"We're one step closer to uncovering the mysteries of the universe. "Webb, welcome home!" said NASA Administrator Bill Nelson in a statement. It will also scan the atmospheres of other worlds for possible signs of life.īefore going into operation, however, the 18 hexagonal segments of the telescope's gold-coated 21-foot (6.5-meter) diameter primary mirror must be precisely aligned with one another. The telescope will have a view of almost half the sky at any given moment
Scientists hope the telescope, which will ultimately cost some $10 billion (€8.8 billion) altogether, will make observations that can provide clues as to the origins of the universe. That is a place where the gravitational forces of the sun and Earth balance each other, meaning that the telescope needs little energy to avoid falling into the gravity well of either heavenly body. The telescope, which was launched from French Guiana on Christmas, is now in orbit at the so-called second Lagrange point.
The trip to the designated orbit point - more than four times further away than the moon - has taken a month. You can read more about the positioning system at the NASA FAQ.The James Webb Space Telescope on Monday reached the spot 1 million miles (1.6 million kilometers) from Earth from where it will begin peering back to the time when the first stars and galaxies were forming 13.7 billion years ago. To power its various moving parts, James Webb has its solar array, capable of providing 2 kW, twice the needed amount. Star trackingįinally, to ensure a perfect pointing, one of Webb's four instruments, NIRISS, is equipped with a "Fine Guidance Sensor" which "locks" the telescope on a target by observing the exact position of a star in its field of view.Įdit thanks to Hammen: In addition to the Fine Guidance Sensor, the JWST also has a few regular star trackers. Unlike Hubble's gyroscopes, however, which are mechanical, Webb uses Hemispherical Resonator Gyroscopes, which have no moving parts susceptible to wear, instead measuring the precession of vibration patterns in a crystal. GyroscopesĪdditionally, Webb has six gyroscopes which tell the telescope which direction it's currently pointing, and how fast it's turning. This causes angular momentum to build up, which must occasionally be dumped by firings Webb's thrusters once per week or so ( JWST Momentum Management). To maintain its position, this is counteracted by adjusting the spin of the reaction wheels. Changing the angular speed of one of the action wheels causes Webb to change its direction along that wheel's axis.Įdit thanks to While James Webb observes, the photon pressure of the Sun's light exerts a torque on the telescope. These wheels rotate constantly, thus storing a large amount of angular momentum to keep the telescope steady. At least three are needed, but James Webb has six more allows for easier control, but are also heavier. To acquire a target, James Webb (and other space telescopes) uses a number of reaction wheels, one for each "axis". A nearby exoplanet and a distant galaxy are both "infinitely far away" for observing purposes (although of course in general more distant object are fainter). Note that the distance to the target is irrelevant. Fuel is used for maintaining its orbit around L2, and was also used three times on its journey to L2, as "corrections burns". It's true that James Webb carries fuel, and you're right that it is not used for positioning, at least not directly (see below).
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