Hyperspectral imaging of aurora and airglow at KHO

Fred Sigernes 1,*, Yuriy Ivanov 2, Sergey Chernouss 3, Trond Trondsen 4, Alexey Roldugin 3, Yury Fedorenko 3, Boris Kozelov 3, Andrey Kirillov 3,

Ilia Kornilov 3, Vladimir Safargaleev 3, Silje Holmen 1, Margit Dyrland 1, Dag Lorentzen 1 and Lisa Baddeley 1

1 The University Centre in Svalbard (UNIS), N-9171 Longyearbyen, Norway 2 Main Astronomical Observatory, National Academy of Sciences, Ukraine 3 Polar Geophysical Institute, Murmansk Region, Apatity, Russia 4 Keo Scientific Ltd., Calgary, Alberta, Canada

MLTI Waves and Dynamics at Polar Latitudes Workshop, Utah State University, 9-11 October 2012

THE KJELL HENRIKSEN OBSERVATORY – KHO 2008 -

Prof. Dr 2 K. Henriksen

KHO 1) Instrumental module (30x)2) Service Section3) Platform

Summer view

Location

More info at: http://kho.unis.no

Instruments @ KHO

TELESCOPE

IN ADDITION a) Magnetometersb) Scintillation receivers (GPS)c) Riometerd) Weather statione) Web cameras

Institutions @ KHO1. University Centre in Svalbard 2. University of Oslo3. University of Tromsø4. University of Alaska, Fairbanks 5. University College London 6. University of Wales Aberystwyth 7. University of Southampton 8. University of New Hampshire 9. Augsburg College10. Tohoku University 11. National Institute of Polar Research Japan 12. Finnish Meteorological Institute 13. Embry Riddle Aeronautical University 14. Danish Meteorological Institute * 15. Air Force Research Laboratory *16. Laboratoire de Planétologie de Grenoble17. Institute of Radio Astronomy18. AVINOR19. The Polar Institute of China 20. The University of Electro-Communications Tokyo

The 10 Nations @ KHO

… & excellent students!

PARTNERS @ LYR

INTERNET

KHO - UNIS – ARS - MINE 7

HYPERSPECTRAL IMAGING AT KHO

Picture of the assembled Spextube Imagers. M is rotary table, T front surface mirror, L1 front lens, A 35mm camera lens adapter, O laser pointer, B barrel contains spectroscope, L3 camera lens, CCD camera head, I lift table, and E two steel bars.

Inspired by SP3 (1993).Fiskeriforskning (1997)

The FishTube spectrograph

1th Samples

(a) Airspex 1 Imager(b) (b) video camera (c) (c) tripod (d) (d) dome

Airspex 2 Imager –Swedish version!

AGF331 Remote Sensing and Advanced Spectroscopy (2000-07)

The Oriel FICS spectral imager

Experimental setup Dornier Dronespex I-IV

Samples

Electronic Machine Shops

~14 days

Purchase optics and mounts

FS-IKEA

?

AURORAL LOW LIGHT HYPERSPECTRAL IMAGING?

The NORUSCA All-sky cameras

Two NORUSCA II 1st Generation all-sky cameras (A) and (B). (1) Front element of all-sky lens, (2) 24 x 4 inch2 mount plate, (3) collimator lens tube, (4) lens mount, (5) ring holders, (6) filter box, (7) camera lens, and (8) EMCCD detector. Instrumental volume is ~ 65 x 18 x 16 cm3. Total mass is 8.9 kg.

NORUSCA II-E fish-eye lens specifications

Spectral range 430 – 750 nm

Paraxial focal length 3.5 mm

F-number f/1.1

Number of lens elements 12

Field of view 180 º (circular)

Filter diameter 35 mm

Angle of incident on filter 7 º

Dimensions Ø110 × 320 mm

Camera lens mount C-mount

EMCCD detector: - PI ProEM 512B- 8.2 x 8.2 mm2

-70 deg. air cooled- Back-illuminated; 90% QE

Optical layout and design of the NORUSCA II Camera

Lens mechanics and optical diagram of the NORUSCA II all-sky lens: (1) focusing mechanism and collimator lenses, (2) filter box - chamber, (2) (3) camera lens, and (4) camera head.

The NORUSCA II Point Spread function

Resolution:~ 60 lp/mm

Filter: Liquid Crystal Tunable Filter (LCTF) (Cambridge Research & Instrumentation, Inc.).

*P. J. Miller, “Use of Tunable Liquid Crystal Filters to Link Radiometric and Photometric Standards”, Metrologia 28, 145 – 149 (1991).

ii

I

2

cos

/22

Spectral tuning is obtained by using electronically controlled liquid crystal wave plates to a Lyot filter design*.

The wave plates behave as optical birefringent elements with an electrically variable retardance.

Retardance is termed the optical path difference between the ordinary and extraordinary rays passing through a birefringent element.

The latter is controllable due the effect that the liquid crystal molecules are orientation sensitive to electric fields applied between the plates. Since the retardance is directly linked to wavelength, the filters are tunable.

Our filter: 400–720nm FWHM=7nm @ 550nm

System performance 1. Focus tests

Crossed scatter plots work best

Source: 1 mm diameter pinhole @ 1m

System performance 2. Mapping function

2210 AAAR

Mapping function coefficients NORUSCAII all-sky lens

R in units of [PIXELS] [mm]

A0 -1.00073 -0.0160274

A1 +244.459 +3.91516

A2 -51.4828 -0.824529

Source: - 1 mm diameter pinhole- Schott NG9 - Distance = 1m- Rotation in steps of 10 deg.

2nd order polynomial fit:

R is for > 30º in-between the mapping functions of an equal area and an orthographic fisheye lens, and its maximum Rmax = 4.08 mm at = 90 º matches the size of the EMCCD.

Note:

System performance 3. Spectral characteristics - center pixel!

,cos2

00

zzBM [mW m-2 nm-1]

8

BPFWHM BPCMK 1 [R s CTS-1]

System performance 3. Spectral characteristics – auroral emissions

Channel#

Wavelength[nm]

Emission species

FWHM[nm]

Calibration factor [R s CTS-1]

1 470.9 N2+ 5.99 5.16

2 557.7 [OI] 7.10 3.673 630.0 [OI] 8.02 2.684 427.8 N2

+ 5.44 6.965 450.0 Background 5.73 5.656 486.1 Hb 6.19 4.887 500.2 NII 6.37 4.648 568.0 NII 7.23 3.509 589.0 NaI 7.50 3.1910 636.4 [OI] 8.10 2.6111 656.3 H 8.35 2.4012 662.4 N21P(6-3) 8.43 2.3413 670.5 N21P(5-2) 8.53 2.2614 676.4 N2 8.61 2.2115 700.0 Background 8.91 2.01

The minimum detection threshold signal is assumed to be 3 times the dark noise level, or 3s = 150 CTS/s. For the green [OI] 557.7 nm emission, the minimum detection limit then becomes 550 R.

First Samples

Screen dump of raw data from the camera at 630 nm. View from authors office desk at UNIS. Exposure time 10 ms at gain 40.

Composite RGB color image. Red (R) 636.4 nm,

green (G) 557.7 nm and blue (B) 486.1 nm.

Or …

Samples

HYPERSPECTRAL

Raw data January 24.01.2012 15:15:03 UT

Nightside aurora

Media 1

Panel (A): Color composite image from the NORUSCA II camera 24th of January 2012 at 15:15 UT. Location is the Kjell Henriksen Observatory (KHO). The Red color component of the image is at center wavelength 630 nm, Green at 557.7 nm and Blue at 400.9 nm

Dayside aurora

Panel (A): Color composite image from the NORUSCA II camera 29th of December 2011 at 08:55:00UT. Location is the Kjell Henriksen Observatory (KHO). The Red color component of the image is at center wavelength 630 nm, Green at 557.7 nm and Blue at 470.9 nm.

Media 2

Concluding remarks (preliminary)

• NORUSCA II: New hyperspectral all-sky camera (430 – 720 nm). • Wavelength element (filter): LCTF with FWHM = 7 nm @ 550 nm. • Novel C-mount NORUSCA II–E All-sky lens f/value=1.1. • Detects ~1/2 kR of auroral emissions in just 1 sec. • No moving mechanical parts to swap center wavelength.• It uses 50 ms to swap between 41 available center wavelengths.• Opens for new processing methods such as classification • The major disadvantage of the system is the low transmission of the

LCTF, especially in the blue part of the spectrum.

Acknowledgement

We wish to thank

The Research Council of Norway through the project named:

Norwegian and Russian Upper Atmosphere Co-operation On Svalbard part 2 # 196173/S30 (NORUSCA2).