Estimate signals

There are different signals to estimate for the radiometric model, that depends on different focal planes:

• source

• foreground

• sub foregrounds

Source and Foreground signal

Source and foreground signal are estimated using aperture photometry in the same way and on the same apertures starting from their focal planes. They are estimated for each channel by using ComputeSignalsChannel task by default.

ComputeSignalsChannel needs a radiometric table with apertures listed and a focal plane, then it runs AperturePhotometry and returns its results.

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

    <radiometric>
        <signal_task> ComputeSignalsChannel </signal_task>
        ...
    </radiometric>

</channel>

Inside RadiometricModel this tasks is handled by the compute_source_signals method for the source focal plane and by the compute_foreground_signals method for the foreground. To use the default task in a script on a channel the user can write:

import exosim.tasks.instrument as instrument

computeSignalsChannel = instrument.ComputeSignalsChannel()
photometry = computeSignalsChannel(table=table,
                                   focal_plane=focal_plane)

Where table is the wavelength radiometric table with apertures and focal plane is the channel source or foreground focal plane array.

Caution

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

The default ComputeSignalsChannel task uses the apertures center, sizes and shapes in the radiometric table to perform aperture photometry with the appropriate apertures using photutils.aperture.aperture_photometry.

Foreground sub focal plane signals

If at least one of the foreground has the isolate option enable, there will be contributions to the focal plane to estimate for the radiometric table. As mentioned already in Foreground sub focal planes, these focal planes are stored in a dedicated directory. To estimate their contribution to the radiometric signal, a default Task has been developed: ComputeSubFrgSignalsChannel. As ComputeSignalsChannel, this task use AperturePhotometry to perform aperture photometry on the same apertures used for source and general foreground focal planes. This task should be indicated in the description document as

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

    <radiometric>
        <sub_frg_signal_task> ComputeSubFrgSignalsChannel </sub_frg_signal_task>
        ...
    </radiometric>

</channel>

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

import exosim.tasks.radiometric as radiometric

computeFrgSignalsChannel = radiometric.ComputeSubFrgSignalsChannel()
signal_table = computeFrgSignalsChannel(table=table,
                                        ch_name=ch,
                                        input_file=input,
                                        parameters=description)

Where table is th wavelength radiometric table with aperture, ch_name is the channel name, input_file is the input hdf5 file containing the focal planes, and parameters is the dictionary containing the aperture photometry information from the xml file.

Caution

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