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More Details for 1999-03-24

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International Space Station flight controllers returned a U.S. communications system to standard operations this week as they continued an analysis of a minor problem with one of the system's two antennas.

The antenna, one of two that are used by the US early communications system, is mounted on the exterior starboard side of the station's Unity module. Earlier this month, controllers noticed that communications with the antenna were impeded when the station was in certain orientations, amounting to about a 15 percent reduction in the total capability of the US communications system to receive signals. Controllers ceased using the antenna when the problem was seen and had been using only the port antenna for communications. Late last week, the starboard antenna reselected and put back into operation, operating well with its slightly reduced capability. The slightly reduced communications capability has had virtually no impact on the station's day-to-day operations. Engineers are continuing to evaluate the information and possible causes for the problem. The US communications system, installed on Shuttle mission STS-88 last year, is one of two complementary communications systems on the station, including a Russian communications system onboard Zarya. Flight controllers may conduct a test of the station's power system next week as part of preparations for the arrival of the Space Shuttle Discovery on mission STS-96 in May. For the test, power used by the Unity module may be gradually increased by turning on several heaters in a variety of different scenarios. The information gathered would provide flight controllers insight that may be useful in planning the best method for warming up the module prior to Discovery's docking with the station. The power test is still under evaluation, but could begin by early next week, when the station's orbital environment will be very similar to what will be experienced when Discovery arrives. The International Space Station is in an orbit with a high point of 256 statute miles and a low point of 242 statute miles, circling the Earth once every 92 minutes, 24 seconds. The station has completed more than 1,900 orbits of Earth since its launch.