPA had been quietly appealing to
the Air Force to keep Orbital Express on orbit a while longer, but were turned
down.
But NASA
spokesman Dwayne Brown said June 29 that there was no disagreement between NASA
and the Air Force about ending the Orbital Express mission.
"There is
no dispute," Brown said. "We elected not to pay to do an extended mission."
According
to e-mails obtained by Space News, the two Orbital Express spacecraft completed
their final rendezvous and capture maneuver shortly after midnight June 29. It
was the second successful grapple of NextSat by the Autonomous Space Transport
Robotic Operations (ASTRO) servicing spacecraft.
"Orbital
Express will perform a mated scenario this weekend, demonstrating the ASTRO
spacecraft's ability to remove and re-insert a spare flight computer with its
robotic arm. Once complete, DARPA's demonstration is done," U.S. Air Force Lt.
Col. Fred G. Kennedy, DARPA's Orbital Express program manager, wrote in a June
29 e-mail to several senior DARPA officials including Tony Tether, the agency's
director.
Tether
forwarded Kennedy's status report to nearly two dozen U.S. government
officials, including Air Force Secretary Michael Wynne and NASA Administrator
Michael Griffin, explaining that the mission was about to complete its final
objective and would be decommissioned at the request of the Air Force.
"This is
the last scenario for Orbital Express which has now set historical records for
the U.S. space effort," Tether wrote. "It was hoped that OE would continue for
NASA missions. However the Air Force is unable to support any further Orbital
Express missions; rationale unknown at least to me but offers of paying the
ground station cost for the next three weeks were rejected."
"Orbital
Express will be 'de-orbited' sometime next week," Tether concluded.
Wynne,
responding to Tether in an e-mail copied to the same long list of recipients,
said he considers the upcoming decommissioning of Orbital Express a settled
issue.
"As I
understand it; it was explained that the science aspects of the mission were
appreciated and completed. There is no intention to maintain this in orbit
forever, and the offers of resources and the risk they offset from other
opportunities for learning about space operations have been evaluated. Great
work by DARPA," Wynne wrote, adding: "I thus do not know what problem we are
trying to solve now?"
DARPA
spokeswoman Jan Walker, reached by telephone and e-mail June 29, would not
immediately comment.
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