The prototype satellite NextSat poses with the Earth as a backdrop in this orbital view taken by its robotic refueling partner, the ASTRO spacecraft.
WASHINGTON - The Pentagon decommissioned its experimental Orbital Express satellites this week, bringing the on-orbit satellite-servicing and robotics demonstration to an irreversible end.
The two spacecraft that comprise Orbital Express - the Boeing-built Autonomous Space Transport Robotic Operations (ASTRO) servicing spacecraft and the Ball Aerospace & Technologies-built NextSat - were launched together in early March on an Atlas 5 rocket. The in-orbit satellite servicing experiment was sponsored by the U.S. Defense Advanced Research Projects Agency, or DARPA.
Over the last four and a half months, ASTRO has demonstrated its ability to approach NextSat with limited interaction from the ground, grapple the spacecraft with its robot arm and transfer fuel and hardware.
According to an update posted Sunday on DARPA's Web site, the two satellites were decommissioned after successfully completing one last maneuver that demonstrated ASTRO's ability to find and home in on NextSat from long range with an assist from the U.S. Space Surveillance Network. ASTRO then switched over to on-board sensors to complete the rendezvous.
The decommissioning was to have begun July 5, but the Pentagon extended the mission two weeks to allow the team to attempt the long-range rendezvous maneuver. The final demonstration entailed putting enough distance between the satellites that ASTRO's sensor suite lost track of NextSat, and thus required input from the ground-based Space Surveillance Network to locate the target satellite and close in.
The maneuver was initiated July 16 and completed over the next few days. By early July 21, Orbital Express flight controllers confirmed that they had successfully repositioned NextSat's solar arrays away from the sun and turned off the spacecraft's on-board computer. Flight controllers confirmed the following day that ASTRO, too, had been successfully decommissioned, a process that in addition to turning off the computer entailed dumping the satellite's remaining onboard fuel.
"The DARPA Orbital Express program met all of its mission success criteria," the agency said. "The end-of-life maneuver demonstrated a capability for long-range rendezvous and track."
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