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Servicing missions are key to Hubble success BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: December 5, 2005 And what a life it's been. NASA began making preliminary plans for a large space telescope in 1973. 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, 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, one of the most ambitious flights on the proposed shuttle manifest. One of the major objectives of the upcoming engineering evaluations in the Neutral Buoyancy Laboratory new Johnson early next year is to refine the exact sequence of spacewalk, or EVA, tasks. Here is how the EVAs are currently envisioned:
Complicating the planning, shuttle managers must weigh the objectives of the servicing mission against time needed to inspect the shuttle's heat shield after it reaches orbit and the impact of potential repairs. The team is looking at "how we need to posture EVAs to get things done in an order that allows you to insert stuff, which will just bump things to the right," Shaw said. "Every one of the EVAs is already full. All of the highest priority stuff is done during the time frame in the flight that really wouldn't be competing against either inspection or repair." In addition to his Hubble chores, Shaw also is heading up a so-called "inspection and repair road map" that will apply to station missions as well. "I'm well motivated," he said. "There are time periods where you inspect and then you've got to do the analysis from the data that you get down from inspection before you can decide to go act on it. And it's those time periods that are analysis intensive that we want to make sure we are busy on board doing things that would compete against doing EVAs for either inspection or even if we had to go out and perform some minor repairs. Shuttle spacewalk time is limited and "the idea is to try to plan out the opportunities for doing inspection and/or repair against lower-priority activities that can be moved to the right." "When you've got five back-to-back EVAs, it's a pretty highly orchestrated timeline," Shaw said. "So you don't want to try to do a lot of broken-field running if you don't have to. And so having these time frames for inspection and repair double book kept against other activities is our strategy. In fact, that's the strategy for all the station flights, too." In the end, he said, "we're going to have to sit and look at the tea leaves before Hubble and decide, you know, one, have we been having any surprises and two, are we starting to get happy with our confidence in our repair capability," he said. "Even if it's not certified, how confident are you? We're not there yet. We've got a lot of homework to do. And we've got another two years before we fly Hubble."
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Scientists marvel at the achievements made by the orbiting Hubble Space Telescope in this produced movie looking at the crown jewel observatory that has served as our window on the universe.
10 years ago: The Solar and Heliospheric Observatory, a joint European and American Sun-watching probe, blasts off from Cape Canaveral aboard a Lockheed Martin Atlas 2AS rocket.
The European Space Agency's Huygens probe, launched from NASA's Cassini spacecraft, descended through the atmosphere of Saturn's moon Titan and landed on its mysterious surface in January. Scientists hold this news briefing to report on new results from the daring mission.
Project scientists working on the European Space Agency's Mars Express spacecraft now orbiting the Red Planet hold a news conference to announce some interesting results from the ongoing mission.
Mercury astronaut John Glenn becomes the first American to orbit the Earth on February 20, 1962, when he is launched aboard Friendship 7.
International Space Station commander Bill McArthur and flight engineer Valery Tokarev mark the Thanksgiving holiday in orbit during this downlinked message.
Expedition 12 Soyuz commander Valery Tokarev and station commander Bill McArthur temporarily leave the International Space Station. They undocked their Soyuz capsule from the Pirs module and then redocked the craft to the nearby Zarya module. The move clears Pirs for use as the airlock for an upcoming Russian-based spacewalk.
Check out NASA's Pluto-bound New Horizons spacecraft undergoing thermal blanket installation inside the cleanroom at Kennedy Space Center's Payload Hazardous Servicing Facility in preparation for launch in January from the Cape.
A new image from NASA's Spitzer Space Telescope reveals billowing mountains of dust ablaze with the fires of stellar youth. The majestic infrared view from Spitzer resembles the iconic "Pillars of Creation" picture taken of the Eagle Nebula in visible light by NASA's Hubble Space Telescope.
This week marks the anniversary of arguably the most daring and complex space shuttle mission. The astronauts successfully launched two satellites and then recovered two others during extraordinary spacewalks by astronauts using jet-propelled backpacks and pure muscle power.
Commander Bill McArthur and flight engineer Valery Tokarev conduct a 5 1/2-hour spacewalk outside the International Space Station, installing a TV camera, doing repair chores and jettisoning a failed science probe.
Return to flight space shuttle commander Eileen Collins narrates an interesting slide show featuring some favorite photographs of Earth taken during her previous shuttle missions.