Shuttle Ready for Sixth Launch Try

So far NASA has had to scrub five previous attempts, based on a gas leak and bad weather. The last attempt, on Monday, was canceled due to weather issues. In June, two attempts were scrubbed due to a gas leak.

Shuttle Endeavor, despite this, is once again fueled and ready on Launch Pad 39A. NASA hopes for 6:03 PM ET blast-off.

Today's weather forecast is slightly better than in recent days. There is currently a 60% chance of good (enough) conditions. The mission for STS-127 is scheduled to last 16 days.

Endeavour commander Mark Polansky will hopefully lead a crew of seven that includes Canadian Julie Payette and NASA astronauts Doug Hurley, David Wolf, Chris Cassidy, Thomas Marshburn and Tim Kopra. Kopra will replace Koichi Wakata of the Japanese Aerospace Exploration Agency as an Expedition 20 flight engineer.

When Endeavor reaches the ISS, the population of the space station will be at 13, an all time high. The current population includes Russian cosmonauts Gennady Padalka and Roman Romanenko, and astronauts Michael Barratt of NASA, Frank De Winne of Belgium, Robert Thirsk of Canada, and Wakata.