'Go' for Hubble servicing mission
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: October 31, 2006;
Updated at 5:15 with quotes from astronauts and program manager
NASA Administrator Mike Griffin today reinstated a final shuttle mission to service and upgrade the Hubble Space Telescope, deciding the scientific value of the orbiting icon justifies the additional cost - and risk - of a stand-alone shuttle flight.
"We are going to add a shuttle servicing mission to the Hubble Space Telescope to the shuttle manifest and fly it before it retires," Griffin told managers and engineers at the Goddard Space Flight Center in Greenbelt, Md.
Sen. Barbara Mikulski, D-Md, a staunch supporter of Hubble and the long-awaited rescue mission, rose to her feet and led a standing ovation.
"What an exceptional day today is," she said a few moments later. "I'm so pleased and so excited that Dr. Griffin has just announced that Hubble will be serviced. ... It's a great day for science. It's a great day for discovery. It's a great day for inspiration, because that's one of the things Hubble has meant for so many people."
Said Preston Burch, manager of the Hubble program at Goddard: "We're elated. I have a hard time finding the right words to express it, but we are extremely pleased, giddy with enthusiasm about this."
Altman served as commander of the most recent Hubble servicing mission, SM-3B, in 2002. Grunsfeld and Massimino participated in spacewalks during that mission and both are experts on Hubble servicing. The rest of the astronauts are making their first shuttle flight.
"It really is a great day for discovery, for exploration and I think for NASA, to be able to go back to the Hubble Space Telescope, extend it's life, keep its vision out there, just a tremendous opportunity for science and I think for the future," Altman said at an afternoon news conference.
"The discoveries we don't know about yet, the observations we haven't taken, it's really thrilling for all of us to be part of the team that's going to work on that."
Five back-to-back spacewalks by Grunsfeld, Feustel, Massimino and Good, working in two-man teams, will be required to install six new batteries, a suite of six new gyroscopes, a powerful new camera, a state-of-the-art ultraviolet spectrograph and a replacement fine guidance sensor to help the observatory find and track its targets.
The astronauts also will attempt to fix a broken imaging spectrometer, a complex task that will require the removal of 111 non-captive screws and the replacement of a power supply circuit board. It is considered the most challenging Hubble repair job since Grunsfeld and Massimino helped replace a power control unit in 2002.
A graphic showing the past HST spacewalks is available here.
In addition, the spacewalkers will install a cooling system to lower the spectrometer's operating temperature, repair degraded thermal insulation and install a fixture that will permit the eventual attachment of a small rocket module to drop it safely out of orbit when it is no longer operational.
"We have conducted a detailed analysis of the performance and procedures necessary to carry out a successful Hubble repair mission over the course of the last three shuttle missions," Griffin said in a statement. "What we have learned has convinced us that we are able to conduct a safe and effective servicing mission to Hubble.
"While there is an inherent risk in all spaceflight activities, the desire to preserve a truly international asset like the Hubble Space Telescope makes doing this mission the right course of action."
If SM-4 is successful, engineers believe Hubble will remain scientifically productive at least through 2013, an additional five years beyond what could be expected based on the current health of its aging batteries and gyroscopes. With any luck at all, the telescope will still be operating when its replacement, the huge infrared-sensitive James Webb Space Telescope, is launched around 2013.
In the meantime, Hubble's two new science instruments will help the iconic observatory address some of the most fundamental questions in astrophysics and cosmology, including the nature of the so-called dark energy, believed to be accelerating the expansion of the universe, and the evolution of galaxies in the wake of the big bang.
Huge ground-based telescope using computer-controlled adaptive optics, which can compensate for turbulence in the atmosphere, rival or exceed Hubble's vision in some areas. But Hubble's resolution, "the sharpness of its vision, is really unparalleled and it will be a long while before that is achieved in the optical by the best adaptive optics," said Mario Livio, a senior astrophysicist at the Space Telescope Science Institute.
"There is some hope it will overlap with the James Webb Space Telescope, which in itself would be incredible. Imagine you would have something (in space observing) from the ultraviolet to the mid-to-far infrared, operating at the same time. This would be incredible."
Grunsfeld, an astronomer by training, said "the biggest discovery that Hubble will make is the next one."
"A lot of folks don't believe that, but from the last mission we were told that and there was this small discussion about something called dark energy, which we now know is about 75 percent of the total energy content of the universe," he said. "Prior to the previous Hubble missions, nobody even knew it existed. So I think that's pretty big. I don't know how we can top that, but I imagine there'll be something."
When Columbia blasted off on Jan. 16, 2003, SM-4 was scheduled for takeoff in early 2005. But in January 2004, former Administrator Sean O'Keefe canceled the Hubble mission, arguing that an HST repair crew could not seek "safe haven" aboard the international space station in case of major problems with the shuttle that might prevent a safe re-entry. The two spacecraft circle the globe in very different orbits and shuttles cannot carry enough fuel to move from one to the other.
Without safe haven or certified techniques for fixing heat shield damage in orbit, O'Keefe said, a Hubble flight was too dangerous.
But Griffin said today the success of three post-Columbia missions proves NASA has dramatically lowered the risk of external tank foam insulation problems like those blamed for Columbia's demise.
Discovery will carry the same heat shield inspection boom and sensors that station flights carry, permitting the crew to inspect all critical areas on the shuttle before rendezvousing with Hubble and again, after Hubble is released. The inspection boom can carry an astronaut to any repair site on the shuttle and if impact damage is found, the crew will have improved repair materials and techniques at their disposal.
Flying in Hubble's orbit, the servicing crew will be exposed to a greater chance of micrometeoroid impacts than a station crew but that threat is offset somewhat by reduced risk in other areas.
Finally, NASA plans to process a second shuttle in parallel and to have it ready for launch on a rescue mission from a different pad within a week or so if Discovery suffers any sort of non-repairable damage. Providing additional margin, Discovery will be launched with enough on-board supplies to support the crew for at least 25 days in orbit.
"The astronaut office was not unified as to the opinion of whether we need a launch-on-need shuttle," Griffin said today. "Statistically, it would be silly to say anything other than we don't need a rescue mission because we have a much higher chance of losing a shuttle from some other cause for which a rescue mission can't help you.
"But there is a small chance that we could lose a shuttle, an event which could be remedied by having a launch-on-need capability. To protect against that small chance, we have decided that we will maintain a rescue capability for this mission."
Said Mikulski, "Is going into space risk free? No. But our astronauts know that. ... They count on us to be as safe as possible. I will pledge to you today no matter what my role is on the appropriations, I will move heaven and Earth, this galaxy and even those unknown to make sure there is money in the budget to always protect our astronauts."
For their part, Altman and his crewmates said SM-4 will be far safer than any previous Hubble servicing mission, thanks to the post-Columbia safety upgrades and the decision to protect a launch-on-need rescue option.
"We definitely did learn from Columbia, and we're changing our culture and we're going to keep watching safety every single mission, including Hubble, including the missions after that," Grunsfeld said. "I feel like a mission to Hubble is worth risking my life for, something I've discussed with my family. It's something that's really important for our country and I firmly believe the next mission to Hubble will be much safer than the missions we've flown before."
Altman agreed, saying "as I look back on what we've learned from then to now, the improvements that we've made, there is no doubt in my mind at all the next time we go to Hubble it will be significantly safer than when we launched on STS-109."
O'Keefe's cancellation of SM-4 in January 2004 touched off a storm on protest, prompting NASA to look into the feasibility of an robotic servicing mission.
The goals of the unmanned mission included the attachment of a propulsion module that could drive Hubble to a safe, targeted re-entry at the end of its useful life. But such a robotic flight ultimately was deemed too technically risky and too expensive.
With relatively minor exceptions, the goals of the currently envisioned shuttle mission are virtually unchanged from the flight O'Keefe cancelled. Five back-to-back spacewalks are planned:
EVA-1: Installation of three rate sensing units (six gyros) and one battery module (three batteries)
EVA-2: Installation of the Cosmic Origins Spectrograph and the second battery module
EVA-3: Installation of the Wide Field Camera 3 and insulation repairs
EVA-4: Space Telescope Imaging Spectrograph repair and installation of a cooling system
EVA-5: Installation of a replacement Fine Guidance Sensor.
The Wide Field Camera 3, installed in place of the current Wide Field Planetary Camera 2, will provide high-resolution optical coverage from the near-infrared region of the spectrum to the ultraviolet
The Cosmic Origins Spectrograph, sensitive to ultraviolet wavelengths, 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
A refurbished fine guidance sensor, removed from Hubble during a 1999 servicing mission, will replace FGS-2R or FGS-3. The fine guidance sensors help Hubble find and lock onto targets and engineers have not yet decided which unit to replace.
But from a life extension viewpoint, the most critical upgrades are the new batteries and gyroscopes.
When Hubble was launched 16 years ago, the observatory's nickel-hydrogen batteries, which provide stored power when the telescope is in Earth's shadow, had about 550 amp hours of capacity. By the end of 2005, that had degraded to 300 amp hours and engineers were worried capacity might eventually drop below the 110 amp hours needed to keep Hubble alive.
Improved recharging techniques were developed and the decline seen earlier dropped off. Burch said the batteries now are expected to keep Hubble electrically alive until around 2010.
"These things are approaching 20 years in age and we can't find anybody who's operated nickel-hydrogen batteries anywhere on the Earth's surface, let alone in space, for this long," Burch said in an interview with CBS News. "So how long will they last? That's anybody's guess. We don't know where the stone wall is out there. Based on what we know today, we feel comfortable saying we're good through 2007 and probably good through 2008. But when you start speculating about 2009 and beyond, well, I think we need a little more data."
Hubble was designed to operate with three stabilizing gyroscopes but it was launched with six to provide redundancy. Four of the units currently installed are operational while two - No. 3 and No. 5 - are considered failed.
Worried about additional failures before SM-4 could be launched, engineers earlier developed software permitting Hubble to operate with just two gyros. As it now stands, gyros 1 and 2 are operational. Gyros 4 and 6 are turned off but are available for use if needed.
Based on past gyro failures, Burch said there is a 50-50 chance three of the four remaining gyros will fail by October 2008.
"That's when we hit the 50-50 point that we will fail three more gyros, leaving us with just one of the six gyros available," he said. "We have two different versions now of zero-gyro safe mode, so we can fly without gyros and just maintain the health of the observatory indefinitely."
The HST project was approved in 1977, it's 94.5-inch primary mirror was completed in 1981, the original suite of science instruments was delivered in 1983 and the telescope was completed in 1985. At that point, launch was targeted for the fall of 1986.
But the flight ultimately was delayed until 1990 because of the Jan. 28, 1986, Challenger disaster. Then, shortly after the telescope finally reached orbit in 1990, scientists were dismayed to discover the primary mirror suffered from spherical aberration.
Because of an oversight during mirror testing, the concave mirror's outer edge was too shallow by two microns - a tiny fraction of the width of a human hair. But that was more than enough to prevent light reflected from the outer regions of the mirror from focusing at the same point as light from the inner regions.
The telescope's original design specification called for 70 percent of a star's light to be concentrated in a very tiny circle. Suffering from spherical aberration, Hubble could only manage 10 percent to 15 percent. The result was blurry images.
Nothing could be done to fix the primary mirror. But engineers quickly came up with ways to reverse the blurring it causes. In a 1993 servicing mission, spacewalking astronauts installed the Wide Field Planetary Camera 2, with built-in corrective optics, and the COSTAR instrument to route corrected light to Hubble's other instruments.
Since then, the Hubble Space Telescope has become an international icon of science, one of the most productive astronomical observatories ever built and the flagship of NASA's exploration of the universe.
The remotely-controlled spacecraft has helped astronomers confirm the existence of black holes, zero in on the true age of the universe and spot the faint glimmer of stars in galaxies born within a billion years or so of the big bang birth of the cosmos.
Its spectacular photographs have charted the life cycles of distant suns in enormous detail, providing unmatched views of stellar nurseries and the explosive end results of stellar evolution.
It has catalogued myriad infant solar systems in the process of forming planets and provided flyby-class views of the outer planets in Earth's own solar system, routinely capturing phenomena as common as dust storms on Mars to the once-in-a-lifetime crash of a comet into giant Jupiter.
More recently, Hubble has shed light on the evolution and ultimate fate of the universe, measuring the light of ancient supernovas to help confirm the expansion of the universe is accelerating, not slowing down as previously thought.
There are more than 40 ground-based telescopes with bigger mirrors than Hubble's relatively modest 94.5-inch primary and more are on the way. But the space telescope remains in a class by itself, thanks to its location high above Earth's turbulent, obscuring atmosphere and periodic shuttle servicing to upgrade its instruments.
"The thing to remember about these Hubble servicing missions is they're not just let's keep a groaning patient on life support," said Bruce Margon, then associate director for science at the Space Telescope Science Institute in Baltimore. "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. In the 15 years since launch, ever year has resulted in more refereed discovery papers than the previous year.
"The reason for that is not that the scientists who are using Hubble are smarter, 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."
Along with installing COSTAR and WFPC-2 during Servicing Mission 1 in 1993, shuttle astronauts also installed two new solar arrays, solar array drive electronics, magnetometers, a coprocessor to boost the speed of Hubble's flight computer, two rate sensor units and two gyroscope electronic units.
Servicing Mission 2, launched in 1997, provided two new instruments - the Space Telescope Imaging Spectrograph and the Near Infrared Camera and Multi-Object Spectrometer - along with a refurbished fine guidance sensor, upgraded electronics, a solid-state data recorder, a reaction wheel assembly, solar array drive electronics and a data interface unit.
Because of gyro failures, Servicing Mission 3 was broken up into two flights, SM-3A and SM-3B. During SM-3A in 1999, shuttle astronauts installed six new gyroscopes, six battery voltage/temperature kits, a faster flight computer, another solid-state data recorder, a new radio transmitter, an upgraded fine guidance sensor and insulation.
NASA's fourth servicing mission, SM-3B, was launched in March 2002. During that flight, astronauts installed the Advanced Camera for Surveys, two new solar arrays, a power control unit, and an innovative "cryocooler," a sophisticated device that restored NICMOS to operation after its internal coolant was exhausted.
SM-4 will be NASA's final Hubble servicing mission.