James Webb Space Telescope MIRI spectroscopy animation: The beam of light coming from the telescope is then displayed in deep blue and enters the instrument through the pick-off mirror, which is located at the top of the instrument and acts like a periscope.
Then a series of mirrors redirects the light to the underside of the instruments where a set of 4 spectroscopic modules are located. There, dichroic optical elements split the light beam into 4 beams corresponding to different parts of the mid-infrared range. Each ray enters its own integral field unit; These components split the light from across the field of view and reformat it so it can be broken down into spectra. This requires the light to be folded, reflected, and split many times, making this probably one of Webb’s most complex light paths.
To complete this amazing journey, each beam’s light is scattered by gratings, creating spectra that are then projected onto 2 MIRI detectors (2 beams per detector). An amazing feat of engineering! Photo credit: ESA/ATG Medialab
Mid-IR instrument operation update
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” data-gt-translate-attributes=”[{” attribute=””>James Webb Space Telescope’s Mid-Infrared Instrument (MIRI) has four observing modes. During setup for a science observation on August 24, a mechanism that supports one of these modes, known as medium-resolution spectroscopy (MRS), exhibited what appears to be increased friction. This mechanism is a grating wheel that allows astronomers to select between short, medium, and longer wavelengths when making observations using the MRS mode. Following preliminary health checks and investigations into the issue, an anomaly review board was convened on September 6 to assess the best path forward.
The Webb team has paused planning observations using this particular observation mode while continuing to analyze its behavior. They are also currently developing strategies to resume MRS observations as soon as possible. The observatory is in good condition and MIRI’s other three observing modes – imaging, low-resolution spectroscopy and coronagraphy – are functioning normally and remain available for scientific observations.
The James Webb Space Telescope’s (Webb) Mid-InfraRed Instrument (MIRI) sees light in the mid-infrared region of the electromagnetic spectrum, at wavelengths longer than our eyes can see.
MIRI enables scientists to use multiple observing techniques: imaging, spectroscopy, and coronagraphy to support the full breadth of Webb’s scientific goals, from observing our own solar system and other planetary systems to studying the early Universe.
To pack all of these modes into a single instrument, engineers designed a complex optical system in which light coming from Webb’s telescope follows a complex 3D path before finally reaching MIRI’s detectors.
This artist’s rendering shows this path for MIRI’s imaging mode, which provides imaging and coronagraphy capabilities. It also includes a basic spectrograph. We first take a look at its mechanical structure, with its three protruding pairs of carbon fiber struts that attach it to Webb’s instrument tray on the back of the telescope.
Acting like a periscope, the pick-off mirror receives the telescope’s light, shown in deep blue, and directs it into MIRI’s imaging module. Inside the instrument, a mirror system reformats and redirects the light beam until it reaches a filter wheel, where the desired range of mid-infrared wavelengths is selected from a set of 18 different filters, each with its own specific function (the beam takes on a light blue color in the Animation).
Finally, another set of mirrors captures the beam of light coming out of the filter wheel and recreates the image of the sky on MIRI’s detectors.
Photo credit: ESA/ATG Medialab
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