Last Hubble Rendezvous

During five successful space walks, astronauts repaired and rejuvenated the space telescope.

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By Ron Cowen, Science News

A group of astronauts-cum-repairmen bid a final adieu to the Hubble Space Telescope at 8:57 a.m. EDT on May 19. Using the robotic arm on the space shuttle Atlantis, Megan McArthur lifted Hubble high above the shuttle’s cargo bay and released it. Thirty-one minutes later, Atlantis fired its thrusters to increase its separation from Hubble.

Five space walks had been the last servicing call for the 19-year-old orbiting observatory. The 11-day servicing mission, scheduled to return astronauts to Earth on May 22, almost never happened. NASA canceled the mission early in 2004 after the Columbia shuttle disaster only to reinstate the trip under a new administrator and after public outcry.

During the space walks astronauts essentially turned Hubble into a new, state-of-the-art observatory. The crew installed two new instruments: A wide-field camera with infrared sensors that will enable the observatory to see assembling galaxies further back in time than ever before; and a spectrograph that will break ultraviolet light up into its component wavelengths and allow astronomers to view supernova remnants, trace the birth of young stars and record superclusters of galaxies, the largest structures in the universe.

Just before re-entering the shuttle airlock on May 18 after the final Hubble space walk, astronaut John Grunsfeld called the successful space walks "a tour de force of tools and human ingenuity.… On this mission, we tried some things that some people said were impossible.”

The impossible included repairing two old instruments that had never been designed to be fixed in space, the Advanced Camera for Surveys and the Space Telescope Imaging Spectrograph. The camera, which has taken some of Hubble’s most spectacular images, stopped working in 2007. On May 16, Grunsfeld and his partner Andrew Feustel removed 32 screws from an access panel to replace the camera’s four circuit boards and install a new power supply — all while wearing bulky, pressurized gloves and with a strut blocking a direct view of the task.

The next day, another team, Mike Massimino and Mike Good, repaired the spectrograph, attaching a “capture plate” over the instrument’s electronics access panel and then using a power tool to remove 111 screws. Massimino and Good then removed a failed power supply card and inserted a new one, covering the electronics cavity with a much simpler panel.

The crew also replaced two aging battery modules on Hubble, each weighing 210 kilograms (460 pounds) and containing three batteries. The batteries provide power to Hubble during the night portion of its orbit.  

Astronauts also replaced three deteriorating thermal blankets with new stainless steel panels to cover Hubble’s most vulnerable spots. The crew installed six new gyroscopes, which are used to change the orientation of the telescope and keep it precisely fixed on a celestial target.

The updates should keep Hubble healthy and sending pictures back to Earth for five more years. And now astronomers are looking forward to seeing what the rejuvenated Hubble can do. Grunsfeld, who is also an astronomer, put it this way: “I want to wish Hubble its own set of adventures and, with the new instruments that we’ve installed, that it may unlock further mysteries of the universe."   

It will take about five to six weeks to check out and recalibrate the two repaired instruments, and nine to 10 weeks for the new camera and spectrograph, says Hubble senior project scientist David Leckrone of NASA’s Goddard Space Flight Center in Greenbelt, Md. The first new images and spectra will likely be released in early September, he said.