ACE-FTS instrument: after 7.5 years on-orbit

1. ACE-FTS instrument: after 7.5 years on-orbit Henry Buijs ABB Ryan Hughes U. Of Waterloo

2. 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 FTS heritage ABB Bomem formerly Bomem Inc.

3. 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 FTS heritage ABB Bomem formerly Bomem Inc. Autonomous operating 3rd gen

4. 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

5. Main Design and Programmatic Requirements • ACE science objectives require • High spectral resolution (0.02 cm-1), • High SNR (> 100) • Widespectral 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.

6. Scisat-1 spacecraft

7. ACE-FTS Optical Layout

8. ACE interferometer

9. The ACE-FTS Instrument Input Optics-side Interferometer-side

10. 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)

11. Integration to spacecraft bus

12. SciSat Inside the Pegasus Fairing

13. ACE in orbit

14. 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) Orbit Characteristics Tangent height

15. Coverage characteristics

16. Coverage characteristics

17. 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 Spectral analysis method

18. Ace spectra NO2 region Many weak lines of NO2

19. B3M compared with ACE data CFC12 region CFC12 HNO3

20. B3M compared with ACE HCl region HCl

21. B3M compared with ACE and DA8 ACE B3M DA8 HCl

22. ACE profiles

23. 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 Profile performance

24. Example result, CO2 study (P.Y. Foucher et al)

25. On-orbit SNR comparison mid-march 2004 (ss3171) and mid-march 2008 (ss24754) SNR increase SNR degradation Source: ACE Science Team (Ryan Hughes, UofWaterloo)

26. Frequency of occultations with ice 2004 to 2007 2004 2005 2006 2007

27. On-orbit FTS temperature (interferometer beamspliter) 2004-2008 Increase of temperature of ~1deg/year observed S/C anomaly Source: ACE Science Team (Ryan Hughes, UoWaterloo) 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.

28. Level 2 data Concentration profiles of molecules Official data processing soon in 5th version Data processing

29. 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) Molecules measured for the first time

30. Improved vertical resolution Image slicing Maintain basic throughput With <1 km vertical resolution Improved solar tracking Account for distortion due to refraction Cloud discrimination Future trends

31. Future trends

32. 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 Future trends

33. Scientific papers About 130 publications identified so far (July 2008) More than 104 with review committees

34. 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 Conclusion Thanks to all ACE/SciSat-1 team !