pyEDITH

Exposure Direct Imaging Timer for HWO (Python Version)

Installation

Create a virtual environment (optional but recommended):

python -m venv venv
source venv/bin/activate  # On Windows, use `venv\Scripts\activate`

Install from pyPI:

pip install pyEDITH

Or, if preferred, clone the pyEDITH repository and install locally:

git clone https://github.com/HabitableWorldsObservatory/pyEDITH.git
cd pyEDITH
pip install -e .

Set up environment variables: Add the following lines to your .bashrc or .zshrc file:

export SCI_ENG_DIR="/path/to/Sci-Eng-Interface/hwo_sci_eng"
export YIP_CORO_DIR="/path/to/yips"

Replace the paths with the actual paths on your system.

Running pyEDITH via Terminal

pyEDITH provides a command-line interface with three main functionalities: etc (Exposure Time Calculator), snr (Signal-to-Noise Ratio), and etc2snr (Exposure Time to Signal-to-Noise Ratio). You will need to compile a configuration file that the code will read. You can find some examples in inputs/.

• Exposure Time Calculation:

pyedith etc --edith path/to/your/config.edith

• SNR Calculation:

pyedith snr --edith path/to/your/config.edith --time 100000

Here, 100000 is the exposure time in seconds.

• ETC to SNR Calculation:

pyedith etc2snr --edith path/to/your/config.edith

In this case, the config file will need to also have a secondary set of parameters (see e.g. inputs/input_secondarybandpass.edith)

Add the -v flag to any command for verbose output:

pyedith etc --edith path/to/your/config.edith -v

Running pyEDITH from Python

This mode offers much more flexibility to run the ETC. We refer to our tutorials in tutorials/ for details on this mode.

Glossary

Within coronagraphs.py

A note on calculating omega_lod:

The photometric aperture omega_lod can be calculated via two methods, and the user should specify either the psf_trunc_ratio or photometric_aperture_radius parameters to do so.

• photometric_aperture_radius simply sets a radius for the photometric aperture, such that omega_lod = \pi * (photometric_aperture_radius * (lambda/D))^2, where omega_lod is the solid angle of the photometric aperture.
• In contrast, psf_trunc_ratio is a more complex way of calculating the photometric aperture solid angle omega_lod, necessary because the off-axis PSF is not always going to be a perfect circle, and can be misshapen. In principle, this method takes an off-axis PSF and calculates omega_lod as all pixels in the PSF that are above the threshold psf_trunc_ratio * max(off-axis PSF), accounting for imperfect PSF shapes. Note: If the off-axis PSF shape is a perfect airy disk, then psf_trunc_ratio is simply 1 - photometric_aperture_radius.
• Finally, photometric_aperture_throughput is an entirely different, but related, parameter, not to be confused with the two parameters above. This parameter is essentially the core throughput of the off-axis PSF. In other words, this is the fraction of light entering the coronagraph that ends up within the photometric core of the off-axis (planet) PSF assuming perfectly reflecting/transmitting optics, where the core is the solid angle area omega_lod and is set by either psf_trunc_ratio or photometric_aperture_radius.

Within telescopes.py

Within detectors.py

Within observation.py

Within astrophysical_scene.py

Within observatory.py

Within parse_input.py

Within exposure_time_calculator.py