Note: This information is not intended for wagering purposes.
The Space Weekly Official odds for an on time launch on Friday, have dropped to 32%.
This reduction is because of 2 factors;
The Florida afternoon showers showed themselves on Wednesday, causing Tornado warnings in Brevard County, the location of the Kennedy Space Center.
There have been reports about concerns with the external tank. Although NASA claims the concerns have been solved, it is an older tank, and when it is finally fueled, it is likely to still have wrong readings. This tank has already been attached and disconnected and reattached.
The chance of total vehicle loss is 11%
The Luck factor as explained below brings the chance of an ATO or RTLS to 17%
Here is what goes into making the odds;
Out of 117 Shuttle missions there have been only 59 that have launched on the scheduled day, so the average chance is about the flip of a coin.
Atlantis the Shuttle slated to be launched has only launched on time 48% of the time.
Of the 14 missions to be rolled back (2 were rolled back twice for a total of 16 rollbacks for 14 missions). Only 2 made their scheduled launch date.
Although the weather for the day is 70% favorable, the weather in the Cape area of Florida tends to be worse in the late afternoon than in the morning.
One of the Unions is moving toward a strike, and so this tends to tilt the balance toward no launch.
The final part of the equation is luck. This will be the first time Atlantis has had a launch attempt since 2002, almost 5 years of sitting.