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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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