Spaceflight Now: Breaking News

'Minor' problem seen in test of power unit aboard ISS
Posted: Jan. 22, 2000

The Zarya and Unity modules form the International Space Station. Photo: NASA
The International Space Station continues to operate in good working order in its fourteenth month on orbit.

Flight controllers continue to manage electrical power through the batteries inside the Zarya module, recharging four of the six on-board power plants. Battery No. 1, which has experienced some problems and will be replaced by Shuttle astronauts later this year on the next mission to the ISS, has been recharged and is currently connected to Zarya's electrical bus while other batteries complete their recharging.

Plans are being developed for a second test of the "Kurs" automatic docking system on Zarya. The previous test showed discrepancies in the relative velocity readings caused, most likely, by some electromagnetic interference (EMI). Though EMI is the leading candidate for the problem, flight controllers in Moscow and Houston are not ruling out a hardware problem. The test will likely confirm EMI as the culprit and a plan will be developed to reduce or eliminate it during actual flight operations when the "Kurs" is used to dock the ISS with the Zvezda Service Module two weeks after Zvezda is launched.

Early Sunday morning, a minor problem occurred during a self-test of one of two active Remote Power Controller Module (RPCM) units in the Unity connecting module designed to route electricity to various Unity systems. There was no impact to flight operations and the controller is fully operational. Engineers are analyzing data to determine what may have caused the momentary problem. A total of four RPCMs are housed in Unity. The other two are used only when a Shuttle is docked to the ISS during assembly operations.

Meanwhile, ISS and Shuttle program managers continue to evaluate whether to schedule a Shuttle mission to the Station this spring to perform maintenance on Zarya to preserve its health in advance of Zvezda's arrival.

A final decision is expected soon, pending plans for the return to flight of the Russian Proton booster, which will be used to lift Zvezda into orbit. Managers plan to meet in Moscow in February to determine the most likely launch target date for Zvezda.

The International Space Station continues to orbit the Earth at an altitude of 247 by 231 statute miles. Since the launch of Zarya in November 1998, the ISS has completed more than 7,600 orbits.

Sign up for Astronomy Now's NewsAlert service and have the latest news in astronomy and space e-mailed directly to your desktop (free of charge).

Your e-mail address: