Taking the shot ...

The James Webb Space Telescope will travel 1.5 million kilometres from Earth and look back thirteen billion years.Illustration by Jonathan Djob Nkondo

The Webb, long delayed and way over budget will, if successfully deployed, change how man views the universe.

Twenty-five years and ten billion dollars in the making, the James Webb Space Telescope will enable scientists to see deeper into the past than ever before.

Next month, the James Webb Space Telescope is scheduled to take a slow boat from Los Angeles, spend a few days traversing the Panama Canal, and arrive at a spaceport in Kourou, French Guiana. The telescope will have been twenty-five years and ten billion dollars in the making. Thousands of scientists and engineers from fourteen countries will have worked on it. It could have flown, sure, but it’s a tight squeeze—plus the telescope weighs seven tons, and Kourou’s airfield is connected to its spaceport by seven bridges not built to endure such a load. The telescope will be put into Ariane 5, a European rocket named for a mythical princess who helped a man she loved defeat the Minotaur and escape a maze. Ariane 5 will carry the telescope some ten thousand kilometres in thirty minutes. The J.W.S.T. will then continue on its own, for twenty-nine days, toward a lonely, lovely orbit in space, about 1.5 million kilometres from Earth, where we will never visit it, though it will stay in constant communication with us. From Earth, it will appear ten thousand times fainter than the faintest star.

On its way, the telescope will slowly unfurl five silvery winglike layered sheets of Kapton foil, about as large as a tennis court. These sheets, each thinner than notebook paper, will function as a gigantic parasol, protecting the body of the telescope from the light and the heat of the sun, moon, and Earth. In this way, the J.W.S.T. will be kept nearly as dark and as cold as outer space, to insure that distant signals aren’t washed out. Then eighteen hexagons of gold-coated beryllium mirror will open out, like an enormous, night-blooming flower. The mirrors will form a reflecting surface as tall and as wide as a house, and they will capture light that has been travelling for more than thirteen billion years.

This is the hope, at least.

There's no safety net

There will be no way to go out and fix the J.W.S.T. if anything goes wrong. It’s too far away. Although it’s difficult to imagine such a complex project succeeding, it’s also difficult to imagine that humans have flown a little helicopter on Mars, or that our cell phones speak to satellites in the sky, which then tell us where we are on the Brooklyn-Queens Expressway. If you were a sky-watcher in the past, you might have looked for the stars to tell you something about your love life, your luck, your finances, or whether or not you should invade Prussia. You might watch to know how to steer your ship, or when to plant your quinoa. What are we looking for now?

The Webb

Infrared differs from visible, the Webb's prime differentiator from the Hubble.

Comparison of the Carina Nebula in visible light (left) and infrared (right), both images by Hubble. In the infrared image, we can see more stars that weren't visible before. Credit: NASA/ESA/M. Livio & Hubble 20th Anniversary Team (STScI)

Overall size comparison of Webb and Hubble. Credit: GSFC

Webb will have an approximately 6.5 meter diameter primary mirror, which would give it a significantly larger collecting area than the mirrors available on the current generation of space telescopes. Hubble's mirror is a much smaller 2.4 meters in diameter and its corresponding collecting area is 4.5 m2, giving Webb around 6.25 times (see calculation) more collecting area! Webb will have significantly larger field of view than the NICMOS camera on Hubble (covering more than ~15 times the area) and significantly better spatial resolution than is available with the infrared Spitzer Space Telescope.

Webb's sunshield is about 22 meters by 12 meters (69.5 ft x 46.5 ft). It's about half as big as a 737 aircraft. The sunshield is about the size of a tennis court.

Webb will orbit the sun 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point or L2. (Note that these graphics are not to scale.)

Taking the shot indeed.