As the Space Shuttle Discovery is readied for a May 20 launch on the next Station assembly mission, flight controllers in Russia and the United States will conduct a "dress rehearsal" of the Shuttle's upcoming docking with the international orbiting laboratory. Simultaneously, the next major station component, the Russian-provided early living quarters, is scheduled to depart the Moscow factory where it was built and be shipped by train to the Russian launch site at the Baikonur Cosmodrome in Kazakstan. Planned for launch on a Russian rocket this fall, the living quarters, previously known by the technical term Service Module, was recently named Zvezda, which translates to "Star" in English.
On Wednesday, flight controllers plan to maneuver the Station to the same orientation it will be in for the docking of Discovery. The docking rehearsal will maneuver the Station from its present orientation, a slow spin with the Unity module pointing to Earth and Zarya toward space, to an orientation that is horizontal to Earth's surface, with Zarya pointed in the Station's direction of travel. The Station will remain in the horizontal orientation for about three hours while the Zarya module's guidance system is calibrated using the horizon of Earth as a point of reference. Then, the Station will maneuver to an orientation again perpendicular to Earth's surface, but without any spin and with Unity pointing to space and Zarya to Earth - the same orientation required for Discovery's docking.
The Station will remain in the docking orientation for about four and half hours - three orbits of Earth - completing its test and then return to its original, spinning attitude. The spinning attitude, with Unity to Earth and Zarya to space, is the preferred orientation for the station's day-to-day uncrewed operations to optimize sunlight on the electricity-generating solar arrays and to provide moderate heating and cooling on the spacecraft.
Flight controllers are continuing to troubleshoot a problem with a portion of the Unity module's communication system, and they are finalizing plans for Discovery's crew to repair the system. Called the Early Communications System, Unity's communications system is a backup to the primary station communications system located in the Zarya module and continues to operate well. The problem with the Unity system has not hampered operations of the Station and poses no problems for the docking with Discovery.
Late last week, flight controllers noted a false indication from one of the eight smoke detectors operating within Zarya. The faulty detector was powered off, and sufficient smoke detection remains available onboard while the problem is being analyzed.
In less than two weeks, flight controllers will begin powering up heaters onboard the Station to begin warming it in anticipation of the arrival of Discovery. This Shuttle flight will bring almost two tons of supplies, preparing the new outpost for the arrival of the Zvezda module this fall and laying out a welcome mat for the first resident Station crew that is planned to launch early next year.
The International Space Station is in an orbit with a high point of 252 statute miles and a low point of 238 statute miles, circling the Earth once approximately every 92 minutes. The Station has completed more than 2,600 orbits of Earth since its launch. As it passes overhead at dawn or dusk, the 35-ton complex is easily visible from the ground, and it will become even brighter once Discovery has docked. S