While NASA starts the countdown for the Hubble servicing mission, everyone watches at both Atlantis and Endeavour as they are prepared for take off. Atlantis will carry seven astronauts to Hubble for one last maintenance mission until at least 2014, while Endeavour will be on stand-by if a rescue mission is ever necessary.

Although NASA hopes Endeavour’s assistance will not be needed, NASA says Endeavour will remain on stand-by “in the unlikely event that a rescue mission for the Atlantis crew would be necessary.” On Friday morning, Endeavour was moved to the Launch Pad 39B. If Endeavour is cleared from the rescue mission, it will then be moved on Pad 39A in preparation for the STS-126 mission in November.

On October 10, Commander Scott D. Altman, and mission specialists Michael J. Massimino, Michael T. Good, K. Megan McArthur, John M. Grunsfeld, Andrew J. Feustel, and pilot Gregory C. Johnson, will commence the final space mission to Hubble, where they are expected to make repairs and upgrades that should leave it ready for at least another 5 years of research.

According to NASA, “Hubble’s triumphs continue to accumulate thanks to a unique design that allows astronauts to repair and upgrade the telescope while it remains in orbit. Repairs keep the telescope functioning smoothly, while upgrades to the instruments bring a slew of new discoveries and science.”

The astronauts are scheduled to make five six-and-a-half-hour spacewalks, when they will install three essential components for Hubble, the Wide Field Camera 3 (WFC3) and the Cosmic Origins Spectrograph (COS). COS will study the evolution and formation of planets, as well as the “cosmic web” of gas between galaxies, NASA explained.

The first images from the telescope following the maintenance mission are not expected to be released earlier than 2009, due to the necessity of a several-month-long testing period. NASA hopes that the STS-125 mission will keep the Hubble telescope ready for new discoveries for years to come.