Nineteen years ago today, on April 24, 1990, NASA launched its greatest Great Observatory — the Hubble Space Telescope — and ushered in a revolutionary era of astronomical discovery.The passage of time has been kind to Hubble and its handlers. We're largely forgotten that, almost immediately after opening its mirrored eye to space, astronomers realized that all was not right. An error in calibrating the focus point during optical fabrication left HST's 94-inch-wide (2.4-m) primary mirror with a bad case of spherical aberration.
It was ultimately due to human error, the kind of too-much-reliance-on-high-tech-wizardry mistake that any decent amateur telescope maker would have caught by using simple traditional testing methods. But it wasn't discovered until Hubble was in orbit. Fortunately, clever opticians designed a set of mirrors to fix the problem (dubbed "Corrective Optics Space Telescope Axial Replacement," or COSTAR). Astronauts installed COSTAR, a new camera, and other tune-up parts during their first in-orbit house call in December 1993. Hubble has been a cosmic discovery machine ever since.
This year I've been teaching astronomy to high-school seniors, and it occurred to me that the Hubble Space Telescope has been churning out observations throughout their young lifetimes. In a way, that's too bad. My schools' observatory boasts an impressive 25-inch Ritchey-Chrétien telescope with beautiful optics — it's essentially a ¼-scale model of that Big Eye in the Sky. But the subtly detailed views of nebulae and galaxies seen through its eyepiece can't hope to compete with two decades of fabulous, oversaturated Hubble results that permeate every astronomy textbook, website, and PBS documentary.
Still, I really can't complain. After all, we're living in a Golden Age of Astronomy. Hubble has been called the greatest telescope of all time. Methinks even Galileo would have agreed with that claim.
In a few weeks, the world's eyes will again be on Hubble, as the final team of spacewalking astronauts hover around it for one last round of repairs and upgrades. They plan to rocket into orbit aboard the Space Shuttle Atlantis on May 11th at 2:02 p.m. EDT, and you can bet that I'll put the textbook and PowerPoints aside that week to let my class watch — if not with wide-eyed wonder, then at least with nodding appreciation.