Prepare Target

The target list

The target to observe are listed in the target list already mentioned. This file is read by LoadTargetList. At the moment only the xlsx and csv format are supported, but more loader can be written for dedicated format if needed. An example of target list is contained in the examples folder as test_target.csv.

Once the target list has been loaded, each target must be prepared before the observation, and this is done by PrepareTarget.

Load the source

Now the target needs a source. ExoRad allow the user to choose between three different kind of source, and this can be set in the payload description file in the common section under the keyword sourceSpectrum.

The first option is planck. In this case a planck function for the target temperature is produced by exorad.utils.exolib.planck().

<sourceSpectrum>planck </sourceSpectrum>

The second option is phoenix. In this case the code select the phoenix star that suits the target best. You have to indicate the directory containing the phoenix spectra. The phoenix spectra should be BT-Settl Phoenix files of the type BT-Settl.spec.fits.gz that can be downloaded from the Phoenix database.

    <StellarModels> path/to/phoenix </StellarModels>

The last option is custom that allows you to use a specific sed input. An example of a custom sed is reported in examples/customsed.csv.


The source is set by LoadSource, that associate a source Sed to the target.

Include foregrounds

ExoRad can handle foregrounds that produce diffuse light between the telescope and the source. These are automatically read and loaded into the target by EstimateForegrounds. This tasks can read the ordered list of foreground contained in the payload description and choose the class to best handle them.

There are two kinds of foregrounds in ExoRad: zodiacal and custom.

Remember that also the foreground order is important, as each of them my have a transmission that filters the signals from sources posed before it. The foreground must be added in the payload description document in the common section.

zodiacal foreground

The zodiacal foreground models the zodiacal light. It is handled by ZodiacalFrg and it’s an implementation of the model presented in Glasse et al. 2010, where the radiance is

\[zodi = A \cdot (3.5 \cdot 10^{-14} BB(T= 5500.0 K, \lambda) + 3.58 \cdot 10^{-8} BB(T= 270.0 K, \lambda))\]

where \(BB\) is the planck model and \(A\) is set by the user in the payload description file under the keyword zodiacalFactor.

To include the zodiacal foreground in your simulation add it in the payload description file as

<foreground> zodiacal
        <zodiacFactor>2.5 </zodiacFactor>

In this case the zodiacal name is important because it tells ExoRad the model to use.

A model for zodiacal foreground depending on target position is also available by using the keyword

<foreground> zodiacal
        <zodiacFactor>2.5 </zodiacFactor>
        <zodiacalMap> True </zodiacalMap>

The fitted coefficient refers to Kelsall et al. 1998 model considering a 90 deg elongation from the Sun


The model for zodiacal foreground depending on target position is still under validation.

This foreground is added to the target by EstimateZodi, that is containted in EstimateForegrounds.

custom foreground

Also a custom foreground can be add. This must be a ‘.csv` file containing at least three columns: Wavelength, Transmission and Radiance. The foreground is used this time as a filter (SkyFilter) and handled by SkyForeground. Such foreground can be added as

<foreground> custom

This time the name is not as important as before, and can be set to identify the filter.

In the payload_example.xml we show how to use a custom foreground using a simulation of atmospheric foreground computed with Modtran and we call it skyFilter.

This foreground is added to the target by EstimateForeground, that is also contained in EstimateForegrounds.