The Hubble Space Telescope.
Credit: NASA/Goddard Space Flight Center
The Hubble telescope is the Ansel Adams of space photography. Its crystal-clear keepsake images have brought great insight into the grand majesty of the cosmos.
While offering clues as to the ultimate fate of the universe, Hubble's own fate now rests within a murky swirl of risk assessments, shuttle safety guidelines, novel telerobotic hardware and, of course, politics and budgetary wrangling.
Next week, NASA will hold a major review regarding the Hubble Space Telescope (HST) with dozens of engineers and other experts. The gathering is seen by some industry sources as a make-or-break event for any possibility of saving the observatory.
The meetings will cap months of heated exchanges between politicians, NASA officials, astronomers and the public.
Early last month, House of Representatives Science Committee Chairman, Sherwood Boehlert, bracketed the conundrum that Congress faces about the space observatory -- in essence, the people's telescope:
"I would dearly love to save the telescope. It has outperformed everyone's fondest hopes and has become a kind of mascot for science, maybe even for our planet. One can't help but root for it," Boehlert said.
"But this can't be an emotional decision or one based on what we would do in an alternative universe that lacked fiscal constraints or uncertainty," he continued. "We have to make hard choices about whether a Hubble mission is worth it now, when moving ahead is likely to have an adverse impact on other programs, including quite possibly other programs in astronomy."
Boehlert called the Hubble matter "vexing" with hard choices ahead: Letting it die, saving it with a shuttle mission, reviving it with a robotic mission, or even sending up a new version of the telescope.
Months of reflection
Last year a specially convened, 20-person blue-ribbon group -- the Committee on the Assessment of Options for Extending the Life of the Hubble Space Telescope -- offered their findings after some six months of reflection. This National Academies' National Research Council (NRC) committee was chaired by Louis Lanzerotti, distinguished research professor at the New Jersey Institute of Technology, Newark, and consultant, Bell Laboratories, Lucent Technologies in Murray Hill, New Jersey.
The group's key finding: To ensure continuation of Hubble's scientific output and to prepare for its eventual de-orbiting, NASA should send a space shuttle mission, not a robotic one.
Time is of the essence, the committee reported, as some of the telescope's components could degrade to the point where the observatory would no longer be usable or could not be safely de-orbited.
As for telerobotic servicing, the committee said that NASA's current planned robotic mission faces the risk of failing to be developed in time. Even if flown, the chances of success for low, the NRC study team advised. In addition, the NRC panel cautioned that there is a chance the robot could critically damage the telescope. A robotic mission should be pursued only for the eventual removal of the Hubble telescope from orbit, not for an attempt to upgrade it, they recommended.
Former NASA administrator Sean O'Keefe departed the space agency last month while still swinging in regards to the Hubble situation. In his final budget briefing he continued to tout his ruling of no human servicing mission to Hubble. O'Keefe remained strong-willed about the space shuttle no longer flying to destinations other than the International Space Station, citing post-Columbia safety concerns and rules.
Furthermore, NASA's 2006 budget plan calls for money to be spent on an automated mission to rendezvous and dock with Hubble, then safely pile drive the observatory to a watery grave.
O'Keefe repeatedly took issue with the Lanzerotti group's recommended stand-alone shuttle servicing mission to Hubble. Similarly, he found the NRC finding that robotic servicing of the telescope was "risky" as "not necessarily an accurate view".
That said, the NRC position "has made it incredibly difficult" for those advocating telerobotic servicing to prove the idea has merit, O'Keefe emphasized.
Indeed, at the American Astronomical Society meeting in January of this year, HST Deputy Program Manager Michael Weiss noted in briefing charts that "a space-flight qualified robot has successfully demonstrated that all life-extension tasks and science instrument change-outs can be robotically performed and a fundamentally sound mission architecture has been produced."
Here on Earth the time for decision-making is at hand. In space, the clock is ticking down on the telescope.
There are issues of the overall lifetime of the telescope's battery and gyroscope functions, as well as the observatory's fine-guidance sensor units, which allow the telescope to accurately track objects during observations.
The HST avionics system -- the electronic inner workings of the observatory -- is vulnerable to the aging of the facility too.
Meanwhile, engineering teams have figured out how to sustain useful astronomical observations on just two gyros, with a one-gyro operation mode being sketched out as well. If Hubble is without any functional gyros the telescope is effectively dead-in-the water, unable to conduct science.
Eventually, barring a mission to return Hubble to a museum, it will be necessary to drop the telescope into a pre-selected patch of ocean. Called a "controlled reentry", Hubble's watery dumping would be done through an attached, liquid-fueled deorbit rocket motor.
There's good reason not to have Hubble fall from space in an uncontrolled manner. At least two tons (2,055 kilograms) of the estimated 26,000 pounds (11,792 kilograms) of the observatory would survive a fiery nosedive through Earth's atmosphere. Such a fall would produce a debris track that would stretch across 755 miles (1,220 kilometers). Pieces of Hubble that would impact the Earth include the massive primary mirror and its surrounding titanium main ring - the structural backbone of the telescope.
Why not have a shuttle crew pluck the observatory from orbit and fly it back to terra firma?
Due to the repeated Hubble makeovers, major disassembly work in space would be required to tuck the telescope safely inside a shuttle's cargo bay. Moreover, landing a shuttle with all that Hubble weight onboard is deemed too risky.
Earlier this month, the American Astronomical Society (AAS) issued a statement that called servicing Hubble important for astronomy. In releasing the declaration, AAS President Robert Kirshner said he was "personally very disappointed" with NASA's current plan not to service HST.
"We know that NASA is committed to doing the world's best astronomy, and servicing Hubble with the shuttle is part of the best program," Kirshner said.
In part, the AAS statement noted: "While we recognize that HST's mission must end at some time, the fact that a servicing mission was a part of NASA's planned activity, and that two key replacement science instruments are already developed to enable important and exciting new science, makes this decision particularly unfortunate and difficult to accept."
One issue that revolves around Hubble is "expectation management," said David Black, President and Chief Executive Officer of the Universities Space Research Association. Black is also chair of the American Astronomical Society's Committee on Astronomy and Public Policy and a highly regarded expert in theoretical astrophysics and planetary science.
Given the cascade of great successes and discoveries in all of the space sciences, there has been a continued infusion of enthusiasm by the public and the scientific community, Black told SPACE.com.
"You just get people pumped up. So how do you manage the expectation? Maybe NASA has not been good at doing that as it should have in terms of dealing with the inevitable conflicts arising from this increased expectation and a limited budget," Black advised.
Focusing on the current dispute over Hubble's future, Black said it's clear that people find it difficult to shut down an operating mission.
"But at some point, you've got to balance all this against bringing new people into the field, opening up horizons and vistas scientifically that haven't been tapped previously," he said. "That's a difficult decision and in the case of Hubble it is made even more difficult by the effective popularizing of results from Hubble."
Black admitted it's a tough call. "Astronomers are responsible taxpayers like everybody else. We recognize it's a tight budget and there's only so much that can be done.
"If enough money isn't made available to do an adequate Hubble servicing," Black continued, "do we want to take money from other missions... or say, 'Thanks, Hubble, you have done the best you can. Now let's move forward and use the money available and open up new horizons.'"
Black said that the astronomical community has done an exemplary job over several decades of working out priorities for its missions, and the working astronomers should be involved in any decision that NASA must make regarding a Hubble servicing mission and other opportunities.
NASA has awarded Hubble-related contracts to Lockheed Martin Space Systems near Denver, Colorado and a Canadian firm, MacDonald Dettwiler Space and Advanced Robotics (MD Robotics) of Brampton, Ontario. These firms, respectively, are to provide a Hubble De-Orbit Module and a two-armed Canadian-built android, the Special Purpose Dexterous Manipulator, also know as Dextre.
All of next week, various Hubble factions are to meet at Goddard Space Flight Center, Greenbelt, Maryland in what's called a preliminary design review, or PDR.
"The actual PDR, as a meeting, is really the culmination of a large amount of detailed work involving hundreds of people," said Mark Borkowski, NASA Deputy Director of the Program Development Office in the Exploration Systems Mission Directorate.
The meeting is to involve contractors and civil servants conducting analyses and preparing technical documentation, to program office personnel and expert reviewers evaluating the many products, Borkowski explained.
"We do not have a detailed estimate for the number of personnel who will attend the actual PDR, but it would not be unusual for a program of this visibility and magnitude to attract over 100 attendees," he said.
This PDR is shaping up to be "the big event," according to one source taking part in the gathering. In essence, the review is more of a "show and tell" to the world. But a lot of technical ground is to be covered. Moreover, the review could be the "make or break" event of Hubble Space Telescope servicing, especially robotic servicing.
Time is on your side
Some industry people believe that a good report card on telerobotic upkeep of Hubble will sway NASA Headquarters' thinking, encouraging a go-ahead of the robotic servicing concept.
Others aren't so sure. The cynical view is that the decision will be based more on NASA's money woes today rather than whether or not the Hubble team is doing good engineering.
"One misconception is the notion that you've got a one-shot chance at doing this," said Dan King, Director of Orbital Robotics for MD Robotics.
That's not the case, King said, noting that the situation is actually opposite that view. Unlike space walking astronauts working under tight timelines, "the kind of robotic mission for Hubble can take months, even more than a year to accomplish," King told SPACE.com. "You have ample time to do a task, back off or re-plan, try again...lots of time to fix the problem. Time is on your side."
MD Robotics experts have overcome many technical hurdles, King said, breaking down Hubble servicing tasks into discreet, manageable steps under what is labeled as supervised autonomous operation. There are checks and balances throughout to guarantee safe operations, he said.
To mimic latency -- the few seconds time lag between a ground command and putting in motion the telerobotic gear on Hubble -- tests have linked NASA's Johnson Space Center in Houston with mock up equipment at the Goddard Space Flight Center. Those tests have shown how time lag and control teleoperation challenges can be overcome, King said.
True "Hubble Huggers" -- astronauts who have physically worked on the orbiting telescope -- have helped in honing telerobotic servicing schemes.
"They are very critical and provide lessons learned," King said, noting, for example, astronaut Michael Massimino's contribution in this regard. Massimino was a member of the fourth and most recent Hubble Space Telescope servicing mission, outfitting Hubble with a new power unit, a new camera -- the Advanced Camera for Surveys -- and new solar arrays.
King said the telerobotic servicing mission to Hubble is a step into the future, be it for piecing together structures far from Earth, on the Moon, or elsewhere.
"Apart from just saving Hubble, there is value in a mission like this to show that astronauts can extend their reach," King said. "With a mission like this it opens up the horizon big time."