JWST : Features

Features of the James Webb Space Telescope:

The JWST is one of the greatest telescopes ever designed and launched into space. Here are some of its features-

Fig. 1- The James Webb Space Telescope

• Mass of JWST - The James Webb Space Telescope is light as compared to its counterpart, the Hubble Space Telescope. Its mass is about half of the Hubble's mass at 6,200 kg including observatory, on-orbit-consumables and launch vehicle adapter as compared to 12,200 kg of the Hubble.
• Mirrors - It has two mirrors; The primary mirror and the secondary mirror. The primary mirror has a diameter of 6.5 metres and is made up of 18 separate hexagonal gold plated beryllium mirrors and has a total collecting area of 25.4m². This is more than 6 times Hubble's collecting area of 4m².  The mirror has a gold plating for infrared reflectivity which is covered by a thin layer of glass to make it durable.
• Sunshield - To observe infrared rays, JWST must be kept under 50K or -223.3 °C otherwise the infrared radiation from the telescope itself would block out the infrared from other sources like celestial bodies.
  So, to protect it from the heat and light of the Sun, Earth and the Moon, it has a sunshield which, due to its orbit, always remains in between the telescope and these bodies.
  The sunshield consists of five layers each about as thick as a single human hair, made up of Kapton E film, coated with aluminium on both sides and doped silicon on two of the hottest sun facing layers to reflect the heat back into space.
  While testing the deployment of the sunshield on ground in 2018, accidental tears in the delicate sunshield delayed the JWST a bit.
  It was designed to be folded 12 times to fit inside the Ariane 5's payload fairing.
  Due to this sunshield, the JWST can see 40% of the sky from any position but can cover the whole sky over a period of 6 months.
  

  

  Fig. 2- The Sunshield of JWST
  

• Location/orbit - The JWST orbits the Sun unlike the Hubble which orbits the Earth. It operates in a halo orbit circling around a point in space known as Sun-Earth L₂ Lagrange point about 1,500,000 km away from Earth's orbit.
  Combined with its wide shadow-avoiding orbit, the telescope can simultaneously block incoming heat and light from all three of these bodies i.e. the Sun, the Earth and the Moon and avoid even the smallest changes of temperature from Earth and Moon shadows that would affect the structure, yet still maintain uninterrupted solar power and Earth communications on its sun-facing side.
  This arrangement keeps the temperature of the spacecraft constant and below the 50 K or −223 °C necessary for faint infrared observations.

That is all about the main features of JWST but stay tuned and follow us for more info on tech and JWST.

Thank you

Aarav Iyer

References:

(1) Wikipedia (Fig. 1, 2 + content)

(2) NASA