The Space Shuttle achieved many historic milestones during its 30 year career, with Friday marking one of the more famous – the 25th anniversary of Discovery launch with the Hubble Space Telescope. Over the following years, Discovery’s achievement was backed up by serving missions involving her sisters, allowing for Hubble to continue on with discoveries of its own, providing humanity with a front row view of the cosmos.
Discovery was less than six years old when she was pressed into service to loft her most important payload to date.
By then she had already earned her place in Shuttle history, returning the fleet to service after the tragic loss of Challenger on STS-26, less than two years before Hubble would ride uphill in her payload bay.
Following a successful return from STS-33, she was processed, mated to her External Tank and Solid Rocket Boosters and rolled out to Kennedy Space Center’s Pad 39B.
Once at the pad, she was joined by her crew, which included the current NASA Administrator Charlie Bolden.
The initial launch attempt on April 10 was scrubbed at the T-4 minute mark due to a faulty valve in one of Discovery’s three APUs (Auxiliary Power Units). The APU in question was replaced and launch retargeted for April 24, 1990.
With the flagship Columbia taking a keen interest from the next door pad, the launch attempt on April 24 was momentarily halted at the T-31 second mark when computer software failed to shut a fuel valve line on the ground support equipment.
The valve was quickly shut by remote command from the Launch Team and Discovery lifted off at 08:33:51 EDT.
Discovery’s crew transitioned into the task of deploying the Hubble the following day, after reaching the 380 statute mile orbit. This was the highest an orbiter had travelled above Earth to date.
Giving birth to Hubble on orbit didn’t go as smoothly as was hoped, as one of the observatory’s solar arrays stopped as it was unfurling.
The plan for such a scenario was to conduct a contingency spacewalk. However, the ground teams eventually persuaded the array to deploy.
While Discovery completed her mission – and landed at Edwards Air Force Base in California on April 29 – scientists were eagerly waiting to get their hands on the first images from the latest NASA hardware in space.
Those first images showed Hubble had a problem.
Ultimately, Discovery’s mission was a success, but the images revealed Hubble’s main mirror had been ground incorrectly, effectively compromising Hubble’s eyesight. A major effort was undertaken to fix the problem, via another Shuttle mission.
It was Discovery’s younger sister that came to the rescue of Hubble in 1993, as Endeavour launched on only her fifth mission to carry out a critical service mission, with the main goal of correcting the telescope’s impaired vision.
STS-61’s five grueling EVAs in a row successfully installing a corrective optics package – along with new solar arrays – during the highly complex 11 day mission.
Hubble was back to full health and started to provide the stunning images of the cosmos that have fascinated the entire human race ever since.
Discovery would return to Hubble in 1997, as STS-82’s mission upgraded the telescope’s scientific instruments and increased its research capabilities.
Discovery would visit her favourite telescope once again on the third servicing mission in 1999, replacing all six of Hubble’s gyroscopes – three of which had failed – along with replacing a Fine Guidance Sensor (FGS) and the telescope’s computer.
In what was Columbia’s penultimate mission prior to her tragic loss, STS-109 carried out the fourth servicing mission in 2002, with each visit extending the life of the telescope.
The five-EVA mission installed the Advanced Camera for Surveys (ACS), new rigid Solar Arrays (SA3), a new Power Control Unit (PCU) and a new Cryocooler for the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). Columbia also provided Hubble with a farewell push, as the orbiter reboosted the telescope to a higher orbit.
However, due to Columbia’s loss the following year, NASA managers were left with a dilemma.
Hubble was next scheduled to be serviced in 2005, yet NASA’s own Return To Flight (RTF) rules insisted on the “safe haven” requirement, allowing for an orbiter, damaged during launch, to fly to the International Space Station (ISS) for its crew to wait for another shuttle to bring them home safe.
Based on these rules, then-NASA Chief Sean O’Keefe resisted the calls for Hubble to be serviced, whilst noting an alternative mission using robotic assets would not be developed in time to save the telescope. Hubble’s gyroscopes were expected to fail – and its batteries to run out – no later than 2010.
Mr. O’Keefe’s successor, Mike Griffin, noted the NASA stance was based mainly on the understandable pain associated with losing Columbia and the need to not take any unnecessary chances with the orbiters and their crews during the final era of their service.
“The decision not to execute the planned Shuttle servicing mission was made in the immediate aftermath of the loss of Shuttle Columbia,” Mr. Griffin told senators at his confirmation hearing. “When we Return to Flight, it will be with essentially a new vehicle that will have a new risk analysis associated with it.
“At that time, I think we should reassess the earlier decision in light of what we learn after the Return to Flight.”
As it stood, NASA was expected to press ahead with a plan to deorbit Hubble into the Pacific Ocean.
Thankfully, the Return To Flight of the Shuttle fleet showed the array of safety improvements allowed for the final Hubble Servicing Mission (SM-4) to be re-evaluated. However, the challenge of launching a mission without the Safe Haven of the ISS being available needed to be solved.
That solution came in the form of another Shuttle, ready to launch within days of a problem on an elaborate rescue mission.
Administrator Griffin eventually approved SM-4 for Atlantis and STS-125, after the Space Shuttle Program (SSP) started to prove its new safety measures were working – such as the increasing the mitigation of External Tank foam loss and advances in Thermal Protection System (TPS) inspection, along with repair techniques – during the opening salvo of post-RTF missions.
The best possible crew were assigned to Atlantis for the final rendezvous between the world-famous vehicles, led by commander Scott Altman, assisted by six crewmembers that included John Grunsfeld and Mike Massimino.
Endeavour would also receive a co-star role by standing by as the STS-400 rescue mission, seeing her sat on Pad 39B ready to launch at short notice in the event Atlantis’ launch – from Pad 39A – suffered a major issue during the ride uphill on what proved to be a delayed launch date, as Hubble itself worked through problems on orbit.
That contingency wasn’t required, as Atlantis and her crew conducted a flawless launch and rendezvous with Hubble in May, 2009 – no easy task even under nominal conditions, as the orbiters use up nearly half of their prop capability just to reach the “height” of the telescope’s orbit and can endure higher MMOD risks.
The 14 day mission involved five back-to-back EVAs, including its own challenges – highlighted by Massimino literally using brute force to pull off the STIS hand rail from the telescope (see L2 video) during EVA-4.
However, the mission achieved all of its primary goals, including the installation of two new instruments, namely the the Cosmic Origins Spectrograph (COS) and the Wide Field Camera 3 (WFC 3), leaving Hubble in a great condition to continue its role for many years to come.
Marking the 25th anniversary since its launch, it was left to Administrator Bolden – who rode uphill with the telescope during STS-31 – to praise Hubble’s achievements.
“I’m proud to have been a part of such a fine crew that launched Hubble in 1990, along with Loren Shriver, Dr. Steve Hawley, Dr. Kathy Sullivan and Bruce McCandless. I’m also immensely proud to work with all of you,” he said in a memo to the workforce.
“It’s a tribute to the hard work, ingenuity and imagination of so many in our NASA Family that this week we’re able to mark the 25th anniversary of the Hubble Space Telescope.
“For a quarter century and counting, Hubble has cast the collective eye of humanity on the previously unknown and unimagined.
“At once a scientific marvel and gallery of wonder, it continues to teach us about the vastness and beauty of the universe.”
To read about the orbiters – from birth, processing, every single mission, through to retirement, click here for the links:
(Article images via L2, L2 Historical and NASA)
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