J/A+A/677/A141 Satellite trails on H.E.S.S. astronomical obs. (Lang+, 2023)
Impact of satellite trails on H.E.S.S. astronomical observations.
Lang T., Spencer S.T., Mitchell A.M.W.
<Astron. Astrophys. 677, A141 (2023)>
=2023A&A...677A.141L 2023A&A...677A.141L (SIMBAD/NED BibCode)
ADC_Keywords: Space observations ; Gamma rays
Keywords: astroparticle physics - light pollution - methods: data analysis -
instrumentation: detectors - gamma-rays: general
Abstract:
The 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.
Description:
This table details the individual satellite trail detections described
and analysed in the paper.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea2.dat 155 1658 Individual satellite trail detections
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- Run H.E.S.S. run number (Run_ID)
8- 10 F3.1 --- Track Track identifier within run (Track_ID)
12- 17 F6.1 MHz MeanTrailBr Mean of NSB map entries attached to
the trail (MeanTrailBrightness)
19- 23 F5.1 s TrailDur Trail duration (Trail_Duration)
25- 31 F7.1 MHz MaxTrailBr Maximum of NSB map entries attached to
the trail (MaximumTrailBrightness)
33- 44 F12.1 s TrailStTime First trail detection timestamp
(TrailStartTime)
46- 48 I3 --- NPixAffec Number of unique pixels attached to the
trail object
(NumberOfPixels_Affected))
50- 54 F5.3 deg/s VelSate Measured velocity for the trail
(VelocityOfSatellite)
56- 62 F7.4 deg MeanRunZA Mean run zenith angle
(MeanRunZenith_Angle)
64- 69 F6.1 s RunDur Run duration (Run_Duration)
71- 89 A19 "datime" RunxStTime Runs star time (UTC) (RunStartTime)
91-106 F16.14 --- MeanAtTrCoeff Mean atmospheric transparency coefficient
as defined in (Hahn et al.,
2014APh....54...25H 2014APh....54...25H)
(MeanAtmosphericTransparency_Coefficient)
108-117 F10.6 deg MeanRunRA Mean run right ascension (MeanRunRA)
119-128 F10.6 deg MeanRunDE Mean run declination (MeanRunDec)
130-136 F7.3 MHz MeanRunNSB Mean NSB value measured for the CT5
camera during the run (MeanRunNSB)
138-155 F18.16 --- RelMeanCT5Eff Mean CT5 muon efficiency during run
(Gaug et al., 2019ApJS..243...11G 2019ApJS..243...11G),
relative to the maximum value in the
dataset (RelativeMeanCT5_Efficiency)
--------------------------------------------------------------------------------
History:
From Samuel Spencer, samuel.spencer(at)fau.de
Acknowledgements:
This work has been through review by the H.E.S.S. collaboration, who
we thank for allowing us to use low level H.E.S.S. data in this work,
and for useful discussions with collaboration members regarding this
paper. We thank Felix Jankowsky for providing data from the H.E.S.S.
all-sky camera monitoring system. This work is supported by the
Deutsche Forschungsgemeinschaft(DFG, German Research Foundation)
Project Number 452934793.
(End) Patricia Vannier [CDS] 29-Jul-2023