J/A+A/677/A141ivo://CDS.VizieR/J/A+A/677/A141doi:10.26093/cds/vizier.36770141CDSLang T.Spencer S.T.Mitchell A.M.W.2025-05-22T20:01:17Z2023-09-19T10:26:21ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frspace-observatoriesobservational-astronomygamma-ray-astronomyThe number of satellites launched into Earth orbit has almost tripled in the last three years (to over 4000) due to the increasing commercialisation of space. Multiple satellite constellations, consisting of over 400000 individual satellites, have either been partially launched or are proposed for launch in the near future. Many of these satellites are highly reflective, resulting in a high optical brightness that affects ground-based astronomical observations. Despite this, the potential effect of these satellites on gamma-ray-observing Imaging Atmospheric Cherenkov Telescopes (IACTs) has largely been assumed to be negligible due to their nanosecond-scale integration times. This has, however, never been verified. As IACTs are sensitive to optical wavelength light, we aim to identify satellite trails in data taken by the High Energy Stereoscopic System (H.E.S.S.) IACT array. 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.2023A&A...677A.141Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/677/A141CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/677/A141https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/677/A141http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/677/A141https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/677/A141https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/677/A141http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/677/A141GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapGamma-raydefaultJ/A+A/677/A141/tablea2Individual satellite trail detectionsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRunH.E.S.S. run number (Run_ID)meta.id;obsintTrackTrack identifier within run (Track_ID)meta.idfloatMeanTrailBrMean of NSB map entries attached to the trail (Mean_Trail_Brightness)MHzphot.mag.sbfloatTrailDurTrail duration (Trail_Duration)stime.durationfloatMaxTrailBrMaximum of NSB map entries attached to the trail (Maximum_Trail_Brightness)MHzphot.mag.sbfloatTrailStTimeFirst trail detection timestamp (Trail_Start_Time)stime.epochdoubleNPixAffecNumber of unique pixels attached to the trail object (Number_Of_Pixels_Affected))meta.numberintVelSateMeasured velocity for the trail (Velocity_Of_Satellite)deg/sphys.velocfloatMeanRunZAMean run zenith angle (Mean_Run_Zenith_Angle)degpos.az.zdfloatRunDurRun duration (Run_Duration)stime.durationfloatRunxStTimeRuns star time (UTC) (Run_Start_Time)stime.epochnullableMeanAtTrCoeffMean atmospheric transparency coefficient as defined in (Hahn et al., 2014APh....54...25H) (Mean_Atmospheric_Transparency_Coefficient)stat.fit.paramdoubleMeanRunRAMean run right ascension (Mean_Run_RA)degpos.eq.ra;meta.maindoubleMeanRunDEMean run declination (Mean_Run_Dec)degpos.eq.dec;meta.maindoubleMeanRunNSBMean NSB value measured for the CT5 camera during the run (Mean_Run_NSB)MHzphot.mag.sbfloatRelMeanCT5EffMean CT5 muon efficiency during run (Gaug et al., 2019ApJS..243...11G), relative to the maximum value in the dataset (Relative_Mean_CT5_Efficiency)stat.paramdouble