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James Webb Space Telescope

(James Webb Space Telescope, JWST) is a planned space telescope for infrared observation. As a follow-up to the Hubble Space Telescope, which will end its observation activities in 2010, it is planned to be launched into space in 2011. However, due to the effects of life-delay measures such as the Hubble Space Telescope’s repairs, the launch date was changed to 2013. It is a joint application plan of the European Space Agency (ESA) and NASA (NASA), and is placed at the second Lagrangian point of the Sun-Earth. Unlike the Hubble Space Telescope, which revolves around the earth, it floats in a space of 1.5 million kilometers from the earth to the back of the sun.

This project was once called the “Next Generation Space Telescope” (Next Generation Space Telescope), and was named after NASA’s second director James Webb in 2002. From 1961 to 1968, James Webb led a series of important US space exploration projects such as the Apollo Project.

The main task of the James Webb Space Telescope is to investigate the residual infrared evidence (cosmic microwave background radiation) as the Big Bang theory, that is, to observe the early state of the visible universe today. To achieve this, it is equipped with high-sensitivity infrared sensors, spectrometers, etc. In order to facilitate observation, the body must be able to withstand the extreme low temperature and avoid the light of the sun and the earth, etc. For this reason, the James Webb Space Telescope is equipped with a foldable light shield to shield the light source that will become interference. Because it is at the Lagrangian point, the earth and the sun are always at the same relative position in the telescope’s field of view, and the light-shielding plate can actually work without frequent correction of the position.

The Hubble Space Telescope is located in a low orbit approximately 600 kilometers from the surface. Therefore, even if the optical instrument fails, it can be repaired by the space shuttle. The James Webb Space Telescope is located at a distance of 1.5 million kilometers from the Earth. Even if it fails, it is impossible to send repair personnel frequently. On the contrary, it is located at the second Lagrangian point and its gravity is relatively stable. Therefore, it can maintain a constant position relative to neighboring celestial bodies. It does not require frequent position corrections and can be observed more stably. Will be affected by dust near the earth.

The planned James Webb Space Telescope has a mass of 6.2 tons, about half of the Hubble Space Telescope (11 tons). The main reflector is made of beryllium with a diameter of 6.5 meters and an area more than 5 times that of the Hubble Space Telescope. It can be expected that it will have a very high observation performance far exceeding the Hubble Space Telescope. At the same time, the weight of the opposite optical lens has been reduced.

The diameter of this primary mirror is now larger than the rocket used to launch it. The main mirror is divided into 18 hexagonal lenses, which will be unfolded under the control of high-precision micro motors and wavefront sensors after launch. However, this method will not be the same as the Kergu telescope. It does not need to be constantly adjusted according to the active optics according to the influence of gravity load and wind like ground-based telescopes. Therefore, the James Webb Space Telescope will not except the initial configuration There are too many changes.

The mirror surface of the main mirror also forms a hexagonal shape as a whole, and the condensing part and the mirror surface are exposed, which is easily reminiscent of the antenna of a radio telescope. In addition, its main body is not cylindrical, but a seat-shaped light shield is deployed under the main mirror.

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