NASA Astronauts Finish Hubble Space Telescope Repairs

NASA astronauts aboard the shuttle Atlantis finished repairs and upgrades to the Hubble Space Telescope today, part of a mission to extend the orbiting observatory’s life by five years.

During the last of their mission’s five spacewalks, astronauts Andrew Feustel and John Grunsfeld replaced the second of two 460-pound (209-kilogram) battery modules, which provide power to the telescope when its solar arrays aren’t exposed to the sun.

They also swapped out one of Hubble’s three Fine Guidance Sensors, used to aim the telescope and measure the position and location of stars, and installed a new thermal protection blanket on the observatory.

Atlantis’ Hubble service trip, the first for a shuttle since 2002, is the last scheduled repair mission for the telescope, a joint venture of the National Aeronautics and Space Administration and the European Space Agency. Hubble, launched in 1990, provides data used by astronomers worldwide.

“This is a really tremendous adventure that we’ve been on, a very challenging mission,” Grunsfeld, a former chief scientist for NASA, said near the end of today’s seven-hour spacewalk, broadcast live on NASA Television. “Hubble isn’t just a satellite, it’s about humanity’s quest for knowledge.”

Extending Hubble’s Life

NASA says the upgrades will extend Hubble’s life to 2014 and help it peer deeper into the universe and capture images closer to the time of the Big Bang. A replacement, the James Webb Space Telescope, is scheduled for launch in 2014.

The school-bus-sized Hubble has become a symbol of U.S. technological achievement during its 19 years in space. On average, 14 scientific articles are published every week from information it provided.

One exposure revealed 10,000 galaxies formed shortly after the Big Bang, the cosmic explosion that scientists say marked the origin of the universe. The telescope also has viewed the evaporating atmosphere of a planet and shot high-resolution, ultraviolet images being used to detect oxygen-rich moon minerals.

During four previous spacewalks of the Atlantis mission, astronauts replaced a camera, the first set of batteries, the gyroscopes that help control Hubble and a computer that sends commands to instruments and formats data for transmission. They also installed a new scientific instrument and repaired two others.

Tools and Ingenuity

Grunsfeld called the servicing mission a “tour de force of tools and human ingenuity.”

“The only way of finding the limits of the possible is by going beyond them into the impossible,” Grunsfeld said. “On this mission, we tried some things that some people said were impossible. We’ve achieved that and we wish Hubble the very best.”

Atlantis, which lifted off on May 11, is scheduled to release the telescope tomorrow and land on Earth on May 22. NASA engineers have cleared the shuttle for return even though astronauts discovered small dents in the heat shield on a wing as it headed for its rendezvous with Hubble.

Hubble’s observations are expected to resume three weeks after the shuttle leaves.

Rendezvous around the Moon

Exactly 40 years ago, Apollo 10 blasted off Earth; its mission in the words of Commander Tom Stafford "to sort out the unknowns and pave the way for a lunar landing". Continuing his series of essays marking the 40th anniversary of the moonshots, Dr Christopher Riley reflects on Nasa's method for landing on the Moon and the Apollo legacy of space rendezvous.

In May 1969, with only seven months to go before the end of the decade, the first Lunar Module to fly in orbit around the Moon was powered up and readied for undocking from the Command Module.

Astronauts Tom Stafford, John Young and Gene Cernan were about to test out a technique for lunar landing which had first been proposed in 1916 by a Russian mechanic called Yuri Kondratyuk.

Kondratyuk's thesis described how a small landing craft could leave a mothership in lunar orbit to ferry its crew to the surface and back - a technique later referred to as Lunar Orbit Rendezvous or LOR.

Forty years after Apollo it's easy to see this method of landing a man on the Moon as the only way it could have been done. But the idea of bringing two vehicles together in space above the Moon had originally been rejected outright by Nasa as simply too difficult.

In 1961, with Kennedy's challenge still ringing in their ears, the agency had favoured a far simpler approach.

From the 1950s, the principal concept for a flight to the Moon involved a streamlined rocket blasting vertically off the Earth, flying straight there and then landing vertically tail first on a column of rocket thrust.

After lunar exploration was completed, it would then perform a similar vertical launch from the Moon and a final vertical landing back on Earth.

Popular in both science fiction and with military feasibility studies at the time, this "Direct Ascent", as it was dubbed, also seemed an obvious solution for Apollo.

But Direct Ascent was not as straight forward as it first appeared. It would need a completely new and truly immense rocket called the Nova to do the job; twice as powerful as the Saturn V and perhaps as tall as the Empire State Building. Secondly, no-one really knew how the astronauts, sitting near the top, could land a very tall rocket on the lunar surface tail first.

Rocket pioneer Wernher von Braun had been championing an alternative concept called Earth Orbit Rendezvous (EOR) since his US Army days in the late 1950s.

His method would eliminate the need for one giant rocket, requiring instead a number of relatively smaller Juno V booster rockets, later to be known as Saturn Vs.

These would launch into orbit the collective hardware necessary to assemble a giant vehicle to travel on to the Moon and return to Earth.

But whilst EOR solved the problem of building a giant rocket on Earth, the difficulty of landing it on the surface of the Moon remained.

In addition, multiple Saturn V rocket launches would be needed for each Moon shot and so EOR would be expensive.

What von Braun and the others had missed was that it was not necessary for the entire spacecraft to land on the Moon. This had been Kondratyuk's breakthrough thought.

Last Hubble rendezvous

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.