NASA - National Aeronautics and Space Administration

Station Crew Prepares for Arrival of New Spacecraft, Tests Station System as Mission Control Monitors Debris

Image above: Station crew members (from left) Nicole Stott, Frank De Winne and Robert Thirsk talk to Belgian media during a European Space Agency in-flight event. Credit: NASA TV

As the International Space Station’s six spacefarers continued preparations Friday for the arrival of a new module and a visiting space shuttle, they also were informed that a small piece of space junk might pass close enough to require precautions. However, flight controllers decided not to put the crew in the Soyuz vehicles at the ISS, declaring that the space debris they have been tracking no longer poses any concern or threat. Mission Control woke the crew members at 10 p.m. EST to inform them that no precautionary measures were needed, and after they returned to sleep the debris passed by harmlessly.

The crew was first notified of the 5-centimeter-long piece of space debris about 10:04 a.m. EST. The U.S. Space Command routinely tracks space debris in orbit around the Earth, and reports to NASA any possible “conjunctions” or close passes to the space station. About 5:15 p.m., Spacecraft Communicator Ricky Arnold radioed the crew that additional tracking passes showed the debris was no longer a threat.

NASA has a set of long-standing guidelines that are used to assess whether the threat of such a close pass is sufficient to warrant evasive action or precautions to ensure the safety of the crew.

These guidelines essentially draw an imaginary box, known as the “pizza box" because of its flat, rectangular shape, around the space station. This box is about half a mile deep by 15 miles across by 15 miles tall (0.75 x 25 x 25 kilometers). When predictions indicate that the debris will pass close enough for concern and the quality of the tracking data is deemed sufficiently accurate, Mission Control centers in Houston and Moscow work together to develop a prudent course of action.

Sometimes these encounters are known well in advance and there is time to move the station slightly, known as a “debris avoidance maneuver” to keep the debris outside of the box. Other times, the tracking data isn’t precise enough to warrant such a maneuver or the close pass isn’t identified in time to make the maneuver. In those cases, the control centers may agree that the best course of action is to move the crew into the Soyuz spacecraft that are used to transport crew members to and from the station so that they could isolate those spaceships from the station by closing hatches, and then leave the station if the debris were to collide with the station and cause a loss of pressure in the life-supporting module. The Soyuz act as lifeboats for crew members in the event of an emergency.

Mission Control also has the option of taking additional precautions, such as closing hatches between some of the station’s modules, if the likelihood of a collision is great enough.

For Friday’s event, the early data suggested that the space debris might come close enough to the station to require the crew to take temporary shelter for a few minutes in their respective Soyuz vehicles. NASA worked with its Russian partners to formulate a plan that would have the crew wake up around 10 p.m. EST, then move into their Soyuz vehicles until the time of closest approach passed.

The International Space Station crew was notified this afternoon of a possible close encounter with a piece of space debris. The time of closest approach of the debris was expected at 10:48 p.m. EST.

Additionally, Expedition 21 Commander Frank De Winne and Flight Engineers Nicole Stott, Jeff Williams, Roman Romanenko, Max Suraev and Bob Thirsk focused their work on preparations for next week’s arrival of the Russian Mini-Research Module 2 (MRM2), recently named Poisk, and the Space Shuttle Atlantis the following week.

Poisk’s launch from the Baikonur Cosmodrome in Kazakhstan, is scheduled for Nov. 10. The MRM2 will arrive at the station on Nov. 12 docking to the top port of the Zvezda service module. Atlantis is scheduled to launch from Kennedy Space Center on Nov. 16, and dock with the station on Nov. 18.

The station crew also continued troubleshooting activities for the Urine Processing Assembly (UPA) which was later shut down. A clogged line appeared to have been cleared earlier in the week, but the water recycling system’s temperature rose higher than expected when recycling resumed early in the day. The ground team is currently looking at the data before deciding when to restart the recycling system.

An experiment that monitors the weakening of heart muscles during long term exposure to the microgravity environment is on hold. Software that had been reloaded for an ultrasound system used in the Integrated Cardiovascular experiment was unable to work properly. Ground controllers are now considering delivering replacement circuit boards on a future flight to the station.

› Read more about Expedition 21
› View crew timelines

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