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More Details for 1999-03-18

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International Space Station flight controllers in Houston and Moscow performed a successful rendezvous system test this week and continued an analysis of a minor problem with an antenna for one of the onboard communications systems.

The antenna, one of two that are used by the U.S. early communications system, is mounted on the exterior starboard side of the station's Unity module. Last week, 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 U.S. communications system to receive signals. Controllers ceased using the antenna when the problem was seen and have been using only the port antenna for communications. On Tuesday, flight controllers powered on a television camera on the Zarya module to attempt to inspect the vicinity of the antenna. The camera views were inconclusive in determining a cause of the problem. Engineers are continuing to evaluate the information and possible causes for the problem, causes that range from loose insulation to damage from orbital debris.

However, managers have determined that the antenna can be used in its current condition with no risk of further damage and controllers plan to reselect it for communications later this week.

Day-to-day operations of the station have been virtually unaffected by the antenna problem. The U.S. 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 that is used for the primary command and control of the station from a control center in Korolev, Russia.

Also this week, controllers in Korolev completed a successful test of the Kurs-P system on the Zarya module, the automated rendezvous system that will be used later this year to steer the station to a docking with the next station component. Called the Service Module, the next station component is planned to be launched later this year by Russia and will serve as an early crew living quarters and station core.

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 1,830 orbits of Earth since its launch.