The University of Toronto

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The University of Torontos 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

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Outline

• Motivation
• MANTRA high-altitude balloon campaign
• FTS instruments on MANTRA
• Instrument The University of Torontos FTS
• History
• Preparation for MANTRA
• Results
• MANTRA
• Mini-MANTRA
• Ground-based intercomparison
• Conclusions and Future Work

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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

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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 (52N, 107W)
• 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 52N

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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)

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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 MANTRAs 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

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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

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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 1990s
  electronics boards and power supplies
• Power consumption 140 W
• Mass 90 kg

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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

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Preparation for MANTRA 2004

• 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

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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

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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 834 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

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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

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Ground-based Measurements Mini-MANTRA

• Comparison between Toronto Atmospheric
  Observatory (TAO) FTS and MSC FTS (will include
  PARIS soon)

• 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

• 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)

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Mini-MANTRA Preliminary Results N2O

• MSC FTS
• SNR 150
• ds 1.5
• rms 0.34
• TAO FTS
• ds 3.3
• rms 0.38

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Mini-MANTRA Preliminary Results N2O
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Mini-MANTRA Preliminary Results N2O
VMR (ppmv)
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Mini-MANTRA Preliminary Results N2O

• Average 1 difference between TAO and MSC
• No clear bias

Concentration (molecules/cm2)
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Mini-MANTRA Preliminary Results CH4

• MSC FTS
• SNR 100
• ds 1.4
• rms 0.5
• TAO FTS
• ds 2.8
• rms 0.25

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Mini-MANTRA Preliminary Results CH4
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Mini-MANTRA Preliminary Results CH4
VMR (ppmv)
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Mini-MANTRA Preliminary Results CH4

• Difference average around 1
• No clear bias

Concentration (molecules/cm2)
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Mini-MANTRA Preliminary Results O3

• MSC FTS
• SNR 200
• ds 0.85
• rms 0.65
• TAO FTS
• ds 1.6
• rms 0.4

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Mini-MANTRA Preliminary Results O3
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Mini-MANTRA Preliminary Results O3
VMR (ppmv)
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Mini-MANTRA Preliminary Results O3

• Differences on order of 25
• MSC FTS consistently lower than TAO and the Brewer

Concentration (molecules/cm2)
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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

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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.