"Webb works in the infrared, which is heat radiation. "A huge advantage of deep space (like L2) when compared to Earth orbit is that we can radiate the heat away," Jonathan Gardner, deputy senior project scientist on the Webb Telescope mission, and chief of the Observational Cosmology Laboratory at NASA's Goddard Space Flight Center, said in a statement. For JWST's sunshield to be effective at this job, the observatory needs to be in an orbit where the sun and Earth are in about the same direction, which is what L2 offers. This is important because Webb's telescope primarily observes the universe in infrared light and thus needs to be shielded from any bright, hot sources, that could interfere with observations. This allows JWST's large sunshield to protect the telescope from the light and heat of the sun, Earth and the moon. The second Lagrange point is special because it enables the telescope to stay in line with the Earth as it moves around the sun. Unlike the pioneering Hubble Space Telescope, which orbits our planet, JWST will technically be in orbit around the sun. Webb's final destination is a special point in space known as the second Lagrange point, or L2, which is located approximately 930,000 miles away from the Earth in the exact opposite direction from the sun. What Next for Iconic Hubble Telescope as James Webb Poised for Launch.When NASA's James Webb Telescope Will Be Operational, Release Images.NASA's New Telescope Will Have 'Tremendous Impact' on Search for Alien Life.You can read more about the positioning system at the NASA FAQ. 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).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |