Three will leave the airlock, but only two will come back in.

Valery Tokarev and Bill McArthur are scheduled to step into space from the Pirs airlock at about 5:20 p.m. EST Feb. 3. With them will be a third Russian Orlan spacesuit, empty except for electronic equipment that should attract considerable attention from students and others around the world.

The spacewalk is expected to last about six hours. Tokarev, Expedition 12 flight engineer, is the lead spacewalker, EV-1. Both he and E12 Commander McArthur will wear red-striped spacesuits.

The third spacesuit, near the end of its useful life, will be jettisoned by Tokarev early in the spacewalk. That suit, called SuitSat-1, will remain in its own orbit for as much as six weeks before re-entering the Earth’s atmosphere and burning.

Image at right: An old Russian Orlan spacesuit, outfitted with a special radio transmitter and other gear, comprises a Russian experiment called SuitSat. Image credit: NASA

For the first part of that time in orbit – for perhaps a week or two – devices in the suit will broadcast recorded ham radio messages in Russian, Japanese, Spanish, German, French and English. Most will be voiced by students.

The transmission, possibly for as much as several weeks or for as little as an hour (depending on battery life), will be on 145.990 MHz FM, in the VHF or 2-meter part of the amateur radio band. Voice transmissions also will include suit data, mission time, suit temperature and battery voltage.

SuitSat-1, called RadioSkaf or Radio Sputnik in Russian, is sponsored by ARISS (Amateur Radio on the International Space Station), an international working group made up of volunteers from national amateur radio societies, including the Radio Amateur Satellite Corporation.

Tokarev will carefully jettison the SuitSat-1 in much the same way McArthur jettisoned the Floating Potential Probe experiment during their November spacewalk. He will push the suit away at about a 30-degree angle upward and about 10 degrees to the left of the back of the station.

After the spacesuit jettison, the crew will relocate a boom adapter for the Strela, a Russian hand-operated crane, from the Zarya module to Pressurized Mating Adapter 3. That is being done to clear the Zarya area for temporary stowage of protective debris panels for the Zvezda Service Module, to be delivered on STS-116.

A two-hour task at the mobile transporter, which can provide a base for the station’s robotic arm for movement along the rails on the orbiting laboratory’s main truss, is next on the schedule.

On Dec. 16 one of two trailing umbilical system cables providing power, data and video was severed by a device designed to cut the umbilical should it become jammed. A second cable provides the same links to the mobile transporter. Spacewalkers will insert a bolt to eliminate the risk of uncommanded cutting of the second, intact cable.

To replace the severed cable, a new umbilical assembly is scheduled to be installed during Discovery’s STS-121 mission to the station.

Back on the hull of the Zvezda service module, spacewalkers will retrieve the Biorisk experiment, which looks at microorganisms in space. Next, they’ll photograph a sensor for a Russian Micrometeoroid Measuring System.

Tokarev and McArthur will inspect and/or photograph several areas on Zvezda’s exterior, including thrusters and nearby areas. They’ll photograph a ham radio antenna and a fuel drain outlet pipe, then retrieve a Kromka panel, part of a thruster contamination experiment.

The spacewalkers will inspect their suits, wipe off suit gloves and then jettison the towels before re-entering Pirs and closing its hatch.

This will be the second spacewalk for Tokarev and the fourth for McArthur.