A modular exposure time calculator for the ESBO telescope. https://esbo-ds.irs.uni-stuttgart.de/esboetcdocs/

astronomy exposure-time-calculator python

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README.md

ESBO-ETC

A modular exposure time calculator for the ESBO telescope.

Introduction

This repository contains the source code of the ESBO-ETC, a highly modular exposure time calculator.

ESBO-ETC aims on modelling the physical aspect of light coming from a target through optical components (e.g. atmosphere, mirrors, lenses, ...) on the detector. The set up of this so called optical pipeline can be individually defined using a configuration file. Additionally, the thermal emission of optical components, the obstruction of components as well as different PSFs including pointing jitter can be considered.

Finally, ESBO-ETC allows the computation of either the necessary exposure time for a desired SNR, the SNR for a given exposure time or, in case of a BlackBodyTarget, the sensitivity as the minimum apparent magnitude for a given exposure time and SNR. All computations support a batch-mode, allowing to compute multiple scenarios at once.

Features

ESBO-ETC offers many different optical components and features which will be explained in the following.

Targets

<target type="" size=""/>

Currently ESBO-ETC supports the following two different types of targets. A configuration can contain only one target which has to be contained in the container <astroscene>. Each target consists of the basic tag <target> and possible other target-type specific attributes.

type: The type of the target. Currently, only BlackBodyTarget and FileTarget are supported.
size: The size of the target which can be either point or extended. In case of a point-source, a PSF will be used to determine the irradiance of each pixel. In case of a extended source, a uniform PSF is assumed, ignoring the tags <psf>, <jitter>, and some instrument specific tags.

BlackBodyTarget

<target type="BlackBodyTarget" temp="5778" temp_unit="K" mag="10" mag_unit="mag" band="B" size="point"/>

Model a target as a black body of a given temperature and magnitude.

temp: The temperature of the black body.
temp_unit optional: The unit of the black body's temperature. This has to be one of [K, Celsius]. The default is K.
mag: The apparent magnitude of the black body in magnitudes.
mag_unit optional: The unit of the black body's magnitude. This has to be mag. The default is mag.
band: The band used for fitting the black body's flux density to Vega's flux density. This has to be one of [U, B, V, R, I, J, H, K, L, M, N].

FileTarget

<target type="FileTarget" val="PathToFile" size="point"/>

Create a target from a file containing the spectral flux densities of the target.

val: The path to the file containing the spectral flux densities. For details on the required structure see section Reading spectral quantities from files.

Optical Components

<optical_component type=""/>

Each optical component consists of the basic tag <optical_component> and the attribute type and possible other component-specific attributes.

type: The type of the optical component. This can be one of the following types.

Atmosphere

<optical_component type="Atmosphere" transmittance="PathToTransmittanceFile" emission="PathToEmissionFile"/>

This component models the behaviour of an atmosphere which has a spectral transmittance and a spectral emission.

transmittance: The path to the file containing the spectral transmittance coefficients. For details on the required structure see section Reading spectral quantities from files.
emission optional: The path to the file containing the spectral radiance of the emission. For details on the required structure see section Reading spectral quantities from files.

StrayLight

<optical_component type="StrayLight" emission="PathToEmissionFile"/>

This component allows to model generic noise sources like stray light or zodiacal light from a file containing the spectral radiance of the emission.

emission optional: The path to the file containing the spectral radiance of the emission. For details on the required structure see section Reading spectral quantities from files.

Mirror

<optical_component type="Mirror" reflectance="PathToReflectance" emissivity="PathToEmissivity" temp="70" temp_unit="K" obstruction="0.2" obstructor_temp="70" obstructor_temp_unit="K" obstructor_emissivity="0.9"/>

Model a mirror including the mirror's thermal emission as well as possible obstruction of the mirror and the thermal emission of the obstructing component.

reflectance: The path to the file containing the spectral reflectance coefficients. For details on the required structure see section Reading spectral quantities from files.
emissivity: The path to the file containing the spectral emissivity coefficients. For details on the required structure see section Reading spectral quantities from files.
temp optional: The temperature of the mirror for the thermal emission.
temp_unit optional: The unit of the mirror's temperature. This has to be one of [K, Celsius]. The default is K.
obstruction optional: The obstruction factor of the mirror as ratio of the areas A_obstructor / A_mirror.
obstructor_temp optional: The temperature of the obstructing component for the thermal emission.
obstructor_temp_unit optional: The unit of the obstructing component's temperature. This has to be one of [K, Celsius]. The default is K.
obstructor_emissivity optional: The emissivity of the obstructing component for the thermal emission. Valid ranges are 0.0 - 1.0. The default is 1.

Lens

<optical_component type="Lens" transmittance="PathToTransmittance" emissivity="PathToEmissivity" temp="70" temp_unit="K" obstruction="0.2" obstructor_temp="70" obstructor_temp_unit="K" obstructor_emissivity="0.9"/>

Model a lens including the lens' thermal emission as well as possible obstruction of the lens and the thermal emission of the obstructing component.

transmittance: The path to the file containing the spectral transmittance coefficients. For details on the required structure see section Reading spectral quantities from files.
emissivity: The path to the file containing the spectral emissivity coefficients. For details on the required structure see section Reading spectral quantities from files.
temp optional: The temperature of the lens for the thermal emission.
temp_unit optional: The unit of the lens' temperature. This has to be one of [K, Celsius]. The default is K.
obstruction optional: The obstruction factor of the lens as ratio of the areas A_obstructor / A_lens.
obstructor_temp optional: The temperature of the obstructing component for the thermal emission.
obstructor_temp_unit optional: The unit of the obstructing component's temperature. This has to be one of [K, Celsius]. The default is K.
obstructor_emissivity optional: The emissivity of the obstructing component for the thermal emission. Valid ranges are 0.0 - 1.0. The default is 1.

BeamSplitter

<optical_component type="BeamSplitter" transmittance="PathToTransmittance" emissivity="PathToEmissivity" temp="70" temp_unit="K" obstruction="0.2" obstructor_temp="70" obstructor_temp_unit="K" obstructor_emissivity="0.9"/>

Model a beam splitter including the beam splitter's thermal emission as well as possible obstruction of the beam splitter and the thermal emission of the obstructing component.

transmittance: The path to the file containing the spectral transmittance coefficients. For details on the required structure see section Reading spectral quantities from files.
emissivity: The path to the file containing the spectral emissivity coefficients. For details on the required structure see section Reading spectral quantities from files.
temp optional: The temperature of the beam splitter for the thermal emission.
temp_unit optional: The unit of the beam splitter's temperature. This has to be one of [K, Celsius]. The default is K.
obstruction optional: The obstruction factor of the beam splitter as ratio of the areas A_obstructor / A_{beam splitter}.
obstructor_temp optional: The temperature of the obstructing component for the thermal emission.
obstructor_temp_unit optional: The unit of the obstructing component's temperature. This has to be one of [K, Celsius]. The default is K.
obstructor_emissivity optional: The emissivity of the obstructing component for the thermal emission. Valid ranges are 0.0 - 1.0. The default is 1.

Filter

<optical_component type="Filter" transmittance="PathToTransmittance" emissivity="PathToEmissivity" temp="70" temp_unit="K" obstruction="0.2" obstructor_temp="70" obstructor_temp_unit="K" obstructor_emissivity="0.9"/>

<optical_component type="Filter" band="M" emissivity="PathToEmissivity" temp="70" temp_unit="K" obstruction="0.2" obstructor_temp="70" obstructor_temp_unit="K" obstructor_emissivity="0.9"/>

<optical_component type="Filter" start="400" start_unit="nm" end="480" end_unit="nm" emissivity="PathToEmissivity" temp="70" temp_unit="K" obstruction="0.2" obstructor_temp="70" obstructor_temp_unit="K" obstructor_emissivity="0.9"/>