Wednesday, August 31, 2011

Who are we?

I wrote here recently about the James Webb Space Telescope, the successor to the Hubble, now under construction. It will have a mirror three times the diameter of the Hubble, providing unprecedented views of the cosmos.
If it's ever successfully deployed. The initial cost estimate of $1.6 billion has soared to $6.5 billion -- and counting -- and I've written before about the hair-raising difficulties of putting the scope on station. Even the biggest fan of the project might have qualms about making such a risky bet that could cost $10 billion of the taxpayer's money, and this in the face of a rising tide of right-wing sentiment for blinkered anti-science and minimal government.
Tracy Vogel of the Space Telescope Science Institute sent me the following description of the Webb, a longer (and slight edited) version of the script for a video.
The Webb telescope’s primary mirror is 21.3 feet across, with about seven times the collecting area of the Hubble Space Telescope. Webb’s resolution will be three times more powerful than Hubble’s at infrared wavelengths. This is particularly important for science, enabling Webb to probe much farther and much more clearly into the early universe than Hubble.

Building the mirrors called for a Herculean task carried out by hundreds of people. Entirely new mirror technologies were invented to give Webb its far-reaching vision. This task involved some of the best and brightest engineers in high-tech industries and universities around the world.

The Webb’s mirror odyssey began in the Topaz-Spor Mountains of Utah. Each mirror segment is made from beryllium, mined from deep within the Earth.

Beryllium is more lightweight and stable that glass, which is traditionally used for telescope mirrors. Webb’s mirror needs to be light but also extremely strong in order to hold its shape, especially in excruciatingly cold temperatures. To collect the faint infrared light from distant galaxies, the mirror must be kept at temperatures of minus 370 degrees Fahrenheit.

The mined beryllium was converted into a powder and shipped to the Brush Wellman facility in Elmore, Ohio, where it was cast into five-foot wide hexagonal segments. The segments then traveled to Axsys Technologies in Cullman, Alabama, where they were milled to remove excess weight. This process creates a honeycomb structure on the back of each mirror.

Each segment was precisely polished to a complex curve that allows it to work in unison with the telescope’s 18-mirror array. Precise computer modeling guides the grinding and polishing of the mirrors so that they will snap into the proper curvature once placed in frigid space.

The polishing took place at Tinsely laboratories in Richmond, California. Each mirror segment was made smooth to within 1/1000th thickness of a human hair. If a segment were the size of the continental United States, the tallest “mountain” would be only an inch above the mean surface.

At NASA’s Marshall Space Flight Center in Huntsville, Alabama the mirrors were placed into a giant thermal vacuum chamber that replicates conditions in space. Engineers precisely measured the performance of the mirrors at very cold temperatures and verified that all met optical perfection.

The fully tested mirror segments are now being coated with a very thin layer of gold. Gold is needed to efficiently reflect infrared light to the telescope’s detectors. This was done at Quantum Coating Inc. in Moorestown, New Jersey.

The mirrors will next be sent back to Boulder, Colorado, to be finally mated to the mechanical actuators that will precisely control their positioning aboard the Webb telescope.

Like gluing tiles onto a wall, the mirrors will all be positioned on a giant skeletal frame at the Goddard Space Flight Center in Greenbelt, Maryland. Cameras and other instruments will be added to the rear of this “backplane.” The complete telescope optical assembly will be tested in Houston, Texas, at NASA’s Johnson Space Center.

It will then be rolled into the giant thermal vacuum chamber that was built to test the manned Apollo moon spaceships. In a giant eye exam, the performance of the entire mirror array will be checked while experiencing the conditions found in space. The tests will ensure that the telescope has picture-perfect vision.

The optical telescope assembly will then travel to Northrop Grumman Aerospace Systems in Redondo Beach, California, where a tennis court-sized sunshade will be attached to it. This giant beach umbrella will shield the telescope from unwanted infrared light, keeping the telescope mirror at low temperatures once it is placed into space.

After travelling back and forth across the United States, the telescope will be launched from French Guiana aboard the European Space Agency’s Arianne rocket to make its one-million-mile journey into space.
Anyone who is half-way curious about the universe cannot but feel a shiver up the spine and a gush of pride. The description makes it all seem fool-proof, but of course it isn't. As we learned from the Hubble, even the best-laid plans can go awry, and this time there will be no astronauts to pull a fix. Still, what a grand adventure. What a thrilling affirmation of human curiosity, the desire to know. The great gothic cathedrals consumed even larger proportions of the resources of the communities that built them; would we wish they had never been built?

Yes, $10 billion could build a lot of hospitals and schools in impoverished parts of the world. It can also build weapons of war. Every great civilization has splurged on one extravagant symbol of its greatness -- the Pyramids, the Parthenon, the Great Wall, Chartres. The Webb Telescope will no doubt be more ephemeral than those other monuments, if it succeeds at all, but it suits me fine as a symbol for a scientific civilization focused on the journey rather than the destination.