1. THE ACE SATELLITE SOLAR SPECTRUM
F. HASE
Institut fur Meteorologie und Klimaforschung, Forschungszentrum Karlsruhe, Postfach 3640, D 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

2. 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)

3. Kitt Peak Solar Spectrum

4. High Res. IR Solar Atlases
Nine Kitt Peak solar atlases recorded with the McMath-Pierce 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.

5. ATMOS Mission
High resolution (0.01 cm-1) FTS covering cm-1 spectral region that flew on the Space Shuttle in 1985 (Spacelab-3), 1992 (ATLAS-1), 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.)

6. ATMOS Solar Atlases
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/
From ten days of data (about spectra; 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

7. 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)
cm-1
ATLAS-3 spectrum (1995)
3026 cm-1

8. ACE Satellite
Bernath et al. GRL, 32, L15S01 (2005)

9. 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

10. Global Distribution of Phosgene, Cl2COװ
Fu et al. GRL, 34, L17815, 2007

11. 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
On average, 4% increase in SNR over full range – some regions up to 10-15%
Even after 6 month, SNR over much of the range was 300 or greater
Performing better now than after launch
Ryan Hughes

12. CH, NH, OH OH
CO Δv=2
CO, Δv=1
ACE solar spectrum (F. Hase): 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 cm-1 vs cm-1.

13. Mg Rydberg Emission Lines
Mg 7i 1,3I - 6h 1,3H
OH v=0 R(24)

14. Confusion Limit! Every bump is an atomic or molecular line.
OH v=2-1 P1(2.5)
OH v=1-0 P1(6.5)

15. ATMOS Spacelab-3, 1985
New atomic and molecular assignments (ACE linelist) by L. Wallace (NOAO); improved spectroscopic data for CH, NH and OH.
For OH, Reg Colin (ULB) finds v=4 can be improved.
ATMOS ATLAS-3, 1994
ACE, 2008

16. 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.