STS-125  - MISSION REPORT

For nineteen years the Hubble Space Telescope has changed the way we look at our universe. From its unique position above our atmosphere, which distorts clear and deep views of the cosmos, the Hubble utilises the ranges of light from visible through ultraviolet and to the near infrared. Complementing studies by the other ‘NASA Great Observatories’, the Compton Gamma-Ray Observatory, the Chandra X-Ray Observatory and the Spitzer Space Telescope. Hubble remains the only facility to be capable of on orbit servicing by Shuttle astronauts. It is this unique capability that had allowed Hubble’s capabilities to be greatly improved over the years with new state of the art scientific instruments and replacement of improved engineering components. The demonstration of replacing aged or failed equipment is a clear demonstration of an ideal blend of manned and unmanned space exploration whilst also encompassing the ancient study of astronomy with modern technology.

After years of development and launch delays Hubble was finally orbited in April 1990 by STS-31 only to find that though deployed successful its primary mirror was incorrectly shaped in its manufacture years before. The result was that the light from distant objects could not be focused into a clear sharp point. Every object had a fuzzy halo around it. It was during the first servicing mission (SM1) in December 1993 that corrective optics was installed and two new instruments replaced along with improved solar arrays. Another service missions was flown in February 1997 (STS-82/ SM2), with the third split over two missions in December 1999 (STS-103/SM3A) and March 2002 (STS-109/SM3B). 

A fourth service mission was planned as well as a possible de-orbit mission towards the end of the telescopes operational life. However the February 2002 Columbia tragedy resulted in a significant review of future Shuttle missions. In January 2004 NASA Administrator Sean O’Keefe announced the cancellation of the SM4 Service Mission to Hubble in light of the recommendation by the Columbia Review Board. This proposed all further shuttle missions should fly in an orbit that, in the event of an emergency which prevented a safe landing could ensure the use of the International Space Station of a ‘safe haven; pending rescue. This ruled out any future Hubble missions where its required orbital track meant that a shuttle could not reach the ISS. However discussions into the fate of the telescope continued along with growing support to fly one more Hubble service mission. With added safety procedures demonstrated on the missions that returned the Shuttle to flight operations and new procedures incorporated into the new service mission evolved beyond discussions..

In October 2006 the new NASA Administrator Michael Griffin officially announced that were would be a final mission to Hubble. The experiences of previous missions had given confidence to the belief that a safe and effective mission could be conducted, recognising that the risk of spaceflight could never be completely eradicated. It was necessary for the agency, the space programme, American, its international partners, the scientific community and education establishments and astronomy groups around the world to continue to benefit from the success that is the Hubble Space Telescope.

Pre-launch and launch operations

Originally scheduled for a 14 October 2008 launch the mission was delayed when the ‘A’ side of the Science Instrument Command and Data Handling SI C&DH) system aboard Hubble that transfers science data to Earth malfunctioned on 27 September. Being such a critical part of the scientific capability of the telescope the mission was delayed until May 2009 to allow time to incorporate a replacement on the Service Mission. In the mean time the ‘B’ side of the SI C&DH was used.

For each Shuttle mission since the loss of Columbia in February 2003 there has been in place a contingent plan to launch another Shuttle on a ‘rescue mission’ should the crew in space become stranded. On ISS dedicated missions the stranded crew could wait out the arrival of a rescue Shuttle on the ISS. As ISS was out of reach for STS-125 it was decided another Shuttle would be on stand ready on launch pad 39B capable of launch in only a few days of the rescue mission (designated STS-400 for planning reasons)  being authorised. A four person flight deck crew from STS-126 were on stand by to fly Endeavour on a possible rescue mission to Atlantis until 21 May.

On 31 March the STS-125 stack was rolled to the Pad 39A complex in preparation for the mission. A month later the date for the launch was confirmed as 11 May by the Mission Management Team. The launch countdown began on 8 May the same day as the flight crew arrived at the launch site from JSC in Houston, Texas. .

A smooth countdown saw an on time launch at 14.01 EDT 11 May, as Hubble passed directly overhead.  Nominal separation of SRBs and cut-off of SSME nine minutes later was followed by the separation of the External Tank. The climb through a clear blue sky was a picture perfect ascent to space. With Atlantis safely in orbit the crew were given the go to proceed with orbital operations and began doffing their launch and entry suits and configuring the flight and middeck for their 11 day mission. The first sleep period began exactly six hours (and four orbits) after lift off.

Orbital Operations

During the two day chase to reach the telescope the crew were far from inactive. During the second flight day the RMS, with the Orbiter Boom Sensor System attached, was used to survey the equipment in the payload bay of Atlantis, perform a scan of the thermal protection system and the leading edges of each wing. These images were then sent to Mission Control for analysis of any launch damage. It was from that survey that one area of damage was noted on the forward part of the wing where it blends into the fuselage. There was no immediate concern though a standard in depth analysis was conducted to look at the damage in more detail. Subsequently the crew were informed that no focused attention requiring an inspection or repair EVA would be required in the affected area and that it was safe for re-entry, though analysis continued on the imagery for some days to provided the most detailed interpretation of the data

Meanwhile Altman and Grunsfeld checked out the Flight Support Systems (FSS) that was to be used to berth the Hubble in the payload bay during the servicing phase of the mission. This would allow rotation of the telescope towards the astronauts easing their access as they worked around the structure.  The four EVA crewmembers also prepared and checked the Extravehicular Mobility Units (EMUs) and the EVA tools they were to use during five spacewalks.

As Atlantis closed in on the telescope ground teams commanded the Hubble’s high gain antenna to retract so as not to hinder the grapple and EVA activities. The ground team was to have commanded the telescope to position itself into the grapple attitude to assist in the transfer of the structure into the payload bay of the Atlantis. In the event this was not possible due to communication problems, meaning that the crew had to fly Atlantis to the correct capture position which delayed the grapple by about 20 minutes later.

On FD3 (13 May), Atlantis closed in on the telescope. Commander Scott Altman assisted by Pilot Greg Johnson and MS Mike Good brought the shuttle to within 50 feet of the telescope. Orbiting 340 miles above Western Australia MS Megan McArthur using the RMS grappled the Hubble, and then manoeuvred it on to a Flight Support System maintenance platform where it would remain during the EVA serving programme. This platform could rotate 360º and tilt allowing better access for the EVA astronauts as well as provided electrical power for thermal control whilst the Hubble was undergoing servicing. With Hubble safely in the payload bay the crew commenced a visual inspection of the telescope meanwhile MS John Grunsfeld and Drew Feustel completed a final EVA review with the assistance of fellow spacewalkers Mike Good and Mike Massimino.

EVA Operations

A total of five EVAs were to be completed by the crew teamed in pairs and rotating the EVAs over five days. Grunsfeld became the first astronaut to exit Atlantis followed minutes later by Feustel, with Megan supporting both astronauts as primary RMS operator. A total of 7 hrs 20 mins was spent on this first EVA (14 May) during which the two astronauts installed the new Wide Field Camera 3 and replaced the Science Instrument Command and Data Handling Unit (SIC&DH). During the EVA Grunsfeld also installed a new mechanism that would allow a future spacecraft to capture the telescope should it be decided to revisit the telescope. Meanwhile in an aid to making the opening and closing of the large access doors for the other four EVAs the Feustel installed two of three Latch Over Center Kits (LOCK), and an aft shroud latch repair was installed on the middle LOCK. Prior to re-entering the airlock the spacewalkers prepared platform that they had previous installed on the Shuttle’s RMS to clear the view for an inspection of some 40 of the Orbiters heat shield tiles that they were unable to view clearly during the earlier inspection. Using the Orbiter boom sensor system these tiles would be inspected prior to the second EVA the next day by Altman and McArthur. These tiles were also cleared prior to a prelanding inspection later in the mission.

The second EVA (15 May) recorded  the eight longest spacewalk in history at 7 hrs 56 min. Astronauts Good and Massimino replaced all three rate sensing units (RSUs) each of which contained two gyros which assisted in the telescope pointing. One of the units would not fit correctly into its slots due to tight tolerances therefore a spare that was carried was installed in its place. One of the original batteries located in Bay 2 was replaced. These power the telescope during the Earth’s shadow (night time) passes each orbit when the solar arrays are not exposed to the sun. As new instruments and equipment was installed controllers at the Space Telescope Operations Control Center located at Goddard Space Flight Center in Maryland checked and confirmed preliminary data which revealed correct and good installation allowing the astronauts to move on to their next tasks and plan subsequent EVA timelines. 

Grunsfeld and Feustel were back outside Atlantis for the third 6 hr 36 min EVA (16 May).  The first task was to remove the Corrective Optics Space Telescope Axial Replacement (COSTAR) ‘corrective lens’ that were installed on the first serving mission in 1993 to improve the focusing on the telescope. The unit was replaced by the Cosmic Origins Spectrograph (COS) that would allow Hubble to explorer further into the universe that previously, in the near and far ultraviolet ranges. The COS would be tested and calibrated over several weeks, though early test results would allow time or the astronaut to return to the unit should the need arise.  The next task was one that was never planned to be completed during an EVA, the repair of the Advanced Camera for Surveys (ACS). This camera had obtained some of the most famous images from the telescope but had stopped working in 2007 when the back up power supply suffered a short circuit.  A total of 32 screws had to be removed from an access panel to allow the astronauts to replace the four circuit boards on the camera and installed a new power supply.  With this EVA, the 80^th conducted from the Shuttle, Grunsfeld moved to fourth in the time accumulate during EVAs at 51 hours 28 minutes over seven EVAs.

Massimino and Good set another EVA record on their second excursion, the mission’s fourth spacewalk (17 May). The 8 hour 2 minute EVA became the 6^th longest spacewalk of all time. During the EVA the two astronauts repaired the Space Telescope Imaging Spectrograph (STIS), which had been installed in 1997, by replacing a power supply, restoring the unit from its ‘safe mode’ it had been in since August 2004 due to a power supply failure. The operation required the removal of 111 screws retaining them for replacement. This was thought to have been the most difficult operation but in the event it was a handrail that proved troublesome. This handrail prevented the path of a fastener capture plate and one stripped bolt prevented its removal. Procedures were developed on the ground at Goddard and sent up to the astronaut on their EVA. This entailed Massimino carefully bending and breaking free the handle allowing the spacewalk to proceed. Initial tests again revealed that the repair seemed to have worked, though more testing would have to be completed after the telescope had been released. One task unable to be completed on this EVA was the installation of the New Outer Blanket Layer (NOBL) on the outer surface of the telescopes Bay 8. This was reassigned to EVA5, where partial blankets would be installed, and if time allowed a full set.

The fifth and final EVA of the mission (18 May) logged 7 hrs 2 minutes was completed by Grunsfeld and Feustel.  During this excursion the astronauts swapping a battery module from Bay 3 with a new one, and removed and replaced Fine Guidance Sensor (FGS) 2. They also fitted three blankets on the outside of the telescopes. They were scheduled to attach only one blanket, but they also managed to add the one leftover from EVA4 and had enough space time to fit a bonus third blanket as well.  

During the five EVAs the crew had completed all of the mission objectives designed to improve the telescopes view of the universe through 2014. Though four months of activities were planned for checking and calibrating the instruments prior to resuming scientific observations the activities were hailed as a major success both for the astronauts and mission but also for the scientific community and NASA. In total the five EVAs logged 36 hours 56 minutes and added to the other Hubble related spacewalks there had been in total 23 EVAs devoted to Hubble servicing and logging 166 hours and 6 minutes.

On 19 May McArthur used the RMS to lift Hubble out of the payload bay and released back into space, with Atlantis performing a separation manoeuvring backing away from the telescope.  For the rest of the day the crew used the RMS in co-operation the Orbiter Boom Sensor System (OBSS) for a final inspection of the heat shield tiles. They worked ahead of the timeline and restowed the OBSS and RMS the same day instead of the next day as originally planned.  STS-125 also carried an IMAX camera to record crew and EVA activities throughout the mission. This will be used in a new IMAX film to be shown from 2010.

Entry and Landing Phase

On 20 May the crew took a day off to talk with the media about the mission, the Hubble and their reflections on being part of the final mission to the telescope.  They also communicated with the ISS Expedition 19 crew of Gennady Padalka, Mike Barratt and Koichi Wakata. The next day they continue stowing the gear used in their twelve days in orbit and during the five EVAs,  checkout the reaction control system thrusters and flight control systems in preparation for the landing. The crew also talked with reporters from some of America’s leading TV networks and, in a first for spaceflight with members of the US Senate Appropriations Committee’s, Sub Committee on Justice, Science and Related Agencies

 As the crew were completing their mission the weather at the primarily landing site at KSC in Florida was not cooperating. On 22 May two landing opportunities at Florida were called off due to bad weather, and the backup site at Edwards in California called to stand by for the next day. Unfortunately the weather at Florida did not improve and the landing was delayed a further 24 hours. An added bonus for the crew during the additional time in orbit, was the chance to look out of the window and enjoy the vision of Earth passing below them, something they had not been able to do, due to the busy time-line.

On 24 May Florida was again waved off but this time the Shuttle was diverted to land at Edwards AFB landing at 10:39:05 CDT with main gear touchdown with the nose gear touchdown ten second later and wheel stop after a one minute and 10 seconds rollout. .

Meanwhile in orbit the Hubble odyssey continues. Over the next few months the systems aboard the Hubble will be calibrated and the improvements made to the telescope check before the scientific investigations resume. The work with Hubble is expected to continue to at least 2014 when it should be replaced by the James Webb Space Telescope. By 2025 Hubble will begin to enter the upper reaches of our atmosphere. The original idea of returning the Hubble on a Shuttle and placing it on a museum is of course no longer an option. Possible return by a future spacecraft may indeed occur but the current plan is to send an automated spacecraft up to the telescope with equipment that will automatically latch onto the structure of Hubble and guide it to a safe and destructive re-entry over the Pacific Ocean.  In any event the mission of Hubble, despite a long delay in getting the telescope into orbit and a rather shaky or rather burred start has been an outstanding success. The telescopes findings have rewritten the astronomy text books and will continue to provide new data and understanding on our universe long after it is decommissioned. Hubble has indeed earned its place in the pages of space history and exploration. It is also due to the mission planners and teams of astronauts of the series of service missions that has allowed the telescope to provide over 20 years of data and breathtaking images that has inspired a generation of young astronomers to take a career path into the space and astronomy programmes of today, and of course tomorrow.