The space station's third man

German astronaut Thomas Reiter became an official member of the international space station's crew today and started a five-month tour of duty, cooped up with two other guys in the equivalent of a three-bedroom house bristling with cameras and computers. Think "Big Brother" in orbit.

It may sound like a claustrophobic nightmare in the making, but instead Reiter compares it to a fishing trip. A really, really long fishing trip.

Reiter's stay on the space station marks several firsts:

• First time in more than three years that three astronauts have been able to live aboard the station for an extended period of time. After the 2003 Columbia tragedy, the space shuttle fleet was essentially grounded. That meant the space station's crew had to be scaled back to two, because only the shuttle could provide enough supplies for a three-person live-aboard crew.
• First European astronaut on a station expedition crew - in fact, the first expedition member to represent a country other than the United States or Russia.
• First station resident scheduled to join one expedition in progress (Expedition 13, with Russia's Pavel Vinogradov and NASA's Jeff Williams) and stay through the transition to a different expedition (Expedition 14, with NASA's Michael Lopez-Alegria and Russia's Mikhail Tyurin due to arrive in September).
• First European astronaut scheduled to perform a spacewalk from the international space station.

Reiter, 48, knows what's involved in a long-distance stay: He spent six months aboard Russia's Mir space station in 1995-1996, conducting a spacewalk during that stint. That whetted his appetite for another turn at living in space, he told NBC News during a pre-launch interview:

"We know the sensation of [zero] gravity is just fantastic. Once you've adapted to it, to use the available space in all three dimensions is something very great. The beautiful view toward the earth, or in the opposite direction ... those are things that come together. I can relate to that now, going on the next mission. And I think everyone who has been in space is infected by all these sensations, all these impressions and experiences, and is longing to get back. So am I."

The smile on Reiter's face as he floated into the space station today showed how thoroughly he has been infected by the space bug - but there are less pleasant side effects as well. Reiter and his wife have two boys in school in Germany, and he admitted that the separation from family - for training as well as for the mission itself - is a hardship. "I've been away from home for almost two years now," he said.

He takes a philosophical stance toward that aspect of the job:

"I try to relate it to other professions. We are living in the north of Germany at the moment, close to the shore where a lot of families are actually in a very similar situation, because people are going to sea on fish trawlers, and they are sometimes gone for the same time. So in this respect there are no big differences. We are in a little bit more exposed location, and the circumstances are a little bit more unique. But I think if we take that all together, my family is, hopefully, as well-prepared as I am."

Reiter won't exactly be on a fishing trip. In addition to the spacewalk and other maintenance chores, he'll be working on an agenda of 19 scientific experiments for the European Space Agency's Astrolab program - and blazing a trail for the ESA's Columbus laboratory module, which is to be added to the station in September 2007:

"We will use this opportunity to prepare our specialists, or flight controllers, for the moment when Columbus is up, and hopefully then they can get in an operational state in a much shorter time, having this experience now."

The addition of Reiter to the Expedition 13 crew became official when his custom-fitted seat liner was transferred from the shuttle to the station's Soyuz escape capsule. That's the traditional transition time because Reiter's nearly 6-foot (182-centimeter) frame will need that cushioning if he has to ride the Soyuz back down to Earth.

When will the earthward ride come? The answer to that question is a bit, well, up in the air. If the shuttle schedule holds, NASA astronaut Sunita Williams would fly up to the station as part of the STS-116 shuttle crew in December and replace Reiter, who in turn would take Williams' place on the outbound shuttle.

If STS-116 is delayed for some reason, Reiter's stay in space would be extended - either until the shuttle flew, or until another Russian Soyuz craft brought Expedition 15 up in March or so. Then Reiter would take a Russian taxi home, and get the chance to use that Soyuz seat liner.

On the subject of an extended stay, Reiter was once again philosophical:

"This is always something you need to consider when you are going on a long-term mission. It might not be exactly five or six months. It could be a little more."

For more Reiterisms, revisit this Cosmic Log item from last month on the space station's significance, and click onto this video interview from NBC News. Biographies are available from NASA as well as ESA, and don't forget this roundup of mini-bios for the entire Discovery crew. To keep posted on Reiter's progress, check our coverage of Discovery's mission.