Wavelength binning#

The first step is to produce the starting radiometric table with the spectral bins and their edges. This can be done for each channel by default EstimateSpectralBinning. The user can specify a dedicated Task in the channel description as described later in this section.

Inside RadiometricModel this tasks is handled by the create_table method. To use the default task in a script on a channel parsed in a dictionary, the user can write:

import exosim.tasks.radiometric as radiometric

estimateSpectralBinning = radiometric.EstimateSpectralBinning()
table = estimateSpectralBinning(parameters=channel_dict)

Caution

If the user doesn’t include the spectral_binning_task keyword in the channel description, the default EstimateSpectralBinning task is used. To develop a custom Task, please refer to Custom Tasks.

This Task returns an astropy.table.QTable for each channel. The table has only the following keywords:

keyword

content

ch_name

channel name

Wavelength

central bin wavelength in \(\mu m\)

bandwidth

band width of the spectral bin in \(\mu m\)

left_bin_edge

left edge of the spectral bin

right_bin_edge

right edge of the spectral bin

The EstimateSpectralBinning task include different methods to estimate the spectral binning, that can be tuned in the channel description document.

Photometer#

For a photometer the description xml file should look like this:

<channel> channel_name
    <type> photometer </type>
    ...
</channel>

In this case the radiometric table is estimated as the central wavelength of the photometer with a bin width equal to the wavelength band. Therefore the maximum and minimum wavelengths must be indicated along with the units in the xml file:

<channel> channel_name
    <type> photometer </type>

    <spectral_binning_task> EstimateSpectralBinning </spectral_binning_task>
    <wl_min unit="micron"> 0.5 </wl_min>
    <wl_max unit="micron"> 0.6 </wl_max>

    ...
</channel>

Spectrometer#

For a spectrometer the description xml file should look like this:

<channel> channel_name
    <type> spectrometer </type>

    ...
</channel>

The wavelength grid can be estimated in 2 modes:

  • native mode. If targetR is set to native the wavelength grid computed is the pixel level wavelength grid, where each bin is of the size of a pixel;

  • fixed R mode. If targetR` is set to a constant value, the wavelength grid is estimated using wl_grid.

The modes must be indicated in the configuration xml file along with the maximum and minimum wavelengths. The native configuration will look like this

<channel> channel_name
    <type> spectrometer </type>

    <spectral_binning_task> EstimateSpectralBinning </spectral_binning_task>
    <wl_min unit="micron"> 2 </wl_min>
    <wl_max unit="micron"> 6 </wl_max>
    <targetR> native </targetR>

    ...
</channel>

The fixed R configuration will be like

<channel> channel_name
    <type> spectrometer </type>
    <spectral_binning_task> EstimateSpectralBinning </spectral_binning_task>
    <wl_min unit="micron"> 2 </wl_min>
    <wl_max unit="micron"> 6 </wl_max>
    <targetR> 50 </targetR>

    ...
</channel>
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