Space Shuttle Atlantis would have to lift off on 7 September to accommodate a Soyuz launch that would carry the International Space Station (ISS) expedition 14 crew to the orbital outpost and the likelihood of NASA meeting that launch window is a "low probability."
With tropical storm Ernesto about to reach the Kennedy Space Center (KSC) the US agency does not know what the impact of that event will be and how quickly the shuttle could be rolled back to launch pad 39B after its return to the vehicle assembly building today to protect it against the storm. NASA needs eight days after a shuttle reaches the launch pad before it can launch. Therefore if Atlantis does not return to the pad on or before 31 August it will miss the window deadline.
The 7 September launch window deadline, that would otherwise be 13 September, exists because Russia's Federal Space Agency (FSA) is preparing for a 14 September launch of its Soyuz rocket that is carrying the ISS expedition 14 crew. The FSA is prepared to move the flight to 18 September if Atlantis' launch was delayed to the seventh, but no later.
This is because an Atlantis flight after the 7 September, for its 11-day STS-115 mission to the ISS, would mean a 20 September launch for the Soyuz and the Soyuz that is already attached to the ISS, and would return to Earth with two of the members of the current ISS expedition 13, would land on the 29 September in darkness. It is landing in darkness that is unacceptable for safety reasons to the ISS international partners' rules.
Another issue is that an Atlantis launch as late as 13 September would mean an October launch for expedition 14 and the Soyuz attached to the ISS would be breaching its certification period. A Soyuz capsule is certified for 200 days in orbit.
During a teleconference today Wayne Hale, NASA's space shuttle programme manager, explained that the US agency had studies underway to examine the possiblity of launching at a time when the lighting was not ideal and in his opinion launching by the 7 September was "a low probability."
The next window that meets NASA's daylight launch criteria begins on 26 October. Hale added that an October launch would not affect the next flight of Discovery, scheduled no earlier than 14 December this year, for mission STS-116.