James Webb Space Telescope
Monday, February 7, 2022
James Webb Space Telescope is a space telescope created by NASA collaborating with ESA (European Space Agency) and CSA (Canadian Space Agency). The telescope is named after James E. Webb who was an administrator of NASA and had played an important role in the Apollo program. The telescope is designed to be the successor of the Hubble Space Telescope. It can see even the most distant things in our universe such as the formation of the first galaxies.
The developments began in 1996 for a launch that was planned for 2007 but numerous obstacles caused delays- a major redesign in 2005, a ripped sunshield during a practice deployment, a recommendation from an independent review board, the COVID-19 pandemic, problems with the Ariane 5 rocket and the telescope itself, and communication issues between the telescope and the launch vehicle etc. The construction was completed in 2016 after which a huge testing phase began. Finally after overcoming many hurdles, JWST was launched on 25th December 2021 on Ariane flight VA256.
The James Webb Space Telescope has a mass about the half of Hubble Space Telescope’s but its primary mirror has an area about six times larger.
JWST is designed primarily for near-infrared astronomy, but can also see orange and red visible light. To observe in the infrared spectrum the JWST must be kept under a temperature of 50 K (223.2 °C). Therefore, the telescope uses a large sunshield to block light and heat from the Sun, Earth and Moon. The sunshield is made of many layers, each of them as thin as a human hair and is constructed from Kapton E. Tearing of the delicate film during testing was one of the many causes for delay.
The JWST’s primary is 6.5 m diameter gold-coated beryllium reflector with a collecting area of 273 sq. ft. It is too large for any existing launch vehicle to carry, so, the mirror is built as 18 hexagonal segments which will unfold once the telescope is launched.
The Space Bus is the support component of JWST. It holds a host of computing, communication, electric power and others. With the sunshield, it make up the spacecraft part of the space telescope. The Spacecraft Bus is on the Sun-facing "warm" side of the sunshield and operates at a temperature of about 300 K (27 °C). The Spacecraft Bus weighs 350 kg and must support the 6,200 kg space telescope. Its construction was completed in 2015 after which it had to be joined to the telescope.
The JWST is among the largest of infrared telescopes. Compared to ground telescopes, space observatories were free from atmospheric absorption of infrared light.
Nevertheless, infrared telescopes have a disadvantage: they always need to stay extremely cold. If not, the background heat of the device itself overwhelms the detectors, making it effectively blind. This can be overcome by careful design, especially, placing the telescope in a dewar with substances such as liquid helium which is very cold. Therefore, most infrared telescopes have a lifespan depending upon the time in which their coolant will run out, a few months at the least and years at the most.
Altogether, the JWST is a new highly developed scientific discovery to many astronomers, one more interesting mission for space- lovers and a new ray of hope to Earth as we reach out to other civilizations which flourish out there, in SPACE.
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