posted 11-06-2009 02:27 PM               

Mission Control monitoring debris

The Expedition 21 crew onboard the International Space Station (ISS) was notified Friday morning of a possible conjunction with a piece of Russian Cosmos space debris. The time of its closest approach is projected to be 9:48 p.m. CST.

Due to the timing of the available tracking data, it is now too late for the crew to perform a debris avoidance maneuver. Tracking of this debris is erratic and taking the appropriate precautions and preparing are prudent measures.

Mission Control in Houston contacted station commander Frank De Winne at 10:04 a.m. informing him of the possible conjunction, as well as the effort to more accurately determine the path of the debris.

Capcom Jason Hutt told De Winne, "We are possibly going to get one more data point on this conjunction." He then added, "We are going to have to make a decision what we're going to have to do with regards to getting in the Soyuz."

posted 11-06-2009 02:39 PM               

Pending additional analysis, flight controllers told the six-member crew of the International Space Station to plan on taking refuge in the lab's two three-seat Soyuz lifeboats late Friday for the expected close approach of a piece of space debris around 10:48 p.m. EST.

The debris, of unknown origin or size, could pass within about six-tenths of a mile of the lab complex toward the end of the crew's normal sleep period. Because all objects in low-Earth orbit, including the space station, are moving at roughly five miles per second, close encounters, or "conjunctions," are carefully monitored and subjected to extensive analysis.

During the evening planning conference Friday afternoon, the astronauts were told to plan on getting up a few minutes early so they can make their way to the Soyuz lifeboats by around 10:30 p.m.

"The ballistics are saying they are looking at conjunction with space debris," Russian mission control radioed. "As you know, this is something we are prepared for. In the past, we have performed avoidance maneuvers, but this time maneuvering away from the path of the debris is not an option.

"Because we cannot perform avoidance maneuver, you will have to ingress Soyuz vehicles. Both Soyuz crews should be in their vehicles. This is what we have. We are going to work on the ballistics data to get greater precision, but right now we are in the red box. The probability of collision is non zero."

...under the current plan, cosmonaut Roman Romanenko, Canadian astronaut Robert Thirsk and European Space Agency commander Frank De Winne would make their way to the Soyuz TMA-15 spacecraft docked to the Earth-facing port of the Zarya module between 10:15 p.m. and 10:30 p.m. EST. Cosmonaut Maxim Suraev and NASA astronauts Jeffrey Williams and Nicole Stott would seek safe haven in the Soyuz TMA-17 spacecraft docked to the aft port of the Zvezda command module.

posted 11-06-2009 05:00 PM               

The six-member crew of the International Space Station was told to get a few hours sleep Friday while flight controllers continued to assess the trajectory of a piece of space debris that was expected to pass close by the lab complex at 10:48 p.m. EST.

The crew was told to be prepared to take refuge aboard the lab's two three-seat Soyuz lifeboats if the analysis indicated a clear threat. But late Friday, flight controllers gave the crew a more upbeat report, saying "the news is getting better."

"We've had two more sites that have tracked the object and they're indicating it is not a valid threat," Ricky Arnold told the crew from mission control in Houston shortly before 5:30 p.m.

"Though due to the uncertainty, we'd like to take the opportunity to get more data in about an hour, we've got another pass that we'll get a look at it. We'd like to have you guys go to bed and we'll wake you a 0300 (GMT; 10 p.m. EST) as planned, even if it's just to tell you to go back to sleep. We don't know when the analysis is going to get in."

"OK, that sounds good," replied station commander Frank De Winne, a European Space Agency astronaut. "So we'll wake up at 0300 and we'll get further words at that moment if we will proceed to our Soyuzes and closing the hatches, or if you want us to just go back to sleep."

"That's a great plan and we thank you guys for the late night and all your hard work," Arnold said. "Hopefully we'll be waking you up here in a few hours with some good news."

posted 11-06-2009 06:10 PM               

Flight controllers have decided not to put the International Space Station crew in the Soyuz vehicles, declaring that the space debris they have been tracking no longer poses any concern or threat. Mission Control will wake the crew as planned as a precautionary measure while the debris passes.

The crew was notified of the 5-centimeter-long piece of space debris about 9:04 a.m. CST. 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 4:15 p.m., capcom 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 today'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 9 p.m. EST, then move into their Soyuz vehicles until the time of closest approach has 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 is expected at 9:48 p.m. EST.