May 11 (Flight day 1, launch) lifts off on STS-125 from
Kennedy Space Center. Following a smooth countdown,
Atlantis launched on time at 2:01 pm EDT. During the post-launch news conference, NASA managers said the initial early review of the launch video showed no obvious debris events, but a thorough analysis would be performed to ensure the orbiter sustained no significant damage during ascent. After working through their post launch checklists, the crew opened the payload bay doors, deployed the
Ku band antenna, and moved into the robotic activities portion of the day, which included a survey of the payload bay and crew cabin survey with the orbiter's
robotic arm. Following the launch of
STS-124, severe damage was seen at the pad where bricks were blasted from the walls, but NASA officials stated the damage from the STS-125 launch was not nearly as severe and should not impact the launch of
STS-127 in June. Mission managers called up to the crew to alert them of the find, advising Altman ("Scooter") that one of the orbiter's wing leading edge sensors recorded a debris event during ascent, around 104 – 106 seconds following liftoff, which may have been the cause of the damage seen in that area. The breaker (Channel 1 Aerosurfaces, ASA 1) is part of the shuttle's Flight Control Systems (FCS), a subsystem of the
guidance, navigation, and control (GNC) systems. The failure would have no impact to the mission, due to redundant systems.
May 13 (Flight day 3) with telephoto lens at an overhead window on the aft flight deck during flight day three activities. Following the crew's post-sleep activities, they went to work performing the rendezvous operations that included burning the orbiter's engines to refine the approach to the Hubble telescope. Following some delays due to communications issues, Altman and Johnson ("Ray-J") guided the orbiter within fifty feet of the telescope. Cain also noted that a debris event was recorded on the orbiter's wing leading edge sensors, but it was far below the force that would indicate a problem, and would not impact the mission. At the start of the spacewalk, Feustel provided managers on the ground with a visual inspection report on the particulate matter seen earlier around the WFC3 box, reporting to the ground team that "I don't really see any of those particles...It's almost imperceivable. I can see some few particles on the front of the W-SIPE, little, whitish, grey looking, real small. It's low density, too." Feustel initially had trouble removing the bolts from the old camera, which after over fifteen years in space required more
torque to remove than expected. After multiple attempts, managers on the ground decided to have Grunsfeld get a contingency torque limiter from the airlock, which would allow Feustel to apply more force without exceeding a specific point, but the bolt would still not release. The next task was to remove and replace the telescope's Science Instrument Command and Data Handling Unit, or SIC&DH, a computer that sends commands to Hubble's science instruments, and formats science data for transmission to the ground. While the spacewalk preparations were underway, Altman and McArthur completed a robotic survey of a small row of heat shield tiles that had not been sufficiently imaged during the day two inspection. Following the analysis of the survey, the managers cleared all of the TPS systems until the pre-landing inspection. The mission's second spacewalk officially began at 12:49 UTC, and the pair set to work removing and replacing the telescope's three gyroscope rate sensing units (RSUs). Each unit contains two gyroscopes that allow the telescope to point itself. Managers decided to put the unit originally intended for the RSU 1 bay into the RSU 3 bay, and it was installed without problems. Instead, it was decided that an additional unit carried as a spare would be placed into the final bay. The installation of all three gyro units was a critical objective of the servicing mission, as three had failed, one was offline due to electrical issues, and the other two had also been experiencing issues with performance. Flight controllers on the ground evaluated the consumables for the two
spacesuits, and decided that if Massimino recharged his suit's oxygen in the airlock, the pair could safely continue with the battery installation. It was the twentieth spacewalk to service Hubble, bringing the total time in EVA servicing the telescope to one hundred forty-four hours and twenty-six minutes. The tasks were to remove the obsolete
Corrective Optics Space Telescope Axial Replacement (COSTAR), originally installed during
STS-61 to correct the spherical aberration of Hubble's mirror, and install the
Cosmic Origins Spectrograph (COS), and to repair the
Advanced Camera for Surveys (ACS). The ACS failed in June 2006 due to an electrical issue, and after being restored partially, failed again in 2007 due to an electrical short. The spacewalk began at 13:35 UTC, and Grunsfeld and Feustel had no problems. The pair worked through their timeline so efficiently that they were over an hour ahead at one point. During the previous day's mission status briefing, Dave Leckrone, Hubble Space Telescope Senior Project Scientist, made a prediction, joking that since the first two spacewalks, which were considered to be straightforward, had run into issues, the most difficult EVA – to repair the ACS, would be the smoothest one of the mission. "I have a prediction, We've always said EVA 3 was going to be the most difficult and the most challenging, and I predict it's going to go more smoothly than any other EVA on this mission. I just think that's some version of Murphy's Law that's going to lead us in that direction." During the functional testing, the wide-field channel passed, but issues were seen with the high-resolution channel, indicating that the power issue may be farther upstream in the electronic circuits than the spacewalk repair addressed. Additional testing would be performed, but Hubble Program Manager Preston Burch noted that the fix was designed to "back power" the high-resolution channel through the paths connected to the wide-field channel, and while feasible, it was a possibility that the short circuit damage was in an area not corrected with the planned repair. As with the ACS, the STIS was not designed with the intention of servicing it while in space, and one of the major challenges was to remove a cover plate held tight with over 100 screws using a specially designed tool called a fastener-capture plate, designed to trap the screws and washers and prevent them from floating into space when removed. The handrail had a stripped bolt on the bottom, preventing it from being released. The procedure was tested at Goddard Space Flight Center prior to approving it, showing that the stripped bolt could be broken off safely using force. Massimino was instructed to return to the orbiter's airlock to retrieve a spare tool and to recharge his suit's oxygen reserves, to allow for completion of the STIS repair. After initial aliveness testing that showed no issues, STIS was taken into functional testing, and issues were seen when the telescope put itself into
safe mode due to a low thermal limit sensor. Beginning the spacewalk at 12:20 UTC, the pair first worked on removing an aging battery module, and replaced it with a new pack, which combined with the battery replacement performed during the second spacewalk, gave the telescope all new nickel-hydrogen batteries. Both the new batteries, and the FGS passed both aliveness and functional testing. The mission's final EVA concluded at 19:22 UTC, after seven hours and two minutes. The total time spent during the mission in extra-vehicular activity was thirty-six hours, fifty-six minutes. In what was likely his last EVA, Grunsfeld's has accumulated fifty-eight hours and thirty minutes spacewalking, just two minutes less than
Jerry L. Ross, who is third on the list of spacewalking time. The completion of all the major objectives, as well as some that were not considered vital, upgraded the telescope to its most technologically advanced state since its launch nineteen years ago, and made it more powerful than ever.
May 19 (Flight day 9) After awakening at 8:31 UTC, the crew set to work preparing to release Hubble from the payload bay of
Atlantis. Using the shuttle's robotic arm, McArthur grappled Hubble at 10:45 UTC, and lifted it out of the orbiter's payload bay to prepare for the release. Good and Massimino were standing by ready to perform a spacewalk in the event that something went wrong during the telescope's deployment. Performing a small separation burn, Johnson backed the orbiter away from the telescope, and Altman called down to managers on the ground confirming the deployment of Hubble. They took their traditional on-orbit crew portrait, and spoke with reporters from around the world in a news conference. The crew also had the opportunity to speak with the
Expedition 19 crew on board the International Space Station, in a conference call routed through satellites. After evaluating the imagery sent down from the late inspection, the ground team officially cleared the orbiter's thermal protection system for re-entry. Obama told the crew, "Like a lot of Americans, I've been watching with amazement the gorgeous images you've been sending back, and the incredible repair mission you've been making in space," he said. "I think you're providing a wonderful example of the kind of dedication and commitment to exploration that represents America and the space program generally. These are traits that have always made this country strong, and all of you personify them." The rest of the crew worked to stow away items that were used during the mission. The crew held a deorbit preparations briefing with the ground teams, and Altman and Johnson worked with the simulator on board to run through a series of landing simulations.
Barbara Mikulski, Chairman of the Senate Appropriations Committee, Subcommittee on Commerce, Justice, Science and Related Agencies, and former astronaut Senator
Bill Nelson of Florida, spoke with the crew about the importance of spaceflight and the repair of Hubble. NASA managers stated that for Friday, they would focus on a KSC landing for Friday, not activating any of the backup sites, but if the weather was not favorable for a Friday landing,
Edwards Air Force Base could be activated on Saturday. The crew was advised that there were low clouds and thunderstorms, both conditions that violated landing criteria, so managers waived the first opportunity. A second opportunity was also not taken, as the weather had not improved.
May 23 (Flight day 13) after a successful STS-125 mission The crew of
Atlantis had six possible landing opportunities on Saturday. Managers evaluated the best three opportunities of the day to try to bring the orbiter home. Weather in California had excellent forecasts, so if the attempts on Sunday to land in Florida were not successful, the shuttle would be able to land at Edwards Air Force Base without weather being an issue. After choosing to pass on the first opportunity for KSC and evaluate the second, managers on the ground decided that the weather in Florida was too dynamic to risk bringing the orbiter in, and opted to land at Edwards Air Force Base instead. The de-orbit burn was initiated at 14:24 UTC, a burn of the shuttle's engines that brought it out of orbit to begin the orbiter's
reentry into the
Earth's atmosphere.
Atlantis successfully landed at Edwards Air Force Base on Runway 22 at 8:39 am PDT after 197 orbits in space and a distance of approximately 5.2 million miles. This was the last landing at Edwards for Atlantis. After working through the checklists to safely power down the orbiter, the crew performed the traditional walk-around of the shuttle and met with employees from NASA. Speaking briefly to the press following the walk around, Altman joked, "I didn't realize it was going to be so hard to get back to the Earth! We're all thrilled to have the mission complete." During the post-landing briefing, Associate Administrator for Space Sciences Ed Weiler declared the mission a total success, and after noting the rocky road that it took to get the mission completed, said he considered the mission to be Hubble's Great American Comeback story, chapter two. ==Post landing==