From: Derek C Breit (
Date: Fri Nov 06 2009 - 23:50:08 UTC

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    A message from my ISS Group...
    ----- Original Message ----- 
    Sent: Friday, November 06, 2009 1:17 PM
    Subject: [International Space Station] ISS DEBRIS COLLISION AVOIDANCE ALERT!
    2:45 PM, 11/6/09, Update: NASA monitors space debris, possible close 
    approach to International Space Station with initial decision to put crew in 
    Soyuz craft for debris encounter.
    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."
    NASA flight controllers told the astronauts the tracking data is uncertain 
    and that engineers did not yet have confidence in the trajectory 
    projections. But pending an additional analysis later in the afternoon, the 
    crew was told to play it safe and plan on boarding the Soyuz lifeboats after 
    shutting internal hatches in the U.S. segment of the lab complex.
    "We have data that indicates we might be heading to a conjunction, however 
    we do not have enough data to have any confidence in the outcomes we're 
    predicting at this point," Ricky Arnold told the crew from mission control 
    in Houston. "We're hoping we're going to be a lot smarter at 2200 (GMT), but 
    right now we have to plan for an indication that we will have a 
    If the initial predictions hold up, "we would like to close all the hatches 
    inside the station," Arnold said. "We're also going to be configuring our 
    cooling to two loops. We're going to need you guys to do some steps on board 
    to get to dual-loop mode."
    With both of the station's cooling systems active, the lab would be 
    protected against an impact that might cause a leak in one of the lab's 
    critical ammonia coolant lines.
    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 
    Flight controllers plan to make a final decision on how to proceed around 5 
    p.m., after getting another update on the object's trajectory.
    "Unfortunately, the particular object is not easy to track, it's not visible 
    by all the different tracking stations every time, and so there's not a lot 
    of confidence in the data on the exact location of this piece of debris," 
    NASA spokesman Kelly Humphries said earlier Friday.
    Last March, the station's three-man crew - Mike Fincke, Yury Lonchakov and 
    Sandra Magnus - faced a similar situation and briefly took refuge in the 
    lab's single Soyuz lifeboat when another piece of debris from an old rocket 
    motor made a close approach.
    There are more than 18,000 pieces of space junk in low-Earth orbit the size 
    of a baseball and larger. U.S. Strategic Command prioritizes radar tracking 
    to protect manned spacecraft first, followed by high-priority military and 
    civilian payloads.
    NASA monitors an imaginary volume around the space station roughly the shape 
    of a pizza box measuring 0.466 miles thick and 15.5 miles square.
    "Initially, we have a screening box, which is .75 kilometers radial miss, 
    which would be up or down, by 25 kilometers in cross track, which would be 
    left or right, by 25 kilometers down track, which is either in front or 
    behind us," space station Flight Director Ron Spencer said in September.
    "Space Command will alert us of any debris objects out there that are going 
    to get that close to us. Then they increase tasking on those objects to try 
    to get a better solution and decrease the uncertainty. Then we calculate a 
    probability of collision based on the data Space Command gives us."
    Spencer said NASA has two levels of concern.
    "We have two thresholds, yellow and red," he wrote in an email exchange. 
    "The yellow is 1-in-100,000 and the red is 1-in-10,000. We will not take any 
    action if it is below the yellow threshold. If it between the yellow and 
    red, we will only take action if it is easy to do so without impacting the 
    mission. For a red threshold violation we will take action in most cases."
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