Cassini ISS
===========
The Cassini Imaging Subsystem comprises two instruments -- a narrow angle camera
and a wide angle camera.  The narrow angle camera contains 24 filters, and the
wide angle camera contains 18 filters.

Processing Cassini ISS Images
-----------------------------
    import ale, json, os
    from ale.drivers.cassini_drivers import CassiniIssPds3LabelNaifSpiceDriver
    from ale.drivers import JsonEncoder

    # Use the images to generate ISDs and create CSM cameras
    # Assume images are in current directory

    nac_stereo_1 = 'N1702360370_1.LBL'
    nac_stereo_2 = 'N1702360308_1.LBL'

    def generate_isd(filename):
        driver = CassiniIssPds3LabelNaifSpiceDriver(filename)

        # SPICE kernels are furnished inside this with
        with driver as d:
            # this is the information for the ISD in a python dict
            aledict = d.to_dict()

            # Export python dictionary ISD to external json file to be used by CSM
            alelabel = os.path.splitext(filename)[0]+".json"
            with open (alelabel, "w") as file:
              json.dump(aledict, file, cls=JsonEncoder)
            return aledict

    # Generate ISD and export to a json file
    nac1_dict = generate_isd(nac_stereo_1)
    nac2_dict = generate_isd(nac_stereo_2)

    # Construct a camera
    camera1 = csm.create_csm(nac_stereo_1)
    camera2 = csm.create_csm(nac_stereo_2)
