These were the first of several large rendezvous burns scheduled over the course of the next 10 days to refine Zvezda’s orbital altitude in relation to that of the ISS in preparation for docking, scheduled for 8:46 p.m. EDT on July 25.
With the Zvezda module flying in an attitude with the forward, or cone end, pointing in the direction of travel, the first burn was carried out at 1:09 a.m. EDT (9:09 a.m. Moscow time). The burn fired both reboost engines raising the orbit to 222 by 114 miles (358 by 183 km). The second burn 45 minutes later at 1:44 a.m. EDT (9:44 a.m. in Moscow), also used both engines – each produces 690 pounds of thrust – to boost Zvezda to an altitude of 224 by 167 miles (361 by 269 km).
As is the case with any firing of the reboost engines, the solar arrays were positioned to minimize the effects of vibrations through the structure. After the burns, the solar arrays were moved back to their normal operating positions.
In addition to the rendezvous burns, the only other planned activity for the day was to verify the accuracy of the solar array drive motors in the backup mode. That was done by analyzing telemetry data gathered on each available communications pass through Russian ground stations.
The correction burn planned for Saturday was cancelled after Russian flight controllers analyzed the results from today’s burns and determined no adjustment to Zvezda’s orbit was required. The only scheduled activity over the weekend is a thorough checkout of the ‘Regul’ telemetry system that includes the receiver/transmitter, antenna and onboard computer. The test will involve cycling through various software modes to ensure good command links from the ground while analyzing the return link from the module.
Telemetry from the module continues to show that sensors are not detecting the deployment of a docking target that only would be required if a manual docking were needed. This will not affect the planned automatic docking July 25. As a reference point, Zvezda and the Zarya control module on the ISS use the same rendezvous hardware as on the Mir space station and all of its modules docked automatically.
Zvezda attitude control is being maintained by 16 of its 32 small control thrusters. The 32 thrusters, which produce 29 pounds of thrust each (roughly equivalent to the vernier jets on a space shuttle orbiter), are divided equally between two manifolds. Only manifold one is being used.
As of 11 a.m. CDT Friday, Zvezda had completed 40 orbits of the Earth. The next Mission Control Center status report will be issued Monday, July 17. For more information, call the Johnson Space Center Newsroom at 281/483-5111.
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