The Space Shuttle Atlantis has moved to its launch pad at Kennedy Space Center, Fla., as NASA prepares for its second shuttle launch in as many months.

Atlantis is poised atop the crawler transporter, which–after weather delays–moved the 4.2 miles from the vehicle assembly building to the launch pad at a top speed of 1 mph, a bit slower than the 17,500 mph the shuttle reaches in orbit.

In the vehicle assembly building, the Atlantis orbiter vehicle was mated to the external fuel tank and solid booster rockets.

While at the pad, the shuttle will undergo final testing, payload installation and a “hot fire” test of auxiliary power units to ensure proper function.

When testing is completed, the rotating service structure will be moved around the vehicle to protect it from the elements.

The launch window for the Atlantis mission to the International Space Station (ISS) opens on Sunday, Aug. 27.

The mission, designated STS-115, will be the first to perform a major expansion of the station since December 2002.

NASA has set an ambitious goal of 16 space shuttle missions over the next four years, and those missions must go well if the ISS is to be built to its full design.

Good progress has been made toward that goal recently.

For example, the Space Shuttle Discovery launched July 4 in a by-the-book mission to the ISS that was flawless, with no damage to the shuttle or to its personnel.

Crew from the shuttle, and later ISS crew, have performed extensive construction and preconstruction work on the ISS, helping to prepare it for a significant expansion.

The artificial moon stands to gain a major increase in its solar displays, for example, which will generate far more electrical output to power the expanded areas of the ISS.

Another positive for the space program, thanks to the Discovery mission, is that there are three crew members on the ISS, so that scientific experiments on the space station can continue.