Satellite trails on H.E.S.S. astronomical obs.

This is to quantify the potential effects on data quality and extensive air shower event classification and reconstruction. Using night sky background measurements from H.E.S.S., we determine which observation times and pointing directions are affected most by these satellite trails, and evaluate the impact on the standard Hillas parameter variables used for event analysis. Due to the brightest trails, false trigger events can occur, however for most modern analyses the effect on astronomical results will be minimal.

We observe a mild increase in the rate of trail detections over time (approximately doubling in three years), which is partially correlated with the number of satellite launches. But the fraction of H.E.S.S. data affected (~0.2% of dark time observations) is currently small. Nevertheless, these trails could have a non-negligible effect on future Cherenkov Telescope Array observations if advanced analysis techniques designed to lower the energy threshold of the instrument are used.