James Webb Space Telescope gets ready to gaze deep into the universe
JWST's unprecedented scientific power is partly a function of the size and extreme sensitivity of its primary mirror, which collects the images from space. The gold-plated mirror is 21 feet in diameter, giving a collecting area of 273 square feet.
JWST has 132 tiny electric motors dedicated to mirror control and each mirror segment requires seven small motors — six to change position and one central motor to adjust the radius of curvature.
An array of features
JWST also has a microshutter array, a grid of 248,000 doors (each 0.004 inch by 0.008 inch) that can be opened or closed to let in light from a particular object in space while blocking light from other objects.
JWST collects infrared (heat) radiation, which has a wavelength longer than visible light but shorter than radio waves. Infrared radiation can pass more freely through regions of cosmic gas and dust,
and perhaps allow JWST to observe the formation of new planetary systems normally shrouded in fine particles.
Infrared radiation traveling from the target object in space is collected by the primary mirror, reflected onto the smaller secondary mirror and then directed into one of four scientific instruments which may focus, filter, or disperse the light.
Infrared radiation traveling from the target object in space is collected by the primary mirror, reflected onto the smaller secondary mirror and then directed into one of four scientific instruments which may focus, filter, or disperse the light.
Four instruments are necessary because some are more suitable than others for observing specific types of objects such as planets, stars, nebulae and galaxies.
JWST has to operate at extremely low temperatures. One of the instruments needs to be held at a temperature of -447 degrees Fahrenheit, a mere 58 degrees above absolute zero.
It uses a huge sunshield 69.5 feet by 46.5 feet to block heat and light from the Sun, Earth and Moon. Further cooling is provided by a cryocooler, a refrigerator based on helium.
Control and monitoring of the telescope is carried out by a team of technicians sitting in front of dozens of screens in the high-tech hub at the Space Telescope Science Institute (STScI) in Baltimore