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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 !