Transcript The University of Toronto’s Balloon

The University of Toronto’s
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
Outline
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Motivation
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Instrument: The University of Toronto’s FTS
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History
Preparation for MANTRA
Flight data
Intercomparison
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MANTRA high-altitude balloon campaign
FTS instruments on MANTRA
Instruments
Results
Conclusions and Future Work
COSPAR; Beijing, July 16-22, 2006
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Motivation: MANTRA
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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
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Measurement of profiles of relevant chemical species
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Intercomparison between instruments
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O3, NO, NO2, HNO3, HCl, ClONO2, N2O5, CFC-11, CFC-12, OH, H2O, N2O, CH4, Jvalues for O(1D) and NO2, aerosol, wind, pressure, temperature and humidity
FTS, grating spectrometers, radiometers and sondes
Solar occultation, emission, in situ
Validation of satellite data
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SCISAT: ACE-FTS, MAESTRO
Odin: OSIRIS, SMR
ENVISAT: SCIAMACHY, MIPAS, GOMOS
COSPAR; Beijing, July 16-22, 2006
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Motivation: MANTRA
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High-altitude balloon platform
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Four campaigns: 1998, 2000, 2002, 2004
in Vanscoy, Saskatchewan (52°N, 107°W)
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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
Supported by extensive ground-based campaign
Launch balloons during late summer
stratospheric zonal wind turnaround
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Photochemical control regime
Low winds allow for longer float times
Launch window is August 26 – September 5 at
52°N
COSPAR; Beijing, July 16-22, 2006
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Fourier Transform Spectrometers on MANTRA
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Absorption FTS instruments measure solar absorption by
atmospheric trace gases in the infrared
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University of Denver FTS on 1998, 2002, 2004
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30 years of flight heritage
0.02 cm-1 resolution; 700-1300 cm-1 spectral range
PARIS-IR FTS on 2004
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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
Portable Atmospheric Research Interferometric Spectrometer for the Infrared,
University of Waterloo
0.02 cm-1 resolution; 750-4400 cm-1 spectral range
Ground- and balloon-based version of ACE FTS
U of T FTS on 2002, 2004
COSPAR; Beijing, July 16-22, 2006
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The Role of the U of T FTS on MANTRA
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Develop a Canadian capacity for balloon-borne FTS
measurements
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Measure trace gases that contribute to the ozone
budget
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Compare a well-understood instrument (U. Denver FTS)
with new Canadian instruments (U of T FTS, PARIS-IR)
Measure HCl, O3, N2O, CH4, etc.
Ground-based and balloon-based intercomparisons
Satellite validation
COSPAR; Beijing, July 16-22, 2006
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The U of T FTS: History
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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
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InSb and MCT detectors that measure simultaneously, CaF2
beamsplitter
Flown on MANTRA 2002 and 2004
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MANTRA 2002 flight was an engineering flight
Test of temperatures and voltages
COSPAR; Beijing, July 16-22, 2006
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The U of T FTS: History
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Original Software
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Original Hardware and Electronics
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Software contained user prompts in the form of
“pop-up” boxes
Inaccessible housekeeping information
Control software embedded in hardware
(BIOS)
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
COSPAR; Beijing, July 16-22, 2006
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Tasks in Preparation for MANTRA 2004
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Convert the U of T FTS from a ground-based
FTS into an instrument that can take groundbased and balloon-based data
Update the software and electronics
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Remove pop-up boxes
Use modern technology without compromising
performance
Address issue of accurate pointing for solar
occultation measurements
COSPAR; Beijing, July 16-22, 2006
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Preparation for MANTRA 2004
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Re-engineered control of the
dynamic alignment system
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Almost entirely new electronics
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3 boards kept (DA), 7 discarded
Replaced two control computers with
one low-power motherboard
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New power supply system
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Vicor power supplies
New data acquisition system
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USB 16-bit ADC for interferograms
USB 12-bit ADC for housekeeping
Wrote control software in
LabVIEW
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Controls DA
Includes automated scheduler
No human intervention required
Full uplink and downlink capabilities
Housekeeping
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Temperatures, voltages,
interferograms
COSPAR; Beijing, July 16-22, 2006
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Preparation for MANTRA 2004: Results
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Mass reduction
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Electronics box no longer
necessary
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Mass reduced from ~90kg to
~55kg
Power reduction
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All necessary electronics fit into
spectrometer box
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
COSPAR; Beijing, July 16-22, 2006
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Preparation for MANTRA 2004: Pointing
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Obtained a dedicated sunseeker that tracks the sun within ±10
degrees in zenith and azimuth
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No longer dependent on main gondola pointing system
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Had flown before on other balloon campaigns
Only dependent on being pointed in general direction of sun
Would still get no data if payload rotated uncontrollably
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True for any solar-mode instrument on payload
COSPAR; Beijing, July 16-22, 2006
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MANTRA 2004 Flight
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Flight on September 1st at
8:34 am
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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°
COSPAR; Beijing, July 16-22, 2006
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U of T FTS Flight Data
MCT Spectrum from the MANTRA 2004 Flight: 2004/09/01 19:53:31
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Signal-to-noise ratio reduced
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lower SNR attributed to rotation
of payload – tracker at ends of
its field of view
reduced resolution attributed to
rotation of payload,
temperature, poor alignment
before flight?
No vertical profile retrievals
possible
No other flight opportunities
0.8
0.6
0.4
0.2
0
1500
2000
2500
3000
3500
4000
4500
5000
5500
-1
Wavenumber (cm )
N2O
CH4
O3
Resolution reduced
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can retrieve slant columns
Intensity (arbitrary units)
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Instrument performed well
under difficult conditions
Can resolve CO, CO2, O3,
CH4, N2O, HCl
Normalized Intensity
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1
1
1
1
0.9
0.95
0.9
1
0.8
0.9
0.8
CO2
0.5
0.7
0.85
0.7
0.6
0.8
0.6
2099.6
0.5
2100.4
2207.54 2207.66
2937.2
Wavenumber (cm-1)
2938.4
3625 3630 3635
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Ground-based FTS Intercomparison in Toronto
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Intercomparison campaign between three FTS instruments
with different resolutions
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Toronto Atmospheric Observatory (TAO)
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Complementary Network for the Detection of Atmospheric
Composition Change (NDACC – formerly NDSC) Station
250 cm MOPD
PARIS-IR
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Two balloon and ground-based instruments, one solely ground-based
instrument
25 cm MOPD
Ground- and balloon-based version of ACE FTS
U of T FTS
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50 cm MOPD
COSPAR; Beijing, July 16-22, 2006
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Intercomparison Goals
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To fully test the two balloon instruments
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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
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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
COSPAR; Beijing, July 16-22, 2006
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Experimental Setup
TAO
U of T FTS
PARISIR
COSPAR; Beijing, July 16-22, 2006
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Instrument Line Shape (ILS)
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Important to know ILS well
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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
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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)
COSPAR; Beijing, July 16-22, 2006
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Instrument Line Shape (ILS): Stratospheric Species
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Stratospheric species:
narrow absorption lines
U of T FTS and PARISIR resolution broader
than absorption line
width
Retrievals very sensitive
to ILS for U of T FTS
and PARIS-IR
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For U of T FTS: 20%
improvement for ozone
columns when
retrieving ILS; 15%
improvement for HCl
columns when
retrieving ILS
HCl - SNR = 250
3.6
Total Column Amount (molecules/cm2)
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3.8
x 10
3.4
3.2
3
2.8
Truth
A Priori
PHS/EAP Retrieved
Standard Retrieval
2.6
2.4
0
50
100
150
200
Optical Path Difference (cm)
250
Ensemble of simulated spectra with imperfect ILS, retrieved with SFIT2 ILS
switch on (“PHS/EAP”) and off (“Standard”)
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Much better results obtained when ILS switch is “on.”
300
Instrument Line Shape (ILS): Tropospheric Species
N2O - SNR = 250
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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
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Truth
A Priori
PHS/EAP Retrieved
6.9
Total Column Amount (molecules/cm2)
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x 10
Standard Retrieval
6.8
6.7
6.6
6.5
6.4
6.3
0
50
COSPAR; Beijing, July 16-22, 2006
200
150
100
Optical Path Difference (cm)
300
250
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O3 Total Column Comparisons
18
9.2
O3
x 10
9
Total Column (molecules/cm2)
8.8
8.6
8.4
8.2
8
7.8
TAO 3040MW
PARIS 3040MW
U of T MCT 3040MW
7.6
7.4
32
34
36
38
40
SZA
42
44
46
48
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HCl Total Column Comparisons
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3.5
HCl
x 10
3.4
Total Column (molecules/cm2)
3.3
3.2
3.1
3
2.9
2.8
2.7
2.6
30
TAO 2925MW
PARIS 2925MW
U of T MCT 2925MW
35
40
45
50
SZA
55
60
65
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N2O Total Column Comparisons
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6.9
N2O
x 10
TAO 2482MW
PARIS 2482MW
U of T MCT 2482MW
Total Column (molecules/cm2)
6.8
6.7
6.6
6.5
6.4
6.3
6.2
30
35
40
45
50
SZA
55
60
65
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CH4 Total Column Comparisons
19
4.1
CH4
x 10
4.05
Total Column (molecules/cm2)
4
3.95
3.9
3.85
3.8
3.75
3.7
TAO 2859MW
PARIS 2859MW
U of T MCT 2859MW
3.65
3.6
30
35
40
45
50
SZA
55
60
65
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Intercomparison Summary
% Difference of Means
O3
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%
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HCl
N2O
CH4
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
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Bold is statistically significant difference within 95% based on the
student’s t-test.
COSPAR; Beijing, July 16-22, 2006
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Conclusions and Future Work
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U of T FTS
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Continuing work
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Lower power consumption
Lower mass
Robust software
Building “delta”-tracker with larger field of view
Uses camera to image sun
Intercomparisons
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ILS vitally important for stratospheric species, less
important for tropospheric species
Low-resolution instruments compare well with TAO for
all species <3.5%.
COSPAR; Beijing, July 16-22, 2006
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Acknowledgements
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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.
COSPAR; Beijing, July 16-22, 2006
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