Despite a
rocky start, two unmanned spacecraft have succeeded in their first autonomous satellite
refueling demonstration while orbiting high above Earth.
The ASTRO satellite,
one of two spacecraft flying the Orbital
Express refueling mission, successfully pumped vital hydrazine fuel into
its NextSat counterpart as part of Scenario 0-1, the first in a series of
increasingly challenging tests.
"The first
Orbital Express demonstration, Scenario 0-1, was very successful," a
spokesperson Jan Walker for the U.S. Defense Advanced Research Projects Agency
(DARPA), which is overseeing the mission, said in a written update Wednesday. "ASTRO
transferred just under 32 pounds (14 kilograms) of hydrazine to the NextSat
client, meeting the scenario objective."
Walker said
the robotic arm-equipped ASTRO, short for Autonomous
Space Transport Robotic Operations, first delivered the hydrazine during the
early hours of April 1 via a fluid hookup, and then followed up by transferring
an additional 19 pounds (8.6 kilograms) of propellant to NextSat a day later. NextSat
was due to return propellant to ASTRO sometime today, she added.
In
addition to refueling demonstrations, ASTRO is also designed to perform tasks
such as autonomous undocking, proximity operations and re-docking, as well as
use its robotic arm to install a battery on NextSat.
Orbital
Express mission managers believe the technology onboard ASTRO and NextSat could
allow future military reconnaissance satellites
keep station over targets on Earth by providing a renewable propellant source.
The technology could also help extend the lifetimes of general-use satellites
by allowing in-flight repairs, equipment replacements or upgrades, mission
managers have said.
The
Orbital Express mission, however, did suffer a glitch shortly after launch.
The
incorrect installation of a pitch momentum wheel aboard ASTRO led the spacecraft
to react opposite of what its onboard navigation software intended, DARPA
officials said.
"It
was a combination of hardware and software issues," Walker said of the glitch,
adding that flight controllers relied on NextSat's navigation systems to orient
ASTRO's solar panels towards the Sun until new software could be uploaded. "With
the updated software, [ASTRO's] commands result in the expected pitch wheel
motion."
ASTRO
has already employed a camera on its robotic arm to snap about 1,600 images of
itself and NextSat, currently mated to one another, which Orbital Express
mission managers assembled into a video.
ASTRO's
April 1 refueling operations with NextSat were performed under a low-autonomy
level, requiring the spacecraft to receive a total of 23 approvals from flight
controllers on Earth, Walker said. Later this week, ASTRO will transfer a
battery from its bay to a corresponding slot aboard NextSat, she added.
On
April 16, the separation ring joining the two spacecraft together will be
jettisoned to mark the beginning of rendezvous and capture activities, Walker
said.
The
Orbital Express mission launched
on March 8 as part of the U.S. Air Force's Space Test Project-1 (STP-1)
mission, with ASTRO and NextSat vehicles successfully reaching orbit alongside four
other small satellites.
The
$300 million mission is expected to run about 91 days. Boeing's Phantom Works
led the 2,100-pound (952-kilogram) ASTRO vehicle's development, while Ball
Aerospace oversaw construction of the 500-pound (226-kilogram) NextSat for
DARPA.
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