HOW JWST WORKS

Integrated Science Instrument Module (ISIM) Near-Infrared Camera (NIRCam)

NIRCam pulls double duty as both an imager and the primary sensor for focusing the telescope. It’s JWST’s highest-resolution detector, with a pixel size of 0.032".

Mid-Infrared Instrument (MIRI)

MIRI is the only JWST instrument equipped with an active cooler, which allows it to operate at a temperature of just −447° F (−266° C or just 7 kelvins).

Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS)

To enable JWST to capture sharp images, FGS locks the telescope’s line of sight onto a reference star in the field of view. The camera can track stars as faint as magnitude 18 and hold the telescope’s aim to within a few milliarcseconds.

Near-Infrared Spectrograph (NIRSpec)

This unique spectrometer uses a microshutter array that can take spectra of 100 galaxies at a time.

Spacecraft bus

The bus (main body) contains supporting equipment and electronics. It’s placed on the warm side of the sunshield so its heat doesn’t affect observations.

Sunshield

Made of five layers of a specially coated film no thicker than a human hair, the sunshield blocks out the light and heat of the Sun and Earth.

Star trackers

These cameras on the warm side of the sunshade help JWST know where it is pointing.

Thrusters (in back)

When the momentum wheels are spinning too fast, these hydrazine rocket jets are occasionally fired to help shed the wheels’ accumulated angular momentum.

Momentum wheels (in spacecraft bus)

JWST orients itself with these flywheel-like devices, which spin up to generate torque and cause the craft to rotate.