Understanding the outputs

It’s easy.

The .h5 file

The main output product is a HDF5 .h5 file. This format has many viewers such as HDFView or HDFCompass and APIs such as Cpp, FORTRAN and Python.

../_images/output_main.png

payload

../_images/output_payload.png

The payload group contains all the information related to the instrument. Inside you will find a group for each channel and a group called payload description containing the parsed xml payload description file.

../_images/output_channels.png

Inside the channels group you will find a group for each channel called as the channel name. In this case you have Phot and Spec as they are the channels contained in payload_example.xml.

Let’s open a channel now.

../_images/output_spec.png

Inside each channel you find a dataset that is called as the channel. This is the main channel output table.

../_images/output_spec_table.png

Inside the text dataset called as the channel plus _table_column_meta_ are contained the table metadata. The couple dataset + metadata text can be read into an astropy quantity table (QTable) with the function load(). The _to_group directory contains the just described table converted into a dictionary and stored.

The description group contains the parsed section of the payload description file that contains the channel information.

Finally, the built_instr directory contains processed information related to the channel that allow ExoRad to load an already built channel without initialize again the instrument.

Understanding the Channel table

The channel table contained in the channels group is a table that contains all the information about the channel. Every row reprents a spectral bin. In the following we describe the columns of the table:

Table keywords

Parameter

Description

ChName

The name of the channel. Which is just the repetition of the channel name.

Wavelength

The central wavelength of the spectral bin.

Bandwidth

The bandwidth of the spectral bin.

LeftBinEdge

The left edge of the spectral bin.

RightBinEdge

The right edge of the spectral bin.

QE

The quantum efficiency of the detector in the spectral bin.

WindowSize

The window size of the detector in the spectral bin in pixels.

TR

The total transmission of the channel in the spectral bin.

instrument_signal

The signal of the instrument in the spectral bin [ct/s].

instrument_MaxSignal_inPixel

The maximum signal collected by a pixel of the instrument in the spectral bin [ct/s].

Target

../_images/output_targets.png

Inside the targets group you will find a directory for each target.

../_images/output_target.png

Inside each target there will be a list of subdirectories containing everything that concerns the target. For example you will find here all the information about the foregrounds and the star. skyTransmission is the total transmission resulting from all the foregrounds.

The final results are stored in the table group.

../_images/output_target_table.png

Understanding the Target table

The target table contained in the targets group, under a folder named after the observed target, is the table that contains all the final products of the simulations. Every row reprents a spectral bin. In the following we describe the columns of the table:

Table keywords

Parameter

Description

ChName

The name of the channel. Which is just the repetition of the channel name.

Wavelength

The central wavelength of the spectral bin.

Bandwidth

The bandwidth of the spectral bin.

LeftBinEdge

The left edge of the spectral bin.

RightBinEdge

The right edge of the spectral bin.

QE

The quantum efficiency of the detector in the spectral bin.

WindowSize

The window size of the detector in the spectral bin in pixels.

TR

The total transmission of the channel in the spectral bin.

instrument_signal

The signal of the instrument in the spectral bin [ct/s].

instrument_MaxSignal_inPixel

The maximum signal collected by a pixel of the instrument in the spectral bin [ct/s].

skyFilter_signal

The signal of the sky filter (e.g. Earth’s atmosphere) in the spectral bin [ct/s].

skyFilter_MaxSignal_inPixel

The maximum signal collected by a pixel of the sky filter in the spectral bin [ct/s].

zodi_signal

The signal of the zodiacal light in the spectral bin [ct/s].

zodi_MaxSignal_inPixel

The maximum signal collected by a pixel of the zodiacal light in the spectral bin [ct/s].

foreground_transmission

The total transmission of the foregrounds in the spectral bin. This is the transmission of all the elements in front of the telescope, as the transmission of the optical elements in the channel optical path is included in TR.

starFlux

The flux of the star in the spectral bin [W/m^2].

star_signal

The signal of the star in the spectral bin [ct/s].

star_MaxSignal_inPixel

The maximum signal collected by a pixel of the star in the spectral bin [ct/s].

MaxSignal_inPixel

The maximum signal collected by a pixel in the spectral bin [ct/s]. This is the combination of previous max signals. Note that the maximum signal in a pixel is the sum of the maximum signals of the instrument, sky filter, zodiacal light and star, and this is because using the same PSF, the most illuminated pixel is always the same.

saturation_time

The time in seconds to saturate a pixel in the spectral bin [s].

frameTime

The time in seconds to read a frame in the spectral bin [s]. This corresponds to the minimum saturation time in the detector.

instrument_signal_noise

The noise of the instrument signal in the spectral bin for an hour integration time [ct h^(1/2)].

skyFilter_signal_noise

The noise of the sky filter signal in the spectral bin for an hour integration time [ct h^(1/2)].

zodi_signal_noise

The noise of the zodiacal light signal in the spectral bin for an hour integration time [ct h^(1/2)].

star_signal_noise

The noise of the star signal in the spectral bin for an hour integration time [ct h^(1/2)].

darkcurrent_noise

The noise of the dark current in the spectral bin for an hour integration time [ct h^(1/2)].

readout_noise

The noise of the readout in the spectral bin for an hour integration time [ct h^(1/2)].

total_noise

The total noise in the spectral bin for an hour integration time [ct h^(1/2)].

Additionally, custom noises can appear in the table if they are included in the simulation (e.g., gain_noise).

Note

The noise values are calculated for an hour integration time. If you want to calculate the noise for a different integration time, you can use the formula:

\[\text{noise} = \text{noise}_{\text{hour}} \times \sqrt{\frac{\text{integration time}}{3600 \text{ s}}}\]

where noise_{hour} is the noise value for an hour integration time.

Note

The first part of the table is the same as the channel table, as the target table is the result of the combination of the channel table with the foregrounds and the star.