(CNN) It's up there right now -- flying about 340 miles over the Earth and circling us every 97 minutes. It's a telescope -- in the sky. Just think about that for a bit.

It's called the Hubble Space Telescope . The telescope itself is not really much to look at. If you could see it right now you might think it's just a big shiny, silver bucket with two gangly solar arms and a couple of dish antennae. It's about the size of a school bus and weighs about as much as two elephants.

But that silver bucket is pure gold for astronomers. It's made such a big impact that NASA , the space agency with a fleet of space probes out there taking amazing pictures, calls Hubble the "most significant advance in astronomy since Galileo's telescope."

Not bad for a 25-year-old floating bucket.

Hubble didn't start out winning high marks. It was launched on April 24, 1990, aboard the space shuttle Discovery from Kennedy Space Center, Florida. The next day, it was released into space, but scientists soon realized they had a big problem. The telescope's primary mirror had a flaw: Its outer edge was ground too flat by a depth of 2.2 microns -- that's about one-50th the thickness of a human hair.

The images that were expected to dazzle the world were fuzzy.

Hubble became the butt of late-night talk show jokes.

But in December of 1993, shuttle Endeavour astronauts repaired the telescope.

So why is Hubble so special? Because it's on what NASA calls "the ultimate mountaintop." Sitting high above the distortion of Earth's atmosphere, far away from our light-polluted cities and hovering far away from clouds and storms, Hubble has "an unobstructed view of the universe."

Hubble Facts The Hubble Space Telescope is named after American astronomer Edwin P. Hubble Hubble is a joint project between NASA and the European Space Agency

Scientists have used that vantage point to make groundbreaking observations about planets, stars, galaxies and to reveal parts of our universe we didn't know existed. The telescope has made more than 1 million observations , and astronomers have used Hubble data in more than 12,800 scientific papers, "making it one of the most productive scientific instruments ever built," according to NASA.

"All the (Hubble) observations are planned here," Levay told CNN. "We get all of the science data from the telescope and provide that data to the astronomers around the world."

Levay oversees the production of the images that are used to illustrate and to publicize the work done by scientists using Hubble. So when someone using Hubble makes a big discovery, Levay's team helps find the right image to illustrate the results. "We take the same data the astronomers use and we produce the pictures."

If you're a photographer or an astronomer -- or both -- you may be a bit jealous right now.

"It's been rewarding and a challenge and a roller coaster," Levay said.

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He says the hardest part of his job is selecting the best photos from the thousands created by Hubble. "It's a challenge to pick out what one would consider the best," he said.

Here's how Hubble creates its amazing photographs : It uses mirrors to gather lots of light from far out into space and then focuses that light on the telescope's cameras and other instruments. These cameras aren't like the digital ones in our smartphones that we use to take selfies or even like old cameras that use photographic film.

Instead, Hubble captures light in many different wavelengths using these cameras and instruments:

• Wide Field Camera 3 (WFC3) sees three different kinds of light: near-ultraviolet, visible and near-infrared.

• Cosmic Origins Spectrograph (COS) sees exclusively in ultraviolet light.

• Advanced Camera for Surveys (ACS) sees visible light.

• Space Telescope Imaging Spectrograph (STIS) sees ultraviolet, visible and near-infrared light.

• Near Infrared Camera and Multi-Object Spectrometer (NICMOS) is Hubble's heat sensor. It's sensitive to infrared light and lets scientists look for objects hidden by interstellar dust.

• Fine Guidance Sensors (FGS) are used to keep Hubble pointed in the right direction.

Eventually, Hubble will stop working. NASA had hoped to use a space shuttle to bring it home for a museum exhibit , but the telescope outlived the shuttle program. Now, NASA says it's studying various options for its superstar telescope after it shuts down.

But Hubble fans shouldn't worry yet. "We expect Hubble to be in the sky for quite a while, around until the 2030s," NASA spokeswoman Felicia Chou told CNN in an email.