The mirror was ever so slightly the wrong shape, which caused light that bounced off the center of the mirror to focus in a different place than the light bouncing off the edge. The flaw was minuscule -- 1/50th the thickness of a sheet of paper -- but it made a significant difference.
"[There were] NASA scientists that stood up and said, "It's a total loss," Launius said.
Members of Congress, including Sen. Barbara Mikulski, D-Md., who was, and still is, a big NASA supporter, were livid that this had taken place.
"This was such a failure, to the tune of $3 billion," Launius said.
Thankfully, the telescope's first servicing mission in December 1993 was a success. After spending 11 months training for what is considered to be one of the most complex missions, astronauts installed a series of small mirrors to fix the flaw.
"They had figured out some ways to work around that problem," Launius said. "But it took a while to generate some of the images that we've seen."
2. Like us, Hubble can't look directly at the sun.
Hubble has photographed every planet in the solar system, with one exception: Mercury.
The solar system's innermost planet is too close to the sun for Hubble to observe. The sun's bright light would permanently damage its optics and electronics.
Mercury's angular separation from the sun is always less than 28 degrees, which means that it's never out of the sun's glare and, therefore, off limits for the Hubble.
3. It's a pop-culture icon.
Hubble and its images have also had their share of cameo appearances in Hollywood flicks and TV shows.
When "Naked Gun 2 1/2" came out in 1991, Hubble was still a national laughingstock.
In the movie, it was pictured in the Blue Moon Cafe on a wall of failures, smack in the middle of the Titanic and the Hindenberg.
Imagery from Hubble has also been spotted in the movies "Happy Feet" and "Contact."
For the album cover of its 2000 release "Binaura," Pearl Jam used an image of Hubble's "Hourglass Nebula."
4. Hubble's namesake almost chose the law over astronomy.
When the U.S. Postal Service released a special 41-cent for Edwin Hubble in 2008, they called him a "pioneer of the distant stars."
But Hubble was close to choosing another path for himself. Born in Missouri in 1889, Hubble studied math and astronomy as an undergrad but then went on to study law as one of the first Rhode Scholars at Oxford University.
He reportedly moved to Kentucky to practice law. But the pull of the cosmos was too great. Hubble spent most of his career at California's Mt. Wilson observatory.
He is credited with many discoveries but most notably for observing that the farther apart galaxies are from each other, the faster they move away from each other. Based on this, Hubble concluded that the universe expands uniformly.
When the Hubble Space Telescope launched, one of its goals was to figure out this expansion rate, called the Hubble Constant.
5. Hubble images are held from the public for one year.
In its 19-year-career, Hubble has made about 880,000 observations and has released about 570,000 images of the universe.
But before any of those images are shown to the public, they are held in a proprietary waiting period. For one year, the scientist (or scientists) involved in the project that took the image have the exclusive opportunity to review the data.