James Webb Space Telescope

Article

January 19, 2022

James Webb Space Telescope (JWST) - an infrared space telescope built in 2007–2021. It is supposed to complement the Hubble Space Telescope. Project supervised and largely financed by NASA in cooperation with ESA and CSA. It is named after James Webb, NASA's second administrator. The most important goals of the mission are: to observe the first stars formed after the Big Bang, to study the formation and evolution of galaxies, and to study the formation of stars and planetary systems.

Construction

The structure of the telescope includes the following components: Spacecraft (Spacecraft Element, SE) Satellite Platform (Spacecraft Bus, SB) Solar visor Solar panels High gain antenna Devices responsible for the control and orientation of the telescope Optical system (Optical Telescope Element, OTE) Main mirror Auxiliary mirror Optical subsystem (AFT) Structural elements Temperature management subsystem Radiators (ADIR) Integrated Science Instrument Module (ISIM) MIRI (Mid-Infrared Instrument) NIRSpec (Near-Infrared Spectrograph) NIRCam (Near-Infrared Camera) FGS / NIRISS (Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph)

Satellite platform (Spacecraft Bus, SB)

The platform is the most important auxiliary component of the telescope. It holds the various parts of the telescope together and houses many structural, computing, communication, and propulsion devices. Some of the scientific devices (Command and Data Handling system and MIRI cooling system) are also located here. The platform supports a 6.5-ton telescope with 350 kg of empty weight, and is mainly made of graphite composite. Important elements placed in SB are: central computer, memory and communication system. The processor and software ensure two-way communication between the scientific instruments, the memory core and the antenna, enabling the collection, storage, and transmission of data to Earth and to the telescope. The computer also controls the position of the telescope in space, collecting data from the gyroscopes and tracking the stars, and transmitting commands to the reaction wheels and thrusters.

Sunshield protection

In order for observations of distant astronomical objects to be undisturbed by the radiation of the telescope itself, it will operate at a very low temperature - below 50 K (−223 ° C). The device is equipped with a shield designed by Northon Grumman to block light and heat from the sun, which when unfolded has a size of 21.197 m × 14.162 m. It consists of five layers - each subsequent layer is cooler, and the vacuum between them will provide insulation. The largest of the layers (marked with the number 1) is facing the Sun, and the smallest (5) is facing the mirror. The layers are arranged in such a way that the sun illuminates almost only the first and a small part of the second, while the mirror "sees" only the layer 5 and sometimes a small fragment 4. The edges of the layers are further apart than their centers, which facilitates the radiation of heat. The first layer retains 90% of the energy. The five-layer cover is made of Kapton coated with aluminum on both sides to improve light reflection. In addition, the two largest membranes are additionally coated on the side facing the Sun with aluminum-doped silicon, which gives them a purple hue. The doping provides electrical conductivity, which prevents the build-up of static charges on the membranes. The layers have the following thickness: kapton - 0.05 mm (shield 1) / 0.025 (shields 2-5) aluminum - 100 nm (all covers, both sides) silicon - 50 nm (shields 1-2).

Optical system

The optical system of the telescope consists of 4 mirrors, structural elements and supporting subsystems.

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