The James Webb Space Telescope, touted the most powerful ever built, has had its sole secondary mirror installed at the Goddard Space Flight Center of NASA last March 3. This is the latest update on what is poised to be the premier space observatory of the next decade.
A collaboration among NASA, the European Space Agency, and the Canadian Space Agency - the JWST is a large infrared space telescope with a 6.5-meter (21 feet) primary mirror. It will be launched on an Ariane 5 rocket from French Guiana in 2018 in aims of imaging the first galaxies formed and studying planets surrounding distant stars.
The equipment boasts of a primary mirror of 18 separate segments unfolding and adjusting post-launch and made up of ultra-lightweight beryllium. JWST’s largest component is a tennis court-sized, five-layer sunshield, attenuating the heat of the sun more than a million times. Its four cameras and spectrometers, too, feature detectors that can record highly faint signals.
Now, since the telescope has an excessively large and final shape to fit into a rocket, engineers have targeted a design where it will unfold in origami fashion – a deployment that involves its mirrors.
According to NASA, the perfectly rounded secondary mirror garners support from three struts – nearly 25 feet in length, yet remain strong and lightweight – extending out of the primary mirror. These are hollow composite tubes that can withstand extreme space temperatures.
“The quality of the secondary mirror surface is so good that the final surface at cold temperatures does not deviate from the design by more than a few millionths of a millimeter - or about one ten-thousandth the diameter of a human hair,” says the space agency.
Beryllium makes up the secondary mirror just like all the separate segments, as it is stiff, lightweight, and stable at cryogenic temperatures. But since its bare form does not greatly reflect near-infrared light, each mirror was coated with gold to reflect infrared light, something that the Webb telescope cameras see.
The primary mirror, intended to gather faint light from the first and most distant galaxies, was completed when the last segment was installed Feb. 4 this year.
All the mirrors were constructed by Ball Aerospace & Technologies Corp., part of the main industrial partner Northrop Grumman. After launch, the Space Telescope Science Institute will operate JWST, which was formerly known as the Next Generation Space Telescope, but was renamed in 2002 after a former NASA administrator.
Also helping unlock the secrets of the universe is the Wide-Field Infrared Survey Telescope (WFIRST), to be launched in mid-2020s to obtain views that are 100 times larger than those of the Hubble Space Telescope.
The mission, green-lighted in February, will also help scientists unravel the mystery of dark matter, which is invisible yet thought to account for 85 percent of the universe. It is believed to dominate thousands of satellite galaxies that could be buzzing through or around the Milky Way.
