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The Pandeia Engine is a Python module (compatible with Python 3.6 8 and later) that functions as the computational engine of the JWST ETC and Roman ETC. It can be imported and run as a standalone module.

The engine itself can be run with the command

from pandeia.engine import perform_calculation

result = perform_calculation.perform_calculation(calculation)

where "calculation" is a heirarchical dictionary describing a scene of sources, an instrument setup, and an extraction strategy.

Engine inputs take the form of a hierarchical Python dictionary describing, in different sections, the instrument setup, the scene with definitions of all sources within it, and the flux extraction strategy.

Such input dictionaries are available in JWST Pandeia Such dictionaries are available in JWST Webapp download files (as a JSON-formatted file named input.json, suitable for reading in with the built-in Python functions) or 'json' module). Alternatively, default versions of calculations can be created with the function build_default_calc() and then edited :

from pandeia.engine import calc_utils

calculation = calc_utils.build_default_calc("jwst","nircam","sw_imaging")

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(this is the only option for Roman Space Telescope calculations)

Create a default calculation

from pandeia.engine import calc_utils
from pandeia.engine import perform_calculation

calculation = calc_utils.build_default_calc("jwst","nircam","sw_imaging")
results = perform_calculation.perform_calculation(calculation)

The command above produces the NIRCam SW Imaging calculation below, and then runs it through the engine. "results" will be a dictionary, defined in the Output API documentation

Load a calculation from the JWST Webapp

Calculation downloads from the JWST Pandeia Webapp contain the engine inputs in a JSON-formatted text file called input.json.

import json
from pandeia.engine import perform_calculation

with open("input.json") as infile:
    calculation = json.load(infile)

results = perform_calculation.perform_calculation(calculation)

The command above reads a file called "input.json" in the current directory, loads it into a Python dictionary, and runs it through the engine. "results" will be a dictionary, defined in the Output API documentation. Results should match the JWST Pandeia Webapp.

Full API

The full API documentation, with all possible options and combinations for any instrument, is in the attached file: View filenamecan be found in engine_input_api_3.1.6.rstheight250

Examples

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The following calculation defines a JWST NIRCam observation in SW Imaging mode using the full subarray and rapid readout pattern and f070w filter, for a flat-spectrum (in fnu) point source normalized to 0.001 mJy, intended to be observed with a 0.2" aperture. Note that it specifies a precomputed backgroundbackground precomputed for the JWST minzodi benchmark position; actual computed user-configured backgrounds are available in the JWST web ETC Webapp (and can be downloaded from there)

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Code Block
language js title JWST NIRCam SW Imaging collapse true
{ "background": "minzodi", "background_level": "benchmark", "calculation": { "backgroundeffects": { "minzodi", saturation": null }, "background_levelnoise": { "benchmark" "crs": null, "calculation": { "effectsdark": {null, "saturationexcess": null, }, "noiseffnoise": {null, "crsreadnoise": null, "ffnoisescatter": null } }, "configuration": { "detector": { "nexp": 1, "ngroup": 10, "nint": 1, "readout_pattern": "rapid", "subarray": "full" }, "instrument": { "aperture": "sw", "disperser": null, "filter": "f070w", "instrument": "nircam", "mode": "sw_imaging" } }, "scene": [ { "position": { "orientation": 0.0, "x_offset": 0.0, "y_offset": 0.0 }, "shape": { "geometry": "point" }, "spectrum": { "extinction": { "bandpass": "j", "law": "mw_rv_31", "unit": "mag", "value": 0.0 }, "lines": [], "name": "generic source", "normalization": { "norm_flux": 0.001, "norm_fluxunit": "mjy", "norm_wave": 2.0, "norm_waveunit": "microns", "type": "at_lambda" }, "redshift": 0.0, "sed": { "sed_type": "flat", "unit": "fnu", "z": 0.0 } } } ], "strategy": { "aperture_size": 0.1, "background_subtraction": true, "display_string": "Imaging Aperture Photometry", "is_aperture_ee": false, "method": "imagingapphot", "sky_annulus": [ 0.22, 0.4 ], "target_source": "1", "target_type": "coords", "target_xy": [ 0.0, 0.0 ], "units": "arcsec" } }

The following dictionary defines a Roman WFI Imaging observation with the F062 filter, 1024x1024 subarray (similar read time to what's expected for Roman WFI Imagingdefocus_small subarray (for a 3.66s read time), medium8 readout pattern, and 6 groups; for a 0.001 mJy flat-spectrum point source (in fnu) intended to be observed with a 0.2" aperture.

(click here to download as a JSON file: anyimaging_f062_hlwas_medium8imaging_1024x1024full.jeng)

Code Block
language js title Roman WFI Imaging collapse true true
{ "background": "minzodi", "background_level": "benchmark", "calculation": { { "backgroundeffects": { "minzodi", "saturation": null }, "background_levelnoise": "benchmark", { "calculationcrs": { null, "effectsdark": {null, "saturationexcess": null, }, "noiseffnoise": {null, "crsreadnoise": null, "ffnoisescatter": null } }, "configuration": { "detector": { "nexpma_table_name": 1, "ngroup": 6"hlwas_imaging", "nintnexp": 1, "readout_patternnresultants": "medium8"5, "subarray": "1024x1024full" }, "instrument": { "aperture": "anyimaging", "disperser": null, "filter": "f062", "instrument": "wfi", "mode": "imaging" } }, "scene": [ { "position": { "orientation": 0.0, "x_offset": 0.0, "y_offset": 0.0 }, "shape": { "geometry": "point" }, "spectrum": { "extinction": { "bandpass": "j", "law": "mw_rv_31", "unit": "mag", "value": 0.0 }, "extinction_first": true, "lines": [], "name": "generic source", "normalization": { "norm_flux": 0.001, "norm_fluxunit": "mjy", "norm_wave": 2.0, "norm_waveunit": "microns", "type": "at_lambda" }, "redshift": 0.0, "sed": { "sed_type": "flat", "unit": "fnu", "z": 0.0 } } } ], "strategy": { "aperture_size": 0.2, "background_subtraction": true, "display_string": "Imaging Aperture Photometry", "is_aperture_ee": false, "method": "imagingapphot", "sky_annulus": [ 0.4, 0.6 ], "target_source": "1", "target_type": "coords", "target_xy": [ 0.0, 0.0 ], "units": "arcsec" } }