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More Details for 1999-10-14

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With International Space Station systems in good shape, flight controllers again demonstrated commanding capability to Zarya's computers from Houston via the early communications system mounted on Unity.

The early communications system allows commanding to Zarya through Houston's Mission Control using the Tracking and Data Relay Satellite System. Because TDRSS is used by other spacecraft, the system was periodically switched off so as not to conflict with data transmission from the Galileo space probe as it passed close to Jupiter's moon Io. These transmission periods typically lasted about 10 minutes.

As was the case last week, the Station's motion control system was turned on to accurately measure the Station's spin rate and make any adjustments necessary. Plans call for this routine procedure to be done every Sunday for the next month or so. Additionally, the communications network through Houston will be used each Monday, Wednesday and Friday to correlate the measurement as well. Currently the ISS is slowly spinning about its axis with Unity pointed toward Earth at a rate of about three tenths of a degree per second. This maintains even temperatures on the overall structure and minimizes propellant usage to maintain the complex's orientation.

Commands also were sent to switch the early communications system from the left antenna to the right for low data rate operations. This procedure calls for switching between the two antennas periodically to ensure good health of the entire system.

The ISS is orbiting at an altitude of 248 by 230 statute miles. Since the launch of Zarya last November, the Station has completed more than 5,120 orbits. S