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NIRCam (Near-InfraRed Camera) is an instrument aboard the James Webb Space Telescope. It has two major tasks, as an imager from 0.6 to 5 micrometre wavelength, and as a wavefront sensor to keep the 18-section mirrors functioning as one. In other words, it is a camera and is also used to provide information to align the 18 segments of the primary mirror. It is an infrared camera with ten mercury-cadmium-telluride (HgCdTe) detector arrays, and each array has an array of 2048×2048 pixels. The camera has a field of view of 2.2×2.2 with an angular resolution of 0.07 at 2 μm. NIRCam is also equipped with coronagraphs, which helps to collect data on exoplanets near stars. It helps with imaging anything next to a much brighter object, because the coronagraph blocks that light.
NIRCam is housed in the Integrated Science Instrument Module (ISIM). It is connected to the ISIM mechanically with a system of kinematic mounts in the structural form of struts. There are thermal straps connecting the NIRCam optical bench assembly to the ISIM structure and to thermal radiators. It is designed to operate between and . The Focal Plane Electronics operate at 290 K.
NIRCam should be able to observe objects as faint as magnitude +29 with a 10,000-second exposure (about 2.8 hours). It makes these observations in light from 0.6 to 5 μm (600 to 5000 nanometre) wavelength. It can observe in two fields of view, and either side can do imaging, or from the capabilities of the Wavefront sensing equipment, spectroscopy. The wavefront sensing is much finer than the thickness of an average human hair. It must perform at an accuracy of at least 93 nanometers and in testing it has even achieved between 32 and 52 nm. A human hair is thousands of nanometers across.
The observed wavelength range is broken up into a short wavelength and a long wavelength band. The short wavelength band goes from 0.6 to 2.3 μm and the long wavelength band goes from 2.4 to 5 μm; both have the same field of view and access to a coronagraph. Each side of the NIRCam views a 2.2 arcminute by 2.2 arcminute patch of sky in both the short and long wavelengths; however, the short wavelength arm has twice the resolution. The long wavelength arm has one array per side (two overall), and the short wavelength arm has four arrays per side, or 8 overall. Side A and Side B have a unique field of view, but they are adjacent to each other. In other words, the camera looks at two 2.2 arcminute wide fields of view that are next to each other, and each of these views is observed at short and long wavelengths simultaneously with the short wavelength arm having twice the resolution of the longer wavelength arm.
NIRCam's four major science goals include:
The FPE provides or monitors the following for the FPA:
By using multiple filters the redshift of distant galaxies can be estimated by photometry.
Filters
NIRcam includes filter wheels that allow the light coming in from the optics to be sent through a Optical filter before it is recorded by the sensors. The filters have a certain range in which they allow light to pass, blocking the other frequencies; this allows operators of NIRCam some control over what frequencies are observed when making an observation with the telescope.
Labeled diagram
See also
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