HOUSTON - After more than a week of busy spaceflight, the astronaut crew of
NASA space shuttle Discovery is taking a well-deserved break from their orbital
duties, while engineers on the ground study a couple of power unit glitches.
The
shuttle's STS-121 crew, commanded by spaceflight veteran Steven
Lindsey, awoke at 1:08 a.m. EDT (0508 GMT) today to the theme song
of the television show Charlie's Angels with little else on their
schedule aside from some rest and relaxation.
"Just
taking the standard taking a break, looking out the window and enjoying the day
on orbit," NASA's lead shuttle flight director Tony Ceccacci
said the astronaut's day.
"Basically,
the only thing we'll do at the end of the day is starting the MPLM closeout
activities."
Discovery's
Leonardo
MPLM, or Multi-Purpose Logistics Module, has been berthed at the
International Space Station (ISS), where the shuttle too has been docked
since July 6. All nine astronauts - six aboard Discovery and three aboard
the ISS - have been shifting thousands
of pounds of cargo between the space station and Leonardo module.
At the same
time, engineers are eyeing two glitches that have popped up with two of the three Auxiliary Power Units (APU) which supply power
to Discovery's hydraulics and other systems during landing.
In an
update to the crew, flight controllers said that Discovery's APU 1 is suffering
from a higher than normal fuel pressure decay, suggesting a small leak in the
unit's hydrazine or nitrogen fuel tanks. APU pressure is expected to drop about
6 pounds per square inch (psi) over eight days,
though APU 1's tank pressure has dropped about 22 psi
in the same time period.
"We hope to have more details on this subject tomorrow but
as of today there is no change to any mission plans based on the data
collected," flight controllers reported today in the crew's Flight Day 10
execute package, adding that APU 1 was not considered failed at this time.
Another unit, APU 3, has a heater hiccup that has caused a
backup heater to fail in the ON position. Engineers on Earth suspect that a new
wrapping on the heater that may have come loose in flight or it may have become
debonded, since both events would prompt the current
glitch.
"APU 3 is not considered failed for entry at this time and
there are no significant impacts to entry operations," flight controllers said
according to the execute package, adding that engineers continue to monitor
this APU as well.
Of the three APUs aboard
Discovery, only one is required to be fully operation for landing.
Flight
controllers radioed the glitches up to Discovery at the end of the STS-121
crew's day Wednesday, with Discovery's commander acknowledging the message.
"We copy
that," Lindsey said.
Lindsey and
his six-astronaut crew are nearing the homestretch of their planned 13-day
mission. The astronauts have completed most of their cargo transfer duties, three
spacewalks and a series of heat shield repair demonstrations during their
flight.
Discovery
also ferried European Space Agency (ESA) astronaut Thomas Reiter
to the ISS, where he joined the then-two astronaut crew of Expedition
13 and returned the space station back to its three-person capacity for the
first time since 2003.
Ceccacci
said that Reiter and his Expedition 13 crewmates also have a light day today,
to give the astronauts some rest and also prevent motivating the shuttle crew
to pitch in.
"The
station crew is very lightly loaded," Ceccacci said.
"If they were doing a lot of work, their shuttle buddies would want to come
over and help and that's what we're trying to avoid."
Instead,
the STS-121 astronauts will spend today enjoying space and speaking with
reporters on Earth and, more importantly, their families, Ceccacci
said.
Discovery
and its six astronaut crew are expected to land at NASA's Kennedy Space Center on July 17 at 9:07 a.m.
EDT (1307
GMT).
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