Atlantis overnight is set to make a space shuttle's final departure from the International Space Station to begin a final journey home to Florida.
The shuttle's four-person crew is scheduled to wake up to start Flight Day 12 around 10 p.m. EDT today.
With pilot Doug Hurley at the controls, Atlantis at 2:28 a.m. Tuesday will begin backing away from the outpost, to a distance of about 600 feet.
The station then will rotate sideways 90 degrees.
At 3:27 a.m., Hurley will guide the orbiter through a half-loop over the top of the station. Take a look at an animation of the unique flyaround here.
The modified flyaround over the station's football field-length structural truss will allow Atlantis crew members to photograph parts of the station not normally seen when the shuttle departs, helping engineers on the ground assess their condition.
By 4:18 a.m., Atlantis will fire its orbital maneuvering engines to separate from the station for the 37th and last time since assembly began in 1998.
Around 6:30 a.m. the crew will begin a standard "late" inspection of critical heat shields lining the Atlantis' wing leading edges and nose cap, to make sure they're in good shape for a final re-entry and landing planned Thursday morning.
Here's a full timeline of the day's highlights:
9:59 a.m. Monday: Atlantis and station crews awake
2:28 a.m. Tuesday: Atlantis undocks
3:27 a.m.: Atlantis begins flyaround
4:18 a.m.: Final separation from station
6:34 a.m.: "Late" heat shield inspection
7:30 a.m.: Mission status briefing
10:49 a.m.: Orbiter boom extension berthed in payload bay
1 p.m.: Mission Management Team briefing
1:59 p.m.: Atlantis crew sleeps