The University of Toronto’s Balloon-Borne Fourier Transform Spectrometer

1. The University of Toronto’s Balloon-Borne Fourier Transform Spectrometer Debra Wunch, James R. Drummond, Clive Midwinter, Jeffrey Taylor, Kimberly Strong University of Toronto Hans Fast Meteorological Service of Canada Network for the Detection of Stratospheric Change Infrared Working Group Toronto, June 13-15, 2005

2. Outline • Motivation • MANTRA high-altitude balloon campaign • FTS instruments on MANTRA • Instrument: The University of Toronto’s FTS • History • Preparation for MANTRA • Results • MANTRA • “Mini-MANTRA” • Ground-based intercomparison • Conclusions and Future Work NDSC IRWG, Toronto, June 13-15, 2005

3. Motivation: MANTRA • Middle Atmosphere Nitrogen TRend Assessment • Investigates the changing chemical balance of the mid-latitude stratosphere, with a focus on the role of nitrogen chemistry on the depletion of ozone. • Scientific Objectives • Measurement of profiles of relevant chemical species • O3, NO, NO2, HNO3, HCl, ClONO2, N2O5, CFC-11, CFC-12, OH, H2O, N2O, CH4, J-values for O(1D) and NO2, aerosol, wind, pressure, temperature and humidity • Intercomparison between instruments using different measurement techniques • FTS, grating spectrometers, radiometers and sondes • Solar occultation, emission, in situ • Validation of satellite data • SCISAT: ACE-FTS, MAESTRO • Odin: OSIRIS, SMR • ENVISAT: SCIAMACHY, MIPAS, GOMOS NDSC IRWG, Toronto, June 13-15, 2005

4. Motivation: MANTRA • High-altitude balloon platform • Float height around 40 km • He-filled balloon • Payload size around 2 m by 2 m by 2 m • Main gondola pointing system • Four campaigns: 1998, 2000, 2002, 2004 in Vanscoy, Saskatchewan (52°N, 107°W) • Launch balloons during late summer stratospheric zonal wind turnaround • photochemical control regime • low winds allow for longer float times • launch window is August 26 – September 5 at 52°N NDSC IRWG, Toronto, June 13-15, 2005

5. FTS Instruments on MANTRA • Measure most atmospheric trace gas species simultaneously • DU FTS on 1998, 2002, 2004 • University of Denver • 30 years of flight heritage • 0.02 cm-1 resolution; 700-1300 cm-1 spectral range • PARIS FTS on 2004 • Portable Atmospheric Research Interferometric Spectrometer, U. of Waterloo • 0.02 cm-1 resolution; 750-4100 cm-1 spectral range • An ACE FTS clone built in 2003/4 as a balloon-borne validation instrument • MSC FTS on 2002, 2004 • Occultation mode instruments (solar absorption through sunrise/sunset) NDSC IRWG, Toronto, June 13-15, 2005

6. The Role of the MSC FTS on MANTRA • Develop a Canadian capacity for balloon-borne FTS measurements • Compare a well-understood instrument (DU) with new Canadian instruments (MSC, PARIS) • Measure HCl, O3, N2O, CO2, CO, etc. • Complement MANTRA’s science goals of measuring ozone depletion and the molecules that contribute to the ozone budget • Ground-based and balloon-based intercomparisons • Compare with ground-based instruments • MANTRA and “mini-MANTRA” • Compare with other balloon-borne instruments • Satellite validation NDSC IRWG, Toronto, June 13-15, 2005

7. The MSC FTS: History • Bomem DA2 instrument built in the 1980s • Purchased by the Meteorological Service of Canada (MSC) • Built as a ground-based instrument • Upgraded to a DA5 instrument with DA8 electronics (including the dynamic alignment) in the mid-1990s • Obtained by the University of Toronto from the MSC in 2001 • 50 cm OPD; 1200-5000 cm-1 spectral range • InSb and MCT detectors that measure simultaneously, CaF2 beamsplitter, Ge filter • Flown on MANTRA 2002 and 2004 NDSC IRWG, Toronto, June 13-15, 2005

8. The MSC FTS: History • MANTRA 2002 engineering flight • Test of temperatures and voltages • Confirmed new software critically necessary • Confirmed need for dedicated suntracker • Original Software • Software contained user prompts in the form of “pop-up” boxes • Inaccessible housekeeping information • Control software embedded in hardware (bios) • Original Hardware and Electronics • Dependable dynamic alignment (compensation for motion in moving mirror) • Large electronics box with circa 1990’s electronics boards and power supplies • Power consumption: 140 W • Mass: 90 kg NDSC IRWG, Toronto, June 13-15, 2005

9. Tasks in Preparation for MANTRA 2004 • Convert the MSC FTS from a ground-based FTS into an instrument that can take ground-based and balloon-based data • Update the software and electronics • Remove pop-up boxes • Use modern technology without compromising performance • Keep the dynamic alignment system • Address issue of accurate pointing for solar occultation measurements • Decouple FTS from main gondola pointing system NDSC IRWG, Toronto, June 13-15, 2005

10. Re-engineered control of the dynamic alignment system Almost entirely new electronics 3 boards kept (DA), 7 discarded Replaced two control computers with one low-power motherboard Wrote control software in LabVIEW Controls DA through Speed & Search Includes automated scheduler No human intervention required Full uplink and downlink capabilities Housekeeping Temperatures, voltages, interferograms New power supply system Vicor power supplies New data acquisition system USB 16-bit ADC for interferograms USB 12-bit ADC for housekeeping Obtained dedicated sunseeker tracks within ±10º in zenith and azimuth flown before on other balloon campaigns Preparation for MANTRA 2004 NDSC IRWG, Toronto, June 13-15, 2005

11. Preparation for MANTRA 2004: Results • Mass reduction • Electronics box no longer necessary • All necessary electronics fit into spectrometer box • Mass reduced from ~90kg to ~55kg • Power reduction • Power reduced from ~140W to ~65W due to new electronic components • Improves temperature performance – less power means less heat • Now about half the mass/power of the other two FTS instruments • Sunseeker decoupled FTS from main gondola pointing system • would still get no data if payload rotated uncontrollably NDSC IRWG, Toronto, June 13-15, 2005

12. MANTRA 2004 • Ground-based campaign • 5 dedicated ground-based instruments • Brewer, grating spectrometers • ~43 days of measurements • MSC FTS obtained measurements at every opportunity – will participate in ground-based campaign • Flight on September 1st at 8:34 am • Successful launch, followed by loss of commanding to the payload • Pointing system overheated before sunset • Payload began rotating • Two spectra recorded on each detector NDSC IRWG, Toronto, June 13-15, 2005

13. MSC FTS Flight Data • Two spectra (on each detector) during sunset on the first MANTRA 2004 flight at ~91° • acquired during rotation of payload at sunset • Signal-to-noise ratio reduced • lower SNR attributed to rotation of payload – tracker at ends of its field of view • Resolution reduced • reduced resolution attributed to rotation of payload, temperature • Can resolve CO, CO2, O3, CH4, N2O, HCl, H2O • should be able to retrieve slant columns • No vertical profile retrievals possible NDSC IRWG, Toronto, June 13-15, 2005

14. NDSC IRWG, Toronto, June 13-15, 2005

15. NDSC IRWG, Toronto, June 13-15, 2005

16. Ground-based Measurements: “Mini-MANTRA” • Comparison between Toronto Atmospheric Observatory (TAO) FTS and MSC FTS (will include PARIS soon) • TAO • Bomem DA8 • 0.004 cm-1 resolution • Spectral range covers NDSC filters • Measures at every clear-sky opportunity • Simultaneous measurements (same atmosphere) • Different resolution • Broad-band versus narrow-band measurements • Compare over overlapping spectral range (F3) • MSC • Bomem DA5 • 0.02 cm-1 resolution • Spectral range: 1200-5000 cm-1 • Uses pick-off mirror to re-direct portion of TAO sunlight NDSC IRWG, Toronto, June 13-15, 2005

17. Mini-MANTRA Preliminary Results: N2O • MSC FTS • SNR 150 • ds 1.5 • rms 0.34 • TAO FTS • ds 3.3 • rms 0.38 NDSC IRWG, Toronto, June 13-15, 2005

18. Mini-MANTRA Preliminary Results: N2O NDSC IRWG, Toronto, June 13-15, 2005

19. Mini-MANTRA Preliminary Results: N2O VMR (ppmv) NDSC IRWG, Toronto, June 13-15, 2005

20. Average 1% difference between TAO and MSC No clear bias Mini-MANTRA Preliminary Results: N2O Concentration (molecules/cm2) NDSC IRWG, Toronto, June 13-15, 2005

21. MSC FTS SNR 100 ds 1.4 rms 0.5 TAO FTS ds 2.8 rms 0.25 Mini-MANTRA Preliminary Results: CH4 NDSC IRWG, Toronto, June 13-15, 2005

22. Mini-MANTRA Preliminary Results: CH4 NDSC IRWG, Toronto, June 13-15, 2005

23. Mini-MANTRA Preliminary Results: CH4 VMR (ppmv) NDSC IRWG, Toronto, June 13-15, 2005

24. Difference average around 1% No clear bias Mini-MANTRA Preliminary Results: CH4 Concentration (molecules/cm2) NDSC IRWG, Toronto, June 13-15, 2005

25. MSC FTS SNR 200 ds 0.85 rms 0.65 TAO FTS ds 1.6 rms 0.4 Mini-MANTRA Preliminary Results: O3 NDSC IRWG, Toronto, June 13-15, 2005

26. Mini-MANTRA Preliminary Results: O3 NDSC IRWG, Toronto, June 13-15, 2005

27. Mini-MANTRA Preliminary Results: O3 VMR (ppmv) NDSC IRWG, Toronto, June 13-15, 2005

28. Mini-MANTRA Preliminary Results: O3 • Differences on order of 25% • MSC FTS consistently lower than TAO and the Brewer Concentration (molecules/cm2) NDSC IRWG, Toronto, June 13-15, 2005

29. Conclusions and Future Work • New instrument is improvement over old • Lower power consumption • Lower mass • Robust software • Continued work • Build “delta”-tracker with larger field of view • Improve detector alignment system • Slant column amounts from balloon data • Intercomparisons of ground-based data • Continued mini-MANTRA through summer (include PARIS when available) • Investigate cause of O3 column discrepancy • Future work • Fly FTS on MANTRA 2006 payload and get data from a full occultation NDSC IRWG, Toronto, June 13-15, 2005

30. Acknowledgements • The authors wish to thank Pierre Fogal, John Olson, Tom McElroy, Kaley Walker, the MANTRA 2002 and 2004 science teams and the TAO scientists. • Funding is provided by the Canadian Space Agency, the Meteorological Service of Canada and NSERC. NDSC IRWG, Toronto, June 13-15, 2005