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On-orbit Calibration and Initial Validation Comparisons for the ACE-FTS

On-orbit Calibration and Initial Validation Comparisons for the ACE-FTS. Kaley A. Walker, Chris Boone, Randall Skelton, Sean McLeod, and Peter F. Bernath Department of Chemistry, University of Waterloo ASSFTS Meeting – May 20, 2005. Size: 1.12 m dia. x 1 m Total mass: 152 kg

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On-orbit Calibration and Initial Validation Comparisons for the ACE-FTS

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  1. On-orbit Calibration and Initial Validation Comparisons for the ACE-FTS Kaley A. Walker, Chris Boone, Randall Skelton, Sean McLeod, and Peter F. Bernath Department of Chemistry, University of Waterloo ASSFTS Meeting – May 20, 2005

  2. Size: 1.12 m dia. x 1 m Total mass: 152 kg Total power: 70 W (from single solar panel) Launch date: August 12, 2003 Launch vehicle: Pegasus XL (provided by NASA) Orbit: 74° inclined circular orbit at 650 km SCISAT-1

  3. ACE Instruments ACE-FTS: • a high resolution (0.02 cm-1) infrared Fourier transform spectrometer operating between 2-13 microns • 2-channel visible/near infrared imager operating at0.525 and 1.02 microns MAESTRO: • dual UV / Visible / NIR diode array spectrophotometer measuring from 0.270 to 1.040 microns, resolution ~1-2 nm Instrument Pointing: suntracker located within ACE-FTS

  4. Baseline ACE Measurements • ACE-FTS: O3, CH4, H2O, NO, NO2, ClONO2, HNO3, N2O, N2O5, HCl, CCl3F (CFC-11), CCl2F2 (CFC-12), HF, CO, temperature and pressure (from CO2) ACE-FTS Imagers: atmospheric extinction • vertical resolution ~ 3-4 km (for both FTS and imagers) • MAESTRO: O3, NO2, atmospheric extinction, (temperature and pressure from O2 A-, B- and -bands) • vertical resolution ~1-2 km Altitude range for retrieved results ~10-50 km (max. 100 km)

  5. On-orbit Commissioning Important phase in early lifetime of a satellite mission • Instrument functional testing and bus commissioning activities – conducted by industrial partners • For ACE mission, “Science” commissioning phase was also undertaken for both instruments by Science Team • Preparation for routine operations • Extend pre-launch calibration and performance verification measurements • Process completed in January 2004

  6. Science Commissioning Activities • Preliminary measurements • Simultaneous commanding, confirming parameter settings for all instruments • Instrument pointing and suntracker offsets • Verify location of instrument FOVs and optimize solar pointing • Refine occultation command sequences • Secondary Science Modes (near-nadir for FTS)

  7. Closed-loop Offsets • From acceptance testing at ABB, it was known that FTS FOV was offset from Sun centre by ~2.9 mrad • So fixed suntracker closed-loop offsets must be used to adjust ACE-FTS FOV to Sun centre FTS FOV position shown here was determined from Science Calibration Testing in Winter 2003

  8. FTS FOV (1.25 mrad) Offset position Suntracker Stepsize Test Investigated closed-loop pointing offsets in both axes to understand dependences and determine stepsize Determined offsets graphically from both VIS and NIR data Average stepsize = 0.0023 mrad Kathy Gilbert

  9. “down” scan “up” scan Co-registration Determination Sunscan in elevation - comparing FTS (MCT DC level) and MAESTRO (UV channel integrated intensity) • Effects of solar limb darkening can be seen Florian Nichitiu

  10. Using Suntracker CL Offsets

  11. Validation Program • Will be starting soon – once data set is available! • Initially limited by availability of processed data • ACE-FTS routine processing version 1.0 was completed for sunsets Jan.-Oct. 2004 – version 2.2 has been started • Imager and MAESTRO data release for Science (and Validation) Team is expected in next month • “Pre-comparisons” have been done with selected data sets • Inter-comparisons between ACE-FTS and MAESTRO • Satellite instruments – POAM III, SAGE III, HALOE, MLS, OSIRIS, GOMOS … • ACE Arctic Validation Campaign at Eureka (Feb. – Apr.)

  12. ACE-FTS MAESTRO comparison O3 and NO2 profiles from 23 February 2004 over Canadian Arctic: 78°N, 134°W MAESTRO retrievals use ACE-FTS T/p and shift applied to account for offset between FOVs and empirically account for timing uncertainty Tom McElroy

  13. ACE-FTS - POAM III: O3 ACE-FTS up to 25% higher than POAM from 40-60 km Lower than POAM III by up to ~10% from 15 and 40 km. Maybe due to difference in vertical resolution? average latitude: 67°N Profiles within 500 km and 2 hours; using POAM III version 4.0 data Thanks to Cora Randall

  14. ACE-FTS - SAGE III comparison ACE-FTS up to 38% higher than SAGE III from 40-55 km No indication of significant altitude registration errors but between 15-40 km, ACE-FTS lower than SAGE III by ~10% average latitude: 76°N Profiles within 500 km and 2 hours; using SAGE III version 3.0 data Thanks to Chip Trepte

  15. ACE-FTS HCl is 10-20 % higher than HALOE in all comparisons Similar results seen for HF HCl Comparisons MLS-ACE-HALOE ACE-FTS is 3-5% higher than MLS ACE version 1.0, HALOE V19, MLS v1.4.8 Lucien Froidevaux and the MLS team

  16. ACE-FTS - Radiosonde Comparison Maximum difference 15-25 km: 1.1 K Overall: 2.1 K For 8 profiles – within 200 km Max. diff. ~ 2-3 K Other comparisons with CHAMP, SABER and lidar in progress T retrieved above this point

  17. Below 0.2hPa (60 km), ACE-FTS and MLS agree to within 1-3 K Coincidence criteria within 1° lat. and 12 ° lon., same day ~600 matched pairs ACE version 2.1, MLS v1.5 ACE-FTS – MLS: Temperature ACE-FTS MLS MLS-ACE Lucien Froidevaux

  18. Summary • ACE satellite is operational and has been performing well taking occultation measurements since February 2004 • ACE-FTS and MAESTRO routine processing operational • Science Commissioning phase completed in January 2004 • Verified performance and completed calibration measurements on-orbit • “Pre-comparisons” have been done between ACE instruments and with satellite, sonde and Eureka campaign data • Results are looking very promising

  19. Acknowledgements Funding for ACE is provided by: • Canadian Space Agency • Natural Sciences and Engineering Research Council of Canada (NSERC) • NSERC-Bomem-CSA-MSC Industrial Research Chair in Fourier Transform Spectroscopy (at U. of Waterloo)

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