Within Hubble, a Plethora of Instruments
Monday, May 11, 2009; 2:48 PM
CAPE CANAVERAL, Fla., May 11 -- With all systems go for a 2:01 p.m. launch of the space shuttle Atlantis on the final servicing mission to the Hubble Space Telescope, a key fact keeps popping up: The Hubble is not a single instrument. It's an agglomeration of instruments. It's a big, cavernous spacecraft capable of housing an ensemble of devices.
If the Hubble were a TV show it would be like "Cheers" or "Hill Street Blues," with each instrument/character bringing eccentricities and subplots to the narrative.
The instruments have been in the media spotlight in the 24-hour countdown to Monday afternoon's scheduled launch of the shuttle Atlantis, with engineers and scientists extolling the virtues of the gadgets and aerospace companies passing out gadget-glorifying press packets.
Consider, for example, the Wide Field and Planetary Camera 2, the subject of an hour-long briefing Sunday by some of NASA's top scientists. The WFPC2 -- "Wiff-pick 2," in NASA vernacular -- captured many of the images that made the Hubble famous. It is now going to be swapped out (replaced by Wiff-pick 3) and lugged back to Earth aboard the shuttle. It will then have a valedictory scientific moment, as NASA plans to study the abundance of micrometeorite impacts on a surface of the instrument that has been exposed to space for 15 years.
Ed Weiler, NASA's head of space science, recounted the bust-and-boom history of the Hubble, and said that this one camera was essentially what saved the telescope.
The telescope had -- and still has, to this day -- a flawed mirror. Although the mirror is perfectly smooth, Weiler said, "It was also perfectly wrong. It had the wrong curve." The announcement of the "spherical aberration" was humiliating for NASA and for a time made Hubble a symbol of incompetence.
But then came the first Hubble repair mission, in 1993, and astronauts swapped the original WFPC with a new version that had its own "flaws" that precisely canceled out the mirror's aberrations. Since then, 50 to 60 percent of all of Hubble's scientific work has been done with the WFPC2, Weiler estimated.
The camera took the iconic Eagle Nebula image known as the "Pillars of Creation." It photographed Comet Shoemaker-Levy breaking up and colliding with Jupiter. It was used for the Hubble Deep Field image that captured the light of thousands of oddly shaped galaxies from the early universe.
The final assignment for the camera has been to photograph a beautiful planetary nebula, Kohoutek 4-55, an exploded red giant star, its galaxy-like structure glowing in red, green and blue, like a gem found in space.
"It's time to retire it. It's time for it to come home," said John Trauger, the principle investigator for the camera. "We're going to celebrate."
Each Hubble instrument has its own purpose, design, personality and supporting cast (scientists, engineers, bureaucrats, aerospace executives) back on Earth.
One new instrument aboard the shuttle and bound for the Hubble is the Cosmic Origins Spectrograph. The question it will address is a grand one, as framed by principle investigator Jim Green of the University of Colorado: "What's the large-scale structure of the universe?"