Note: This information is not intended for wagering purposes.
The Space Weekly Official odds for an on time launch on Friday, is 38%.
Here is why;
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.
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.