MINI-DOASJochen StutzMax Spolaor
University of California Los Angeles
Identify and quantify trace gases using their narrow band absorptions.
Airborne remote sensing Slant Column Density (SCD)
What is Mini-DOAS ?
Rotating Telescopes
Alternating viewingdirections
+1˚ 0˚-1˚-1.5˚-2˚-2.5˚-3˚-4˚-5˚-15˚
How does Mini-DOAS work?
PCElectronicsTelescopes for UV, VIS, near-IR
Spectrometers
Optics
Scanner
Vacuum VesselIce-WaterInsulation
Spectrometer Assembly
QuartzFibers
Power consumption: 29VDC at 1.4A = 41W Size and Weight:11.8x9.84x8.0 inches; 75pounds including
9L ice-water
Spectrometers
Telescopes
… on NASA’s Global Hawk
Quartz fibers
Identification and quantification of trace gases by their unique narrow band absorption in the open atmosphere
B
'
()
[cm2 ]
[nm]
D'
I'0I0
I()
250 300 350 400 450 600 650 7000
100200
detection limits
200 pptL=1km
1 pptL=16km
2 pptL=12km
20 pptL=12km
500 pptL=5km
5 pptL=5km
100 pptL=5km
200 pptL=5km
1 ppbL=5km
Phenol Wavelength [nm]
04080
20 pptL=1km
50 pptL=1km
250 pptL=1km
para-Cresol
05
10
Toluene
01020
Benzene
0100200
IO
050 BrO
020 ClO
01
HCHO
0100 NO
3
04
HONO
0
2NO
2
048
SO2
0
4250 300 350 400 450 600 650
50 pptL=5km
'[1
0-1
9 c
m2 ]
O3
DOASDifferential Optical Absorption Spectroscopy
BrO and O4 data analysis
BrO fit range: 345 – 360nm O4 fit range: 338-347nm 352-360nm
BrO
3x10-4
Inte
nsity
9x10-3
Inte
nsity
O4
0
0
Species to be measured & DL: NO2 50 ppt HONO 20 ppt BrO 0.75 pptHCHO 150 pptSO2 200 pptglyoxal: ?aerosol extinction (via
O4)
Alti
tude
[103
m]
ATTREX Data ExampleRe
lati
ve
Radi
ance
[cou
nts/
ms*
scan
s]
BrO
DSC
D[1
014
mol
ec./c
m2 ]
Universal Time [5th November 2011]
+1˚ 0˚-1˚-1.5˚-2˚-2.5˚-3˚-4˚-5˚-15˚
Elevation
Angle
O4
DSC
D[1
043
mol
ec2 ./
cm5 ]
From SCDs to trace gas concentration
BAMFs derived via radiative transfer calculations
Optimal Estimation Inversion to derive concentration profile c(h)
dhhcAngElBAMFAngElSCD )(.).(.).(VCD
SCDScattered
sunlight
0 20 40 60 80 1000
2
4
6
8
10Detector at 4km
Box Airmass Factor (DBAMF)
Alti
tude
(km
)
-90.0°-45.0°-30.0° -4.0° -3.0° -2.5° -2.0° -1.5° -1.0° -0.5° 0.5° 1.0° 1.5° 2.0° 2.5° 3.0° 4.0° 5.0°
BrO vertical concentration profile retrieval
BrO at flight altitude:~(1.8 ± 0.25) x107 molec/cm3= (5.0 ± 0.75) ppt
flight level
Modeled SCDs fit well
SZA=74°
SZA=56°
Science flight 2 on 11/05, 18:00 UTC
x1E14 Retrieved BrO profile
BrO vertical profiles
Consecutively retrieved BrO profiles
BrO at flight altitude
Science flight 2 on 11/05
34°N
30°N
Questions / Issues Telescope fairing (pressure seal).
Calibration of telescope geometry after installation Meeting NSF specs for instrument
Instrument has undergone environmental testing at NASA Fast information on pitch, roll, acceleration ?
Addition of sensor to instrument of from aircraft? Data archive on C130 server (~5000 spectra each
10kbyte)? Change of measurement strategy depending on flight
status Profiling through elevation scanning vs limb during
ascent/decent