Hubble's science has pinpointed the age of the universe, almost 14 billion years and proved the existence of massive black holes.
It's the most powerful telescope ever, taking astronomers of all ages beyond the wildest dreams of Galileo.
Ask a kid to name a scientific instrument today, and "it will be hubble," says Dr. Ed Weiler of the Goddard Space Flight Center.
"Hubble has entered the vernacular of the American public," says Weiler. "I hear commercials about health plans or something and they say, 'If this health plan were a telescope, it would be the Hubble.'"
But the Hubble is now in trouble. Its gyros and batteries need replacing, or the telescope will eventually die. The problem is NASA's nervous that a manned, in-space service call could be too dangerous.
After the shuttle Columbia's disaster, NASA nixed the idea of some future crew returning to fix Hubble. Hubble fans were outraged that the show would soon be over.
But next month, the shuttle returns to space for the first time since Columbia. If all goes well, the agency's new administrator Michael Griffin may reconsider servicing the Hubble.
"In light of what we learn after we return to flight we should revisit the earlier decision," says Griffin.
That could keep Hubble adding to its spectacular portfolio into the next decade - a relief to stargazers like Joseph Guzman in Chicago. He's a self-styled "Hubble Hugger," desperate for the next shuttle mission to succeed.
"We got to get out the bugs, get out the kinks, and the second mission after this one in May should be a 'save-the-Hubble mission,'" says Guzman.
For 15 years, the Hubble's focused on the wonders of what's out there, and how it all began.
But now the mystery is the telescope's own future.