MIRI spectroscopy animation from the James Webb Space Telescope: The light beam coming from the telescope is then shown in deep blue as it enters the instrument through the pickup mirror located on top of the instrument and acts as a periscope.
Then, a series of mirrors redirect the light to the bottom of the instruments where a set of 4 spectroscopic modules is located. Once there, the light beam is divided by optical elements called dichroics into 4 beams corresponding to different parts of the mid-infrared region. Each beam enters its own integral field unit; These components split and reshape light from across the field of view, ready to spread out into spectra. This requires light to bend, bounce, and split many times, making this probably one of Webb’s most complex light paths.
To complete this incredible journey, the light from each beam is scattered by gratings, creating spectra that are then projected onto 2 MIRI detectors (2 beams per detector). An amazing feat of engineering! Credit: ESA/ATG medialab
Mid-Infrared Instrument Operations Update
the[{” 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.
Webb’s team has stopped scheduling observations using this particular observing mode while they continue to analyze its behavior. They are also currently developing strategies to resume observations of the MRS as soon as possible. The observatory is in good health and MIRI’s other three observing modes (imaging, low-resolution spectroscopy, and coronagraphy) are operating normally and remain available for science 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 that are longer than our eyes can see.
MIRI enables scientists to use multiple observing techniques: imaging, spectroscopy, and coronagraphy to support the full range of Webb’s science goals, from observing our own Solar System and other planetary systems, to studying the early Universe.
To bundle all these modes into a single instrument, engineers designed a complex optical system in which light 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 contains a simple spectrograph. We first take a look at its mechanical structure with its three protruding pairs of carbon fiber struts that will attach it to Webb’s instrument compartment at the back of the telescope.
The receiving mirror, which acts like a periscope, receives light from the telescope, shown in deep blue, and directs it towards MIRI’s imaging module. Inside the instrument, a system of mirrors reformats the light beam and redirects it 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 turns light blue in the animation).
Finally, another set of mirrors takes the light beam that comes out of the filter wheel and recreates the image of the sky in the MIRI detectors.
Credit: ESA/ATG medialab
