All eyes on shuttle's dance with Hubble
Spacewalks are the trickiest part of the mission. Other recent failures
Somewhere over the Gulf of Mexico on Tuesday evening, NASA carried out a flawless extraterrestrial tango as the shuttle Discovery danced closer and closer to its ungainly partner, the broken Hubble Space Telescope, 370 miles above Earth.
Seconds ahead of schedule, mission specialist Jean-Franois Clervoy artfully snagged the Hubble with Discovery's 50-foot robot arm and stowed the $3 billion telescope snugly in the shuttle's cargo bay.
The rendezvous was but the first step in a mission critical not only for NASA's public image, but also for space science - some scientists hail the Hubble as the most productive scientific instrument to date.
For NASA, the mission is as close as it gets to a sure thing - the Hubble was designed for occasional cosmic tune-ups. But with the world paying close attention after two recent failed missions to Mars and nine delays on this shuttle voyage, NASA needs the spacewalks to fix the Hubble to go flawlessly. And in the vacuum of space, just tightening a bolt can become a task of intestinal fortitude.
"All [spacewalks] are very complicated. It is a little bit like doing brain surgery while you are hanging upside down and feeling nauseous," says Bruce Margon, a University of Washington astronomer who helped design Hubble components. "With Hubble, it's even worse because it is an extraordinarily large and intricate machine."
During three long spacewalks scheduled for yesterday, today, and tomorrow, the astronauts will replace faulty gyroscopes, a broken radio transmitter, and a misguided guidance system. They will also hang stainless-steel panels over cracking insulation blankets, put in a new battery-temperature-regulation system, and give Hubble a zippier computer and hard drive.
Spacewalks, not cakewalks
While much of the replacement work will involve loosening and tightening standard Earth-issue nuts and bolts or screwing things into grooved sockets, these spacewalks will not be cakewalks.
Decked out in bubble suits and floating in the unfamiliar environment of zero gravity, the astronauts need to work quickly. NASA had originally hoped to accomplish its goals during four spacewalks. Launch delays due to bad weather forced it to forgo the final spacewalk.
The astronauts labor tethered to the orbiting spacecraft, with tools that are tied to a caddy around their waists. This ensures that nothing floats away or, worse, hits the shuttle or telescope and causes damage. Wearing thick, unwieldy gloves and maneuvering their bodies into tight crevices, the astronauts have to complete their chores with monstrous backpacks and bulbous helmets.
"The task of pulling the old [gyroscopes] out and putting the new ones in is something that needs to be done meticulously," says Keith Kalinowski, Hubble's systems manager. "But everything we are going to do has been practiced many times by the astronauts."
As the first of NASA's so-called "great observatories," the Hubble is valuable because it orbits above the atmospheric distortions that hinder terrestrial scopes. Its lofty location provides stunning clarity and also can see wavelengths of light that do not pass through Earth's atmosphere.
During its life span, the Hubble telescope has produced an impressive parade of discoveries, including insights into how galaxies evolve, the composition of black holes, and the age of the universe.
"It has had all of the impact that everyone originally dreamt about before the launching," says Dr. Margon.
But the Hubble lost its ability to focus when the fourth of its six gyroscopes failed a month and a half ago. This left the telescope unable to maintain a steady bearing or focus well on distant objects.
Hurry it up
As Hubble has a finite life span of about 20 years, scientists and NASA are very eager to get the instrument back on line and to maximize priceless observation time. Meanwhile, precious dollars continue to go towards the Hubble's program infrastructure and staff.
"It's the worst all worlds. Not only are you eating away at your lifetime but you are spending money to do it," says Margon.
Hubble's builders expected downtime. A satellite suffers all manner of astronomical indignities from solar radiation to space junk to general wear and tear. "You can't build something as big as a boxcar and as intricate as a Swiss watch and not expect things to go wrong," says Margon.
For this reason, engineers designed the Hubble with repair missions in mind. Replacement procedures for components like computers, memory devices, and gyroscopes incorporate either unique tools or special designs to make fixing easier.
"These connectors are designed to be EVA [extra-vehicular activity] friendly," says Dr. Kalinowski. "They are designed to be removed and put back on by an astronaut wearing gloves."
Been there, done that
To NASA's credit, the two previous missions to fix Hubble flaws in 1993 and 1997 went smoothly. And should this current mission go well, Hubble should be sharper and more useful than ever.
The new computer, which carries an Intel 486 microprocessor, will significantly boost the speed at which data can be processed aloft and the complexity of operations that Hubble can support. The stainless-steel shields should stabilize the thermal environment around Hubble's sensitive instruments and augment image quality. And the new memory device will increase Hubble's memory nearly fivefold.
Should things go awry, NASA has planned for numerous contingencies to make sure the mission is productive. At the least, the first space walk to replace the gyroscope will reopen Hubble's eyes.
"We are prepared to deal with surprises if we encounter any," says Kalinowski. "We're in a business where difficulties are part of the game."
(c) Copyright 1999. The Christian Science Publishing Society