The STS-125 mission of the National Aeronautics and Space Administration (NASA), is a service-and-repair mission to the Hubble Space Telescope, which is orbiting in space about 559 kilometers (347 miles) above the Earth in low-earth orbit (LEO).
The other launch that is schedule on that same earlier-scheduled day (May 12) is a GOES-O (Geostationary Operational Environmental Satellite-O) Earth-watching satellite for the National Oceanic and Atmospheric Administration (NOAA).
The GOES-O payload will use a United Launch Alliance (ULA) Delta 4 rocket to attain its geosynchronous orbit. The launch is expected to occur on May 12, 2009, from the Cape Canaveral Air Force Station, at Cape Canaveral, Florida.
According to the NASA/GOES website, “Launch remains targeted for no earlier than May 12. The date will be adjusted accordingly based on the readiness of the Delta IV, the status of space shuttle Atlantis' STS-125 mission launch and the availability of the Eastern Range.”
NASA makes launches from the Eastern Test Range (ER), which includes two major rocket and missile ranges, NASA’s Kennedy Space Center (KSC, on Merritt Island, Brevard County, Florida) and the U.S. military’s Cape Canaveral Air Force Station (at the Patrick Air Force Base).
Multiple launches at the same time are not allowed, which means that schedules must be revised to accommodate the ever-increasing number of launches from this location.
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According to the GOES Project website, the GOES-O is the “… newest generation of environmental satellites built by Boeing for the National Oceanic and Atmospheric Administration (NOAA) under the technical guidance and project management of NASA's Goddard Space Flight Center, Greenbelt, MD.”
NASA mission STS-125 is fifth and final space shuttle mission to service and upgrade the orbiting Hubble Space Telescope. Space shuttle Atlantis will launch two new science instruments, along with stabilizing gyroscopes, batteries and thermal blankets to refurbish the orbiting space telescope and to extend its lifetime for another five years, probably until at least 2013.
Five spacewalks are scheduled to be conducted during STS-125 in order to make all the necessary repairs and upgrades to Hubble.
Although not yet approved, if NASA does authorize the one-day earlier launch of STS-125 on May 11, it will be scheduled to occur at 2:01 p.m. Eastern Daylight Time (EDT).
Deputy Space Shuttle program manager Leroy Cain stated, “I feel fairly confident that we can make a May 11 launch date.” [Space.com: “Mission to Save Hubble Could Launch a Day Early”]
The launch can be watched on NASA Television (check your local listings) or on NASA TV on the Web.