After more than a week of joint operations between the shuttle and station crews, Pilot Steve Frick backed Atlantis away to a distance of about 400 feet in front of the outpost, where he began a 1 1/4 lap flyaround of the ISS, newly equipped with the 27,000 pound S-Zero truss, the first segment of a truss structure which will ultimately expand the station to the length of a football field. Aboard the station, Flight Engineer Dan Bursch rang a ship's bell in the Unity module to mark Atlantis' departure in what has become a tradition.
Finally, at 3:15 p.m., as Atlantis flew directly above the station, Frick fired the shuttle's jets one more time in a separation maneuver to depart the station for good.
Left behind on the ISS are Expedition Four Commander Yury Onufrienko and Flight Engineers Carl Walz and Bursch, now in their 133rd day in space and their 131st day on board the outpost.
Also left behind on the station were more than a ton of supplies, almost 200 pounds of oxygen and nitrogen for the station's Quest Airlock, 1,463 pounds of water and the new truss, which will serve as a backbone for future station construction and a power switching station for new solar arrays to be delivered to the ISS next year. Atlantis's week-long visit to the ISS was the 13th shuttle mission devoted to station assembly and resupply.
Earlier today, Commander Mike Bloomfield, Frick and Mission Specialists Rex Walheim, Ellen Ochoa, Steve Smith, Lee Morin and Jerry Ross completed final transfers of logistical supplies to the station and bid farewell to their station counterparts in the Destiny Laboratory. Hatches between the station and the shuttle swung shut at 11:04 a.m. Central time and leak checks were performed to insure that all was in order for the undocking.
As Atlantis' crew turns its attention to preparations for landing at the Kennedy Space Center Friday afternoon, the Expedition Four crew will prepare to button up the ISS temporarily and enter its Soyuz return craft early Saturday for a brief flyover from one docking port to another.
With Onufrienko at the controls, the Soyuz will undock from the station's Zarya nadir docking port at around 4 a.m. Central time Saturday, back out to a distance of about 250 feet and redock to the Pirs Docking Compartment 35 minutes later. That will clear the Zarya docking port for the arrival of a new Soyuz return vehicle and a three-man taxi crew on April 27 for a week-long visit.
Both Atlantis and the International Space Station are in excellent shape following their joint mission. Atlantis' astronauts are scheduled to begin an eight-hour sleep period at 6:44 p.m. Central time and will be awakened just before 3 a.m. Thursday for what is expected to be their final full day in orbit.