Very Large Space Optics for anVery Large Space Optics for an Investigation of the Extreme

Universe

Presented by Jim Adams for the Super EUSO Collaboration*for the Super EUSO Collaboration

*Eberhard Karls Universität Tübingen; MPI für Physik, München; Universidad de Alcalá; APC (France); Swedish Institute of Space Physics; LIP (Portugal); Università di Genova; INAF (Palermo Italy);Physics; LIP (Portugal); Università di Genova; INAF (Palermo, Italy); INFN and INOA, (Florence, Italy); Università di Roma Tor Vergata; Università di Perugia; Observatoire de Neuchâtel; Skobeltsyn Institute; UNAM, Mexico; RIKEN, Japan; Univ, of Ala., Huntsville; Vanderbilt Univ ; Sp Sci Lab UCB; UCLA; Univ of Utah; NASA

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Vanderbilt Univ.; Sp. Sci. Lab., UCB; UCLA; Univ. of Utah; NASA-MSFC and NASA-GSFC

https://ntrs.nasa.gov/search.jsp?R=20090002566 2018-07-11T17:43:42+00:00Z

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(cosmic rays); X (active galactic nuclei); blue shading (exposure)

Event Arrival Direction Reconstruction

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Extreme Energy Cosmic Rays (EECR )(EECRs)

• Energies extending to at least 50 Joules/particleg g p• Fluxes of 1 particle/(km2∗century)

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Shower Time Profile

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Hybrid Ground-based ArrayHybrid Ground based Array

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Fluorescence Detector

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Super-EUSO

•Variable orbit 1000 km

•Free Flyer•Variable orbit 1000 km

• FOV

• yr5Life ≈sr km104.2A 26inst

aper ⋅×≈

25° y5ife% 2010cycle ÷≈η

( ) yrsrkm104221A 26×≈

25

( ) yrsrkm104.22.1Aexp ×−≈

Tilted mode (?)

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exp →

Super EUSO Instrument R iRequirements

• Very large wide-angle telescope with high optical th h t d 1 illi di l l tithroughput and ~1 milliradian angular resolution

• High efficiency pixelated photo-detectors with single photon sensitivity– Photomultiplier tubes with ultra-bialkali photocathodes or– Silicon photomultipliers

• Optics Design Options– Reflective optics:

• Schmidt or Maksutov optics– Convex focal surface

– Refractive optics (the JEM-EUSO concept)Refractive optics (the JEM EUSO concept)• Very large and light-weight Fresnel lenses • Diffractive lens for chromatic correction

– Antireflective coatings needed in either case

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Photomultiplier Tubesp• Hamamatsu Ultra-Bialkali photocathodes

40 45% Q E f 330 400– 40-45% Q.E. from 330-400 nm– Off the shelf (Hamamatsu)

L i t t b f– Large inter-tube gaps on a convex surface• Back-illuminated Silicon Photomultipliers

– 90% Q.E. from 330-400 nm– Requires cooling– Developmental (Siemens)– Small inter-device gaps on a convex surface

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g p

Optics Design ConceptsOptics Design Concepts

Maksutov optical design with an Schmidt design with an f/# of 0.7 and a

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f/# of 0.66, CAO at UAH, Huntsvilleg

50° field of view, CNR- INOA, Firenze

Optics Throughput

Obscuration due to focal surfaceObscuration due to focal surface

+ Mirror reflectivity + transmission of Schmidt corrector reduce of ~ 0.9

Filt t id d f !!

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Filters not considered so far!!

Refractive Opticsp

500.00 MM Diffractive/Fresnel

Focal Surface

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Achromatic Fresnel- Diffractive, f/1.0 Scale: 0.05 AZ 28-Apr-04

Throughput is less than with reflective systems

Shower Imaging and ReconstructionSuper-EUSO functions like a high-speed and wide angle video camera• Frame rate: ~3 μsec/frameFrame rate: 3 μsec/frame

• Pixel Size: 4×4 mm2 on the focal surface or 1×1 km2 on Earth

R t ti i 1 1 1 k 3 l• Reconstruction in 1×1×1 km3 voxels

• Arrival direction reconstruction to <0.2°

• Energy reconstructed from fitted e gy eco st ucted o ttedintensity at shower maximum

For those events with a detected Cherenkov reflection at a knownCherenkov reflection at a known altitude:• Shower profile versus atmospheric depth will be reconstructed

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depth will be reconstructed.

Optics Manufacturing R iRequirements

• Surface RoughnessSurface Roughness– 20 nm RMS on refractive elements

5 nm RMS on reflective elements– 5 nm RMS on reflective elements• Tilt errors

– <0.5 milliradian• Anti-reflective Coatings on refractive

elements– >90% transmission in the 330-400 nm band

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Super EUSO Spacecraft Concepts

These folding concepts were developed to fit Super-EUSO into an existing faring.

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ARES V OptionARES V Option• Launch Super p

EUSO as a rigid unit– Spherical mirror

constructed from regular hexagonalregular hexagonal zones

– Segmented corrector plate in the style of a lighthouse lens

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lighthouse lens

Notional Designg

Segmented Corrector Plate Mirror constructed from

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hexagonal spherical segments

Summaryy• Super EUSO is needed to find out how the

most energetic cosmic accelerators workmost energetic cosmic accelerators work and what they are accelerating?

• The Super-EUSO instrument must be aThe Super EUSO instrument must be a very large high-speed and wide-angle video camera in space.p

• We are open to suggestions for improvements in design and also concepts p g pfor manufacturing such an instrument.

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The End

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