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ACE-FTS instrument: after 7.5 years on-orbit
Henry Buijs
ABB
Ryan Hughes
U. Of Waterloo
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FTS heritage ABB Bomem formerly Bomem Inc.
Balloon borne solar occultation (1975-1980) To elucidate Stratospheric chemistry related to ozone depletion
Successful commercialization of very high resolution FTS DA8 series with 0.0026 cm-1 resolution (1980-2005)
Dynamic alignment flat mirror interferometer
Technology used for Cris
Used in many labs to contribute to HITRAN data base
Successful commercialization of a rugged industrial FTS MB100 series 1986-present
“Wishbone” scan arm with cube corner mirrors
No alignment required
Technology used for most ABB satellite FTS projects
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FTS heritage ABB Bomem formerly Bomem Inc.
Ground based Hyper-spectral sounder Measures down-welling spectral radiance
Permits Temperature and moisture profiling from ground
Good vertical resolution in boundary layer
Joint development project with U of Wisconsin
Autonomous operating 3rd gen
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Background
• Atmospheric Chemistry Experiment (ACE) development started early 1999 (Phase B contract award) under Canadian Space Agency’s Space Science program.
• Mission objectives: better understanding of atmospheric chemistry of ozone
•The instrument suite includes an FTS, two 128x128 sun imagers and an active sun-tracker
• Prime contractor is ABB Bomem Inc., with main subcontractors
•Ball Aerospace and EMS Technologies.
•Many persons have contributed to the ACE-FTS development, including universities and research labs.
• The FTS design is based on the classical Michelson interferometer with a double-pass optical layout.
•It is tilt and shear compensated and requires no active alignment.
• The ACE-FTS Instrument was launched August 12th, 2003
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Main Design and Programmatic Requirements
• ACE science objectives require•High spectral resolution (0.02 cm-1),•High SNR (> 100)•Wide spectral coverage (750-4100 cm-1)
• Combination of these three requirements resulted in a challenging instrument design.
•Jacquinot merit factor W is >3x107 •Highest merit factor ever targeted for a space-borne spectrometer operating in the infrared.
• Instrument design is also constrained by low mass (40 kg), power (40 W) and volume allocations from the spacecraft bus.
•Scisat-1 mission is a small satellite mission concept
• Program required to design and manufacture a low cost, quickly-developed instrument while keeping risks as low as possible.
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Scisat-1 spacecraft
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ACE-FTS Optical Layout
Secondaymirror (6)
Field stop (5)
IR Filter(7)
Suntrackermirror (1)
Aperturestop (4)
PV MCTDetector
(18)
Glare stop(16)
Coolerwindow (17)
Outputcondenser
(14)
INTcorner-cubemirror (10)
End mirror(13)
INTcorner-cubemirror (11)
(12)
(9)
(12): Reflective coating(9): B/S coating
Beamsplit ter/compensatorassembly (8)
Primary mirror (3)
Fold mirror(22)
Lenses(23)
0.525 mimager (28)
1.02 mimager (26)
Dichroic(24)
Solarinput
Compensator
VIS/NIR-Quad CellDichroic
Quad Cell(21)
Lenses(20)
LaserMetrologyDetection
1.02 mfilter (25)
0.525 mfilter (27)
Beam splitter
Foldmirror(15) Laser Metrology Insertion
MAESTROInterface (2)
PV InSbDetector
Lens
Lens Glare stop
Dichroic
1.55 mfilter (19)
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ACE interferometer
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The ACE-FTS Instrument
Interferometer-side Input Optics-side
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ACE-FTS Interferometer Sub-System
• ACE-FTS still operating on the primary redundancy side at full resolution
• Metrology laser power shows a decrease of less than 2% observed over 7.5 years
• Excellent reliability of the ACE-FTS (more than three original mission lifetime requirement)
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Integration to spacecraft bus
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SciSat Inside the Pegasus Fairing
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ACE in orbit
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Orbit Characteristics
Circular orbit Altitude 650 km,
Orbital period 98 min. Inclination 74°
Selected to provide high latitude occultations
Solar occultation mission Approximately 15 occultations /day (~5400/year)
Tangent height
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Coverage characteristics
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Coverage characteristics
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Spectral analysis method
Exo-atmospheric spectra Do not contain any atmospheric features
Provide instrument response to solar spectrum Atmospheric spectra include above + atmospheric absorptions
Ratio atmospheric/exo-atmospheric provides precise atmospheric transmission
Subtracting transmission loss of higher layers provides transmittance at tangent height only
Optical beam at tangent height is ~ 3 km Limits vertical resolving power
Scan time is 2 s. Rate of change during scan depends on beta angle
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Ace spectra NO2 region
Many weak lines of NO2
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B3M compared with ACE data CFC12 region
CFC12 HNO3
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B3M compared with ACE HCl region
HCl
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B3M compared with ACE and DA8
HCl
B3M
DA8
ACE
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ACE profilesprofile altitude ranges
0
20
40
60
80
100
120
140
H2OCO
2CH4
CON2O
NO2
NON2O5
HNO3
HO2N
O2
ClONO2
HClHF
CFC-11
CFC-12
CFC-113
HCFC-141
b
HCFC-142
b
HCFC-22
CF4CCl4
COF2
COCl2
CH3Cl
C2H2
C2H6
CH3OH
HCOOH
H2COH2O2
HCNSF6
OCS O3 O2 N2 P T
he
igh
t k
m
low
high
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Profile performance
Very good absolute concentration determination Limited by HITRAN issues
Calibration cannot change over time Does not rely on blackbody calibration sources
Exo-atmosphere/atmosphere ratio
Vertical resolution ~ 3 km Vertical sampling < 1km
Lower limit of profile Limited by cloud Limited by spectral saturation
Upper limit of profile Limited by sensitivity
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Example result, CO2 study (P.Y. Foucher et al)
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25On-orbit SNR comparison mid-march 2004 (ss3171) and mid-march 2008 (ss24754)
Source: ACE Science Team (Ryan Hughes, UofWaterloo)
SNR increase
SNR degradation
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Frequency of occultations with ice 2004 to 2007
2004 2005 2006 2007
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27On-orbit FTS temperature (interferometer beamspliter) 2004-2008
In date of June 2008, the temperature of the instrument is 25 degrees Celcius in average; there is still room for further temperature increase as the instrument was qualified during TVAC for temperatures from 0 to 40 degrees Celcius.
S/C anomaly
Increase of temperature of ~1deg/year observed
Source: ACE Science Team (Ryan Hughes, UoWaterloo)
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Data processing
Level 2 data Concentration profiles of molecules
Official data processing soon in 5th version
Version 1.0 Version 2.0 Version 2.1 Version 2.2 Version 3.0 (tentative)
H2O, O3, N2O,
CO, CH4, NO,
NO2, HNO3, HF,
HCl, N2O5,
ClONO2,
CCl2F2, CCl3F,
COF2, CHF2Cl,
HDO, SF6
H2O, O3, N2O,
CO, CH4, NO,
NO2, HNO3, HF,
HCl, N2O5,
ClONO2, CCl2F2,
CCl3F, COF2,
CHF2Cl, SF6,
OCS, HCN, CF4,
CH3Cl, C2H2,
C2H6, N2
H2O, O3, N2O, CO,
CH4, NO, NO2,
HNO3, HF, HCl,
N2O5, ClONO2,
CCl2F2, CCl3F,
COF2, CHF2Cl,
SF6, OCS, HCN,
CF4, CH3Cl, C2H2,
C2H6, N2, ClO
H2O, O3, N2O, CO,
CH4, NO, NO2,
HNO3, HF, HCl,
N2O5, ClONO2,
CCl2F2, CCl3F,
COF2, CHF2Cl,
HDO, SF6, OCS,
HCN, CF4, CH3Cl,
C2H2, C2H6, N2,
ClO, as well as isotopologues for some of these molecules
H2O, O3, N2O, CO,
CH4, NO, NO2, HNO3,
HF, HCl, N2O5,
ClONO2, CCl2F2,
CCl3F, COF2, CHF2Cl,
HDO, SF6, OCS, HCN,
CF4, CH3Cl, C2H2,
C2H6, N2,
ClO,HCOOH,CH3OH, CCl4, CFC-
113, HCFC-142b, COCl2,
COClF, H2CO, HFC-
134a, as well as isotopologues for some of these molecules
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Molecules measured for the first time
ACE-FTS is the first instrument on-orbit to measure the following molecules:
CFC-113 HCFC-142b COClF
COCl2 (phosgene)
formic acid methanol Ethene Propyne Formaldehyde Acetone PAN (peroxyaceylnitrate)
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Future trends
Improved vertical resolution Image slicing
Maintain basic throughput With <1 km vertical resolution
Improved solar tracking Account for distortion due to refraction Cloud discrimination
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Future trends
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Future trends
Lower cost missions To increase number of sensors
Some reduction of spectral resolution Since ACE has shown the detailed spectrum
Good retrievals are possible at lower resolution
Smaller instrument Faster scanning Higher SNR
Include shorter wavelength To avoid saturation of spectra at lowest altitudes
Using weaker overtone Near IR bands
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Scientific papers
About 130 publications identified so far (July 2008)More than 104 with review committees
020406080
100120140160180
2001 2002 2003 2004 2005 2006 2007 2008
Year
Pu
bli
cati
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Conclusion
ACE-FTS on Scisat-1 has significantly exceeded its 2 years mission
7th anniversary on August 12, 2010
Very good in-flight performances
Excellent scientific returns
Thanks to all ACE/SciSat-1 team !