This is the directory where any downloaded cached instruments are stored. 

Instruments can be downloaded using the synthesizer-download CLI.

    synthesizer-download --instrument <instrument class name>

The instruments can be downloaded by passing the class name of the instrument to the synthesizer-download command. For instance

    synthesizer-download --instrument JWSTNIRCamWide 
    synthesizer-download --instrument JWSTNIRCamNarrow
    synthesizer-download --instrument JWSTNIRSpec 
    synthesizer-download --instrument Euclid
