News from the Phoenix press briefing Saturday
Posted by Emily Lakdawalla
24-05-2008 15:16 CDT
As I expected, there wasn't a lot of news from today's Phoenix press briefing, which I watched from home on NASA TV as my daughter industriously colored at the coffee table. One item is that their landing ellipse has shrunk slightly. The three-sigma ellipse (see Rob Manning's message to me for background on what that means) used to be about 20 kilometers across and 100 kilometers long. The length of the ellipse results mostly from uncertainty in the atmospheric conditions that will prevail during the landing. Just as weather predictions on Earth are more reliable for tomorrow's than they are for next week's weather, the Phoenix team's weather predictions are getting more certain as the day draws closer, so that uncertainty is decreasing, and the ellipse is now only 80 kilometers long. (That's what they said, but if I've interpreted their map correctly, the ellipse is actually roughly 23 by 70 kilometers.)
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|(optional) Your name:|| However, as the length of the ellipse has shrunk, its center has moved slightly off target, a bit to the northwest of the desired target point. They do have one more chance to change course, but they explained at today's press conference that it is not so off-target that the course correction would be necessary if they had to make the decision right now. They'll make the final decision tonight.|
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