We keep talking about all the cool stuff the JWST is doing with its instruments. One of the more important instruments is the Mid Infrared Instrument MIRI, a combination camera and spectrograph which supports four modes – imaging, imaging with a coronagraph, low-resolution, and medium-resolution spectroscopy. MIRI has its own dedicated cryocooler to ensure a cold enough temperature for the very sensitive imagers to not pick up their own heat.
To switch between all of these modes, MIRI has three selectable wheels – one with filters for the imager and two with different filters and gratings for the spectrograph. A spectrograph splits the light coming from a target into its individual parts, creating a spectrum that can then be analyzed to determine the chemical makeup of the object. Combined with the coronagraph, this technique has already been used to identify the atmospheres of exoplanets.
All of the pieces of the instrument are working. However, one of the grating wheels used for medium-resolution spectroscopy is not functioning properly. On August 24, the instrument was moving a grating wheel to get ready for another observation, and the operations team noticed that the movement was slower than expected. Whatever has increased the friction for the wheel is a cause for concern, and NASA assembled an anomaly review board on September 6. In the meantime, JWST will not do observations requiring this mode.
We hope the issue is easily resolved.
Mid-Infrared Instrument Operations Update (NASA Blogs)
JWST Mid Infrared Instrument (JWST)
MIRI Spectroscopic Elements (JWST)