Hubble’s ‘grand finale’ set

Edwin Hubble revolutionized the understanding of the universe with his discovery that our own Milky Way was just one among innumerable galaxies. His namesake, the Hubble Space Telescope, has carried on his work for almost 20 years, providing unprecedented views of unimaginably distant places. On Monday, the space shuttle Atlantis is to take off on an 11-day mission to give the Hubble a final, major tune-up before its eventual replacement is launched in 2014.

A clear view

Scientists had long wanted to have a way of making telescopic observations of space without the interference of the earth’s atmosphere.

Design of the Hubble began in the 1970s as a joint project of NASA and the European Space Agency. It was only after the Hubble reached orbit 350 miles above earth in April 1990 that they made the embarrassing discovery that the mirror had a tiny but fundamental flaw, resulting in blurry images. The first shuttle mission to service the Hubble followed in 1993, and astronauts were able to install smaller mirrors that compensated for the defect, allowing the telescope to be used to its full potential.

Lots to do

In addition to the original repair trip in 1993, there have been two Hubble servicing missions. The last was in 2002, and the seven years since then have taken their toll. A data router failed last fall, meaning Hubble’s instruments rely on a single backup. Only two are fully functional: the Wide-Field Planetary Camera 2 and the fine guidance sensors, which measure star positions.

Hubble’s main camera lost two of its three channels to mechanical failure in 2006; a spectrograph failed in 2005; and an infrared camera has not worked since last fall.

The Hubble also needs routine maintenance: replacement of its batteries and gyroscopes.

Hubble’s greatest hits

A panel of distinguished astronomers said the Hubble “has arguably had a greater impact on astronomy than any instrument since the original astronomical telescope of Galileo.” Among its achievements:

> Provided the observations needed to accurately determine the rate of expansion of the universe, showing it to be 12 to 14 billion years old.

> Found strong evidence that the expansion of the universe is accelerating.

> Provided visual proof of the theory that young stars are surrounded by disks of dust and gases, the raw materials from which planets form.

> Made observations that added credence to the theory that there are supermassive black holes at the cores of galaxies.

> Sent back to earth what have become iconic images of space, including the vast Eagle Nebula.

Canceled, then revived

Monday’s scheduled mission almost didn’t happen. Planned long ago, it was canceled after the 2004 Columbia shuttle disaster because the course to be flown by the Atlantis will take it too far from the international space station to allow the astronauts to take shelter there if something goes wrong.

The mission was reinstated in 2006. The shuttle Endeavour will be standing by on a launch pad in case a rescue mission is needed.

The $1.4 billion mission is still fraught with risk. The astronauts will have to make five spacewalks, in some cases replacing hard-to-reach parts that were never designed to be worked on in space. If they fail, commander Scott Altman told USA Today, the Hubble will become “a piece of space junk.”

Meet the crew

Making the trip will be three shuttle veterans —- the commander, Scott Altman, and mission specialists John Grunsfeld, an astronomer; and Mike Massimino, a mechanical engineer —- and four rookies —- pilot Gregory C. Johnson and mission specialists Michael Good, an Air Force colonel; Megan McArthur, an oceanographer; and Andrew Feustel, a geologist.

Replacement to come

With the shuttles set to retire in 2010, this will be the final chapter for the Hubble. David Leckrone, the Hubble project scientist, calls it the “grand finale of the Hubble symphony.”

But a replacement is on the way: In 2013, NASA is scheduled to launch the James Webb Space Telescope, with a mirror almost three times the size of Hubble’s. Designed to detect light in the infrared spectrum, it will need to operate at near absolute zero degrees, with an orbit in the frigid reaches of space a million miles from earth. Among its expected capabilities is the detection of distant solar systems that, like ours, have the chemical building blocks of life.

Sources: New York Times, NASA, Associated Press, Georgia Tech

Compiled by A-section editor Bill Steiden