Update 4: The latest weather forecast predicts a 5% chance of weather prohibiting tanking and 40% probability of weather prohibiting launch, while showers and thunderstorms within 20 Nautical Miles (~37km) of the Shuttle Landing Facility remain the primary concerns.
Update 3: The Mission Management Team is scheduled to meet at 12:00 UTC to give a “go” for the fueling of Endeavour and the tanking should commence at 12:30 at slow phase with filling the External Tank (ET) with liquid hydrogen (at 20K).
Update 2: Currently teams are working on resolving a fuel cell issue but the management team is not sure about the impact on the scheduled launch.
Update 1: Thursday will be the last possible launch attempt until July 26 due to the Progress 34P mission to the ISS.
The mission’s four scrubs place STS-127 only two scrubs behind the “record” of six called-off launch attempts held by STS-73 and STS 61-C. The first two scrubs (June 13 and June 17) were due to gaseous hydrogen leak on a vent line near the Ground Umbilical Carrier Plate (GUCP). Because of a planned launch of the LRO/LCROSS mission on June 18, there was no time to attempt another launch of Endeavour before the beta angle cutout started on June 20. After that, it was not possible to launch the shuttle before the cutout ended on July 10.
Coincidently, the beta angle cutout provided NASA technicians with enough time to carefully examine the GUCP problem. During a meticulous investigation and data analysis engineers determined that the most likely cause of the leak was a misalignment in the External Tank Carrier Assembly. Technicians replaced the old seal with a two-piece seal enabling it to counter any movement of the external tank carrier assembly as the tank was being fueled. On July 1, NASA conducted a live tanking test to ensure repairs to the external tank (ET) were successful. (Source: NASA)
On July 11, NASA first postponed the ET tanking and consequently decided to delay the launch by 24 hours to give ground team extra time to examine ground equipment and systems aboard Endeavour for possible damage from lightning strikes. Although none of the 11 lightning strikes recorded within 0.5km of the launch pad were direct hits to either the orbiter, the external tank or the solid rocket boosters (SRB’s), the Ground Lightning Monitoring System (GLMS) declared a “lightning event” at 06:00 UTC and additional checks were needed to reach 100% confidence that orbiter electronic boxes and the solid rocket booster circuitry were functioning within the norms.
On Sunday, July 12, NASA’s launch director (LD) Pete Nickolenko coordinating with the Mission Management Team (MMT) called off the launch during the final Go/No-Go station polls, as the Mission Control Center in Houston (MCC-H) declared a No-Go due to unacceptable weather forecast at the Shuttle Landing Facility (SLF) for a possible Return To Launch Site abort. For the launch to proceed, weather conditions must be acceptable not only at the launch pad and one of the Transoceanic Abort Landing (TAL) sites, but also within 20 Nautical Miles (roughly 37km) of the SLF for about 20 minutes after liftoff.
Another lunch attempt was scrubbed on July 13, shortly after the MCC-H declared a No-Go because of the weather forecast at SLF for a possible RTLS, and the Launch Weather Officer Kathy Winters informed LD and MMT about Phase 1 lightning alert, the violation of restrictions on anvil clouds and the field mill violations. After a short discussion with the launch teams, Pete Nickolenko made a decision for a 48-hour turn-around, setting the next launch attempt for Wednesday at 22:03:10 UTC.