TwoPassWindowSum

class ctapipe.image.TwoPassWindowSum(**kwargs)

Bases: ctapipe.image.extractor.ImageExtractor

Extractor based on [1] which integrates the waveform a second time using a time-gradient linear fit. This is in particular the version implemented in the CTA-MARS analysis pipeline [2].

Notes

1. slide a 3-samples window through the waveform, finding max counts sum; the range of the sliding is the one allowing extension from 3 to 5; add 1 sample on each side and integrate charge in the 5-sample window; time is obtained as a charge-weighted average of the sample numbers; No information from neighboouring pixels is used.

2. Preliminary image cleaning via simple tailcut with minimum number of core neighbours set at 1,

3. Only the brightest cluster of pixels is kept.

4. Parametrize following Hillas approach only if the resulting image has 3 or more pixels.

5. Do a linear fit of pulse time vs. distance along major image axis (CTA-MARS uses ROOT “robust” fit option, aka Least Trimmed Squares, to get rid of far outliers - this should be implemented in ‘timing_parameters’, e.g scipy.stats.siegelslopes).

6. For all pixels except the core ones in the main island, integrate the waveform once more, in a fixed window of 5 samples set at the time “predicted” by the linear time fit. If the predicted time for a pixel leads to a window outside the readout window, then integrate the last (or first) 5 samples.

7. The result is an image with main-island core pixels calibrated with a 1st pass and non-core pixels re-calibrated with a 2nd pass.

References

1

10. Holder et al., Astroparticle Physics, 25, 6, 391 (2006)

2

https://forge.in2p3.fr/projects/step-by-step-reference-mars-analysis/wiki

Attributes Summary

apply_integration_correction	a TelescopeParameter with Bool trait type
core_threshold	a TelescopeParameter with Float trait type
disable_second_pass	A boolean (True, False) trait.

Methods Summary

__call__(waveforms, telid, selected_gain_channel)

Call this ImageExtractor.

Attributes Documentation

apply_integration_correction

a TelescopeParameter with Bool trait type

core_threshold

a TelescopeParameter with Float trait type

disable_second_pass

A boolean (True, False) trait.

Methods Documentation

__call__(waveforms, telid, selected_gain_channel)

Call this ImageExtractor.

Parameters

waveformsarray of shape (N_pixels, N_samples)

DL0-level waveforms of one event.

telidint

Index of the telescope.

selected_gain_channel: array of shape (N_channels, N_pixels)

Array containing the index of the selected gain channel for each pixel (0 for low gain, 1 for high gain).

Returns

chargearray_like

Integrated charge per pixel. Shape: (n_pix)

pulse_timearray_like

Samples in which the waveform peak has been recognized. Shape: (n_pix)