PARIS
-- Managers of Europe's large cargo vessel launched Sunday to the International
Space Station said they likely will modify their planned in-orbit test schedule
as they investigate why one of the vehicle's four propulsion systems was shut
down by an on-board computer shortly after launch.
They
said that even if the affected system remains shut down, the Automated Transfer
Vehicle (ATV) can continue its mission and dock as planned with the space
station. The ATV Jules Verne lifted
off Sunday at 3:03 a.m. GMT (11:03 p.m. March 8 GMT) atop an Ariane 5
rocket that launched from European spaceport in Kourou, French Guiana.
In
a March 9 press briefing, officials from the European Space Agency (ESA) and
from the ATV's prime contractor, Astrium, said the vehicle's on-board computer
did its job correctly in shutting down one of the four propulsion systems after
finding an unexpected difference in pressure between the system's fuel lines
and its oxidizer lines.
The
propulsion function was automatically transferred to a second system, which
reported no similar problems.
John
Ellwood, ESA's ATV mission manager, said in an interview that all other ATV
systems appear to be in good health, with the craft in a stable, 161-mile (260-km)
circular orbit. While the ATV had been scheduled to climb closer to the
station's 214-miles (345-km) orbit in the next couple of days, Ellwood said there
is "absolutely no rush for us to do this. We have plenty of time and we
are going to be looking carefully at this anomaly."
Nicolas
Chamussy, Astrium's ATV program manager, said the vehicle -- often described as
the most
complex machine ever launched into space by Europe -- is designed to function with only three of
the four propulsion systems operating.
"What
we have had so far is the nominal operation of the ATV failure detection,
isolation and recovery system," Chamussy said during the press briefing,
held at Europe's Guiana Space Center spaceport in French Guiana several hours
after the launch aboard a specially designed Ariane 5 rocket. "We had
detection of an anomaly, and its isolation, with the [propulsion] chain being
put aside. Now we are in recovery mode, and we can reintegrate this chain if it
is demonstrated that it is safe and will not endanger anything."
The ATV had
been scheduled to climb into its operational orbit and then begin a series of maneuvers
to demonstrate to the station's partners -- the United States, Russia, Japan
and Canada in addition to Europe -- that the 41,887-pound (19,000-kg) vehicle
can safely
dock with the station. The ATV is about three times the size of Russia's
unmanned Progress cargo vessel.
A
collision-avoidance maneuver demonstration had been planned for March 12, but
Ellwood said that could be postponed if ATV controllers want to spend more time
examining the propulsion issue.
Docking
with the station still is tentatively scheduled for April 3.
Ellwood
said the ATV's Propulsion Drive Electronics (PDE) element controlling the
affected propulsion system shut itself off after transferring propulsion
responsibility, as it is designed to do.
"The
PDE detected some difference in pressure between the [oxidizer and the fuel
lines]," Ellwood said. "As planned, the software took over, put
control over to the other [propulsion] chain, and then it turned itself off,
just in case the anomaly is in the [PDE] itself.
Ellwood
said ATV managers have a large amount of telemetry data on the vehicle's
different systems, including the propulsion system, that they will need to
analyze before deciding how to proceed.
"We have a
10-day margin before we need to start going into demo days at the end of the
month," Ellwood said. "We are obviously not going to take any
risks."
Ellwood
said the only other notable glitch during the launch was a short-lived issue
with NASA over the use of the U.S. space agency's Tracking and Data Relay
Satellite System (TDRSS), which the ATV needs during launch to communicate with
the ground.
ATV
managers during the launch realized they were not getting the planned level of
use of TDRSS as the ATV climbed into orbit. "You know, a lot of satellites
are using" TDRSS, Ellwood said. "We were in touch with NASA and they
realized the priorities weren't quite right. They actually got rid of another
payload, which wasn't a high-priority payload. That was 30 seconds after the
second boost [of the ATV by the Ariane 5's specially designed upper stage].
That could have been horrific, but we had a good procedure [with NASA] to do
that."
advertisement
