Mission
The JWST's primary scientific mission has four main components: to search for light from the first stars and galaxies that formed in the Universe after the Big Bang, to study the formation and evolution of galaxies, to understand the formation of stars and planetary systems and to study planetary systems and the origins of life. All of these jobs can be done more effectively by analyzing near-infrared light rather than light in the visible part of the spectrum. For this reason the JWST's instruments will not measure visible or ultraviolet light like the Hubble Telescope, but will have a much greater capacity to collect infrared light. In its present design, the JWST will detect a range of wavelengths from 0.6 (orange light) to 28 micrometers (deep infrared radiation at about 100 K (−173 °C; −280 °F)).
Due to a combination of redshift, dust obscuration, and the low temperatures of many of the sources to be studied, the JWST must be able to measure infrared light with a very high degree of precision. To ensure that infrared emissions coming from the telescope or its instruments do not interfere with these observations, the entire observatory must operate at a very low temperature. Moreover, it must be well shielded from radiation coming from the Sun, the Earth and the Moon. To accomplish this, the JWST incorporates a large metalized fan-fold sunshield, which will unfurl to block infrared radiation and allow the telescope to radiatively cool down to roughly 40 K (−233.2 °C; −387.7 °F). The telescope's location at the Sun-Earth L2 Lagrange point ensures that the Sun, Earth, and Moon all occupy roughly the same position relative to the telescope, and thus make the operation of this shield possible.
The observatory is currently scheduled to be launched by an Ariane 5 from Guiana Space Centre Kourou, French Guiana into an L2 orbit with a launch mass of approximately 6.2 tons. After a commissioning period of approximately six months the observatory will begin the science mission which is expected to last a minimum of five years. The potential for extension of the science mission beyond this period exists and the observatory is being designed accordingly.
Read more about this topic: James Webb Space Telescope
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