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March
5, 2007: It's the year 2020, and space has never
been so busy. Picture this:
In
Earth orbit, a robotic maintenance ship skitters from one
weather satellite to another, upgrading powerful optics
that help meteorologists track dangerous storms.
Four
hundred thousand kilometers away, a cargo ferry arrives
at the Moon. It spots an orbiting depot, makes its approach
and mates flawlessly, offloading drill heads, solar panels
and other supplies for a frontier outpost at the Moon's
south pole.
Meanwhile,
down on the the lunar surface, mining buggies trundle along
a "sensor highway" between the outpost and some
nearby hills. They're harvesting lunar ice hidden in the
shadows of a deep, cold crater.
Oh
yeah – there's not a single human operator in this hypothetical
scenario.
It's
not as far-out as it sounds. All of these spacecraft and satellites,
even the mining buggies, could one day operate on their own,
guided not by humans but by automated rendezvous and docking
technologies now in development by NASA and its partners.
 Some
of those technologies are about to get a field test onboard
Orbital Express--a space mission managed by the Defense Advanced
Research Projects Agency (DARPA) and a team led by engineers
at NASA's Marshall Space Flight Center. Slated for launch
this week, March 8, on an Atlas V rocket, Orbital Express
will deploy two test satellites: the Autonomous Space Transport
Robotic Operations (ASTRO) service vehicle, and the Next-generation
serviceable satellite (NextSat).
Right:
An artist's concept of ASTRO and NextSat docking in Earth
orbit. [More]
"Our
goal is to demonstrate on-orbit refueling, component exchange
and satellite repair--all without a human operator,"
says James Lee, the MSFC Automated Rendezvous and Docking
Projects Lead.
In
a nutshell, ASTRO will dock with NextSat and service it.
Who
will pilot ASTRO? The answer is not who but what:
the Advanced Video Guidance Sensor or AVGS for short. Mounted
on ASTRO, the AVGS shoots infrared laser beams, which bounce
off a pattern of retroreflectors
on NextSat. By analyzing the reflections, ASTRO adjusts its
speed and angle of approach to safely close the distance and
make contact.
Right:
An artist's concept of ASTRO and NextSat exchanging components.
[More]
 Eight
test series will be conducted during the three-month mission.
ASTRO and NextSat will conduct approach and docking maneuvers
from starting points up to 4.3 miles (6.9 km) away. Once docked,
they'll also swap propellants and trade and install batteries--the
first unassisted component exchange in space history. Tests
will be conducted at different times of day to see if darkness
on Earth's night side confuses the imaging system.
If
Orbital Express is a success, use of autonomous rendezvous
and docking systems could become a viable alternative to human-piloted
missions in the next decade.
"Automated
systems will take ship-to-ship mating duties off the hands
of busy flight crews," says AVGS flight software project
leader Keith Cornett of Marshall. "They can solve issues
associated with tricky repairs and provide cost-effective
options for servicing permanent satellites in orbit around
the Moon or Mars."
Automated
systems could also benefit surface operations, Lee notes,
particularly on the airless moon where global positioning
systems won't work without relays. That "sensor highway,"
dotting the surface with reflective markers to shine the way,
could one day guide robots from place to place – surveying,
sampling and laying the groundwork for human expeditions to
come.
"When
it comes to exploring new worlds, robots can't beat human
beings for capturing the experience," Lee says. "But
to make those human missions possible, we need to set the
stage as completely as we can. Automation is crucial."
For
more information about the Orbital Express mission, click
here. And
stay tuned to Science@NASA for updates about this week's launch
and the mission to follow.
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Author: Rick Smith
| Editor:
Dr. Tony Phillips | Credit: Science@NASA
|
