James Webb Space Telescope
Tell Me About It

Construction and History

Click for more info

Where is it?

The telescope is currently located at the Goddard Space Flight Center in Greenbelt, Maryland.

How much did it cost?

The total cost of construction, 5 years of operation and 2 additional years of data analysis is $8.835B

Who operates it?

The JWST will operate collaboratively between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA).

The Telescope

Physical Description and Characteristics

Gold-plated beryllium mirror array (Source)

The unique feature of JWST is its primary mirror array composed of separate segments which combine to a diameter of about 6.5 meters. Each mirror segment is made of lightweight gold-plated beryllium.

Each mirror has a mass of 20.1 kg alone and 39.48 kg with the primary mirror segment assembly (PMSA). In total, the primary mirror has a mass of 705 kg and the entire telescope approx 6200 kg, including observatory, on-orbit consumables and launch vehicle adaptor.

At the core of the telescope is the Integrated Science Instrument Module (ISIM), a rigid frame housing the electronics systems and the four science instruments or ISIM.

These components include the Near-Infrared Camera, or NIRCam, the Near-Infrared Spectrograph, or NIRSpec, the Mid-Infrared Instrument, or MIRI, and the Fine Guidance Sensor/ Near InfraRed Imager and Slitless Spectrograph , or FGS/NIRISS.

Complete ISIM with components(Source)

Optical Abilities

What can it see?


The Near Infrared Camera (NIRCam) will be the primary JWST imager in the wavelength range of 0.6 to 5 microns. NIRCam is required by many of the core science goals of JWST, including the detection of the early phases of star and galaxy formation


The Near-Infrared Spectrograph is a near infrared multi-object dispersive spectrograph capable of simultaneously observing more than 100 sources over a field-of-view larger than 3' x 3'.


The Mid-Infrared Instrument has both a camera and a spectrograph that sees light in the mid-infrared region of the electromagnetic spectrum, covering the wavelength range of 5 to 28 microns.


The Fine Guidance Sensor allows Webb to point precisely and obtain high-quality images. FGS/NIRISS has a wavelength range of 0.8 to 5.0 microns, and has three main modes, each of which addresses a separate wavelength range.

Unlike its predecessor, Hubble Space Telescope, JWST’s primary goal is to observe very highly redshifted objects in the infrared spectrum. It has four instruments, each with a distinct purpose in observation. Together, the telescope will be able to observe wavelengths in the range of 0.6 - 28.5 micrometers with a resolution of ~0.1 arc-seconds.

Comparison of JWST's instruments (Source)

Other photographs taken in infrared (and false colored for observation) that showcase what JWST's photographs will look like.

Research and Purpose

What do we learn from JWST?

L2 Point

JWST allow researchers to see objects so old and so distant that they have never been observed before

Along with ESA’s Herschel Space Observatory, JWST will be placed at the second Lagrange point (L2); however, unlike Herschel, JWST Webb will find the first galaxies to form in the early universe, for which it needs extreme sensitivity in the near-IR where Herschel looks for the extremes, the most actively star-forming galaxies, which emit most of their energy in the far-IR.

For more reading, see the Space Science Reviews on JWST, the many SPIE publishings on JWST, or STScI's dedicated site.