HOUSTON - After more than a week of busy spaceflight, the astronaut crew ofNASA space shuttle Discovery is taking a well-deserved break from their orbitalduties, while engineers on the ground study a couple of power unit glitches.
Theshuttle's STS-121 crew, commanded by spaceflight veteran StevenLindsey, awoke at 1:08 a.m. EDT (0508 GMT) today to the theme songof the television show Charlie's Angels with little else on theirschedule aside from some rest and relaxation.
"Justtaking the standard taking a break, looking out the window and enjoying the dayon orbit," NASA's lead shuttle flight director Tony Ceccaccisaid the astronaut's day.
"Basically,the only thing we'll do at the end of the day is starting the MPLM closeoutactivities."
Discovery'sLeonardoMPLM, or Multi-Purpose Logistics Module, has been berthed at theInternational Space Station (ISS), where the shuttle too has been dockedsince July 6. All nine astronauts - six aboard Discovery and three aboardthe ISS - have been shifting thousandsof pounds of cargo between the space station and Leonardo module.
At the sametime, engineers are eyeing two glitches that have popped up with two of the three Auxiliary Power Units (APU) which supply powerto Discovery's hydraulics and other systems during landing.
In anupdate to the crew, flight controllers said that Discovery's APU 1 is sufferingfrom a higher than normal fuel pressure decay, suggesting a small leak in theunit's hydrazine or nitrogen fuel tanks. APU pressure is expected to drop about6 pounds per square inch (psi) over eight days,though APU 1's tank pressure has dropped about 22 psiin the same time period.
"We hope to have more details on this subject tomorrow butas of today there is no change to any mission plans based on the datacollected," flight controllers reported today in the crew's Flight Day 10execute package, adding that APU 1 was not considered failed at this time.
Another unit, APU 3, has a heater hiccup that has caused abackup heater to fail in the ON position. Engineers on Earth suspect that a newwrapping on the heater that may have come loose in flight or it may have becomedebonded, since both events would prompt the currentglitch.
"APU 3 is not considered failed for entry at this time andthere are no significant impacts to entry operations," flight controllers saidaccording to the execute package, adding that engineers continue to monitorthis APU as well.
Of the three APUs aboardDiscovery, only one is required to be fully operation for landing.
Flightcontrollers radioed the glitches up to Discovery at the end of the STS-121crew's day Wednesday, with Discovery's commander acknowledging the message.
"We copythat," Lindsey said.
Lindsey andhis six-astronaut crew are nearing the homestretch of their planned 13-daymission. The astronauts have completed most of their cargo transfer duties, threespacewalks and a series of heat shield repair demonstrations during theirflight.
Discoveryalso ferried European Space Agency (ESA) astronaut Thomas Reiterto the ISS, where he joined the then-two astronaut crew of Expedition13 and returned the space station back to its three-person capacity for thefirst time since 2003.
Ceccaccisaid 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 crewto pitch in.
"Thestation crew is very lightly loaded," Ceccacci said."If they were doing a lot of work, their shuttle buddies would want to comeover and help and that's what we're trying to avoid."
Instead,the STS-121 astronauts will spend today enjoying space and speaking withreporters on Earth and, more importantly, their families, Ceccaccisaid.
Discoveryand its six astronaut crew are expected to land at NASA's Kennedy Space Center on July 17 at 9:07 a.m. EDT (1307GMT).
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