Handprints on Hubble    
       
   June 26, 2015: It's funny, the things you notice hanging upside down in space.   
       
   Astronaut John Mace Grunsfeld remembers a quirky discovery back in 1999. He   
   had just arrived at the Hubble Space Telescope and climbed out of the airlock   
   of Space Shuttle Discovery to begin a servicing mission. Clinging to a   
   handrail running down the side of Hubble's gleaming exterior, he ran his eyes   
   over the blue planet 350 miles below and tried not to think too hard about the   
   yawning starry expanse behind him.  The astronaut, Hubble, and Discovery,   
   connected together, raced around Earth at 17,000 mph.   
       
   That's when he noticed the handprints.   
       
   "The outside surface of Hubble is covered with them-scuff marks and other   
   signs of handling by astronauts," says Grunsfeld.   
       
   A ScienceCast video explores the deeper meaning of superficial 'handprints' on   
   Hubble.   
       
   http://youtu.be/R9fYj1YCGJ0   
       
   Astronauts visited the orbiting telescope five times since it was launched in   
   April 1990, conducting 23 spacewalks to repair and improve it. The   
   "handprints" come from oil and silicon on the astronauts' gloves, which make   
   an impression on Hubble's exterior foil.  Initially invisible, these residues   
   darken over time as they are exposed to solar ultraviolet radiation.   
       
   The prints Grunsfeld saw are more than chemical scuff marks, though.   
       
   "They are a symbol," he says, "of a unique human-robotic partnership."   
       
   Hubble's designers intended for astronauts to lay hands on Hubble.  The   
   telescope is festooned with knobs and handrails, hinged doors, and crawl   
   spaces fit for astronauts to visit and tinker. This has allowed Hubble to do   
   something no other spacecraft has done before-evolve.   
       
   When Hubble left Earth 25 years ago it was equipped with reel-to-reel data   
   recorders, 1980s-era microprocessors, and some of the earliest digital   
   cameras.  Fast forward to the present:  Almost every scientific instrument   
   onboard the telescope has been replaced at least once. Hubble now has   
   solid-state recording devices, upgraded computers, and astronomical detectors   
   that far outperform the older technology it originally took to space.   
   Astronauts have also replaced the telescope's aging solar arrays, batteries,   
   gyroscopes, some reaction wheels and fine guidance sensors. Keeping pace with   
   technological advances on its home planet, Hubble is very much a creature of   
   the 21st century.   
       
   Astronauts have done more than just upgrade Hubble.  They have also saved it.   
       
   The first time was in 1993.  When Hubble reached orbit, images revealed that   
   the telescope's mirror was flawed.  It suffered from a distortion called   
   spherical aberration.  Hubble could still take pictures of the cosmos but not   
   with the sensitivity or resolution its designers envisioned.   
       
   "The first servicing mission in 1993 took care of that," says Grunsfeld. That   
   December, seven astronauts flew to the telescope onboard Space Shuttle   
   Endeavour.  Over a period of 11 days, the crew conducted 5 spacewalks and used   
   more than 100 specialized tools, many of which were invented specifically for   
   the mission.  They installed corrective optics, a new main camera, new solar   
   arrays, and two new gyro packages.   
       
   Not everything went smoothly.   
       
   During the mission, spacewalkers Story Musgrave and Jeff Hoffman opened a pair   
   of service doors to swap out gyros but could not get them closed again. The   
   door bolts would not reset. Engineers on Earth speculated that when the doors   
   were opened, a temperature change caused them to expand or contract.   
       
   "They ended up using a make-shift ratchet to squeeze those doors together,"   
   recalls Grunsfeld. "That was a very bad idea. It could have broken Hubble, but   
   at the time, they didn't know that.  Anyway, they squeezed the doors together   
   using brute force."   
       
   Evidence of the wrestling match is evident today in a confusion of   
   'handprints' and scuff marks around the doors.  The marks tell a silent story   
   of ingenuity, risk, and triumph.   
       
   "Without that first servicing mission, Hubble would have been a nice telescope   
   but not a great one," opines Grunsfeld.  "We would not have measured the edge   
   of the universe, validated black holes, or discovered dark energy. The   
   fingerprints of astronauts are all over those advances."   
       
   Another difficult moment came in the late 1990s. Mission planners were growing   
   nervous as Hubble's gyros unexpectedly started to fail-one in 1997, another in   
   1998, and a third in 1999. If one more gyro went offline, the telescope would   
   not be able to point accurately.   
       
   The whole telescope was on the razor's edge of failure as Grunsfeld and six   
   other astronauts readied themselves for Servicing Mission 3A. Indeed, just   
   weeks before their Space Shuttle, Discovery, was scheduled to launch, a fourth   
   gyro failed and Hubble science came to a screeching halt.   
       
   "We felt some urgency to get up there and fix the telescope," he recalls.   
       
   It would be Grunsfeld's first mission to Hubble, the first time he touched the   
   telescope, and the first time he added his own prints to those of his   
   predecessors. Discovery lifted off on Dec. 20, 1999. During the week-long   
   mission, the crew installed new gyros, replaced a Fine Guidance Sensor (FGS)   
   and swapped out the main computer. The new computer was 20 times faster and   
   had six times the memory of the one it replaced.   
       
   "Coming out of that mission, we left the telescope in pretty good shape," he   
   says. "We saved Hubble."   
       
   Little did he know, that rescue merely set the stage for a more thrilling one   
   to come.   
       
   In 2000, engineers working on Hubble noticed a curious anomaly: The   
   telescope's batteries were not charging as quickly as they should.  It was a   
   tiny effect, measured in units as small as micro-ohms, but over time it could   
   add up to catastrophe: Hubble could "go dark" as early as 2003. With detective   
   work that insiders still remember with awe 15 years later, engineers figured   
   out the problem. There was a subtle ground fault in the telescope's Power   
   Control Unit-or PCU.   
       
   The PCU is essentially a bank of relays that routes power from Hubble's solar   
   arrays to its batteries and other systems.  It is a very complicated device,   
   and the only way to service it is to turn it off.  Completely.  No power to   
   Hubble at all.   
       
   "This was kind of a big deal," says Grunsfeld. "If we didn't repair it, Hubble   
   would die in about 3 years.  On the other hand, if we tried to fix it, Hubble   
   might die right away. Powering down Hubble had never been done before.   
   Hundreds of relays would be switched to their powered-off state. A clock would   
   be ticking because Hubble would get cold.  There was a window of only a few   
   hours to do the repairs because overnight Hubble would freeze,the optical   
   bench would warp, and Hubble would no longer be functional."   
       
   NASA decided to go for it, and Grunsfeld started training for the most   
   challenging mission of his career: Hubble Servicing Mission 3B.   Flying Space   
   Shuttle Columbia one last time before the disaster of 2003, the mission's crew   
   would ultimately invent new tools, new training procedures, and new repair   
   techniques to tackle the PCU problem.  "We really upped our game," says   
   Grunsfeld.   
       
   Around NASA, many experts worried about the PCU repair. Could it really be   
   done? The astronauts themselves were worried.  Sleepless in space, Grunsfeld   
   and Rick Linnehan woke up early on March 2, 2002, and started prepping for   
   their spacewalk more than two hours ahead of schedule. NASA prepared to cut   
   power to the telescope as soon as they were ready to step outside.   
       
   "Keep in mind that as soon as power was off, we were on a ticking clock," says   
   Grunsfeld. "There was a real sense of urgency, no question about it."   
       
   Immediately something went wrong:  "Astronauts Mike Massimino and Jim Newman   
   were preparing us to go outside," he says. "When Jim released me from the   
   latches on the wall of the airlock, he noticed that my backpack was wet. A   
   valve inside my spacesuit had failed and was leaking water.  That's very bad.   
   Had I gone outside, that water would have frozen, cracked an airline, and I   
   could have been killed."   
       
   Suddenly the spacewalkers were behind schedule. Tick. Tock. Tick. Tock.   
   Working quickly, astronauts in the airlock helped Grunsfeld out of his suit   
   and assembled a new one from parts of other suits that fit him.   
       
   "In less than two hours-record time, by the way-we were able to get me back   
   into a spacesuit.  By the time we started the EVA, we were about two hours   
   late. There was some mild panic on the ground because Hubble had been cooling   
   off," he recalls.   
       
   The astronauts, however, were even cooler.   
       
   "You might think, 'Oh gosh, Rick and I must have been in a panic because we   
   had already lost two hours of the day,'" says Grunsfeld, "But no. We went out   
   the hatch as if everything was completely normal.   We had that kind of focus   
   from the training we had done.  As soon as I was in the spacesuit again, I   
   totally forgot that we had had all of those earlier problems. Rick and I went   
   out and did it in 6.5 hours, exactly as we had trained."   
       
   The PCU was repaired, and the telescope powered up in good condition. Hubble   
   was saved again.   
       
   NASA retired its Space Shuttle fleet in 2011, but not before one last visit to   
   a telescope Grunsfeld now considered "an old friend."   
       
   Originally, plans called for Hubble to be serviced in February 2005, but the   
   Columbia tragedy of 2003 changed everything.  A trip to Hubble was deemed too   
   risky, and for a while, it seemed that the telescope might never be serviced   
   again.   
       
   "That would have spelled the end of Hubble," says Grunsfeld.  "The telescope's   
   batteries were 13 years old, and they were beginning to fail. Without   
   replacements, the mission would have ended as early as 2007."   
       
   And it would have ended, except for the ensuing public outcry.  Not only did   
   astronomers wish to save Hubble but also millions of ordinary people did too.    
   For more than two years, 2004-2006, school children wrote letters to the   
   President, public hearings were held in Congress, and the "human connection"   
   to Hubble became as clear as the glove-marks on its gleaming foil.   
       
   NASA reconsidered.   
       
   In May of 2009, Space Shuttle Atlantis blasted off for one last mission to   
   Hubble.  On the ground below, Space Shuttle Endeavour waited on the launch   
   pad, ready to fly to the rescue if the crew of Atlantis got into trouble. This   
   is how NASA managed the risk of flying the soon-to-be-retired spacecraft.   
       
   "By 2009 a ton of things were going wrong on Hubble," says Grunsfeld. "We did   
   5 EVAs to fix those things."   
       
   As usual, the astronauts had to invent new procedures and do the   
   unprecedented-"like removing hundreds of tiny screws in bulky space suits," he   
   recalls. They replaced batteries, swapped out all six gyros (again), installed   
   a new Fine Guidance Sensor, repaired two of Hubble's scientific instruments   
   and completely replaced two others. Mindful that astronauts might never visit   
   Hubble again, the spacewalkers installed a soft-capture mechanism that would   
   allow a future robotic spacecraft to grapple Hubble to ensure a safe   
   conclusion to its operational lifespan.   
       
   For one last time, Grunsfeld saw the marks of the Hubble repair crews, the   
   handprints of 16 spacewalkers: Story Musgrave, Jeff Hoffman, Kathryn Thornton,   
   Thomas Akers, Mark Lee, Steve Smith, Greg Harbaugh, Joe Tanner, Mike Foale,   
   Claude Nicollier, Rick Linnehan, James Newman, Mike Massimino, Andrew Feustel,   
   Michael Good, and Grunsfeld himself.   
       
   "Leaving Hubble in 2009 was bittersweet," says Grunsfeld.  "I was sad to see   
   my old friend go.  However, as a crew we were thrilled that we had   
   accomplished all of our goals and a little more, sending Hubble off in the   
   best shape ever."   
       
   Current estimates suggest that Hubble will continue doing great science until   
   2020 and possibly longer.  All thanks to the human touch.   
       
   Credits:   
   Author: Dr. Tony Phillips | Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.99   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)