WASHINGTON
- Decommissioning of a pair of experimental Pentagon satellites known as
Orbital Express is due to begin today and wrap up two days later, bringing the
120-day satellite-refueling demonstration to an irreversible end.
Led by the
U.S. Defense Advanced Research Projects Agency (DARPA) with an assist from
NASA, the Orbital Express mission was launched
March 8 on an Atlas 5 rocket to show that two specially-built satellites
could link up on orbit and transfer
fuel and hardware with limited interaction from the ground.
Despite
some early glitches, the mission is considered a success, with the
two Orbital Express spacecraft completing their final rendezvous and capture
maneuver June 29. It was the second successful grapple of the Ball Aerospace
& Technologies-built NextSat by the Boeing-built Autonomous Space Transport
Robotic Operations (ASTRO) servicing spacecraft.
In a July 3
e-mail, DARPA spokeswoman Jan Walker described the decommissioning process,
which she said would get underway after the United States' Independence Day
holiday July 4.
"The
decommissioning process will consist of de-mating the two satellites,
separating them to approximately 1,000 [kilometers] apart, dumping propellant
from the ASTRO, and then decommissioning the computers," Walker wrote.
"We expect to de-mate the satellites on 5 July, and decommission the computers
on 7 July."
The two
satellites will eventually re-enter the Earth's atmosphere and burn up. NextSat,
the lighter of the two satellites, is expected to re-enter in three to five
years, according to Walker, while Astro should remain in orbit for another 12
to 15 years before coming in.
DARPA and
NASA had been quietly lobbying to keep Orbital Express in service a while
longer to test techniques applicable to future Mars
sample return missions, according to sources familiar with the situation,
but were rebuffed by the U.S. Air Force.
A glimpse
of the behind-the-scenes jockeying is provided by an e-mail DARPA director Tony
Tether sent June 29 to nearly two dozen U.S. government officials, including
Air Force Secretary Michael Wynne and NASA Administrator Michael Griffin
discussing the impending deactivation of Orbital Express.
"It
was hoped that [Orbital Express] would continue for NASA missions. However the
Air Force is unable to support any further Orbital Express mission; rationale
unknown at least to me," Tether wrote, "but offers of paying the
ground station cost for the next three weeks were rejected."
According
to sources, three weeks was the amount of time NASA needed to prepare for a
hand off of the Orbital Express spacecraft to its flight controllers.
NASA
spokesman Dwayne Brown denied any disagreement between NASA and the Air Force
about ending the mission when speaking to Space News June 29. "There is no
dispute," Brown said. "We elected not to pay to do an extended
mission."
advertisement
advertisement
