Comparison with CTA-MARS: Image cleaning & parametrization

[HealthyPear]

This issue is part of a project described in issue #24

The following is a "real-time" list of points that are found to be differences between the pipelines using the comparison.
Not all features are critical to recover the missing performance, but all should be implemented (as more similar as possible) in order to allow their optional use when comparing different algorithms.

---

• Cleaning thresholds (OPTION)

These quantities depend on the calibration process (see issue #31) and in principle could be defined via benchmarking.
Currently we define them by requiring the rejection of 99.7% of the noise (which in the case of the pure MonteCarlo simulation means pixels where the true number of photoelectrons is 0).
Preliminary testing without double-pass image extraction (see below) shows that such thresholds are ~(8,4) for core and boundary pixels respectively for both LSTCam and NectarCam.
These values should decrease as we approach the method implemented in CTA-MARS.

---

• miss parameter and its use in direction reconstruction (TESTING - done in the benchmarks but should be moved to code)

This is more relevant for direction reconstruction, but it is done using output of this data-level.
Description is here.
In protopipe, this requires the output of parameters that are currently missing from the generated DL1 files (the coordinates of the Center of Gravity of the parametrized image - see ISSUE #40 ).

---

• Double-pass image extraction

SEE ISSUE #31 FOR LATEST NEWS

---

• Apply correction for optical aberrations ( in PR Upgrade of data training #58 )

Even if in the end we will most likely use the leakage parameter to assess if an image is clipped, this is still relevant for image parametrization.
In CTA-MARS the conversion between distances and degrees in each camera is done via a linear factor. Such quantity depends on the geometry of the dish containing the mirrors and takes into account optical aberrations.
This is explained in more detail in the second point of this section of the wiki