Mission preview: One last shuttle visit to Hubble
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: May 6, 2009
"I don't think anybody except Arthur C. Clarke could have crafted such a great story," said astronomer-astronaut John Grunsfeld, the mission's lead spacewalker. "If it were just about Hubble, it would be a great story. But when you look about the science and the discoveries scientists have made using Hubble, then it just becomes an unbelievable story.
"I'm relatively glib in saying Hubble is perhaps the most important and productive scientific instrument ever created by humans. Only history will tell, but it's a truly remarkable story."
Grunsfeld, commander Scott Altman, pilot Gregory C. Johnson, robot arm operator Megan McArthur and fellow spacewalkers Michael Massimino, Andrew Feustel and Michael Good are scheduled for launch aboard shuttle Atlantis on May 11 at 2:01:49 p.m. It will be the second Hubble visit in a row for Altman and Massimino and the third for Grunsfeld. The rest are shuttle rookies.
Launch originally was scheduled for last Oct. 14, but just three weeks before takeoff a critical circuit in the telescope's science instrument data system malfunctioned. To restore full redundancy, NASA managers decided to delay the servicing mission to give engineers time to check out and certify a flight spare that had been used for ground testing. The replacement computer was delivered to the Kennedy Space Center on March 30, setting the stage for launch.
Hoping to extend Hubble's life well into the next decade, the four spacewalkers, working in two-man teams, plan five back-to-back excursions to install six new stabilizing gyroscopes, six new nickel-hydrogen battery packs, the new data computer and two new instruments, the $126 million Wide Field Camera 3 and the $81 million Cosmic Origins Spectrograph. Like all modern Hubble instruments, both are equipped with corrective optics to counteract the spherical aberration that prevents Hubble's 94.5-inch mirror from achieving a sharp focus.
The repair crew also plans to install an upgraded fine guidance sensor, new insulation and a grapple fixture that will permit attachment of a rocket motor or even NASA's new Orion manned spacecraft in the future to drive Hubble out of orbit when it is no longer able to do science.
"On Servicing Mission 4, we're going to give Hubble another extreme makeover," said Program Manager Preston Burch. "This makeover will be the best one yet because we will outfit Hubble with the most powerful and advanced imaging and spectrographic instruments available and we will extend Hubble's operating lifetime for five additional years."
Without Servicing Mission 4, engineers believe Hubble would be hard pressed to survive past 2010. But if the Atlantis astronauts are successful, they will leave behind an essentially new telescope, one that is equipped with a full suite of five operational scientific instruments for the first time since launch in 1990. And with new gyros and batteries, Hubble has a good chance of remaining fully operational long enough to work in concert with its eventual replacement, the James Webb Space Telescope.
"It's been seven years since we've serviced the Hubble space telescope," said Project Scientist David Lekrone. "And that interval of time, seven years, is twice as long as we should go in terms of servicing intervals. As a consequence of that, over the last few years we've seen significant deterioration within the set of scientific instruments that we provide to the astronomical community. The toolkit that the community uses to do all kinds of science has really diminished in its capabilities.
"I liken this to the situation of a champion athlete who is playing hurt, who has an injury and who is playing through the pain, still doing very well. But now, by golly, it's time to go off and get our surgery and get back to a hundred percent."
NASA has spent about $10 billion on the Hubble Space Telescope to date, making it one of the most expensive science projects in history. Asked whether it made sense to spend more money on a 20-year-old space telescope, former NASA Administrator Mike Griffin, the man who approved Hubble Servicing Mission 4 after it was canceled in the wake of the 2003 Columbia disaster, said it makes all the sense in the world.
"After we get done with it, it's not an old telescope," he told CBS News in a recent interview. "Every subsystem that needs refurbishment is being refurbished and it's getting a new complement of instruments. So the only part of it that's old is the optical metering structure and the glass. And the glass doesn't care. When they're done, it really is not an old telescope, it's a new telescope."
"So the question you want to ask yourself when you look at the value proposition, if for the cost of this shuttle flight - and bear in mind, most of the instrument costs and all that were already paid for - plus the team that we've been carrying, and it's about a $10-million-a-month team, if for whatever all that adds up to you could get yourself a new telescope in space, would you think that would be worthwhile? And I think most people, most astronomers, would say yes.
"Not because it's the biggest telescope, because we can build bigger ones on the ground. And with the new flexible mirror technology and multiple mirror technology, we can get some pretty large apertures," Griffin said. "But, being above the atmosphere still has value, and the best value of all is the coordination of ground-based observations and space-based observations. Between the two, you get a picture that is more than the sum of the parts.
"The question in brief is, if for what we're spending on this mission you could have a new telescope, would you buy one? And I think the answer is yes."
"The thing to remember about these Hubble servicing missions is they're not just 'let's keep a groaning patient on life support,'" he said. "When you put new focal plane instruments into Hubble, you essentially leave with not only a brand new, but a much better observatory. And when you look at our graph of discoveries as reflected by published scientific papers versus year, it's an amazing thing because it just goes up every single year.
"The reason for that is not that the scientists who are using Hubble are smart. It's servicing. That's the reason, because when you leave Hubble you have not just something with better longevity but something that is an order of magnitude more capable than the previous thing, almost like it's a brand new generation of satellite. And the two new focal plane instruments for SM-4 are predicted to do the same thing. And it's not a whistling in the wind prediction."
For Ed Weiler, NASA's associate administrator for space science and a former Hubble project scientist, the key point is not the telescope's serviceability or even its obvious value to the astronomical community. It's the way Hubble has "brought the universe close up and personal to the average citizen."
"It's images have become part of our culture in our textbooks, magazines, art and even popular movies and TV programs," he said. "Although we probably never will be able to visit these places or objects, Hubble actually allows our human minds and spirits to travel light years and even billions of light years to the farthest reaches of the cosmos. And SM-4 will allow that dream to continue."
As for the telescope's astronomical price tag, Weiler agreed "you can build a lot of ground-based telescopes for that kind of money. But you can't get rid of the atmosphere."
"We've heard about adaptive optics (for ground-based telescopes) and how that's going to blow Hubble out of the water," he said. "We've heard that for 20 years now. We haven't seen it. What's amazing is, whenever a new telescope comes out on the ground, a press release will always come out that 'oh, this can see a hundred times better than Hubble, or 10 times better.' Yeah, it can, probably, over a very, very tiny field of view. But you don't see Eagle nebulas on the cover of Time Magazine taken from the ground. It's taken from Hubble."
Malcolm Niedner, deputy senior project scientist, said the repaired and upgraded Hubble will be "a new machine that's going to be more powerful than the machine we've had."
"It is enough to make your mouth really water," he said. "Hubble is really going to be loaded to the max with capability. I think it's going to be a mission for the record books."
But as with any good thriller, there is more at stake than just the obvious.
"Leaving Hubble in the best possible shape is very important to NASA," Altman said in an interview. "It could really carry the flag for NASA or it could be a huge black eye if we don't do well. So I think we have a challenge in front of us to do the best that we possibly can."
It has captured light from infant galaxies in the process of colliding and merging less than a billion years after the big bang birth of the universe. And it has helped refine our understanding of the life cycles of stars, from their birth in vast stellar nurseries to the supernova explosions and more common slow fading that mark old age and death.
In recent years, Hubble's remarkable vision has played a key role in the worldwide effort to understand the nature of dark energy, the enigmatic repulsive force that astronomers believe is accelerating the expansion of the universe.
Throughout it all, Hubble has beamed back a steady stream of spectacular photographs of planets, stars, nebulae and galaxies that have found their way into all facets of modern society, making the telescope an instantly recognized icon of science.
But keeping Hubble healthy in the unforgiving environment of space has not been easy. During a second servicing mission in February 1997, shuttle astronauts installed two new instruments - the Space Telescope Imaging Spectrograph and an infrared camera known as NICMOS - replaced a fine guidance sensor, a gyroscope assembly and installed a solid-state data recorder.
Because of multiple gyro failures in the late 1990s, Servicing Mission 3 was broken up into two shuttle flights, SM-3A in December 1999 and SM-3B in March 2002. During SM-3A, spacewalking astronauts installed a new flight computer, a second solid-state recorder, another fine guidance sensor and a full suite of six gyroscopes.
The objectives of SM-3B included installation of two new solar arrays, the Advanced Camera for Surveys, an experimental cooling system to revive Hubble's infrared camera and a replacement power control unit. The latter operation was analogous to a heart transplant, requiring the telescope to be shut down for the first time since launch.
One year after SM-3B, NASA was well into planning the fifth and final service call when the shuttle Columbia disintegrated during re-entry on February 1, 2003, the victim of heat shield damage caused by a piece of foam insulation falling from the ship's external fuel tank during launch.
A year later, in January 2004, then NASA Administrator Sean O'Keefe sent shock waves through the astronomical community when he abruptly canceled SM-4. The decision was announced two days after President Bush ordered NASA to complete the international space station and retire the shuttle by the end of 2010.
Citing safety concerns in the wake of Columbia and a lack of time and money to properly address them, O'Keefe said it was simply too dangerous to launch astronauts to the space telescope. Heat shield inspection and repair techniques were immature and NASA was still struggling to prevent foam insulation from falling off the shuttle's external tank.
More important, a Hubble crew could not seek "safe haven" aboard the international space station if some post-launch mishap or orbital debris impact prevented a safe re-entry. Hubble and the space station operate in different orbital planes and the shuttle does not carry enough rocket fuel to move from one to the other.
O'Keefe defended his hugely unpopular decision by citing the Columbia Accident Investigation Board, which recommended autonomous heat shield inspection and repair capability for any non-station shuttle flights. Under pressure from Hubble supporters in Congress, he agreed to let engineers explore options for a robotic servicing mission. But the scope of that mission was more limited, the technical risks were high and the projected cost was extreme.
Even so, project managers pressed ahead, fearing subsequent equipment failures in orbit that would knock the observatory out of action once and for all. And they had reason for concern.
In August 2004, the Space Telescope Imaging Spectrograph's one operational channel failed because of a power supply problem. The observatory's stabilizing gyroscopes were suffering problems and engineers worried the telescope's crucial battery packs, operating continuously since launch in 1990, were slowly degrading. No one knew when one might suddenly fail.
Against this backdrop of concern, NASA pressed ahead with space station assembly flights, implementing a series of upgrades to minimize foam shedding from external tanks. The agency also carried out a series of tests to perfect heat shield inspection and repair techniques.
In one critical test, spacewalking astronauts showed the shuttle's robot arm and a new 50-foot-long tile inspection boom were strong enough to support an astronaut if repairs were needed and the station was not available.
O'Keefe's replacement, Mike Griffin, made no secret of his desire to fly Servicing Mission 4, saying "Hubble servicing represents the highest priority utilization of a single shuttle mission that I can conceive."
Finally, after three successful post-Columbia missions and tests to demonstrate heat-shield repair tools and techniques, Griffin officially reinstated SM-4 in May 2006.
"I don't believe I've talked to anyone in the agency, from flight crew to flight ops managers to, you know, even budget guys, I don't believe I've talked to anyone who thinks we shouldn't do this," he said.
To address the safe haven concern, he ordered the shuttle program to process a second orbiter - Endeavour - in parallel and to have it ready for takeoff within a few days of an emergency being declared to carry out a rescue mission if needed (see "STS-400: Just in Case" for additional details).
"The way we've designed the mission, we've got an answer to each of the risk points that, I think, brings us right into the family of same risk level as going to the station," said Altman. "First, get rid of the debris at the source, fixing the tank. Number two is the ability to detect damage, we've got that. Three is the ability to repair, that's come along pretty well.
"And then the final thing is OK, if you screw all that up and you're stuck there with an unsafe vehicle to come home, what do you do? I think that was a big sticking point before with the administrator and now that we have this launch-on-need plan where another shuttle will come to us and rescue us, we have an answer for that, too."
As if to drive home the need for another servicing mission, the Advanced Camera for Surveys failed in January 2007, the apparent victim of a short circuit in its CCD control electronics. Its high resolution and heavily used wide field channels were knocked out of action, although its more limited solar blind channel continued to operate. That left Hubble with two fully operational instruments: The Wide Field Planetary Camera 2 and the Near Infrared Camera and Multi-Object Spectrometer, or NICMOS.
Then, after a software upgrade prior to the original October launch date for Atlantis, engineers were unable to restart the NICMOS cooling system, presumably because of ice particles that had formed in the coolant lines. Engineers are optimistic about ultimately melting the ice and restarting NICMOS, but as of this writing, the space telescope only has one fully operational instrument - WFPC-2 - and the solar blind channel of the Advanced Camera for Surveys.
"The WFPC-2 has proved to be very durable, but it's been there since December of '93," Burch said. "So it's close to 15 years old and really doesn't owe us anything. So we've got aging science instruments, we've got a weak complement of gyros. I think it's really tough to imagine going much beyond 2010 (without SM-4). And if we lost NICMOS and just became basically the WFPC-2 observatory in space, I think our operation would be cut back substantially. It costs a lot to operate this observatory, the operational cost per year is on the order of a hundred million dollars plus, which includes all the science grants and what not. And to only have the use of WFPC-2 with no prospects of a future servicing mission, I think NASA would feel strongly that they'd want to start putting the money toward the future rather than the past."
* Installation of three new rate sensing units, or RSUs, containing two gyroscopes each to restore full redundancy in the telescope's pointing control system
* Installation of six new nickel-hydrogen batteries to replace the power packs launched with Hubble in 1990
* Installation of the Wide Field Camera 3 (in place of the current Wide Field Planetary Camera 2), providing high-resolution optical coverage from the near-infrared region of the spectrum to the ultraviolet
* Installation of the Cosmic Origins Spectrograph, sensitive to ultraviolet wavelengths. COS will take the place of a no-longer-used instrument known as COSTAR that once was used to correct for the spherical aberration of Hubble's primary mirror. All current Hubble instruments are equipped with their own corrective optics
* Repair of the Advanced Camera for Surveys
* Repair of the Space Telescope Imaging Spectrograph
* Installation of a refurbished fine guidance sensor, one of three used to lock onto and track astronomical targets (two of Hubble's three sensors suffer degraded performance). The refurbished FGS, removed from Hubble during a 1999 servicing mission, will replace FGS-2R, which has a problem with an LED sensor in a star selector subsystem
* Installation of the replacement science instrument command and data handling system computer
* Attachment of new outer blanket layer - NOBL - insulation to replace degrading panels
* Attachment of the soft capture mechanism to permit future attachment to a deorbit rocket motor or NASA's planned Orion capsule
"All of the tasks kind of break down into two big categories," said SM-4 mission director Chuck Shaw, an accomplished amateur astronomer. "The life extension tasks and then the mission science extension tasks. And the life extension tasks are clearly the most important, to keep the facility operating, and we'll get those done and then the mission science extension tasks, where we install new capability to do science above what it can do now."