After 19 eventful years, both for astronomy and for itself, NASA has finally said goodbye to the Hubble Space Telescope.

Early Tuesday morning, space shuttle Atlantis astronauts undocked the telescope from the shuttle's cargo bay.

Mission Specialist Megan McArthur held on with the robotic arm as the orbiting observatory gently drifted away.

When it reached an optimal distance at 8:57 a.m. EDT, as both shuttle and telescope hovered over North Africa, she let go and the telescope went off on its own, never again to be touched by human hands.

"Hubble has been released," reported commander Scott Altman. "It's safely back on its journey of exploration as we begin steps to conclude ours. Looking back on this mission, it's been an incredible journey for us as well."

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"It's wonderful to see Hubble, the most famous scientific instrument of all time, newly upgraded and ready for action thanks to you," Mission Control in Houston radioed back.

The shuttle astronauts spent the rest of the afternoon inspecting Atlantis' exterior to make sure it hadn't been hit by space junk.

The telescope's unusually high orbit had placed the shuttle and its crew at increased risk and, because of the lack of a refuge, prompted NASA to keep space shuttle Endeavour on standby as a rescue ship until Atlantis' 11-day mission ends Friday.

Five spacewalks over as many days encountered some stuck bolts and mismatched parts, but were overall extremely successful, with the installation of two new scientific instruments, the fixing of two broken ones and much general maintenance.

"It's a little bittersweet that it's over," telescope repairman Michael Massimino said late Monday after the final spacewalk.

"The big drama's coming," teased pilot Gregory Johnson. "Landing, baby."

NASA says the handyman mission not only fixed Hubble, but ensured it will last five to 10 more years and unlock even more mysteries of the cosmos.

There will be no more repair missions to Hubble. Sometime after 2020, NASA will send a robotic spaceship to steer Hubble back into the atmosphere and a watery grave in the Pacific.

Despite Hubble's eventual fate, the "110 percent successful mission," as one scientist on the ground put it, was a bright clear spot in an otherwise muddled outook for NASA.

The space agency is in virtual limbo, having been without an official leader for four months, and its once-firm agenda for the next decade is under review by an independent team appointed by President Obama.

Obama could conceivably scrap the entire Constellation program -- an ambitious plan, spurred by President George W. Bush, to get Americans back on the moon by 2020 and from there to go on to Mars.

When the Hubble Space Telescope went into orbit in 1990, the shuttle program was recovering from the 1986 Challenger disaster and was entering more than a decade of smooth operation.

But badly engineered optics on Hubble meant that the telescope couldn't operate as planned.

It wouldn't be for another three and a half years before a wildly successful shuttle mission fixed the main mirror, and the orbiting observatory's amazing images began to be transmitted to the ground.

And the sudden loss of shuttle Columbia upon re-entry in 2003 showed how old and creaky the shuttle program, which began development under President Nixon in the early 1970s, had become.

The Ares rockets and Orion crew capsules, larger and more powerful updates on the Saturn rockets and Apollo spacecraft that flew to the moon, are meant to replace the three remaining space shuttles.

But the Ares rockets are behind schedule and over budget, and some space experts think their jobs could be done more cheaply and easily by existing launchers.

The Associated Press contributed to this report.