Actually, that's wrong
STS-127 won't launch in May, if STS-125 does. It's confusing as NASA.gov did bad job in explaining.
Right now, the plan is:
Discovery/119: Feb 12
Atlantis/125: May 12
Endeavour/400: May 19 (standby).
Endeavour/127: Mid June.
OR, if HST hardware is delayed, making May impossible for 125...
Discovery/119: Feb 12.
Endeavour/127: May 12
Atlantis/125: July ish
Discovery/401: July ish (standby).
They just can't launch two within two weeks of each other (as it can be mistranslates on the NASA.gov release). Still going to a busy period of a busy year, with Ares I-X somewhere in the middle, if they find a solution for 39B modifications/launch 400 off Pad 39A.
400 vs 401, to explain, is still the LON (Launch On Need) standby for STS-125, but different Shuttles require slightly different assignments, so Endeavour is STS-400, and Discovery would be STS-401.
We covered the manifest meeting the day before NASA.gov did the release, so here's my article if it helps explain - mainly based on the likely plan as 125 is tracking May.
http://www.nasaspaceflight.com/2008/12/sts-125s-tank-manifest-meeting-ares-i-x-iss-food-shortage-2/
