Space Shuttle Astronauts Take Time Off
The core STS-124 crewmembers pose for a portrait in the Kibo Japanese Pressurized Module of the ISS on June 9, 2008. Pictured (clockwise) from the bottom are NASA astronauts Karen Nyberg, Ken Ham, Mark Kelly (commander), JAXA astronaut Akihiko Hoshide, NASA astronauts Ron Garan and Mike Fossum.
Credit: NASA.

This story was updated at 2:51 p.m. EDT.

HOUSTON ? After successfully delivering the largest-ever lab to the International Space Station (ISS), the seven astronauts returning home aboard NASA?s shuttle Discovery are taking some much deserved time off Thursday as they prepare for a weekend landing.

Discovery commander Mark Kelly and his crew took a few hours to rest after their busy construction flight to install the station?s billion-dollar Japanese Kibo laboratory, a roomy module the size of a large tour-bus.

?It was a really exciting mission,? Kelly said before Discovery undocked from the station Wednesday.

Shuttle astronauts delivered the 37-foot (11-meter) Kibo lab, added its rooftop storage room and performed three spacewalks to maintain the station and prime the new Japanese module?s robotic arm for work during nine days docked at the orbiting laboratory. They also swapped out one member of the station?s three-man crew during their trip.

The shuttle is set to land Saturday at 11:15 a.m. EDT (1515 GMT) at the agency?s Kennedy Space Center in Cape Canaveral, Fla.

Kelly told SPACE.com before the flight that he hoped to spend at least some of his free time hunting for Mt. Everest from space. Though he?s now flying his third space mission, the tallest mountain on Earth has proven oddly elusive.

?It?s hard to identify because you?re looking down and you can?t tell which one is the biggest one,? Kelly said then, adding that you also need to plan for the right time, camera, lens and window view. ?To take a picture of Earth, you?ve got to plan about halfway around the planet.?

Meanwhile, Discovery mission specialist Garrett Reisman is spending his last few days in weightless after living aboard the space station for the past three months. His replacement, NASA astronaut Gregory Chamitoff, arrived with Discovery?s crew last week.

?We call it floating, but really it?s more like flying because as soon as you push off, you?re flying through the air like some sort of superhero,? Reisman said before leaving the station. ?To be able to do that every day as you?re coming in to work, it?s unreal. That?s what I?ll miss the most.?

Returning to Earth with Kelly and Garrett are shuttle pilot Kenneth Ham and mission specialists Karen Nyberg, Ronald Garan, Michael Fossum and Akihiko Hoshide, a Japanese spaceflyer who helped deliver his country?s new space lab. The astronauts talked about their flight with reporters on Earth Thursday, including a call from ESPN?s ?Mike & Mike in the Morning,? where Ham discussed the challenge of orbital athletics.

?We?ve been trying to invent new sports, which is kind of an interesting endeavor,? Ham said, adding that you could set up the perfect baseball hit on the space station, just not whack it. ?We?re surrounded by a lot of expensive equipment in all directions, so it?s sort of hazardous to our paychecks to really experiment in the fullest.?

Shuttle heat shield check

While the shuttle crew rests, engineers on Earth are hard at work sifting through images and data beamed home Wednesday by the astronauts during their detailed inspection of Discovery?s heat-resistant wing edges and nose cap.

The survey was identical to now-standard scans performed on the second day of NASA shuttle flights to search for dings or damage from launch debris. A second inspection performed before landing is aimed at spotting pockmarks from orbital debris. The 50-foot (15-meter) boom tipped with laser and cameras used in the survey was developed after the 2003 Columbia tragedy.

But NASA launched Discovery without its own boom because Japan?s massive Kibo lab took up too much room in the shuttle?s payload bay. Instead, astronauts performed a limited scan using the orbiter?s robotic arm, then retrieved an inspection boom left outside the station by a previous shuttle mission.

?I will say, to my untrained eye, I personally didn?t see anything unusual and we were very pleased with the data that we were able to get,? lead shuttle flight director Matt Abbott said Wednesday.

Tetsuro Yokoyama, the deputy Kibo project operations manager for the Japan Aerospace Exploration Agency (JAXA) that built the new lab said Japan?s mission control center at the country?s Tsukuba Space Center is running at full speed and beaming with pride.

The main Kibo lab is the second of three parts of the station?s Japanese segment. It includes comes ready with two windows, a 33-foot (10-meter) robotic arm and a small airlock to move experiments to a third component - a porch-like external platform slated to launch next year. A smaller robot arm for fine movements is also due to be delivered next year.

Kibo is the third orbital room to be installed at the station this year and follows its own storage module and the European Space Agency?s Columbus lab, which were delivered earlier this year.

?We feel very good about the configuration of the International Space Station,? said Kenny Todd, NASA?s station program manager for mission operations and integration. ?Clearly where we are now with the arrival of this pressurized module, this new laboratory capability on orbit, is a crowning achievement not only for our Japanese colleagues, but for our international partnership.?

NASA is broadcasting the Discovery's STS-124 mission live on NASA TV on Saturday. Click here for SPACE.com's shuttle mission updates and NASA TV feed.

Editor?s note: This story was written in Houston and updated in Cape Canveral, Fla.