Shuttle and Station managers yesterday selected April 24 as the launch target date at the conclusion of the Flight Readiness Review, while engineers evaluate an issue with the power drive unit (PDU) for Atlantis' rudder speed brake. Following a hydraulic system test, a higher than normal pressure reading in the suspect PDU was identified. Ongoing analysis will confirm if the PDU needs to be replaced. Managers are evaluating plans to perform the work at the launch pad and currently expect no impact to the launch date.
Launch is set to occur at about 4:15 p.m. Eastern time to perform life-extension maintenance tasks on the Zarya module, and to deliver supplies to the inside and outside of the Station for use by future crews.
Commander Jim Halsell has resumed full training activities after spraining his ankle a couple weeks ago and practiced landings in the Shuttle Training Aircraft last night. Joining Halsell on the mission are Pilot Scott Horowitz and Mission Specialists Mary Ellen Weber, Jeff Williams, Jim Voss, Susan Helms and Yuri Usachev. The latter three will focus their attention during the docked phase of the flight on repairing some equipment inside their future home.
Awaiting Atlantis’ arrival, the International Space Station continues to operate with no major systems problems. Its electrical power system is being strategically managed to maximize the power required by operating systems inside the Zarya and Unity modules.
Meanwhile, in Moscow, the second and third stage engines have been delivered for final inspection and installation into the Proton rocket that will carry the next component of the ISS – the Zvezda service module – to orbit. Zvezda’s launch remains slated between July 8 and 14 from the Baikonur Cosmodrome in Kazakhstan.
The current orbit of the ISS is 232 by 215 miles. The average decay of the Station’s orbit is about 1-1 ½ miles per week. The altitude can be raised by using Zarya’s thrusters, but will be unnecessary if Atlantis arrives later this month since the orbiter will perform an altitude reboost of the ISS before departing near the end of the flight. The ISS now has completed more than 7,860 orbits since Zarya was launched in November 1998.
NOTE: The next Mission Control Center ISS Status Report regarding on-orbit activities will be issued on Thursday, April 13, unless mission events warrant. For further information, please contact the NASA Public Affairs Office at the Johnson Space Center, Houston, Texas, 281-483-5111.