The Webb 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.
The Optical Telescope Element (OTE) is the eye of the James Webb Space Telescope Observatory. The OTE gathers the light coming from space and provides it to the science instruments. The OTE consists of the mirrors as well as structures and subsystems that support the optics.
![2 3d rendering views of the Webb space telescope from the rear quarter and from below front quarter labelling with the major components.](https://science.nasa.gov/wp-content/uploads/2023/06/webb-observatory-components-jpeg.webp?w=4096&format=png)
Webb Observatory major components.
NASA/GSFC CIL
![The OTIS out of cryovac chamber at NASA Johnson.](https://science.nasa.gov/wp-content/uploads/2023/09/webb-ote-isim.jpg?w=4096&format=jpeg)
The OTIS (OTE+ISIM) out of cryovac chamber at NASA Johnson. The OTIS is an acronym that includes the OTE plus the Integrated Science Instrument (ISIM) package - essentially the optics and science instruments.
NASA/Chris Gunn
- 6.5 meter diameter primary mirror made of 18 hexagonal segments
- Round 0.74 meter Secondary mirror (image gallery)
- Tertiary mirror (image gallery) and Fine Steering Mirror, both of which are contained in the Aft Optics Subsystem (image gallery).
- Telescope structure (image gallery) (which includes the primary mirror backplane assembly, the main backplane support fixture (BSF), the secondary mirror support structure, and the deployable tower array) The BSF houses the instrument module.
- Thermal Management Subsystem
- Aft Deployable ISIM Radiator (ADIR)
- Wavefront sensing and control
![OTE engineering diagram](https://science.nasa.gov/wp-content/uploads/2023/09/ote1.jpg?w=4096&format=jpeg)
OTE Engineering Diagram