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The University of Toronto

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The University of Toronto s Balloon-Borne Fourier Transform Spectrometer Debra Wunch, James R. Drummond, Clive Midwinter, Jeffrey R. Taylor, Kimberly Strong – PowerPoint PPT presentation

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Title: The University of Toronto


1
The University of Torontos Balloon-Borne Fourier
Transform Spectrometer
  • Debra Wunch, James R. Drummond, Clive Midwinter,
    Jeffrey R. Taylor, Kimberly Strong
  • University of Toronto
  • Dejian Fu, Kaley A. Walker, Peter Bernath
  • University of Waterloo
  • C. T. McElroy, Hans Fast
  • Environment Canada
  • COSPAR Conference
  • Beijing, July 16-22, 2006
  • COSPAR paper number A1.1-0068-06

2
Outline
  • Motivation
  • MANTRA high-altitude balloon campaign
  • FTS instruments on MANTRA
  • Instrument The University of Torontos FTS
  • History
  • Preparation for MANTRA
  • Flight data
  • Intercomparison
  • Instruments
  • Results
  • Conclusions and Future Work

3
Motivation MANTRA
  • Middle Atmosphere Nitrogen TRend Assessment
  • Investigate 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
  • 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

4
Motivation MANTRA
  • High-altitude balloon platform
  • Float height around 40 km
  • 18-24 hour flight duration
  • 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)
  • Supported by extensive ground-based campaign
  • 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

5
Fourier Transform Spectrometers on MANTRA
  • Absorption FTS instruments measure solar
    absorption by atmospheric trace gases in the
    infrared
  • High spectral resolution, high signal-to-noise
    ratio
  • High vertical resolution (occultation mode
    solar absorption through sunrise/sunset)
  • Broad-band measure most atmospheric trace gas
    species of interest simultaneously
  • University of Denver FTS on 1998, 2002, 2004
  • 30 years of flight heritage
  • 0.02 cm-1 resolution 700-1300 cm-1 spectral
    range
  • PARIS-IR FTS on 2004
  • Portable Atmospheric Research Interferometric
    Spectrometer for the Infrared, University of
    Waterloo
  • 0.02 cm-1 resolution 750-4000 cm-1 spectral
    range
  • Ground- and balloon-based version of ACE FTS
  • U of T FTS on 2002, 2004

6
The Role of the U of T FTS on MANTRA
  • Develop a Canadian capacity for balloon-borne FTS
    measurements
  • Compare a well-understood instrument (U. Denver
    FTS) with new Canadian instruments (U of T FTS,
    PARIS-IR)
  • Measure trace gases that contribute to the ozone
    budget
  • Measure HCl, O3, N2O, CH4, etc.
  • Ground-based and balloon-based intercomparisons
  • Satellite validation

7
The U of T 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
  • 0.02 cm-1 resolution 1200-5000 cm-1 spectral
    range
  • InSb and MCT detectors that measure
    simultaneously, CaF2 beamsplitter
  • Flown on MANTRA 2002 and 2004
  • MANTRA 2002 flight was an engineering flight
  • Test of temperatures and voltages

8
The U of T FTS History
  • 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

9
Tasks in Preparation for MANTRA 2004
  • Convert the U of T 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
  • Address issue of accurate pointing for solar
    occultation measurements

10
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
  • 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

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

12
Preparation for MANTRA 2004 Pointing
  • Obtained a dedicated sunseeker that tracks the
    sun within 10 degrees in zenith and azimuth
  • Had flown before on other balloon campaigns
  • No longer dependent on main gondola pointing
    system
  • Only dependent on being pointed in general
    direction of sun
  • Would still get no data if payload rotated
    uncontrollably
  • True for any solar-mode instrument on payload

13
MANTRA 2004 Flight
  • 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 at solar
    zenith angle of 89

14
U of T FTS Flight Data
  • Instrument performed well under difficult
    conditions
  • Can resolve CO, CO2, O3, CH4, N2O, HCl
  • can retrieve slant columns
  • 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, poor alignment before
    flight?
  • No vertical profile retrievals possible
  • No other flight opportunities

15
Ground-based FTS Intercomparison in Toronto
  • Intercomparison campaign between three FTS
    instruments with different resolutions
  • Two balloon and ground-based instruments, one
    solely ground-based instrument
  • Toronto Atmospheric Observatory (TAO)
  • Complementary Network for the Detection of
    Atmospheric Composition Change (NDACC formerly
    NDSC) Station
  • 250 cm MOPD
  • PARIS-IR
  • 25 cm MOPD
  • Ground- and balloon-based version of ACE FTS
  • U of T FTS
  • 50 cm MOPD

16
Intercomparison Goals
  • To fully test the two balloon instruments
  • Develop analysis packages
  • Debug software/hardware
  • Determine the important parameters to consider in
    the intercomparison
  • Investigate whether instruments of differing
    spectral resolutions can retrieve the same column
    amounts of trace gases
  • Coincident measurements
  • Consistent a priori profiles, spectroscopic
    parameters, atmospheric ZPT profiles
  • Same retrieval package (SFIT2 v. 3.82)
  • Reduces comparison errors to instrument
    resolution or alignment

17
Experimental Setup
TAO
U of T FTS
PARIS-IR
18
Instrument Line Shape (ILS)
  • Important to know ILS well
  • Any vertical information in the spectral line is
    retrieved from line shape
  • Ensure instrument broadening is not interpreted
    as higher atmospheric concentrations
  • ILS sensitive to temperature, instrument
    alignment
  • ILS should be taken into account, spectrum by
    spectrum
  • Can measure ILS prior to solar measurements with
    gas cell appropriate for ground-based
    measurements, but for balloon-based retrievals,
    need a more robust method
  • SFIT2 provides switch to retrieve ILS parameters
    (PHS/EAP Retrieved)

19
Instrument Line Shape (ILS) Stratospheric Species
  • Stratospheric species narrow absorption lines
  • U of T FTS and PARIS-IR resolution broader than
    absorption line width
  • Retrievals very sensitive to ILS for U of T FTS
    and PARIS-IR
  • For U of T FTS 20 improvement for ozone columns
    when retrieving ILS 15 improvement for HCl
    columns when retrieving ILS
  • Ensemble of simulated spectra with imperfect ILS,
    retrieved with SFIT2 ILS switch on (PHS/EAP)
    and off (Standard)
  • Much better results obtained when ILS switch is
    on.

20
Instrument Line Shape (ILS) Tropospheric Species
  • Tropospheric species broad absorption lines
  • U of T FTS and PARIS-IR resolution on order of
    absorption line width
  • Retrievals much less sensitive to ILS
  • No drop-off of columns like in stratospheric case

21
O3 Total Column Comparisons
22
HCl Total Column Comparisons
23
N2O Total Column Comparisons
24
CH4 Total Column Comparisons
25
Intercomparison Summary
Difference of Means O3 HCl N2O CH4
U of T FTS to TAO 3.3 1.7 0.4 2.3
PARIS-IR to TAO 0.8 3.2 0.4 0.5
U of T FTS to PARIS-IR 2.5 1.5 0.8 1.7
  • The lower-resolution PARIS-IR and U of T FTS
    instruments, when retrieving ILS information from
    the spectrum can produce good agreement with the
    high-resolution TAO-FTS
  • Bold is statistically significant difference
    within 95 based on the students t-test.

26
Conclusions and Future Work
  • U of T FTS
  • Lower power consumption
  • Lower mass
  • Robust software
  • Continuing work
  • Building delta-tracker with larger field of
    view
  • Uses camera to image sun
  • Intercomparisons
  • ILS vitally important for stratospheric species,
    less important for tropospheric species
  • Low-resolution instruments compare well with TAO
    for all species lt3.5.

27
Acknowledgements
  • The authors wish to thank Pierre Fogal, John
    Olson, and the MANTRA 2002 and 2004 science
    teams.
  • Funding is provided by the Canadian Space Agency,
    Environment Canada, the Canadian Foundation for
    Climate and Atmospheric Sciences and the Natural
    Science and Engineering Research Council of
    Canada.
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