INTERNATIONAL SPACE STATION STATUS REPORT #99-17
4 p.m. CDT, Thursday, April 29, 1999
Mission Control Center, Houston, Texas

Space Shuttle Discovery rolled to its sea-side launch pad earlier this week in preparation for the first flight of the year to visit the International Space Station, which is monitored nearly around the clock by flight control teams in Houston and Moscow. Troubleshooting of the Unity module's communication system downlink capability continues, but hasn't hampered the health of the overall complex.

Monday's transport of Discovery to the launch pad at the Kennedy Space Center in Florida sets the stage for its planned launch to the ISS next month to deliver supplies and logistics that will be used by the first astronauts and cosmonauts to live on the outpost.

As the shuttle preparations continue, flight controllers monitoring the systems onboard the Station continue to evaluate the loss of downlink capability through the Unity module's Early Communications System, which supplements the primary commanding capability through Russian ground stations. While troubleshooting continues, station managers are considering flying some components on Discovery that may be used as replacements should that become necessary to restore full use of the early communications system. The problem with the system was detected last week during routine 'characterization' testing of the Station's two high-gain antennas. The testing is designed to provide ground controllers data for future use in calibrating or measuring changes to the signal strength over long periods of time.


Late this week, the third and final test planned prior to Discovery's arrival at the station was carried out when the Russian flight control team uplinked and tested an update to the onboard software permitting use of only the small thruster jets on the Zarya module. This update prevents Zarya's 40 kilogram thrusters from firing during maneuvers while the shuttle is in proximity or docked to the ISS.

Test one, completed April 2, gathered insight in how best to plan for warming the ISS modules prior to Discovery's docking with the station. Test two was completed April 16 and demonstrated the ability of Zarya to deliver 1,500 watts of power to Unity.

As the ISS remains in good health circling the Earth at 252 miles altitude, around the world here on the ground hardware continues to be readied for eventual delivery to space aboard U. S. Space Shuttles and Russian rockets.

The next component of the Station and the first fully Russian contribution to the ISS program was "rolled out" of its testing plant Monday. During the ceremony, the certificate of flight readiness was signed signaling the official handover of the Service Module from RSC Energia Corporation to the launch processing team at the Baikonur Cosmodrome in Kazakhstan, and will be shipped May 11 by rail to the launch site from its initial manufacturing plant at the Krunichev State Research and Production Company. The official launch date will be determined once the module reaches Baikonur and assessments can be made on the remaining testing to be done.


Back in the U.S. at the Kennedy Space Center, Discovery was rolled out to the launch pad earlier this week for final preparations for the first Shuttle flight of the year. The mission will include a spacewalk to install a couple of cranes on the outside of the modules for use by astronauts and cosmonauts during future assembly flights. The launch is targeted for May 20. Updates on preparations for the launch of Discovery can be found in the Kennedy Space Center's Shuttle status report located on the Internet at:


http://www-pao.ksc.nasa.gov/kscpao/status/status.htm

In the Space Station Processing Facility, assembly hardware for four flights is being processed and readied for the next Multi Element Integrated Test to begin in the next couple of weeks. This test is a dress rehearsal to verify that the various components work together before being launched into space. Components are interconnected by cabling as they will be on orbit and run through a series of "shakedown" tests proving the hardware and software's intergrated operation.
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 2,504 orbits of Earth since its launch. ISS viewing opportunities from the ground can be found on the Internet at:

http://spaceflight.nasa.gov/realdata/sightings/

The next International Space Station status report is planned to be issued on Thursday, May 6, 1999.

Note: For further information, please contact the NASA Public Affairs Office at the Johnson Space Center, Houston, Texas, 281-483-5111.

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