The Hubble Space Telescope, the most productive scientific instrument of all time, is slated for its fifth and final repair mission later this year. The space shuttle astronauts will launch from Kennedy Space Center, Fla., match orbits with the telescope, capture it, service it, upgrade it, and replace its broken parts—on the spot.
Roughly the size of a Greyhound bus, Hubble was launched aboard the space shuttle Discovery in 1990 and already has outlived its 15-year life expectancy. Students in high school today have never known a time without Hubble as their conduit to the cosmos. This new servicing mission will extend Hubble’s life several more years. It also will replace burned-out circuit boards to the Advanced Camera for Surveys. That’s the instrument responsible for Hubble’s most memorable images since it was installed in 2002.
Servicing Hubble is a task that requires exquisite dexterity. Filmed as part of a PBS NOVA segment on the Hubble repair mission, I recently had the opportunity to visit NASA’s Goddard Space Flight Center in Maryland. There, I donned puffy, pressurized astronaut gloves, wielded a space-age portable screwdriver, stuck my head in a space helmet, and attempted to extract a faulty circuit board in a model of the Advanced Camera for Surveys, which was embedded within a full-scale mockup of the Hubble Telescope. This was a darn-near impossible feat. And I wasn’t weightless. I was not wearing the full-body spacesuit. Nor were Earth and space drifting by.
We normally think of astronauts as brave and noble. But, in this case, having the “right stuff” includes being a hardware surgeon extraordinaire.
Perhaps you didn’t know, but Hubble is not alone up there. About two dozen space telescopes of assorted sizes and shapes orbit Earth and the Moon. Each of them provides a clear view of the cosmos that is unobstructed, unblemished, and undiminished by Earth’s turbulent and murky atmosphere. But most of these telescopes were launched with no means of servicing them. Parts wear out. Gyroscopes fail. Batteries die. These hardware realities limit a telescope’s life expectancy to anywhere from three to seven years.
These telescopes all advance science, but most perform their duties without the public’s awareness or adulation. They are designed to detect bands of light invisible to the human eye, some of which never penetrate Earth’s atmosphere. Entire classes of objects and phenomena in the cosmos reveal themselves only through one or more of these invisible cosmic windows. Black holes, for example, were discovered by their X-ray calling card—radiation that was generated by the surrounding, swirling gas just before it descended into the abyss. Telescopes also have captured microwave radiation—the primary physical evidence for the Big Bang.
Hubble, on the other hand, is the first and only space telescope to observe the universe using primarily visible light. Its stunningly crisp, colorful, and detailed images of the cosmos make Hubble a kind of supreme version of human eyes in space. Yet Hubble’s appeal to us comes from much more than parades of pretty portraits. Hubble came of age in the 1990s, during an exponential growth of access to the Internet. That’s when its digital images were first cast into the public domain. As we all know, anything that’s fun, free, and forwardable spreads rapidly online. Hubble images, one more splendorous than the next, became screen savers and desktop “wallpaper” for computers owned by people who never before would have had the occasion to celebrate, however quietly, our place in the universe.
Indeed, Hubble brought the universe into our backyard. Or, rather, it expanded our backyards to enclose the universe itself. It did that with images so intellectually, visually, and even spiritually fulfilling that most don’t even need captions. No matter what Hubble reveals—planets, dense star fields, colorful interstellar nebulae, deadly black holes, graceful colliding galaxies, the large-scale structure of the universe—each image establishes your own private vista on the cosmos.
Hubble’s scientific legacy is unimpeachable. More research papers have been published using its data than have ever been published for any other scientific instrument in any discipline. Among Hubble’s highlights is settling the decades-old debate about the age of the universe. Previously, the data were so bad that astrophysicists could not agree. Some thought 10 billion years. Others, 20 billion. Yes, it was embarrassing. But Hubble enabled us to measure accurately how the brightness varies in a particular type of star that resides in a distant cluster of galaxies. That information, when plugged into a simple formula, tells us their distance from Earth. And because the entire universe is expanding at a known rate, we can then turn back the clock to determine how long ago everything was in the same place. The answer? The universe was born 14 billion years ago.
Another result, long suspected to be true but confirmed by Hubble, was the discovery that every large galaxy, such as our own Milky Way, has a supermassive black hole in its center that dines on stars, gas clouds, and other unsuspecting matter that wanders too close. The centers of galaxies are so densely packed with stars that Earth-based telescopes see only a mottled cloud of light—the merged image of hundreds or thousands of stars. From space, Hubble’s sharp imagery allows us to see each star individually and to track its motion around the galactic center. Behold, these stars move much, much faster than they have any right to. A small, unseen yet powerful source of gravity must be tugging on them. Crank the equations, and we are forced to conclude that a black hole lurks in their midst.
In 2005, the Bush Administration announced that Hubble would not receive the needed funds for this last servicing mission. Curiously, the loudest voices of dissent were not from the scientists but from the general public. Akin to a modern version of a torch-wielding mob, angry editorials, snippy letters to the editor, and no end of radio and television talk shows all urged NASA to restore the funding and keep Hubble alive. Congress ultimately listened and reversed NASA’s decision. Democracy had a shining moment: Hubble would indeed be serviced, one last time. For the first time in the history of civilization, the public took ownership of a scientific instrument—they took ownership of the Hubble Space Telescope.
Of course, nothing lasts forever—except, perhaps, the universe itself. So Hubble eventually will die. But in the meantime, NASA is building the James Webb Space Telescope, specially designed to see deeper into the universe than Hubble ever could. When launched early next decade, it will allow us to plumb the depths of gas clouds in our own Milky Way galaxy in search of stellar nurseries, as well as probe the earliest epochs of the universe in search of the formation of galaxies themselves.
Meanwhile, NASA plans to retire the aging space shuttle by 2010. This step will enable its aerospace engineers, assembly lines, and funding streams to focus on a new suite of launch vehicles that will do what the shuttles are not designed to do—return us to the Moon and take us on to Mars and beyond.
The march of discovery continues, driven by our timeless and collective urge to explore.