FACT - Threshold prediction for higher duty cycle and improved scheduling

TL;DR

This paper presents a method for predicting sensor currents and energy thresholds in the FACT Cherenkov telescope using moon and source positions, enabling optimized observation scheduling and higher duty cycles.

Contribution

It introduces a novel predictive approach leveraging moon and source geometry to dynamically set thresholds and improve scheduling in Cherenkov telescope operations.

Findings

Accurate prediction of sensor currents based on moon and source positions.

Enhanced scheduling efficiency with higher duty cycles.

Potential for improved sensitivity and background suppression.

Abstract

The First G-APD Cherenkov telescope (FACT) is the first telescope using silicon photon detectors (G-APD aka. SiPM). The use of Silicon devices promise a higher photon detection efficiency, more robustness and higher precision than photo-multiplier tubes. Being operated during different light-conditions, the threshold settings of a Cherenkov telescope have to be adapted to feature the lowest possible threshold but also an efficient suppression of triggers from night-sky background photons. Usually this threshold is set either by experience or a mini-ratescan. Since the measured current through the sensors is directly correlated with the noise level, the current can be used to set the best threshold at any time. Due to the correlation between the physical threshold and the final energy threshold, the current can also be used as a measure for the energy threshold of any observation. This presentation introduces a method which uses the properties of the moon and the source position to predict the currents and the corresponding energy threshold for every upcoming observation allowing to adapt the observation schedule accordingly.