CAPECANAVERAL, Fla. - NASA is poised to launch seven shuttle astronauts toward theInternational Space Station (ISS) Tuesday on what some have called the mostambitious orbital construction mission to date.
Commandedby veteran spaceflyer Pamela Melroy, the shuttle Discovery is slated tolaunch from Pad 39A here at NASA?s Kennedy Space Center (KSC) at11:38 a.m. EDT (1538 GMT). Melroy and her crewmates plan to swap out one ISScrewmember, deliver an orbital hub to anchor future laboratories to the stationand perform the complicated move of a 17.5-ton solar array segment to boost theoutpost?s power grid.
?I think,by any measure, this will is one of the most challenging and audacious missionsof the shuttle era,? said Discovery astronaut Scott Parazynski, leadspacewalker for the NASA?s STS-120 mission. ?We?re all very proud to serve andbe a part of this flight.?
Set tolaunch spaceward with Melroy and Parazynski are Discovery pilot George Zamkaand mission specialists Stephanie Wilson, Douglas Wheelock, Daniel Tani andEuropean Space Agency astronaut Paolo Nespoli. Together, they will install theItalian-built Harmony node - the connecting point for European andJapanese laboratories waiting to fly.
During fiveplanned spacewalks - the most-ever during a shuttle flight to the ISS - theSTS-120 astronauts will also test new space shuttle heat shield repair methods,move the station?s $276 million Port 6 (P6) solar power truss segment from itsmast-like perch to the station?s port-most edge, and then unfurl its expansivearrays. Parazynski compared the P6 relocation to moving an entire house fromone neighborhood to another.
?We hit thejackpot, I won?t kid ya. I think this is every astronaut?s dream of a mission,?Melroy said before launch day. ?It?s going to be an enormous challenge.?
The flight will also be historic. Melroy, NASA?s secondfemale shuttle commander, is set lead her crew into space to theISS, where veteran U.S. astronaut Peggy Whitson is serving as the orbital laboratory?s first femalecommander. Whitson and her Expedition 16 crewmates took charge of the spacestation on Friday from its outgoing crew.
?The thing that is the best about this is that it happened totally byaccident,? Melroy said. ?Nobody planned it.?
Tani willreplace NASA astronaut Clayton Anderson, who is currently living aboard the ISSas an Expedition 16 flight engineer, during Discovery?s spaceflight. He and hiscrewmates hope to beat the weather for Tuesday?s planned launch. Currentforecasts predict a 60 percent chance that rain showers and thick clouds couldprevent the planned space shot.
Gatewayto new labs, larger crews
Discovery?sSTS-120 spaceflight will mark NASA?s 120th shuttle flight to dateand the third mission this year to continue space station assembly.
But unlikethis summer?s previous flights of the Atlantis and Endeavour orbiters - whichdelivered new truss segments, cargo, spare parts and solar arrays - Discoveryis hauling up Harmony, which will increase the internal space of the ISS forthe first time since Russia?s Pirs docking port arrived in 2001.
?Manypeople look at it as the gateway to the international partner piece of thespace station,? Derek Hassmann, NASA?s lead ISS flight director during STS-120,told SPACE.com.
Harmonywill serve as the anchor for the European Space Agency?s Columbus laboratory - slated to launch aboard Atlantis in December - and Japan?sthree-segmentKibo laboratory. The new module will also hold quarters for ISSastronauts once the station?s crew complement doubled to six spaceflyers in2009.
?It?s veryexciting to think that the work we?re doing is going to enable this exciting newresearch and also enable a six-person crew capability in the future,?Parazynski said.
WhileParazynski is making his fifth spaceflight with Discovery?s planned launchTuesday, Zamka, Wheelock and Nespoli are making their first forays into orbitduring the STS-120 mission.
?I can?twait for the clock to count down to zero and the solid rocket boosters ignite,?said Zamka. ?Because that will be a nice reminder that the training is over.?
NASAwill begin broadcasting Discovery?s STS-120 launch and mission operations liveon NASA TV at 6:30 a.m. EDT (1030 GMT) on Tuesday. Click here for SPACE.com?s live launchcoverage, mission updates and NASA TV feed.
- SPACE.com Video Interplayer: Delivering ?Harmony? with NASA's STS-120 Mission
- Test Your Smarts: Space Shuttle Countdown Quiz
- Complete Space Shuttle Mission Coverage