CAPE CANAVERAL, Fla. -- Three of six crew members living aboard the International Space Station are poised to undock and return to earth on Tuesday after 168 days in space.
Outgoing Expedition 36 space station commander Pavel Vinogradov handed over command of the orbiting outpost to fellow cosmonaut Fyodor Yurchikhin on Monday in preparation for his crew's planned departure.
Russians Vinogradov and Alexander Misurkin and American Chris Cassidy, who arrived aboard the space station on March 28, are due to board their Soyuz TMA-08M craft at about 4:00 p.m. EDT on Tuesday in preparation for the craft's hatch closure at 4:20 p.m.
They will leave behind Yurchikhin, NASA astronaut Karen Nyberg and Italian astronaut Luca Parmitano who will stay aboard the space station until their departure in November.
Cassidy, along with Luca, performed two spacewalks during his stay to prepare the orbiting outpost for an upcoming Russian research module this December.
Based on the Russian timeline, the Soyuz spacecraft will undock from the Poisk docking port at 7:35 p.m., and slowly back straight out to a distance a few hundred feet out before circling around the station and departing.
Vinogradov will then maneuver the Soyuz to a proper attitude to allow a section of the Soyuz to fall away prior to leaving orbit at 10:05 p.m. in what is know as a deorbit burn.
The smaller Soyuz will slam into earth's atmosphere about thirty minutes later.
As a fireball surrounds the crew during re-entry, temperatures of nearly 3,000 degrees Fahrenheit will light up the Soyuz heat shield. The craft's approach has to be so precise or else the Soyuz could either burn up if it's angle is too shallow, or even skip off the atmosphere if it's attitude is too high.
The atmosphere will then help slow the Soyuz during it's decent as three massive parachutes deploy a few minutes prior to landing.
As the red and white parachutes gently lower the craft toward a region near Dzhezkazgen, Kazakhstan, blue skies, light winds and temperatures near 65 degrees F will welcome the crew home after 5 ½ months in earth orbit.
Landing of the Soyuz on the deserts of central Kazakhstan is planned for 10:58:50 p.m., which will be 8:58 a.m. local time on Wednesday, and will be carried live on NASA TV.
Two weeks later, a new crew of three will lift-off from Kazakhstan aboard a new Soyuz bound for their new home in space.
(Charles Atkeison reports on aerospace, science and technology. Follow his updates via Twitter @SpaceFlight360. )