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Studying Telescope PropertiesUsing an Airborne Light Source
Next-Generation Techniques for UHE Astroparticle Physics, Chicago, ILLenka Tomankova, for the Pierre Auger Collaboration | 29th Feb 2016
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Contents
1. Idea of the flying light source
2. Airborne platform
3. Isotropic point-like light source
4. Measurements at the Pierre Auger Observatory
5. (Other) Applications
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Idea of the flying light source
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Idea of the flying light source
Light sourceof known properties
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Idea of the flying light source
Light sourceof known properties
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Idea of the flying light source
Light sourceof known properties
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The Octocopter
Commercial platform from www.mikrokopter.de
80 cm
LiPobattery
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The Octocopter
● Remotely controlled● Electronically stabilized● GPS-assisted positioning
Commercial platform from www.mikrokopter.de
● Payloads up to ∼1 kg● Flight time up to 20 min● Rising speed up to 40 km/h
80 cm
LiPobattery
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Add-ons & modifications● GPS device and 3D compass:
Extend position controller from 2D to 3DImplement programmable pointing
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Automatically fly into the FOV of a pixel with defined pointing
Add-ons & modifications● GPS device and 3D compass:
Extend position controller from 2D to 3DImplement programmable pointing
key features!
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Automatically fly into the FOV of a pixel with defined pointing
Add-ons & modifications
● Pressure sensor:Altitude stabilization
● GPS device and 3D compass:Extend position controller from 2D to 3DImplement programmable pointing
key features!
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Automatically fly into the FOV of a pixel with defined pointing
Add-ons & modifications
● Pressure sensor:Altitude stabilization
● Bi-directional radio link (868 MHz):Receive diagnostic info (battery voltage)Configure and send instructions during flight
● GPS device and 3D compass:Extend position controller from 2D to 3DImplement programmable pointing
key features!
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Automatically fly into the FOV of a pixel with defined pointing
Add-ons & modifications
● Pressure sensor:Altitude stabilization
● Bi-directional radio link (868 MHz):Receive diagnostic info (battery voltage)Configure and send instructions during flight
● Extension port:Hardware schematics and source code are open → interface with electronic board of the light source
● GPS device and 3D compass:Extend position controller from 2D to 3DImplement programmable pointing
key features!
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Ground station software
→ Simplify planning and execution of flights during the night
diagnostic infoduring flight
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Ground station software
→ Simplify planning and execution of flights during the night
diagnostic infoduring flight
program 3D waypoints
configure light sourcelog nav data
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Light source requirements
Emission spectrum in UVIsotropic & homogeneousPoint-like
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regular dodecahedron structure12 individually driven LEDs
∅ 10 cm, 150 g total
coated with Tyvek
polyethylenediffuser sphere
Design & construction
110 cm
LED type H2A1-H375by Roithner LaserTechnik
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Spectrum & isotropy
λmax= 376 nm
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Spectrum & isotropy
isotropic to ±0.5%
0.7%
Longitude (deg)
Latit
ude
(deg
)
λmax= 376 nm
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● 12 current-stabilized independent outputs
● Measurement of electronics & light source temperature
● Configuration via I2C:
AmplitudePulse delay 50 – 1000 μsPulse length 2 – 64 μs
Driving electronics
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● Mounted on optical bench● NIST-calibrated photodiode
+ Keithley electrometer● Baffle system
→ measurement of charge per pulse
Calibrationsetup
2.3 m
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Temperature correction
Ctemp= (-6.158 ± 0.007 ) × 10−3 ∆T - (5.413 ± 0.035) × 10−5 ∆T2
● Significant temperature gradient ∼5% per 10°C● Temperature difference between calibration and
flight temperature ~15°C→ average correction of 8%
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Achievable accuracy
Error source %Radiant energy 1.4
Intensity stability 1.2Atmospheric effects1 1.4
Flight distance1 0.6Isotropy 0.5
Other 0.2TOTAL 3.7
Pulse charge → radiant energy
→ photons on aperture
1at 1 km distance
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Achievable accuracy
Error source %Radiant energy 1.4
Intensity stability 1.2Atmospheric effects1 1.4
Flight distance1 0.6Isotropy 0.5
Other 0.2TOTAL 3.7
Pulse charge → radiant energy
→ photons on aperture
Pulse area Position on camera
2.0%1.1%
Additional error sources during analysis:
1at 1 km distance
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The Octopad at 1 km distance
Ideally no wind (
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Octocopter measurements
1000 m
250 m
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Octocopter measurements
1000 m
250 m
2000 pulses per pixel
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Point spread function
∅ of pixel FOV 1.5°Effective spot size ∼0.6°
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Point spread function
∅ of pixel FOV 1.5°Effective spot size ∼0.6°
2000 pulses per pixel
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Point spread function
∅ of pixel FOV 1.5°Effective spot size ∼0.6°
Reflections on PMTs
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Point spread function
∅ of pixel FOV 1.5°Effective spot size ∼0.6°
Reflections on PMTs
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Point spread function
∅ of pixel FOV 1.5°Effective spot size ∼0.6°
Reflections on PMTsScattering by dust
layer on mirror 8% at the bottom < 1% at the top
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End-to-end simulation
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End-to-end simulation
Replace ray-tracing by photon-to-ADC maps measured by the Octocopter
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Cross-calibration of Auger and TA (2013)
Independent calibration at TA → difference in radiant energy 1.3%
[1] J. N. Matthews, [2] K. Machida, for the Pierre Auger and Telescope Array Collaborations, Proc. of the ICRC 2013.
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Other applications
● CROME: antenna array for detecting GHz radiation from air showers (KIT)
● Microwave emitter to study– pointing– radiation patterns– end-to-end sensitivity
● Also used at:AERA, LOFAR, Murchison Widefield Array
R. Šmída et al., Phys. Rev. Lett. 113, 221101; F. Werner, PhD thesis, KIT, 2013
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Summary
Accuracy
FlexibilityVersatilityPortability
Number of photons on aperture to 3.7%End-to-end calibration to 5%Calibration, PSF, timing, simulation verification, photon-to-ADC mapsPick your sourceFits into a carry-on → cross-calibration of observatories
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Backup
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Absolute Auger FD calibrationLarge-diameter Lambertian sourceEntire camera read out simultaneouslyInsensitive to PSF9.9% systematic uncertainty
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