Five days of work on the orbiting Hubble Space Telescope should end Tuesday morning with the release of what one astronomer said is "in many ways ... a brand new telescope."
"At this point, Hubble actually has the largest complement of functioning instruments it has ever had" since its launch in 1990, said Mario Livio, senior scientist at the Space Telescope Science Institute in Baltimore. "This is going to be an observatory that is just so much more powerful and more promising."
The crew of the shuttle Atlantis was to release the telescope just before 9 a.m. Tuesday. After further tests, the first images demonstrating the capabilities of the new and repaired instruments are due late this summer.
But, at first blush, it appeared that nearly everything the astronaut/mechanics set out to do was accomplished, despite a succession of stuck bolts, balky latches and dead batteries on a power tool.
"At some level, you are extraordinarily impressed when things go as well as they do," Livio said. "But you are even more impressed when they manage to overcome unexpected obstacles and still get everything done. ... It is absolutely amazing."
If continuing tests prove all the new and repaired components are working as designed, Hubble is expected to extend astronomers' view deeper into the universe than ever before, and farther back toward the beginning of the evolution of stars and galaxies.
NASA also hopes new gyroscopes, batteries and other new gear will extend the observatory's lifetime for at least five more years.
The mission's apparent success may also help to preserve as many as 900 jobs in Maryland that are tied in whole or in part to the telescope's well-being.
As he prepared to bid Hubble farewell and float back into the shuttle's air lock, spacewalker John Grunsfeld - veteran of two previous Hubble repair missions - paused to pay tribute to all who had a hand in the telescope's success.
"This is really a tremendous adventure that we've been on," he said. "Hubble isn't just a satellite. It's about humanity's quest for knowledge."
He mentioned the late astrophysicists Lyman Spitzer and John Bahcall, who conceived the idea of an orbiting telescope, and saw it to fruition. He credited the work of living Hubble scientists, leaders and team members. He mentioned Sen. Barbara Mikulski of Maryland, whose advocacy helped marshal the political support and funding for a fifth servicing mission, which had been canceled in the wake of the 2003 Columbia shuttle accident.
"On this mission, we tried things that many people said were impossible," Grunsfeld said. "We've achieved that, and we wish Hubble the very best."
Four Atlantis spacewalkers and their crew mates installed two new scientific instruments and repaired two others that had broken down since the last servicing mission in 2002.
One of the few disappointments was the discovery after Saturday's repairs to the Advanced Camera for Surveys (ACS) that the camera's high resolution channel is still not functioning. But Livio said a second channel that failed in 2007 is working again, and so the more important goal of the repair was accomplished. "The wide-field channel is back," he said, "and that is actually the most widely used, so we're ... extremely happy with this result."
The new Wide Field Camera 3 installed last Thursday is expected to push astronomers' view closer to the limits of time and space. "We have seen galaxies back to a time when the age of the universe was about 750 million years," Livio said. "We will now see galaxies [as they were] when the universe was about 500 million years old."
"It gets us closer to the very first galaxies that formed" after the Big Bang more than 13 billion years ago. Those first galaxies will be the quest of the James Webb Space Telescope, targeted for launch in 2014.
Hubble's sharpened vision is also expected to reveal exploding stars, called supernovae, 8 to 11 billion light years away. They will appear as they were before the expansion of the universe began to accelerate, helping scientists get a better handle on the mysterious "dark energy" thought to be responsible for that acceleration.
The Cosmic Origins Spectrograph, installed on Saturday, will enable astronomers to use light from distant quasars to study and map the sparse, weblike intergalactic medium between galaxies. The repaired Space Telescope Imaging Spectrograph will go back to work helping astronomers study the chemistry of the atmospheres of planets circling other stars.