Optical Telescope Element

Optical Telescope Element (OTE) is a sub-section of the James Webb Space Telescope, a large infrared space telescope launched on 25 December 2021, consisting of its main mirror, secondary mirrors, the framework and controls to support the mirrors, and various thermal and other systems.

The OTE collects the light and sends it to the science instruments in Webb's Integrated Science Instrument Module. The OTE has been compared to being the "eye" of the telescope and the backplane of it to being the "spine".

The primary mirror is a tiled assembly of 18 hexagonal elements, each 1.32 meters (4.3 ft) from flat to flat. This combination yields an effective aperture of 6.5 meters (21 ft) and a total collecting surface of 27 square meters (290 sq ft). Secondary mirrors complete anastigmatic imaging optics with effective f/20 focal ratio and focal length of 131.4 meters (431 ft). The main three-mirror telescope is a Korsch-type design, and it feeds into the Aft Optics Subsystem (part of OTE), which in turn feeds into the Integrated Science Instrument Module which holds the science instruments and fine guidance sensor.

The other two major sections of the JWST are the Integrated Science Instrument Module (ISIM) and the Spacecraft Element (SE), which includes the spacecraft bus and sunshield. The components of OTE were integrated by L3Harris Technologies to form the final system.