Webb's Instruments

Webb's high-resolution cameras will work across a wide range of visible red through mid-infrared colors. Each camera is uniquely designed to look at particular details. The cameras have filters for isolating particular color ranges and masks to block light from bright objects whose glare might otherwise hide faint, nearby targets.

NEAR INFRARED CAMERA (NIRCam)

Webb's Near Infrared Camera (NIRCam) will help scientists answer questions about the early phases of star and galaxy formation. It will yield data about the shapes and colors of faraway, young galaxies, allowing astronomers to determine how galaxies changed over time. In addition, NIRCam will help astronomers to determine the ages of stars in nearby galaxies.

NIRCam is equipped with coronagraphs, instruments that allow astronomers to take pictures of very faint objects around a central bright object, such as a star. NIRCam's coronagraphs work by blocking a brighter object's light, making it possible to view the dimmer object nearby — just like shielding the sun from your eyes with an upraised hand can allow you to focus on the view in front of you. With the coronagraphs, astronomers hope to determine the characteristics of planets orbiting nearby stars.

NIRCam also will help ensure the perfect alignment and shape of the different primary mirror segments. NIRCam is equipped with special optics that can capture the image of a single, bright star and deliberately place it out of focus, spreading out its light. Astronomers then analyze that out-of-focus image, looking for patterns that are consistent with all the mirrors being in alignment, or indicative of a problem.

NIRCam will be the primary camera for wavelengths from 0.6-5 microns.

NIRCam is being built by the University of Arizona and Lockheed Martin.

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NEAR INFRARED SPECTROGRAPH (NIRSpec)

The Near-Infrared Spectrograph (NIRSpec) is the Webb telescope's spectrograph, unraveling the light of faint objects and their components. A spectrograph is an instrument that spreads light into its various wavelengths, allowing them to be analyzed. This helps scientists determine which elements the object contains, the velocity of various parts of the object, and its redshift.

NIRSpec will be used to measure accurate redshifts to distant galaxies and to measure their chemical evolution. NIRSpec will also be used to study how gas and dust clump together to form new stars and planets.

A unique capability of NIRSpec will is its capability to study the light of more than 100 objects at once. This is made possible by Micro Shutter Assembly (MSA). The MSA consist of arrays of thousands and thousands of tiny shutters that can be opened in the pattern of objects on the sky, allowing only the light from objects of interest into the instrument.

NIRSpec will operate in the 0.7- to 5-micron wavelength range.

NIRSpec is being built by the European Space Agency, with the detectors and multi-shutter array provided by Goddard Space Flight Center/NASA..

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MID-INFRARED INSTRUMENT(MIRI)

MIRI's sensitive camera and spectrograph will be able to see far away in time and space, back to a time when galaxies were young.

Because the universe is expanding, the light from stars similar to our Sun in these galaxies has been redshifted to mid-infrared wavelengths. MIRI will be able to detect these. MIRI is also equipped with a complex coronagraph, which blocks the glare of nearby bright objects to allow clear observations of faint objects.

MIRI will play a large role in Webb's mission to understand faraway galaxy formation and evolution, the physical process of star formation, and the creation of the heavier chemical elements, such as carbon, oxygen, and iron.

MIRI will operate in the 5- to 28-micron wavelength range.

MIRI is being built by the MIRI Consortium, a group that consists of scientists and engineers from European countries, a team from the Jet Propulsion Lab in California, and scientists from several U.S. institutions.

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FINE GUIDANCE SENSORS/Near-Infrared Imager and Slitless Spectrograph (FGS/NIRISS)

Two instruments – the Fine Guidance Sensor (FGS) and the Near-Infrared Imager and Slitless Spectrograph (NIRISS) – are packaged together, but have separate purposes. The FGS is the guide camera for the observatory, which helps point the telescope, while NIRISS is a specialized science instrument.
Like NIRSpec, NIRISS is a spectrograph, designed to break light apart into the lines known as “spectra” for analysis. NIRISS will be able to take extremely precise spectra of bright objects, capturing more light than NIRSpec. NIRISS will also be used to detect faint objects, like planets, that are very near their parent stars. Since it doesn’t use a coronograph, it will excel at capturing objects that have that kind of close proximity. And like NIRCam, NIRISS can make its observations through a variety of specially selected filters. 

NIRISS will tackle a diverse range of science topics. It will be well-suited to both discover distant galaxies in the universe and measure the composition of the atmospheres of nearby planets in our galaxy. NIRISS will also be able to make detailed maps of the centers of objects such as quasars.

Balancing Act

The FGS helps point the telescope in two ways. First, at the start of an observation, it takes pictures to identify where the telescope is pointing. Then, it finds a “guide star” that is close to the field of view containing the object to be studied. As long as the guide star stays in exactly the same position in the field of the FGS, the telescope will point at the target of scientific interest, which can be examined by one of the science instruments.

Unfortunately, the telescope tends to wander by small amounts, since it is orbiting in space and affected by solar radiation, its own moving parts, the sloshing of its propellant, and other forces. To track these changes, the FGS measures the position of the guide star 16 times per second and relays these measurements to the onboard computer. When the computer detects small drifts, it orders the telescope to correct itself in order to keep its positioning relative to the guide star.

The FGS and NIRISS are provided by the Canadian Space Agency.
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