Calculating throughputs

All files relevant for calculating throughputs for the 4 JWST science instruments are found in the "jwst" folder of "pandeia_data". The subdirectories in this folder are "detector", "miri", "nircam", "niriss", "nirspec", and "telescope". Relevant subdirectories in each of the instrument folders are "filter", "optical", and "qe".

Users interested in throughputs for the various instrument modes should use the get_total_eff() function included in the Pandeia engine. This function considers all files for relevant instrument elements and properties (listed in the sections below) and outputs the throughput across a desired wavelength range. Below is a code snippet showing the use of the get_total_eff() function.

from pandeia.engine.instrument_factory import InstrumentFactory

# set up your wavelengths
wave = [wavelengths_you_want]

# create a configured instrument
instrument_factory = InstrumentFactory(config=conf)

# where conf is a configuration dictionary for a calculation:
#     see below for examples

# get the throughput of the instrument over the desired wavelength range
eff = instrument_factory.get_total_eff(wave)

pupil = instrument_factory.psf_library.get_pupil_throughput(wave[0],conf['instrument']['instrument'],conf['instrument']['aperture'])
eff = eff * pupil

Example configuration dictionaries

For a more comprehensive list of instrument mode, disperser, and filter keys, see Pandeia Quickstart.

# MIRI Imaging

conf={
	"detector": {
    "nexp": 1,
    "ngroup": 10,
    "nint": 1,
    "readout_pattern": "fastr1",
    "subarray": "full"
    },
    "dynamic_scene": True,
    "instrument": {
    	"aperture": "imager",
        "filter": "f1800w",
        "instrument": "miri",
        "mode": "imaging"
	},
}

# MIRI LRS Slit

conf={
	"detector": {
    "nexp": 1,
    "ngroup": 10,
    "nint": 1,
    "readout_pattern": "fastr1",
    "subarray": "full"
    },
    "dynamic_scene": True,
    "instrument": {
    	"aperture": "lrsslit",
		"disperser": "p750l",
        "instrument": "miri",
        "mode": "lrsslit"
	},
}

# NIRCam Imaging

conf={
	"detector": {
    "nexp": 1,
    "ngroup": 10,
    "nint": 1,
    "readout_pattern": "deep2",
    "subarray": "full"
    },
    "dynamic_scene": True,
    "instrument": {
    	"aperture": "sw",
        "disperser": "null",
        "filter": "f150w2",
        "instrument": "nircam",
        "mode": "sw_imaging"
    },
}

# NIRCam Coronagraphic Imaging

conf={
	"detector": {
    "nexp": 1,
    "ngroup": 10,
    "nint": 1,
    "readout_pattern": "bright2",
    "subarray": "sub640"
    },
    "dynamic_scene": True,
    "instrument": {
    	"aperture": "mask210r",
        "disperser": "null",
        "filter": "f210m",
        "instrument": "nircam",
        "mode": "coronagraphy"
    },
}

# NIRISS Imaging

conf={
	"detector": {
    "nexp": 1,
    "ngroup": 10,
    "nint": 1,
    "readout_pattern": "nis",
    "subarray": "full"
    },
    "dynamic_scene": True,
    "instrument": {
    	"aperture": "imager",
        "disperser": "null",
        "filter": "f200w",
        "instrument": "niriss",
        "mode": "imaging"
    },
}

# NIRISS SOSS

conf={
	"detector": {
    "nexp": 1,
    "ngroup": 10,
    "nint": 1,
    "readout_pattern": "nisrapid",
    "subarray": "substrip96"
    },
    "dynamic_scene": False,
    "instrument": {
    	"aperture": "soss",
        "disperser": "gr700xd",
        "filter": "clear",
        "instrument": "niriss",
        "mode": "soss"
    },
}

# NIRSpec IFU spectroscopy

conf={
	"detector": {
    "nexp": 1,
    "ngroup": 10,
    "nint": 1,
    "readout_pattern": "nrs",
    "subarray": "full"
    },
    "dynamic_scene": False,
    "instrument": {
    	"aperture": "ifu",
        "disperser": "g140m",
        "filter": "f100lp",
        "instrument": "nirspec",
        "mode": "ifu"
    },
}

# NIRSpec IFU Verification Imaging

conf={
	"detector": {
    "nexp": 1,
    "ngroup": 3,
    "nint": 1,
    "readout_pattern": "nrs",
    "subarray": "full"
    },
    "dynamic_scene": False,
    "instrument": {
    	"aperture": "ifu__ver",
        "disperser": "null",
        "filter": "f110w",
        "instrument": "nirspec",
        "mode": "ifu_ver"
    },
}

Detector

• The quantum efficiency (QE) files in this directory are not used by the ETC or the Pandeia engine. The relevant QE files for the science instruments are in the "/miri/qe", "/nircam/qe", "/niriss/qe", and "/nirspec/qe" subdirectories.

MIRI

• Words in bold italics are also buttons 
  or parameters in GUI tools. Bold 
  style represents GUI menus/
  panels & data software packages.

  The "/miri/optical" subdirectory contains files for the 3 MIRI MRS dichroics that split the light into the 4 separate IFUs (channels). Reflection and transmission profiles are provided for each of the 3 dichroics. As shown in the schematic in the MIRI Optics and Focal Plane article, the light path to the 4 different channels is complex. Two separate wheels contain 3 dichroics for each of the 3 wavelength ranges (Short (A), Medium (B), and Long (C)). In the file names, the dichroics are labeled "dich1", "dich2", and "dich3", followed by an "s" for the short wavelength range, "m" for the medium wavelength range, or "l" for the long wavelength range, and "trans" for transmission or "refl" for reflection. The light paths taken to each channel are outlined below and indicate which files are used in calculating the throughput for each:

  • Channel 1: Reflection off dichroic 1.

  • Channel 2: Transmission through dichroic 1, reflection off dichroic 2.

  • Channel 3: Transmission through dichroics 1 & 2, reflection off dichroic 3.

  • Channel 4: Transmission through dichroics 1, 2, & 3.
    
    

• The "/miri/optical" subdirectory also contains transmission files for the germanium coatings on the 4-quadrant phase masks (4QPMs) for coronagraphic imaging. Keep in mind that these transmission files are also relevant for target acquisition (TA) using the 4QPMs.
  • The "jwst_miri_ge_ar1_trans" file applies to the F1065C and F1140C 4QPMs.
  • The "jwst_miri_ge_ar2_trans" file applies to the F1550C 4QPM.
    
    
• The QE file for the MIRI imaging detector, "jwst_miri_imager_qe", is used for calculating throughputs for MIRI imaging, MIRI imaging time series, MIRI low resolution spectroscopy (LRS) slit, MIRI low resolution spectroscopy (LRS) slitless, and MIRI coronagraphic imaging.
  
  
• The MIRI MRS is composed of 2 separate detectors. The "jwst_miri_mrs-sw_qe" file is the relevant QE file for Channel 1 and Channel 2 of the MRS ("sw" stands for short wavelength). Similarly, "jwst_miri_mrs-lw_qe" is the relevant QE file for Channel 3 and Channel 4 of the MRS ("lw" stands for long wavelength).

NIRCam

• The "jwst_nircam_sw-lyot_trans_modmean" and "jwst_nircam_lw-lyot_trans_modmean" files in the "/nircam/optical" subdirectory are the average transmissions of module A and module B for coronagraphic imaging with the Lyot spots.
  
  

• The "jwst_nircam_wlp4" and "jwst_nircam_wlp8" optical transmission files correspond to the weak lenses, used in the NIRCam SW time-series mode.
  
  

• The "jwst_nircam_sw_dbs" and "jwst_nircam_lw_dbs" files are the dichroic beam splitter (DBS) for each channel which directs incoming illumination to the shortwave (SW) or longwave (LW) channel.
  
  
• The "jwst_nircam_moda_com_substrate_trans" is for the coronagraphic optical substrate for Module A which is used for coronagraphic imaging mode. 
  
  
• The "jwst_nircam_sw_qe" and "jwst_nircam_lw_qe" files apply to any observations made from 0.6 to 2.3 μm and 2.4 to 5.0 μm, respectively.

NIRISS

• The "jwst_niriss_nrm_trans" file under the "filter" subdirectory is used for the aperture masking interferometry (AMI) mode. "nrm" refers to the non-redundant mask that enables the AMI mode.
  
  

• Three options are available in the "/niriss/optical" subdirectory:
  • "jwst_niriss_internaloptics_throughput": Used when neither the CLEAR nor CLEARP slots are selected in the filter and pupil wheels, respectively.
  • "jwst_niriss_internaloptics-clear_throughput": Used when the CLEAR slot is selected in the filter wheel and a filter or grating is selected in the pupil wheel.
  • "jwst_niriss_internaloptics-clearp_throughput": Used when the CLEARP slot is selected in the pupil wheel and a filter or grating is selected in the filter wheel.

NIRSpec

• Under "/nirspec/optical", the "jwst_nirspec_mos_internaloptics_throughput" file is applicable to the fixed slits and the bright object time-series modes.

Telescope

• The "telescope" subdirectory contains the throughput of the optical telescope element (OTE), "jwst_telescope_ote_thruput". This file is relevant for calculating throughputs for all observing modes since all light first passes through the OTE before entering the optical paths of the science instruments.