The astronauts of the Expedition 6 International Space Station crew are preparing for a first in NASA's history of human space flight. They're scheduled to return to Earth aboard a Russian Soyuz capsule. grounded.

While the Russians have been using the Soyuz for decades and American astronauts have flown into space twice before on the craft, NASA has never before put one of its own on a Soyuz for a landing.

The Expedition 6 astronauts, Ken Bowersox and Don Pettit, with their cosmonaut counterpart Nikolai Budarin at the controls, are scheduled to touch down May 4 (10:03 p.m. EDT May 3) in northern Kazakhstan. The crew is leaving the Station after a successful, but emotional, five months in orbit. During that time, the Space Shuttle Columbia was lost and the Shuttle fleet was temporarily grounded.

From undocking to landing, the crew's Soyuz trip is expected to last about three hours and 23 minutes. Just about everything that happens is automated; the crew has little to do but hold on tight.

About 15 minutes before the Soyuz lands, it begins to deploy a series of parachutes to slow its descent. Then, a mere two seconds before landing -- less than three feet above the ground -- six engines on the spacecraft fire toward the Earth to cushion the touchdown.

A landing in a Soyuz is generally bumpier than on a Shuttle, so Bowersox, Pettit and Budarin will ride home in custom-built reclining seats formed to fit their bodies. The seats help cushion the landing and distribute the shock; the impact measures about four times the force of gravity, or four Gs.

In the past, cosmonauts have suffered some minor injuries -- bumps and bruises -- during a Soyuz landing, NASA flight surgeon Dr. Terrance Taddeo, says. But "nothing we're medically concerned about," he says.

The Expedition 6 crew will also be wearing what Dr. Taddeo calls "anti-G" garments, which help to prevent blood from pooling in their legs when gravity kicks in.

Of course, after more than five months in space, any gravity will be a shock to the crew. Within minutes of landing, Russian space officials will set up a portable medical tent and carefully take the Soyuz crew members to it, one-by-one. Bowersox, Pettit and Budarin will spend their first moments back on Earth in special recliners, readapting to gravity's pull. About two hours later, they'll begin a trip to Star City, Russia -- outside Moscow -- where they'll spend at least 16 days undergoing medical tests and physical therapy.

Back on orbit, another first: the typical three-person Space Station crew scaled down to two. NASA and its International Partners have determined a smaller crew will be able to maintain the Station and the scientific experiments on board, while reducing the need for water and other supplies aboard the Station. For now, Russian Progress and Soyuz spacecraft will be the only means of ferrying supplies to the Station, and those vehicles have far less cargo room than the Shuttle. Once the Shuttle is back to flying, it will be able to carry enough supplies to support a three-person Station crew again.

The grounding of the Shuttle fleet affects the Space Station in another way; construction is on hold for now. Before the Columbia accident, the Shuttles were scheduled this year and next winter for a series of missions to complete America's portion of the International Space Station, known as Node 2. That construction plan will kick back into gear as a first priority, once the Shuttles return to flight.

For the reentry, all crewmembers will wear the Russian Kentavr anti-G suit.  The suits are kept in the habitation module of the Soyuz TMA until undock day.  How will the crew experience the ballistic reentry in the Soyuz 5S Descent Module, a First for Bowersox and Pettit  as well as for the TMA model?  See Appendix, below. [The Russian Kentavr garment is a protective anti-g suit ensemble to facilitate the return of a long-duration crewmember into the Earth gravity.  Consisting of shorts, gaiters, underpants, jersey and socks, it acts as countermeasure for circulatory disturbance, prevents crewmember from overloading during descent and increases orthostatic tolerance during post-flight adaptation.]

Upcoming Crew Rotation Events (all on Saturday, 5/3)  revised times!:

• Exp. 6/Exp. 7 Change of Command Ceremony -- 2:11pm EDT
• Farewells & Hatch closing -- 3:32pm EDT
• Soyuz TMA-1/5S undocking (Exp. 6):  6:43pm EDT (2:43am Moscow, 1:43am DMT (TsUP), on 5/4);
• Soyuz TMA-1/5S landing:  10:06pm EDT (6:06am Moscow; 5:06am DMT; 8:06am Kazakhstan, on 5/4).
• Preferred landing will be on the first oirbit, with the resulting site at 51.2 n.Lat, 67.1 e.Long, about 89 km north from the center of the nominal landing ellipse (Arkhalykj/Astana region in Turgay province of Kazakhstan).  There will be two additional/backup landing opportunities on subsequent orbits.

Predicted weather conditions at Landing Site (to be updated 30 min. prior to undock, with MCC-H being informed ~6:15pm EDT):  Partially cloudy,  temperature: around 7 degC; stort periods of rain; wind 5-10 m/s from S, cloud layer between 300/600 m and 1000m.  Conditions are acceptable.  MCC-H and MCC-M will confer 30 min. before undock.;

According to a summary uplinked by MCC-Moscow to the ISS crew, main features of their return on 5S/Soyuz TMA-1 are as follows:

On descent day:

Special attention will be paid to the need for careful donning of the medical belt with sensors and securing tight contact between sensors and body.

During preparation for descent, before atmosphere reentry, the crew should settle down comfortably in the seat, fasten the belts, securing tight contact between body and the seat liner in he couch.

During de-orbit: Dust particles starting to sink in the Descent Module cabin is the first indication of atmosphere reentry and beginning of G-load effect.  From that time on, special attention is required as the loads increase rapidly.

Under G-load effect during atmosphere reentry the crew can expect the following sensations: Sensation of G-load pressure on the body, "burden in the body", labored breathing and speech. These are normal sensations, and the advice is to "take them coolly". 

In case of the feeling of a "lump in the throat", this is no cause to "be nervous".  This is frequent and should not be fought.  Best is to "try not to swallow and talk at this moment".   Crew should check vision and, if any disturbances occur, create additional tension of abdominal pressure and leg muscles (strain abdomen by pulling in), in addition to the anti-G suit ("Kentavr").

During deployment of drogue and prime parachutes the impact accelerations will be perceived as a "strong snatch".  No reason to become concerned about this but one should  be prepared that during the parachutes deployment and change of prime parachute to symmetrical suspension swinging and spinning motion of the Descent Module occurs, which involves vestibular (middle ear) irritations.

It is important to tighten restrain system to fasten pelvis and pectoral arch.

Vestibular irritation can occur in the form of different referred sensations such as vertigo, hyperhidrosis, postural illusions, general discomfort and nausea.  To prevent vestibular irritation the crew should "limit head movement and eyes movement", as well as fix their sight on motionless objects.

Just before the landing (softened by six small rocket engines behind the heat shield): Crew should be prepared for the vehicle impact with the ground, with their bodies fixed along the surface of the seat liner in advance.  "Special attention should be paid to arm fixation to avoid the elbow and hand squat".

After landing:

Crew should not get up quickly from their seats to leave the Descent Module. They are advised to stay in the couch for several minutes and only then stand up.  In doing that, they should limit head and eyes movement and avoid excessive motions, proceeding slowly.  They and their body should not take up earth gravity in the upright position too quickly.

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