Webb Observatory

Did you know that the telescope’s history stretches back before the Hubble Space Telescope was launched?  Learn about the design and the major components and subsystems of Webb and see Webb in a 3d in a 3d Solar System.

Webb Space Telescope composited with a blue print of Webb and one of the first images of light to ever go through the telescope during its commisioning phase showing stars and galaxies all in a blue print colored field.

Designing Webb Video

The Webb Space Telescope is the most powerful space telescope ever made – and the most complex one yet designed. Did you know that the telescope’s history stretches back before the Hubble Space Telescope was launched? This video explores the various early concept designs for Webb, including the criteria and the players. Learn more about Webb’s final design, how it evolved, and how the completed telescope was tested and prepared for its historic launch.

Major Components

The Observatory is the space-based portion of the James Webb Space Telescope system. It is comprised of the Optical Telescope Element (OTE), the Integrated Science Instrument Module (ISIM), the sunshield and the spacecraft bus.

Webb observatory major components

Optical Telescope Element OTE

The OTE is the eye of the Observatory. It consists of the mirrors and the backplane. The OTE gathers the light coming from space and provides it to the science instruments located in the ISIM. The backplane is like the “spine” of Webb. It supports the mirrors.

ISIM and Instruments

The Integrated Science Instrument Module  ISIM contains Webb’s cameras and instruments. It integrates four major instruments and numerous subsystems into one payload.


The sunshield separates the observatory into a warm sun-facing side (spacecraft bus) and a cold anti-sun side (OTE and ISIM). The sunshield keeps the heat of the Sun, Earth, and spacecraft bus electronics away from the OTE and ISIM so that these pieces of the Observatory can be kept very cold (The operating temperature has to be kept under 50 K or -370 deg F).

Spacecraft Bus

The spacecraft bus provides the support functions for the operation of the Observatory. The bus houses the six major subsystems needed to operate the spacecraft: the Electrical Power Subsystem, the Attitude Control Subsystem, the Communication Subsystem, the Command and Data Handling Subsystem, the Propulsion Subsystem, and the Thermal Control Subsystem.

Key Elements

Labeled image showing major Webb observatory subsystems

Webb’s major subsystems and components.

The Observatory consists of:

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Gallery: The Story of Webb's Build

A curated gallery of over a decade of images of Webb's design, build, test and integration leading to it's launch on December 25, 2021.

Click any image to go to an image detail page with description, additional information and the ability to download the image in various resolutions (use the download arrow icon in lower right corner on Flickr click through image).

James Webb Space Telescope Primary Mirror Prepared for Testing at Johnson Space Center

How Webb Unfolds

Webb in a 3d Solar System