Each of the seven NASA astronauts set to launch to the Hubble Space Telescope next week has a favorite view of the universe courtesy of the long-lived observatory, adding some extra motivation to their vital orbital repair mission.

Veteran commander Scott Altman and his crew are poised to rocket toward Hubble on May 11 aboard the space shuttle Atlantis to overhaul the iconic telescope for the fifth and final time. If all goes well, the tricky 11-day mission – which includes five back-to-back spacewalks and some unprecedented repairs – will extend Hubble's cosmic scan of the universe through at least 2014.

"I remember when I was a kid going outside and looking up at the stars and going, 'Wow, I wonder what's out there,'" Altman said in NASA interview. "Hubble is a tool that can take you out there to those distant galaxies, those pictures that come back ... I think it connects with people on a very visceral level."

Since its launch in 1990, Hubble has collected more than 880,000 observations and taken over 570,000 images of about 29,000 celestial objects in the universe. Altman and his crew took some time recently to review their all-time favorite images from Hubble's ongoing mission to peer into the cosmos:

Of Mice and astronauts

Of the mountain of images beamed to Earth by Hubble, Altman holds the telescope's view of two colliding juggernauts - nicknamed the "Mice galaxies" - as his personal favorite.

Taken in 2002 just after Altman led NASA's most recent Hubble servicing mission STS-109, the image shows the two galaxies - each sporting a long tail (hence the nickname) - as they close in on one another some 300 million light-years from Earth in the constellation Coma Berenices, or Berenice's Hair.

"Just thinking about that being out there amazes me," Altman said, adding that behind the two colliding galaxies are some 1,500 other distant galaxies, each with a billion or so stars. "You start thinking, this is a soda straw slice of the night sky with a number that's huger than I can really comprehend of other galaxies with billions of stars in each one of them. And I'm saying, wow, this is a big place we live in."

Hubble used its then-new Advanced Camera for Surveys, which is now in need of repair, to take the snapshot.

Gaze of the Cat's Eye

Hubble's stellar views of the Cat's Eye nebula, a distant planetary nebula first spotted by the telescope in 1994, take center stage for Atlantis pilot Gregory C. Johnson.

"Obviously we launched Hubble in 1990, we fixed its optics in '93 and in 1994 they found this nebula outside of our galaxy," Johnson said. "The picture is just astounding."

The Cat's Eye nebula is also known as NGC 6543 and sits about 3,000 light-years from Earth in the constellation Draco. The nebula's concentric rings are the result of eruptions of mass ejected away from its central star every 1,500 years or so.

An image unseen

For U.S. Air Force Col. Michael Good, part of the four-man spacewalking team that will perform the upcoming Hubble repairs, the pinnacle of the telescope's cosmic vision used to be the Ultra Deep Field.

Compiled over the course of 400 orbits between September 2003 and January 2004, the Ultra Deep Field is a portrait of some 10,000 galaxies in a patch of sky in the constellation Fornax. The image revealed galaxies that emerged just 700 million years after the theoretical Big Bang.

"It's probably not the most beautiful image out there," said Good, who added they it was what the image represented that struck him. "To literally be looking at the first light of the universe, I think that's a pretty interesting and pretty amazing capability."

But as launch day nears, Good said recently that he has a new top pick for Hubble's finest.

"My answer now is going to be the next image. The next image we get from the telescope after we leave," Good told reporters in a recent briefing. "That'll be my favorite."

The Hubble library

Shuttle robotic arm expert Megan McArthur, who will use Atlantis' robotic appendage to pluck Hubble from its orbit so it can be fixed, has said she's also fond of the telescope's views of the Ultra Deep Field and the Cat's Eye nebula.

But the sheer wealth of data and imagery collected by the telescope's camera eye over the last 19 years is much richer than a single snapshot, she added.

"I think that, in general, almost every picture I see is my favorite," she told reporters recently. "They're all just awe-inspiring to me. I really can't pick just a single one."

Tadpoles in space

Hubble's spacewalk repair chief John Grunsfeld, a self-labeled "Hubble hugger making his fifth spaceflight and third trip to the telescope, said the image closest to his heart is a 2002 snapshot of a pair of galaxies caught in the act of colliding.

The image depicts the Tadpole galaxy, known as UGC 10214, which Hubble spotted after it had been walloped by a smaller galaxy that gave it a trademark tail that stretches 280,000 light-years away from the collision. The image was one of the first released after Hubble's 2002 service call, which Grunsfeld also flew on.

"That was one of the first released images after we put the Advanced Camera for Surveys in on our last mission," said Grunsfeld, who will perform three of the five spacewalks to upgrade Hubble this month. "I'm looking forward to the early release images from this mission."

The cone of success

Veteran Hubble spacewalker and repairman Michael Massimino has tapped the Cone Nebula as his choice for the space telescope's greatest hit. Like the Mice galaxies and the Tadpole galaxy, it was among the first images following Hubble's STS-109 servicing flight in 2002, which Massimino participated in with Grunsfeld and Altman.

The Cone Nebula, or NGC 2264, sits about 2,500 light-years from Earth in the constellation Monoceros and earned its nickname from its conical appearance in ground-based images. The nebula is vast, stretching across 7 light-years in length, but the Hubble image released in 2002 revealed only its upper 2.5 light-years.

"I liked it because it was beautiful, but also because we put the camera in correctly," Massimino said in a recent briefing. "It all worked and we didn't break anything, and that was our final validation that the job we did on STS-109 was a good one."

Hubble's birthday snapshot

Until recently, first-time spaceflyer Andrew Feustel said that visions of the Eskimo and Ant nebulae were his favorite views from Hubble. But that changed last month when NASA unveiled the Cosmic Fountain, a new image from the observatory's Wide Field Camera 2 to celebrate the telescope's 19th birthday.

The image revealed three interacting galaxies that resulted in a fountain-like object dubbed Arp 194. It sits about 600 million light-years from Earth in the constellation Cepheus.

Feustel said he was so impressed by the image, which resembles a cosmic question mark or fountain, he immediately set it as the desktop wallpaper for his computer.

"It's pretty spectacular and I think it's Hubble's way of asking us what's next," Feustel said. "I'm curious to see what's next as well."

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