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 0.6- 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 choronagraph, 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-TUNABLE FILTER AND GUIDER (FGS-TF)

The Fine Guidance Sensors-Tunable Filter (FGS-TF) consists of two components with different functions: a camera and a "guider," which helps point the telescope. The FGS-TF camera will be able to focus on extremely specific portions of the light being emitted by an object. Other cameras also focus on specific wavelengths, but they can select from only a few. FGS-TF can choose from a wide array of wavelengths. Parallel plates situated in the camera widen or narrow to capture the particular wavelength scientists are interested in studying.

FGS-TF will look at the internal workings of galaxies, examining their structure and looking for gas disks in the centers of galaxies that could harbor black holes. It will examine the structure of protoplanetary objects - disks of dust that may become planets someday. Coronagraphs will allow FGS-TF to block out bright light to examine protoplanetary disks around stars, and perhaps even newly formed planets.

FGS-TF will also be able to discover which molecules and elements are present in clouds of dust and gas, and their energy level. It can help determine the density and temperature of the gas, and what's happening to it.

Balancing Act

The FGS Guider helps point the telescope. To lock onto an object, the telescope finds a guide star, a star located close to the field of view that contains the object to be studied. As long as the telescope points at that star, it also points at the object to be studied.

But the telescope, adrift in space and affected by solar radiation, its own moving parts, and other various stresses, tends to wander. The FGS Guider has an imaging camera will detect this movement by measuring the position of the guide star many times per second.

When it detects motion, it orders the telescope to shift to keep the telescope pointed at the guide star.

The chosen wavelength can be anywhere within the 1.6 to 4.9 micrometer range, with an accuracy better than 1 percent.

FGS-TF is being built by the Canadian Space Agency.

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