After arriving at NASA's Kennedy Space Center in Florida to prepare for space shuttle Endeavour's July 11 launch on the 29th assembly flight to the International Space Station, the STS-127 crew members pose for a final photo before leaving the Shuttle Landing Facility. Image credit: NASA/Kim Shiflet.

Stormy weather conditions may delay the launch of space shuttle Endeavour, currently scheduled for liftoff on Saturday, July 11. This comes on the heels of two delays last month caused by a hydrogen gas leak. A similar problem delayed the launch of space shuttle Discovery in March.

The 16-day mission will feature a number of  spacewalks intended to complete construction of the International Space Station’s “porch.” The new addition is officially known as Japanese Experiment Module – Exposed Facility. It will be a platform attached to the Japan Aerospace Exploration Agency’s Kibo laboratory. The “porch” will allow for experiments to be exposed to the unique environment of outer space.

Endeavour’s crew members are Commander Mark Polansky, Pilot Doug Hurley and Mission Specialists Dave Wolf, Christopher Cassidy, Tom Marshburn, Tim Kopra and Canadian Space Agency (CSA) astronaut Julie Payette.

Payette will join Robert Thirsk, also of the CSA. This marks the first time that two Canadian astronauts have been in space at the same time.

The shuttle-ISS combo will house a total of 13 crew members for the duration of the mission, a record number.

NASA aims to launch seven further shuttle missions before the aging fleet is finally retired in 2010.