Space Shuttle and ISS managers discussed the option of flying a maintenance mission to the Station prior to the launch of Zvezda. At the request of the ISS program, Shuttle managers approved an option of scheduling the next mission to the Station no earlier than April 13, prior to the Zvezda launch, to perform maintenance tasks on the Zarya and Unity modules. The official scheduling of a second flight to outfit Zvezda for the first permanent crew, which would follow the launch of Zvezda by about 30 days, was deferred to enable Shuttle and mission operations officials to evaluate overall vehicle processing strategy and crew training issues.
A Proton failure in October led to the formation of an investigation commission, which presented its findings to Russian officials recently. NASA has been thoroughly briefed by the Russians on the Proton failure analysis results and the options to improve the Protonís engine system. A Joint Program Review (JPR) will be held next month at which a target launch date for the Zvezda service module will be selected. Once a launch date is established, NASA will determine if an early maintenance mission to the ISS is required.
On orbit, the Stationís power system remains stable. With four of six batteries operating normally and another periodically available, the Station has plenty of electrical power to manage the onboard systems, including heaters designed to maintain temperatures aboard the complex.
Additionally this week, the secondary channel of the solar array drive tracking system on Zarya was tested without problem. Following the three-hour test, the system was switched back to the primary channel. This test ensures the redundancy to the system that controls the movement of the twin solar arrays that capture the Sunís energy and stores it in the batteries.
Plans are still being developed for further testing of the Kurs automatic docking system on Zarya. A previous test showed uncharacteristic readings in relative velocity, which is thought to be caused by electromagnetic interference from other hardware components or transmission signals through the Unity moduleís early communications system. Though further investigative work is to be conducted, the Kurs hardware itself does not appear to have any problems. Kurs is used to automatically dock the ISS with Zvezda two weeks after its launch.
The International Space Station is in an orbit of 245 by 230 statute miles. Since the launch of Zarya in 1998, the ISS has completed more than 7,765 orbits. Space Station viewing opportunities worldwide are available on the Internet at: http://spaceflight.nasa.gov/realdata/sightings/
NOTE: The next International Space Station status report will be issued on Thursday, February 3, unless mission events warrant. For further information, please contact the NASA Public Affairs Office at the Johnson Space Center, Houston, Texas, 281-483-5111.