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 -
Location
Summer view
KHO
1) Instrumental module (30x)
2) Service Section
3) Platform
More info at: http://kho.unis.no
Prof. Dr 2 K. Henriksen
Instruments @ KHO
TELESCOPE
IN ADDITION
a) Magnetometers
b) Scintillation receivers (GPS)
c) Riometer
d) Weather station
e) Web cameras
Institutions @ KHO
1.
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University Centre in Svalbard
University of Oslo
University of Tromsø
University of Alaska, Fairbanks
University College London
University of Wales Aberystwyth
University of Southampton
University of New Hampshire
Augsburg College
Tohoku University
National Institute of Polar Research Japan
Finnish Meteorological Institute
Embry Riddle Aeronautical University
Danish Meteorological Institute *
Air Force Research Laboratory *
Laboratoire de Planétologie de Grenoble
Institute of Radio Astronomy
AVINOR
The Polar Institute of China
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.
The FishTube spectrograph
Fiskeriforskning (1997)
Inspired by SP3 (1993).
1th Samples
AGF331 Remote Sensing and Advanced Spectroscopy (2000-07)
(a) Airspex 1 Imager
(b) (b) video camera
(c) (c) tripod
(d) (d) dome
The Oriel FICS spectral imager
Airspex 2 Imager –
Swedish version!
Experimental setup Dornier
Dronespex I-IV
Samples
AURORAL LOW LIGHT HYPERSPECTRAL IMAGING?
FS-IKEA
~14 days
?
Electronic Machine Shops
Purchase optics and mounts
The NORUSCA All-sky cameras
NORUSCA II-E fish-eye lens specifications
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.
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.).
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.
  2  / 
I  cos 2 
i  2 i 
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
*P. J. Miller, “Use of Tunable Liquid Crystal
Filters to Link Radiometric and Photometric
Standards”, Metrologia 28, 145 – 149
(1991).
System performance
1. Focus tests
Crossed scatter plots work best
Source: 1 mm diameter pinhole @ 1m
System performance
2. Mapping function
Source:
-1 mm diameter pinhole
-Schott NG9
-Distance = 1m
-Rotation in steps of 10 deg.
2nd order polynomial fit:
R  A0  A1    A2   2
Note:
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
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.
System performance
3. Spectral characteristics - center pixel!
2
z 
M   B0       0   cos  , [mW m-2 nm-1]
 z 

FWHM  BP 
K  M   C1  BP
[R s CTS-1]
8
System performance
3. Spectral characteristics – auroral emissions
Channel
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Wavelength
[nm]
470.9
557.7
630.0
427.8
450.0
486.1
500.2
568.0
589.0
636.4
656.3
662.4
670.5
676.4
700.0
Emission
species
N2+
[OI]
[OI]
N2+
Background
Hb
NII
NII
NaI
[OI]
H
N21P(6-3)
N21P(5-2)
N2
Background
FWHM
[nm]
5.99
7.10
8.02
5.44
5.73
6.19
6.37
7.23
7.50
8.10
8.35
8.43
8.53
8.61
8.91
Calibration
factor [R s CTS-1]
5.16
3.67
2.68
6.96
5.65
4.88
4.64
3.50
3.19
2.61
2.40
2.34
2.26
2.21
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
Composite RGB color image. Red (R) 636.4 nm,
green (G) 557.7 nm and blue (B) 486.1 nm.
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.
Or …
Samples
H
Y
P
E
R
S
P
E
C
T
R
A
L
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
Media 2
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.
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).