THE ACE SATELLITE SOLAR
SPECTRUM
F. HASE
Institut fur Meteorologie und Klimaforschung, Forschungszentrum Karlsruhe, Postfach
3640, D-76021 Karlsruhe, Germany
S. D. McLEOD
Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
K. A. WALKER
Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7
P. F. BERNATH
Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
R. COLIN
Spectroscopie de l’Atmosphere…, Université Libre de Bruxelles, B1050, Brussels,
Belgium
L. Wallace
National Optical Astronomy Observatories, Tucson, AZ, 85732, USA
Introduction
• High quality solar spectra (with
assignments) are useful as models in
astronomical spectroscopy
• Often needed as reference spectra for
atmospheric spectroscopy (e.g., to apply
Beer’s law need I/I0 and I0 is a pure solar
spectrum); see Hase et al. JQSRT 102,
450 (2006)
Kitt Peak Solar Spectrum
High Res. IR Solar Atlases
Nine Kitt Peak solar atlases
recorded with the McMathPierce Fourier transform
spectrometer (available at
ftp://nsokp.nso.edu/pub/atlas)
plus some work at
Jungfraujoch
High quality spectra but
telluric absorption is a
problem. Solution is
satellite observations.
ATMOS Mission
High resolution (0.01 cm-1)
FTS covering 650-4750 cm-1
spectral region that flew on
the Space Shuttle in 1985
(Spacelab-3), 1992 (ATLAS1), 1993 (ATLAS-2) and
1994 (ATLAS-3). Used
photoconductive MCT
detectors and filters to
improve the signal-to-noise
ratio. (Good spectral
coverage, but severe
nonlinearity and spectra
were recorded in pieces.)
ATMOS Solar Atlases
1. From two days of data from 1985 Spacelab-3 mission the “ATMOS Solar
Atlas” was created. NASA publication 1989NASRP1224: A high-resolution
atlas of the infrared spectrum of the Sun and Earth atmosphere from space:
a compilation of ATMOS spectra of the region from 650 to 4800 cm⁻¹ (2.3 to
16 μm) by C. B. Farmer, R. H. Norton and M. Geller (3 volumes); digital
data available at ftp://nsokp.nso.edu/pub/atlas/
2. From ten days of data (about 10000 spectra; 600-4800 cm-1 in 4 filter
regions) from 1994 ATLAS-3 mission at new solar “atlas” was created. See
Abrams et al. Applied Optics, 35, 2747 (1996); digital data for 4 filter regions
available from http://remus.jpl.nasa.gov/atmos/
ATMOS Spectra
Good spectra,
but contain
strong H2O and
CO2 lines form
residual gas in
the instrument
container on
orbit and optical
filters chop
spectra into
pieces.
Spacelab-3
spectrum (1985)
3026
cm-1
ATLAS-3 spectrum
(1995)
3038.5
cm-1
ACE Satellite
Bernath et al. GRL, 32,
L15S01 (2005)
Solar Occultation
Advantages:
•Radiance of sun gives higher S/N than emission
•Limb view gives longer path length ~500 km (lower detection limits) than nadir
•“Self-calibrating” so excellent long-term accuracy and precision
Disadvantages:
•Modest global coverage
•Samples only free troposphere
Global Distribution of
Phosgene, Cl2CO
Fu et al. GRL, 34, L17815, 2007
Cl
O
‫װ‬
C
Cl
2004-2005-2006 COCl2 Volume Mixing Ratio (in pptv)
40
60
30
50
25
40
20
35
25
20
30
15
20
Altitude (in km)
Altitude (in Km)
30
15
85oS-60oS
o
o
60 S-30 S
30oS-30oN
10
30oN-60oN
o
10
5
o
60 N-90 N
Wilson et al. 1988
Kindler et al. 1995
10
5
o
o
50 N-80 N
o
o
o
o
0 -90 N
0
-80
-60
-40
-20
0
20
Latitude (in Degrees)
40
60
80
0
0 -85 S
0
-10
0
10
20
Volume Mixing Ratio (in pptv)
30
40
FTS – Spectral Range &
SNR
ACE Fourier transform
spectrometer (FTS)
Range: 750 – 4400 cm-1
(2.2 to 13 microns)
Resolution: 0.02 cm-1
Continuum SNR up to 400
Ryan Hughes
CH, NH, OH
OH
CO
Δv=2
CO, Δv=1
ACE solar spectrum (F. Hase): 224782 spectra added, improvement over ATMOS, no
telluric lines, but 0.02 cm-1 vs 0.01 cm-1 resolution (resolution largely determined by
width of solar lines) and 750-4400 cm-1 vs 600-4800 cm-1.
Mg Rydberg Emission Lines
Mg 7i
1,3I
- 6h
1,3H
OH v=0 R(24)
Confusion Limit!
Every bump is
an atomic or
molecular line.
OH
v=2-1
P1(2.5)
OH
v=1-0
P1(6.5)
ATMOS Spacelab-3, 1985
New atomic and
molecular
assignments
(ACE linelist) by
L. Wallace
(NOAO);
improved
spectroscopic
data for CH, NH
and OH.
ATMOS ATLAS-3, 1994
For OH, Reg
Colin (ULB) finds
v=4 can be
improved.
ACE, 2008
Future Plans
• ACE Solar Atlas will be published with
spectra (ps & pdf), digital data and revised
solar linelist with assigned atomic and
molecular lines.
• Less than ½ of ACE solar data used so far
and mission might last for some additional
years (with support from Canadian Space
Agency).
• Improved analysis of CH, NH and OH.