Boeing Orbital
Express Achieves Another First in Space
(22 June 2007) The Boeing Company
today announced that the Orbital Express system, a program to validate
spacecraft servicing capability led by the Defense Advanced Research Projects
Agency (DARPA), has performed a fully-autonomous "fly-around and capture" of
its NextSat client spacecraft, marking another industry first for the
innovative program.
During the five-hour test on June 16,
Boeing's Autonomous Space Transport Robotic Operations (ASTRO) servicing
spacecraft used its onboard cameras and advanced video guidance system to
separate from, circle and re-mate with the Ball Aerospace NextSat client
spacecraft. The test primarily used passive sensors with no active exchange of
relative navigation information or involvement by ground
controllers.
Positioned in orbit 60 meters above NextSat, ASTRO followed
an imaginary line called the "Rbar," which extends from the Earth's centre to a
satellite and beyond, to capture the spacecraft. The manoeuvre simulated the
direction of approach needed to effectively service a satellite without
interfering with its cameras or antennas.
"This scenario validated
autonomous fly-around capability, which is needed for inspecting spacecraft,"
said Alex Lopez, vice president of Boeing Advanced Network and Space Systems.
"The team also proved that approaching a satellite from 'minus Rbar' means that
Orbital Express can conduct on-orbit servicing operations without disrupting
satellite service for customers. This capability is considered highly desirable
by satellite operators."
ASTRO and NextSat began the demonstration
(Scenario 5-1) in the Mated Nominal mode. At the predicted time, ASTRO's
autonomous systems separated it from NextSat to a range of up to 120 meters.
ASTRO then circled NextSat using its sensor systems to continuously track
NextSat during the fly-around. If sensor inputs had deviated outside of the
established limits, an autonomous safing action would have repositioned the
spacecraft to a safe location.
After completing the fly-around, ASTRO
maintained its relative position with NextSat at 120 meters for 17 minutes then
manoeuvred above NextSat to perform a corridor approach to within centimetres
of the client spacecraft. The capture mechanism grappled NextSat and performed
a soft berth, drawing NextSat and ASTRO together.
The test marked the
first unmated operation since mid-May when the Orbital Express team experienced
a computer sensor anomaly during the unmated portion of Scenario 3-1. The
system's autonomous safing feature manoeuvred the spacecraft to a safe location
until the team could re-mate them. The team has since resolved the anomaly from
this scenario.
During the next major unmated operation (Scenario 7-1),
ASTRO will depart NextSat to a range of four kilometres before approaching the
client spacecraft and performing a free-fly capture using its robotic
arm.
Orbital Express team members include NASA, Ball Aerospace, Northrop
Grumman Space Technology, MacDonald, Dettwiler and Associates Ltd., the Charles
Stark Draper Laboratory Inc., and Starsys Research.
A unit of The Boeing
Company, Boeing Integrated Defense Systems is one of the world's largest space
and defence businesses specialising in innovative and capabilities-driven
customer solutions. Headquartered in St. Louis, Boeing Integrated Defense
Systems is a US$ 32.4 billion business with 72,000 employees
world-wide.
(source: Boeing)