CLASSI Spectrograph Instrument Simulator

Detector, instrument, throughput, and WCS models for the MLO CLASSI spectrograph.

Install

Install the shared data package first when developing from sibling checkouts:

python -m pip install -e ../shared-data
python -m pip install -e .

The distribution is named classi-sim; its import namespace is simulator:

from simulator import InstrumentSimulator, SpectrographModel

Physical hardware models live in simulator.components. The component catalog keeps hardware geometry and calibration-data associations together so the simulator and ETC can use the same definitions. For example:

from astropy import units as u
from simulator import AtmosphericExtinction, InstrumentSimulator, SpectrographModel
from simulator.components import (
    CANON_EF100_F2,
    CLASSI_FIBER,
    DESI_SKY_DARK,
    CLAUD_50INCH,
    E02_PICKOFF,
    FGL400S,
    FLI_AR571,
    NEWPORT_MASTER_1294,
    THORLABS_AC508_180_AB,
)

spectrograph = SpectrographModel.from_components(
    detector=FLI_AR571,
    grating=NEWPORT_MASTER_1294,
    collimator=THORLABS_AC508_180_AB,
    camera_lens=CANON_EF100_F2,
    fiber=CLASSI_FIBER,
    incidence_angle=32 * u.deg,
    diffraction_angle=-20 * u.deg,
    fiber_count=7,
    fiber_pitch=250 * u.um,
    optical_elements=(E02_PICKOFF, FGL400S),
)

sim = InstrumentSimulator(
    spectrograph=spectrograph,
    telescope=CLAUD_50INCH,
    atmosphere=AtmosphericExtinction(airmass=1.3),
    sky=DESI_SKY_DARK,
)

When the spectrograph is constructed from components, the simulator obtains the fiber, collimator, grating, camera-lens, detector-window, and detector-QE throughput curves directly from those components. CLASSI_FIBER carries the installed 10 m fiber length used for its attenuation curve. Additional passive optics such as the pickoff mirror and order-blocking filter are attached once through optical_elements.

DESI dark, grey, and bright sky spectra are provided by shared_data and are treated as at-observatory surface brightnesses. The simulator scales them by the circular fiber sky area and applies downstream instrument throughput, but does not apply atmospheric extinction to them a second time.

The existing numeric SpectrographModel(...) constructor remains available for custom geometries and backward compatibility.