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Two shuttles sighted

Stunning aerial views of shuttles Atlantis and Endeavour perched atop launch pads 39A and 39B on Sept. 20.

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Endeavour to the VAB

For its role as a rescue craft during the Hubble servicing mission and the scheduled November logistics run to the space station, Endeavour is moved to the Vehicle Assembly Building.

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STS-125: The mission

A detailed step-by-step preview of space shuttle Atlantis' STS-125 mission to extend the life and vision of the Hubble Space Telescope.

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STS-125: The EVAs

The lead spacewalk officer provides indepth explanations of the five EVAs to service Hubble during Atlantis' flight.

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STS-125: The crew

The seven shuttle Atlantis astronauts hold a press conference one month before their planned launch to Hubble.

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STS-125: NASA leaders

The leaders of NASA's Space Operations and Science directorates give their insights into the upcoming shuttle mission to the Hubble Space Telescope.

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STS-125: Shuttle boss

The head of NASA's space shuttle program discusses the risks and plans for Atlantis' trek to Hubble.

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The Hubble program

An overview of the Hubble Space Telescope program and the planning that has gone into the final servicing mission.

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Hubble's future science

The new instruments to be installed into Hubble and the future science objectives for the observatory are previewed.

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Atlantis on the pad

Shuttle Atlantis makes the slow journey from the Vehicle Assembly Building to launch pad 39A for the STS-125 mission to service Hubble.

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Meet the Hubble crew

Meet the crew launching on Atlantis' STS-125 mission to service the Hubble Space Telescope and learn how each became an astronaut in this special biography movie.

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Engineers not yet sure about cause of Hubble glitches
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: October 21, 2008

After a weekend of troubleshooting, engineers at NASA's Goddard Space Flight Center have not yet pinned down the cause of two glitches last week that prevented restart of the Hubble Space Telescope's science instruments, officials said today.

The restart, switching instrument control to a backup payload computer and components, was required because of a failure in the A channel of the telescope's control unit science data formatter, or CU/SDF-A, on Sept. 27. To restore the lost redundancy, NASA managers decided to delay the shuttle Atlantis' planned Oct. 14 launch on a final Hubble servicing mission, known as SM-4, to give engineers time to prepare replacement hardware. That flight now is targeted for no earlier than mid February.

In the meantime, Hubble managers wanted to restart the telescope's science instruments by reconfiguring six components in the observatory's data management system and five in the instrument command and control system. Several of the components in question had not been turned on since launch in 1990.

The initial stages of the complex restart procedure went smoothly, but improper voltage levels were seen in one of the instruments, aborting the startup sequence. Later, the data management subsystem computer also suffered an unexpected glitch. It is not yet clear whether the two events were related.

"On Monday, October 20, engineers at NASA's Goddard Space Flight Center met to discuss their next steps toward resolving two anomalies which caused the B-side of the Science Instrument Control and Data Handling System (SI C&DH-B) and the Advanced Camera for Surveys (ACS) Solar Blind Channel (SBC) to return to a 'safe hold' status on October 16," NASA said today in a status report.

Over the weekend, "the Hubble team continued detailed reviews of all the data available when last week's anomalies occurred. A suspect 8-volt power source within the SBC's low voltage power supply (LVPS) reached its nominal output value just after failure of an internal check monitoring its health. Hubble engineers are evaluating alternative procedures and determining whether another attempt to restart the LVPS presents a risk to the instrument or to the planned SM-4 repair of ACS's other cameras."

The Advanced Camera for Surveys, installed in 2002, suffered an earlier failure that knocked out its visible light wide-field and high-resolution cameras. Only its solar blind channel, which is sensitive to ultraviolet light, is still in operation. The Atlantis astronauts hope to repair the ACS during the upcoming servicing mission.

In the meantime, before engineers can restart the solar blind channel - assuming they can resolve the voltage anomaly - they must first coax the B-side science instrument command and data handling system back into operation.

"Intensive study of the SI C&DH-B shutdown also continues," today's status report said. "Analyses done thus far suggest that an electrical event of unknown origin and characteristics caused a reset of both the Control Unit/Science Data Formatter-B (CU/SDF-B) and the NASA Standard Spacecraft Computer-1 (NSSC-1) Central Processing Module-B (CPM-B). Both of these modules were activated on-orbit for the first time on October 15. Additional analyses and a risk assessment of SI C&DH-B reactivation have begun."

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