Fwd: Happy 24th Birthday, Hubble

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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: April 28, 2014 10:37:05 AM CDT
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: Happy 24th Birthday, Hubble

 

 

AmericaSpace

For a nation that explores
April 26th, 2014

'Repairing Hubble' Showcases Space Telescope's Components on Anniversary

By Emily Carney

 

The NASA/ESA Hubble Space Telescope was photographed by Space Shuttle Discovery's IMAX Cargo Bay Camera being deployed on April 25, 1990. Photo Credit: NASA

On Wednesday, April 23, Washington, D.C.'s Smithsonian National Air and Space Museum observed the 24th anniversary of NASA/ESA's Hubble Space Telescope's launch into orbit by unveiling "Repairing Hubble." This new exhibit displays two vital instruments that were once part of the space telescope. Since its inception in 1990, Hubble has uncovered—and continues to uncover—discoveries changing how researchers and scientists see astronomy. Before its string of discoveries, though, Hubble famously underwent a series of repairs that saved its cosmic "eyesight."

Hubble's journey into spaceflight history began on April 24, 1990, when the telescope was launched during STS-31 aboard Space Shuttle Discovery (which is now displayed at the museum's Steven F. Udvar-Hazy Center in Chantilly, Va.). However, shortly after its deployment it was discovered that the telescope's primary mirror contained a serious flaw that made it produce "nearsighted," distinctly out-of-focus images.

Astronaut Story Musgrave is positioned to replace components at the end of Endeavour's Remote Manipulator Arm on its first servicing mission in late 1993. Photo Credit: NASA

But all was not lost. Two instruments were designed to help address the flaw. The Wide Field and Planetary Camera 2 (WFPC2) and the Corrective Optics Space Telescope Axial Replacement (COSTAR) system were designed to work together and jointly correct the abberation in Hubble's primary mirror. By December 1993, these instruments were ready to do their work. In addition, other repairs were scheduled to lengthen the telescope's operational life and replace failing components.

COSTAR and WFPC2 were launched on STS-61 aboard Space Shuttle Endeavour that month. Astronauts Story Musgrave, Jeffery Hoffman, Kathryn Thornton, and Thomas Akers performed a series of five spacewalks during what has been historically referred to as the "Hubble Rescue Mission." Shortly thereafter, the telescope began returning stunning imagery back to Earth, living up to its initial promise.

Hubble was serviced four more times in orbit on STS-82 in 1997, STS-103 in 1999, STS-109 in 2002, and STS-125 in 2009. Its last servicing mission was chronicled in the 3D IMAX film Hubble 3D, which was released in 2010; it was performed by astronauts aboard Space Shuttle Atlantis. The achievements of these servicing missions—and the shuttle itself—are chronicled and displayed at the Kennedy Space Center's Visitor Complex in Florida.

The last Hubble servicing mission saw the end of COSTAR and WFPC2′s service lives, as they were removed and replaced. The two instruments were previously shipped to NASA's Goddard Space Flight Center in Greenbelt, Md. WFPC2 was particularly studied for showing effects from being in space, as it was dimpled and dented by micro-meteoroids and other space debris. These pockmarks from a life of service to space are visible to visitors who view the instrument at the museum.

A reception heralding the opening of the exhibit—showcased appropriately under the museum's Hubble mockup—was held Wednesday at the museum. NASA Administrator Charlie Bolden, who piloted STS-31 in 1990, made remarks at the event. Thanks to astronauts like Bolden—and scores of ground controllers, scientists, astronomers, researchers, and other personnel—the Hubble Space Telescope's story was transformed from one of disappointment to one of runaway success.

 

Copyright © 2014 AmericaSpace - All Rights Reserved

 

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AmericaSpace

For a nation that explores
April 26th, 2014

The Eighth Wonder: Happy 24th Birthday, Hubble (Part 1)

By Ben Evans

 

Since its inaugural deployment from the shuttle in April 1990, the Hubble Space Telescope has peered deeper into the cosmos than ever before in human history. Photo Credit: NASA

"If there were ever two missions that were completely opposite in terms of the public attention that was given to them," astronaut Loren Shriver once said, "it would be my first and second missions." It was no understatement. His first shuttle flight, in January 1985, had been totally cloaked in military secrecy, whereas his second, in April 1990, launched NASA's scientific showpiece: the $1.5 billion Hubble Space Telescope. Today, 24 years later, Hubble has earned itself a well-deserved reputation as one of the most successful astronomical observatories ever launched, peering deeper into the Universe than ever before, acquiring images of distant galaxies, creating breakthroughs in physics and cosmology, witnessing a comet hitting Jupiter, tracking wind patterns on Uranus and Neptune, and creating the first detailed "map" of Pluto. "There was no doubt in my mind," said Charlie Bolden, today's administrator of NASA, "from the moment I was assigned to the Hubble deployment mission about the historical significance of what we were doing. That was one monster flight!" Yet a mix of misfortune, poor manufacturing, and inadequate oversight almost turned Hubble from a white knight into a white elephant.

With the advent of the Space Age, it came as little surprise when plans for an orbiting telescope materialized as an important next step in astronomy. Since the Second World War, physicist Lyman Spitzer of Yale University argued that such a telescope would offer enormous advantages over ground telescopes, unimpaired by the distorting effect of Earth's atmosphere and empowered with the ability to detect high-energy emissions, including X-rays, from distant celestial sources. In 1975 NASA tried to sell the telescope idea to Congress. It was rejected by the House Appropriations Subcommittee, which reasoned that it was too ambitious, too expensive (at $400 million), and did not have the necessary support from the National Academy of Sciences. Co-operation with the newly-formed European Space Agency (ESA) changed all that. The telescope would carry inexpensive solar panels, and its mirror was reduced in size from 10 feet (3 meters) to 8 feet (2.4 meters), effectively halving its cost.

By 1977 Congress had agreed to fund what was then named the "Large Space Telescope." Prime candidates to build the mirror were Perkin-Elmer, with a bid of $64.2 million, and Eastman Kodak, teamed with the defence contractor Itek, which quoted almost $99.8 million. Despite being more expensive, Kodak-Itek offered two independent tests of the grinding and polishing quality of the finished optics; this "double-checking" provision was something Perkin-Elmer did not provide … and it would not go unnoticed when investigators dug into the causes of the telescope's embarrassing problems, more than a decade later.

Perkin-Elmer received approval from NASA in 1979. Lockheed would build the spacecraft to house the mirror, and the Europeans would construct the solar panels. A Space Telescope Science Institute (STScI) was founded at Johns Hopkins University in Baltimore, Md., to handle the data, and the telescope was scheduled for a shuttle launch in 1985. By this time, it had been named in honour of Edwin P. Hubble, the American astronomer who not only conducted extensive research into the structure of stars and galaxies, but whose work also led to the surprising discovery that the Universe is expanding.

Of all the 135 missions executed during the 30-year shuttle program, the flight of STS-31 and the deployment of the Hubble Space Telescope was without doubt one of the most significant. The five-member crew knew that theirs was, in the words of Charlie Bolden, a "monster flight." From left are Bolden, Steve Hawley, Loren Shriver, Bruce McCandless, and Kathy Sullivan. Photo Credit: NASA

Optically, Hubble was a Cassegrain reflecting telescope, and its twin hyperbolic mirrors were sold on the basis of their good imaging performance … but their shapes made them difficult to fabricate and test. Perkin-Elmer used special polishing machines to grind them, and, in case of problems, NASA directed them to subcontract to Kodak to build a backup mirror using traditional polishing techniques. (The Kodak mirror today sits in the Smithsonian.) In the meantime, Perkin-Elmer's mirror was completed in 1981, washed in hot, de-ionized water and coated with aluminum and a protective layer of magnesium fluoride. NASA, though, remained sceptical that the company was competent enough to fabricate the mirror, and delays quickly pushed Hubble's launch back from April 1985 to the late summer of 1986. By this time the total project had soared to a little more than $1 billion.

Still, Hubble promised to whet every astronomer's appetite. Five instruments—a wide-field planetary camera, a high-resolution spectrograph, a high-speed photometer, a faint object camera, and a faint object spectrograph—would provide the telescope with the capability to explore not only the visible region of the electromagnetic spectrum, but also the ultraviolet. Physically, the craft was as monumental in size as it was in performance: it ran to more than 43 feet (13 meters) in length and weighed nearly 24,250 pounds (11,000 kg), virtually filling the cavernous payload bay. Plans to regularly service it in orbit meant that it was dotted with EVA-friendly hand holds, and it would be deployed by means of the shuttle's Canadian-built Remote Manipulator System (RMS) mechanical arm. That arm would be under the direction of astronaut Steve Hawley. Nicknamed "Attack Astronomer," he had worked on Hubble ever since September 1985, when he was assigned as a crew member on Mission 61J, the flight to launch the telescope.

In his NASA oral history, Hawley quipped that he was chosen for the role because he was such a good robot arm operator, but he was convinced that the need for an astronomer on this most astronomical of missions was crucial, "for the simple reason that we want to make sure … that the needs and requirements of the customer are understood and dealt with appropriately." Of course, Hawley would not actually be using Hubble, nor would there be any real astronomy for him to perform, but he believed that it helped the scientists by having someone aboard who knew what they wanted to accomplish, knew the constraints, and, in a nutshell, cared about it.

By the time Challenger was lost, in January 1986, Hubble had been further delayed to October. In addition to Perkin-Elmer's problems, Lockheed had also thrown itself over-budget by upwards of 30 percent and was three months behind schedule. This brought the project dangerously close to breaking a Congressional-imposed budget "ceiling." In perhaps the most cruel of ironies, the agony of Challenger actually worked in Hubble's favor, for it provided the breathing space to get everything ready. In June 1986, the telescope passed a major thermal vacuum test with flying colors and the enforced delay time was used to add more powerful solar arrays, improve redundancy of on-board systems, and fit better connectors. Nickel-cadmium batteries were prone to failure and were replaced by nickel-hydrogen ones, and by early 1990 the Hubble team was electrified by the realization that their observatory would herald a new era of astronomy.

Pictured here during their deployment on STS-31, Hubble's gigantic British Aerospace-built solar arrays would provide critical electrical power for the telescope's systems. Photo Credit: NASA

The international participation added a unique, and sometimes humorous, new angle. Astronauts Kathy Sullivan and Bruce McCandless closely monitored the development of Hubble's solar arrays, which were being built by British Aerospace in Bristol, England. During one trip to England to work on the arrays, the pair arrived at London's Heathrow Airport, after an exhausting flight, and drove through the night to Bristol for several tests. Sullivan expected to immediately don clean-room garb and begin work, but the British Aerospace team had other ideas. "We found ourselves in these rather more formal Welcome the flight crew events," she said, "which I hadn't expected." A brief walkthrough of the solar array, suspended in a rig above a water table, followed, after which the astronauts expected to dig into the tools and procedures they might someday need in the event of a contingency EVA on the telescope. However, it was lunch time and the astronauts were instead ushered into a management dining room, where—to their horror—they beheld engineers and technicians drinking pints of ale or glasses of wine. Who in their right minds, they wondered, would possibly consume alcohol, minutes before handling delicate flight hardware?

Answer: The English, naturally.

For her part, Sullivan enjoyed Bristol, although when she later spoke to fellow astronaut Kathy Thornton—who flew the first Hubble repair mission in 1993—it became clear that in addition to visiting British Aerospace, her crew also got an extended tour of English historic landmarks, including Stonehenge. "Maybe that's what you get if you've successfully fixed their solar array," Sullivan said. "We didn't get that. We just went over there, worked and came home." Aside from the humour of the episode, British Aerospace's treatment of the crew was entirely understandable; for in addition to the technical role, Hubble had major European involvement and the arrival of the shuttle astronauts who would deploy it was accorded the right level of significance.

Nor was that significance lost on the part of NASA Administrator Jim Beggs. He had encouraged his subordinates to regard Hubble on a par with the shuttle and even went so far as to label it "the eighth wonder of the world." With this in mind, it is unsurprising that John Young, the agency's chief astronaut, was selected to command Mission 61J to deploy the telescope. He had barely begun training with his crew when Challenger was lost, and in April 1987—for reasons explored elsewhere—he was removed from flight status. When the "new" Hubble deployment crew of STS-31 was named in March 1988, with launch set for June of the following year, Young was replaced by Loren Shriver. As the shuttle returned to normal operations after Challenger, it became clear that Hubble was not an "infrastructure-critical" mission and would have to take its place in the line behind the Tracking and Data Relay Satellites (TDRS), Department of Defense assignments, and planetary missions tied to specific, and largely immovable, launch windows.

Eventually, the crew found themselves targeted for the March-April 1990 timeframe, and that posed its own challenges. "The year 1990 was close to a solar maximum year," said Kathy Sullivan, "so the envelope of the atmosphere is physically larger." This had implications for the precise altitude of Hubble's orbit. As the launch slipped from 1986, in a time of reduced solar activity, to 1990, closer to the maximum, the Hubble deployment altitude was raised to a little more than 380 miles (610 km). This high altitude meant that a long-duration Orbital Maneuvering System (OMS) firing of more than five minutes was needed for orbital insertion, and the effect upon the shuttle's performance was that no less than 50 percent of the available OMS propellant for the whole five-day mission would be consumed … by the time Discovery achieved orbit!

Surrounded by the surnames of the five-member crew, the STS-31 official patch carried all of the symbolism of what would be one of the grandest adventures of discovery in human history. It is an adventure which continues to this day. Image Credit: NASA

On top of this was the need for sufficient margin to re-rendezvous with Hubble, if necessary, after deployment, and perhaps repair it, then re-release it, perform another separation maneuver, and still have enough propellant stores for the de-orbit "burn" and return to Earth. (The de-orbit from Hubble's altitude was expected to require an OMS burn of almost five minutes, some 60 percent longer than other shuttle missions.)

In the weeks before launch, it was evident that STS-31 would have much lower reserves of propellant at the start of its mission than had been typically on other flights. As a result, a significant amount of training time was devoted to how the crew responded to propellant leak alarms; on an "ordinary" mission, the first prudent step would have been to verify if the alert was a false one, but on STS-31 the assumption had to be taken that it was a leak and preparations to either substantially lower their altitude or de-orbit had to be made quickly. All of those steps had to be performed in parallel.

Yet the launch was eagerly anticipated by the astronomical community. "After 45 years of dreaming," wrote John Noble Wilford of the New York Times on 9 April 1990, "and almost 20 years of planning, development and delays, the Hubble is ready to be taken into orbit." No one could possibly have foreseen the tortured childhood that this icon of astronomy would have to endure in the months and years to come, and, by the end of 1990, as public and politicians alike came to regard Hubble as a laughing-stock and bait for late-night TV jest, few could have imagined that the telescope would go on to become NASA's salvation. In its own way, the success story that Hubble became helped to assure NASA the political support it needed to build today's International Space Station.

 

Copyright © 2014 AmericaSpace - All Rights Reserved

 

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AmericaSpace

For a nation that explores
April 27th, 2014

To the Brink, From the Brink: Happy 24th Birthday, Hubble (Part 2)

By Ben Evans

Discovery rockets into the highest orbit ever attained by a shuttle on 24 April 1990. Photo Credit: NASA

More than two decades ago, this very week, one of the most important missions in the annals of scientific discovery got underway with the launch of NASA's Hubble Space Telescope. This enormous, $1.5 billion observatory, with its five instruments and finely ground mirrors, promised to revolutionize astronomy: It would peer deeper into the cosmos than ever before, unhindered by the distorting effects of Earth's atmosphere. In time, it would examine "nurseries" of young stars and "graveyards" of ancient ones, would study galaxies in unprecedented depth, would watch as a comet smashed into Jupiter, would trace violent storms on Uranus and Neptune, and would create maps of far-off Pluto, whose resolution will remain unmatched until the New Horizons probe reaches the tiny world in 2015. Twenty-four years later, Hubble remains priceless, its images having long since become art, such is their majestic beauty. Yet as yesterday's AmericaSpace history article described, its success began with a tortured childhood which made it the butt of cruel humor and an object of criticism from NASA's political opponents. In the first few months of its orbital life, Hubble was in serious trouble.

None of this could have been further from anyone's mind on 10 April 1990, as controllers counted down toward the launch of the telescope on STS-31. Aboard Shuttle Discovery were five astronauts—Loren Shriver, Bruce McCandless, Steve Hawley, Kathy Sullivan, and the man who would one day become NASA's first African-American Administrator, Charlie Bolden—who were tasked with the enormous responsibility of getting this gigantic icon of astronomy into the highest orbit ever attained by the shuttle, some 380 miles (610 km) above Earth. However, the 10th was not to be their day. The countdown clock stopped at T-4 minutes, when abnormal pressures and turbine speeds were detected in one of Discovery's Auxiliary Power Units. Two weeks later, on the 24th, they were back for another try. This time, the clock halted at T-31 seconds, just before the on-board computers assumed primary control, due to glitch with a liquid oxygen fill and drain valve. When this had been rectified, STS-31 roared into space. "Our window on the Universe!" crowed the launch announcer as Discovery speared towards orbit, atop a pillar of golden flame.

Within hours, the shuttle's payload bay doors were open, revealing the monster telescope in all its splendour. More than 43 feet (13 meters) long, glistening with shiny insulation and weighing an impressive 24,250 pounds (11,000 kg), Hubble filled the bay and left the astronauts awestruck. In fact, its aluminum coating was so reflective that it blazed brightly in the harsh, unfiltered sunlight … so brightly that Steve Hawley would later recommend that future servicing missions should rendezvous with the telescope during orbital darkness to avoid momentarily blinding the astronauts or their cameras.

Completely filling the shuttle's payload bay, the Hubble Space Telescope glistens in the incessant glare of orbital daytime, shortly after arrival in space. Photo Credit: NASA

Deployment occurred on the second day of the mission, 25 April 1990, when Hawley gingerly grappled the massive payload and positioned it above the bay, with its large aperture door facing forward. Its two high-gain antennas were released, springing "downward" and "outward", and the next step was to open British Aerospace's solar arrays, which would unfurl like kitchen roller blinds. The first array came out perfectly, and Shriver reflected that it was incredible to behold. The second array was more problematic. It began to unroll for a few centimetres, then abruptly stopped. Everyone's heart skipped a beat. Time was of the essence. After cutting umbilical power to the telescope, the astronauts had just two hours on internal batteries to get the arrays open and enable Hubble to draw its own electricity. If that did not happen, the batteries would die … and so would the telescope. The worry went up in notches with the realisation that Hubble might be in severe difficulty.

An EVA repair seemed the only solution. Having reduced Discovery's cabin pressure the previous night, McCandless and Sullivan were already downstairs, clad in their space suits, in the airlock, with tools, ready to go outside. McCandless was convinced that he knew the source of the problem: a glitch with a tension monitoring module. This was a unit of software to detect any excessive strain on the array and prevent it from tearing or binding. It would stop the array-deployment process and the spacewalkers would then have to fix it manually. To give them more time, they had partially completed their pre-EVA procedures before Hubble was grappled. "What's left," said Sullivan, "is to button up the suit, breathe 40 minutes of pure oxygen, close the hatch, depress and get outside."

It was a double-edged sword, for despite having a spacewalk it also meant that Sullivan's other task of photographing the deployment would be missed. Before launch, she had resolved to literally "wallpaper the telescope with photos" … in fact, she wanted a cover shot on Aviation Week. Now, after working for five years on Hubble, she was locked up in the airlock and might not even see the instant of its release. With only minutes remaining before she and McCandless would have been directed to fully depressurize the airlock, Mission Control told them that the problem was an erroneous software indication … from the tension monitoring module. An engineer requested permission to command the module to "No Op" ("No Operation," effectively taking it "out of the loop") and was certain that this would enable the stubborn second array to unfurl. Flight Director Bill Reeves concurred and Capcom Story Musgrave radioed up the news: Hawley was to orient Hubble in a ready-to-deploy attitude and if the attempt to "No Op" worked, the array would probably start unfurling immediately and they would have to release the telescope as quickly as possible.

It worked.

Charlie Bolden was astounded, but McCandless offered a wizened grin. He had worked on Hubble for so long that he knew, instinctively, what had caused the problem.

Astronauts Bruce McCandless, Steve Hawley, and Loren Shriver peer through the flight deck windows during pre-flight training. Photo Credit: NASA

Steve Hawley's primary concern during the deployment, aside from the array, was the very remote chance that Discovery's Canadian-built Remote Manipulator System (RMS) mechanical arm might fail. The joints of the arm were intentionally limited in terms of their speed, thereby offering him some margin to respond to contingencies, and that meant that the motion he could command was restricted. As he lifted Hubble, it "wobbled"—a lot more than the simulator had taught him that it should—and not until after landing did he realize that the signal "noise" in the joints contributed to random imparted motions. In his post-mission debriefings, he recommended that future simulations should take joint noise into account … a recommendation which would prove hugely beneficial for Swiss astronaut Claude Nicollier, who would grapple Hubble on the first servicing mission in December 1993 and for Hawley himself, who would fly the second in February 1997.

Charlie Bolden was not immune to the irony that the crew had actually practiced a solar array deployment failure during their last integrated simulation, shortly before launch. In that instance, McCandless and Sullivan had manually wound out the array, although they knew that doing such an action for real had the potential to severely damage the telescope. "Once you did that," Bolden said, "it took it out of its automatic mode and it would no longer be able to take care of itself … sort of like taking a baby from the womb, putting it on a respirator and putting it in a position where the rest of its life it would need something. That was what that would have meant for Hubble … until you send another crew up and put on another set of solar arrays and reset the clock."

Disappointment at being unable to perform an EVA was stretched a little further when McCandless and Sullivan were unable to see the moment of deployment. Bolden certainly felt for them, still cooped up in the airlock. "So we deploy Hubble, coming off the Pacific Ocean, across the west coast of South America," he told the NASA oral historian, "and it's just the most beautiful thing you can imagine. It comes off the end of the arm and down. We're looking at the Andes Mountains and it goes right across the coast between Bolivia and Venezuela." Shortly afterward, he and Shriver pulsed Discovery's thrusters, twice, to raise their orbit slightly, causing them to fall steadily "behind" the telescope. As Hubble drifted serenely away, the three men on the flight deck gaped at what they were seeing. Then, all of a sudden, and in unison, they all barked: "Camera! Somebody get a camera!"

Bolden helped to save the day in terms of the photography. An IMAX large-format camera was already filming the deployment from the rear of the payload bay, and Bolden also acquired some spectacular footage from the cabin, with the hand-held IMAX. Having sealed McCandless and Sullivan in the airlock, he shot a length of film as he floated upstairs to the flight deck, focusing firstly on Shriver at the orbiter's controls, then on Hawley at the RMS controls, and then through the windows to reveal Hubble in all its magnificence. It was not like a "normal" camera, where it was possible to see what was going through the lens; instead, Bolden had nothing to gauge whether he was doing the right thing. After the flight, his biggest surprise was not just that the camera worked, but that it also stayed in focus. Later, IMAX would include Bolden's imagery as part of its Blue Planet and Destiny in Space documentaries.

Discovery touches down at Edwards Air Force Base, Calif., on 29 April 1990, after the longest de-orbit burn and the longest re-entry ever performed in the shuttle program at that time. Photo Credit: NASA

Four days later, on 29 April 1990, Shriver and Bolden brought Discovery onto the concrete runway at Edwards Air Force Base in California's Mojave Desert, capping a mission which promised to open a new set of eyes on the Universe. In the first few weeks, Hubble's early problems seemed benign: a few communications glitches, drifting star trackers, and snagged coaxial cables were part and parcel in the process of wringing out a new spacecraft. More serious concerns arose when temperature changes bent materials in the solar arrays' booms, the effect of which was magnified by the orientation mechanism in such a way that it physically "bounced" the whole telescope. The result was a "jittering" in Hubble's images and, since the booms only stabilized in the final few minutes of orbital daylight, the pointing system was only able to meet its design specifications for a fraction of each orbit. NASA engineers worked with their counterparts at Lockheed to change the control program in Hubble's computer and successfully counteracted the vibrations. On 21 May, the telescope returned its first images of a double star in the Carina system, and these were lauded as being much clearer than were achievable with ground-based instruments.

Four weeks later, calamity befell the mission: On 24 June Hubble failed a focusing test. Its secondary mirror had been adjusted to focus the incoming light from a celestial source, but a fuzzy ring—like a halo—encircled even its best images, creating a blur. Additional tests revealed that the telescope was suffering from a condition known as a "spherical aberration" in its primary mirror. In essence, the manufacturer, Perkin-Elmer, had ground it to the wrong specification, removing too much glass and polishing it too flat … by a mere fiftieth of the width of a human hair. The consequence was that Hubble was unable to acquire sharp images. With mounting horror, NASA realized that its attempts to sell its scientific showpiece on the basis of its ability to see further into the cosmos than ever before, with unprecedented clarity, now became increasingly hollow. The promised white knight of astronomy was turning instead into a white elephant.

Even Hubble's chief scientist, Ed Weiler, admitted that its capabilities were comparable only to "a very good ground telescope on a very good night." The politicians were quick to vent their fury. Senator Barbara Mikulski from Maryland, exploded that Hubble was "a techno-turkey" and wasted taxpayers' money. Meanwhile, Senator Al Gore of Tennessee—later vice president during the Clinton administration—observed that, for the second time in less than half a decade, NASA's quality control shortcomings had been exposed. The press had a field day. Particular venom was leveled at the fact that NASA had accepted Perkin-Elmer's $64.2 million bid to build the mirror and rejected a more expensive, though more thorough, $99.8 million proposal from Eastman Kodak and defence contractor Itek. On 28 July, the New York Times reported that Kodak-Itek's bid would have subjected the mirror to two independent checks of its grinding and polishing accuracy. Almost certainly, this would have caught the error before launch.

NASA responded that, with 20-20 hindsight, it would have cost $100 million to incorporate additional tests and independent checks of the telescope optics into the Perkin-Elmer contract, but the effect upon the general public was the same. The space agency was rendered a laughing-stock on late-night TV talk shows. David Letterman compiled a pejorative list of Top Ten Hubble Excuses, whilst others criticized NASA for its mismanagement of both the Hubble development and the Solid Rocket Boosters which doomed Challenger. Several space policy analysts, including John Logsdon, noted that attitudes had changed from the 1960s, in which problems were anticipated and incorporated into planning, to the late 1970s and 1980s when little effort was made to prepare for unforeseen obstacles.

After 24 years, the Hubble Space Telescope remains the crown jewel of NASA's astronomy and astrophysics programs. It has taught us more than we could have ever imagined about the true nature of our world, our cosmos, and ourselves. Photo Credit: NASA

In early July 1990, NASA established an investigating committee, chaired by Lew Allen, the head of the Jet Propulsion Laboratory. His report—published the following November—harshly criticized the incorrect assembly of the "reflective null corrector," an optical device used to determine the figure of Hubble's mirror. The location of a lens in the device was improperly measured and the null corrector guided the polisher to shape a perfectly smooth mirror … with the wrong curvature. Analysis revealed that the curvature flaw in the primary mirror exactly matched the flaw in the null corrector. A second null corrector, made only with lenses, was also built to measure the vertex radius of the finished mirror. It, too, clearly identified an error in the primary mirror. However, neither warning sign was heeded and Allen's report noted that "both indicators of error were discounted at the time as being themselves flawed." During the fabrication process, technicians simply assumed the perfection of the mirror and of the reflective null corrector and rejected information from other independent tests, convincing themselves that no problems existed.

The errors went back to 1981-82, when Perkin-Elmer and NASA were both distracted by cost and schedule difficulties. Allen's report particularly condemned Perkin-Elmer's quality control and communications failures, as well as NASA's own failure to correct them. In orbit, the spherical aberration was particularly obvious in its effect on Hubble's wide-field planetary camera and faint object camera, both of which suffered in terms of their spatial resolution and their ability to acquire images of distant sources. Having said this, the aberration was well characterised and stable and, over time, enabled astronomers to optimize the results obtained by Hubble with sophisticated techniques, such as "deconvolution," whereby software algorithms and image processing methods removed many of the blurring effects of optical distortion. Spectroscopy was less severely affected, because the instruments required less focused light and by increasing the exposure times it became possible to gather valuable images. However, the jittering of the solar arrays left Hubble's high-speed photometer virtually useless. Nevertheless, by the end of 1991, the telescope had made almost 2,000 quality observations of hundreds of astronomical objects, including storms on Saturn and images of Pluto's moon, Charon.

At the start of the following year, 1992, a quarter of all the papers presented before the American Astronomical Society drew on Hubble data. A repair was critical in order to restore the telescope to its pre-flight billing and, although the primary mirror could not be replaced, a new device—the Corrective Optics Space Telescope Axial Replacement (COSTAR)—was built to restore its vision. COSTAR was manifested onto the first shuttle servicing mission to Hubble. Many senior administrators had little faith that the repair would work, but its success contributed greatly to a changing attitude toward the shuttle. As for Hubble itself, hardly anyone remembers the circumstances surrounding the spherical aberration today; Wikipedia, for one, gushes in far more detail about its astounding scientific discoveries, its contributions to physics and astronomy and cosmology, and its importance to humanity as a species. The mirror problem is now little more than a footnote in history … and it should be, for Hubble has overcome the torment of its early childhood and performed grandly.

When the crew of the final shuttle servicing mission departed the telescope in May 2009, they left an observatory far more powerful and considerably more capable than even the magnificent showpiece which STS-31 had launched, almost two decades earlier. In the words of John Grunsfeld, who visited the telescope in space more times than any other human being, the honor and the privilege of being involved with such an icon made it worthy of the risk to his own life. Doubtless the other astronauts associated with Hubble feel the same way. "Hubble is worth risking my life," he once said. "It's that important. It's teaching us so much about our world, the Universe, who we are and our place in the cosmos."

And today, in 2014, after 24 years, Hubble remains important and its teaching goes on.

 

Copyright © 2014 AmericaSpace - All Rights Reserved

 

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