Title: The University of Toronto
1The 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
2Outline
- 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
3Motivation 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
4Motivation 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
5Fourier 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
6The 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
7The 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
8The 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
9Tasks 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
10Preparation 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
11Preparation 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
12Preparation 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
13MANTRA 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
14U 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
15Ground-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
16Intercomparison 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
17Experimental Setup
TAO
U of T FTS
PARIS-IR
18Instrument 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)
19Instrument 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.
20Instrument 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
21O3 Total Column Comparisons
22HCl Total Column Comparisons
23N2O Total Column Comparisons
24CH4 Total Column Comparisons
25Intercomparison 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.
26Conclusions 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.
27Acknowledgements
- 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.