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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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Russians believe cause of recent Soyuz problems found
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: September 25, 2008

Russian troubleshooters believe electrical arcing between the space environment and the international space station most likely caused recent problems with explosive bolts used to separate Soyuz re-entry vehicles just before atmospheric entry.


This artist's concept shows how the three modules of the Soyuz spacecraft are supposed to separate, with the crew aboard the middle section. Credit: NASA TV
 
The two most recent Soyuz entries ended with off-course landings that subjected crew members to extreme buffeting and vibration. A top U.S. space station manager said today the Russians believe they have resolved the problem and that the next landing in October and subsequent flights will go smoothly.

"Our Russian colleagues have taken a number of steps," said space station Program Manager Michael Suffredini. "For the ascent vehicle, they've actually changed the pyros to a configuration that's less sensitive to this. ... In addition to that, the vehicle that's due to return home (in October) has, as you know, through a pair of EVAs, a pyro was removed therefore freeing up the mechanism."

In the two most recent Soyuz re-entries, one of five pyrotechnic separation bolts failed to disengage properly, causing the central descent module carrying the crew to remain attached to another module longer than usual. In both cases, the modules eventually broke free, but the malfunctions caused steeper-than-usual "ballistic" re-entries, shaking up the crews and resulting in off-course touchdowns.

The Soyuz currently docked to the station, TMA-12, was launched last April, after the first unusual entry but before the second. During a spacewalk this summer, Expedition 17 commander Sergei Volkov and flight engineer Oleg Kononenko released the mechanism and removed the pyro in question so it can be returned to Earth for analysis.

The Russians plan to launch Soyuz TMA-13 on Oct. 12 to ferry two fresh station crew members - Expedition 18 commander Michael Fincke and flight engineer Yuri Lonchakov - to the lab complex, along with Richard Garriott, a U.S. space tourist. Volkov, Kononenko and Garriott then will return to Earth in the TMA-12 vehicle on Oct. 23.

Suffredini said the TMA-13 spacecraft has been modified to minimize the threat of arcing.

"Our Russian colleagues have spent an enormous amount of time, a very structured effort, to create a fault tree and then work off the fault tree to come to a most probable cause," Suffredini said. "They have concluded the most probable cause to be related to the plasma environment and the delta potential between the plasma environment, the environment around space station, and the space station itself.

"The way the space station is wired together, there actually is a voltage, a delta voltage potential, between the environment around the ISS and the ISS itself and what happens over time is occasionally that potential tries to equalize. And when it tries to equalize, you get what essentially is a spark to the ISS. This is an environment we've been living in since we starting flying ISS, it's why we have what we refer to as the plasma contactor units that we operate during EVAs to prevent that from occurring during EVAs."

The plasma contactor units use xenon gas to equalize electrical potential around the station. The xenon supply is limited and the PCUs are only operated during spacewalks to prevent any chance of arcing while astronauts are working outside. Testing showed no obvious threat to the station's systems when the PCUs were turned off.

"What our Russian colleagues have determined is because of the very specific configuration of the pyros ... on the Soyuz, where it's failed to separate each time, they've determined that there's been some arcing, if you will, or equalizing of voltage in this area," Suffredini said. "And this over time has caused the pyros to be ineffective."

The culprit apparently involves insulation on the Soyuz near the pyro in question that includes an ungrounded aluminized layer.

The huge U.S. solar arrays that provide most of the station's power affect the electrically charge plasma around the lab. The recent Soyuz problems occurred after a major change in the configuration of the arrays. Another major change is expected next February, when a fourth and final set of arrays is added to the starboard side of the station's main power truss.

NASA engineers are not convinced the evidence supporting the arcing theory is conclusive, but "it certainly implies that it's a plausible scenario," Suffredini said.

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VIDEO: ISS PROGRAM MANAGER UPDATES SOYUZ INVESTIGATION PLAY
VIDEO: ISS PROGRAM MANAGER DESCRIBES SARJ REPAIR PLAN PLAY
VIDEO: ISS PROGRAM MANAGER DISCUSSES RADIATOR DAMAGE PLAY
VIDEO: EXPEDITION 18 PRE-FLIGHT MISSION BRIEFING PLAY

VIDEO: DEMONSTRATION OF PYROBOLT REMOVAL TASK PLAY
VIDEO: NASA FLIGHT DIRECTOR SUMMARIZES SPACEWALK PLAY
VIDEO: RUSSIAN FLIGHT DIRECTOR GIVES CREW A PEP TALK PLAY
VIDEO: FIRST SPACEWALKER EMERGES FROM THE STATION PLAY
VIDEO: VOLKOV HANDS TOOL BAGS OUT OF THE AIRLOCK PLAY
VIDEO: TELESCOPING STRELA BOOM EXTENDED TO REACH SOYUZ PLAY
VIDEO: KONONENKO BEGINS CLOSE-UP INSPECTIONS OF SOYUZ PLAY
VIDEO: PROTECTIVE COVERS PLACES OVER THRUSTER NOZZLES PLAY
VIDEO: WATCH AS THE HOLE IN SOYUZ INSULATION IS CUT PLAY
VIDEO: PYROBOLT REMOVED AND PLACED IN BLAST-PROOF CASE PLAY
VIDEO: AIRLOCK HATCH CLOSED TO CONCLUDE THE SPACEWALK PLAY
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