Global Measurements of Pollution from Space - The MOPITT Experiment

1. Global Measurements of Pollution from Space - The MOPITT Experiment James R. Drummond, Department of Physics, University of Toronto james.drummond@utoronto.ca Tel: 416-978-4723 Institute of Environmental Physics and Remote Sensing University of Bremen – 23 October 2001

2. AGENCIES University of Toronto York University University of Saskatchewan McGill University National Center for Atmospheric Research (NCAR) Oxford University Canadian Space Agency (CSA) Meteorological Service of Canada (MSC) North Carolina State University (NCSU) COM DEV International Hughes-Leitz BOMEM SED NSERC NASA Principal Investigator James R. Drummond Co-Investigators G.P. Brasseur, Max-Plank G.R. Davis, Saskatchewan J.C. Gille, NCAR G. Mand, Toronto J.C. McConnell, York G.D. Peskett, Oxford, UK H.G. Reichle, Jr., NCSU N. Roulet, McGill J. Wang, SPIE MOPITT Team http://www.atmosp.physics.utoronto.ca/mopitt/home.html http://www.eos.ucar.edu/mopitt/home.html JRD - Bremen

3. MOPITT • Introduction • How it all works • How we put it together • Events of the last 600 days • Some successes (it’s working well..) JRD - Bremen

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5. MOPITT • MOPITT measures gas concentrations in the troposphere (0-15km) • A very challenging region because of • Underlying surface • Heterogeneous structure • Clouds JRD - Bremen

6. MOPITT • The troposphere couples to the surface and to biological processes • Region of the atmosphere most prone to modification, natural or induced • MOPITT is making global measurements of: • Carbon monoxide profiles • Methane column amounts JRD - Bremen

7. The MAPS instrument on the shuttle showed some of the features of the global CO field. Outflow from biomass burning events can be seen in this map. Other features can be seen in other seasons. But… incomplete... The MAPS Experiment JRD - Bremen

8. The lifetime of CO (about a month) means it is moved by the dynamics Studies of tropospheric chemical transport CO is also involved in tropospheric chemistry. It interacts with OH and O3 Tropospheric Chemistry JRD - Bremen

9. Methane is a greenhouse gas and a chemical agent. Most measurements of methane have been made from the ground (e.g.this picture) Considerable debate about the methane budget (sources/sinks) and possible climatic and anthropogenic influences The Methane Problem JRD - Bremen

10. MOPITT Measurements JRD - Bremen

11. Measurement Scenario • MOPITT operates by sensing infra-red radiation from either: • The surface thermal emission at 4.7µm for CO profiles • Reflected sunlight at about 2.2-2.4µm for CO and CH4 column measurements in daylight • The radiation is modified by absorption/emission processes in the atmosphere and these changes are detected in the MOPITT instrument using Correlation Radiometry (CR) techniques JRD - Bremen

12. Correlation Radiometry • Correlation Radiometry (CR) Uses a sample of the gas of interest as a filter to separate out the required emissions from the background. • It has been used on a number of spacecraft instruments. • MOPITT uses two methods of CR • Pressure modulation using Pressure Modulator Cells (PMCs) • Length modulation using Length Modulator Cells (LMCs) JRD - Bremen

13. Simple CR System JRD - Bremen

14. In a CR system the amount of the gas is modulated and the incoming radiation is passed through the gas cell. Radiation is modulated at the cell frequency if it's optical frequency coincides with that of a spectral line of the gas in the cell. Detection of the modulated part of the radiation is performed digitally and this is a better indicator of the spectrum of interest than the raw radiance. Advantages are the reduction of required dynamic range and rejection of other gaseous emission Disadvantage is the complexity of the resulting signal JRD - Bremen

15. Wavelength Regions • CO fundamental band at 4.7um • Gives information on profile • But no sensitivity at ground • CO overtone at 2.3um • Sensitive to column • Only works in sunlight • CH4 at 2.2um • Same as CO overtone • Quite weak JRD - Bremen

16. Atmospheric Spectrum JRD - Bremen

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18. Uses cooled detectors cooled preamplifiers cooled optics Active cooling Digital Signal Processing Length Modulators Pressure Modulators MOPITT - Technology JRD - Bremen

19. LMCs are the two circular object LMCs are made of Ti Windows are coated Ge “Gold” object is a molecular sieve JRD - Bremen

20. MOPITT - Instrument JRD - Bremen

21. MOPITT Calibration • MOPITT has a saw-tooth scan - takes 13 secs • A space view is taken every 10 scans • A two-point calibration is taken every 11 minutes • A long calibration is performed monthly. JRD - Bremen

22. MOPITT - Scanning JRD - Bremen

23. MOPITT - Vertical Resolution JRD - Bremen

24. MOPITT - Instrument JRD - Bremen

25. Terra Spacecraft JRD - Bremen

26. Terra - Other Instruments • ASTER - Advanced Spaceborne Thermal Emission and Reflection Radiometer • 15m resolution, 0.5-12um • Surface Imager • MISR - Multi-angle Imaging SpectroRadiometer • 9 cameras, 275m resolution 0.44 - .87um • Multi-angle surface imager • MODIS - Moderate Resolution Imaging Spectrometer • 250m resolution 0.4-14.5um • Surface imager • CERES - Clouds and the Earth’s Radiant Energy System • 10km resolution, 0.3-50um • Global radiation budget JRD - Bremen

27. LAUNCH!! • Failed launch attempt • December 16, 1999 • Change of procedure • Successful launch • Dec 18, 1999, 18:57GMT (10:57PST) • 9 seconds before end of window! • Orbit: • polar, sun synchronous, • Altitude, 705km, inclination 98.4 • 10:43am desc. node JRD - Bremen

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30. The First Map! JRD - Bremen

31. Instrument Maintenance • MOPITT is mostly self-calibrating • Thermal (longer wavelength) channels calibrate • every 2 minutes to space • Every 11 minutes to internal (room temperature) target • Solar (shorter wavelength) channels calibrate • Every 2 minutes to space • Every 11 minutes to internal (room temperature) target • Every few months to internal (hot – 450K) target • Cold systems need monitoring • Gas cells need attention…. JRD - Bremen

32. On-Orbit Gain Trend • Icing on the cold optics leads to a change in transmission and hence a gain change • Thermal channels • Initial rate of change 1%/21 days • 2nd de-contamination brought gain values to within 1% of initial values • Present rate is 1%/60 days • Solar channels • Initial rate of change 1%/100 days • 2nd de-contamination brought gain values to within 0.5% of initial values • Present rate is 1%/120 days • De-contamination criteria in the future may depend on a filter shift criteria rather than a gain change JRD - Bremen

33. Before After MAPS JRD - Bremen

34. One Day of MOPITT Data JRD - Bremen

35. Map average global may JRD - Bremen

36. Map average global october JRD - Bremen

37. Map average NA may JRD - Bremen

38. Map average NA october JRD - Bremen

39. MOPITT – THE MOVIES - I JRD - Bremen

40. MOPITT – THE MOVIES - II JRD - Bremen

41. China Weather and MOPITTCO for 22nd August 2000 • MOPITT data are not available under hurricane “BIBILIS” • - Transition from high CO to low CO visible across the front JRD - Bremen

42. MOPITT - Validation Strategy • Pre-launch algorithm test and verification • Use aircraft data • Add to spectral database • Validation of MOPITT level 1 data: • Comparison with model calculations • MOPITT airborne simulator (MOPITT-A) • MOPITT Algorithm Test Radiometer - MATR • FTIR Measurements • MODIS/MAS. • Comparison of derived products (mainly level 2 data) with correlative measurements. • Ground-based spectroscopy • Airborne in situ measurements • ground-based in situ measurements at selected sites JRD - Bremen

43. Circles: ground-based spectrometer (column) Open Triangles: MOPITT 850hPa Solid Triangles: MOPITT, middle & upper troposphere JRD - Bremen

44. MOPITT Anomalies • MOPITT has been operational at 100% since March 2000 • The first event occurred on May 7th 2001 (OPS127/04:07:00) • The telemetry indicated that displacer B amplitude was excessive • Triggered Red Limit • MOPITT to SAFE as per pre-arranged procedure • Red condition occurred for about 11 minutes before SAFE mode • Subsequent analysis indicated that during the 11 minutes • Tip B temperature increased at a rate higher than if coolers had been turned off • Compressors A and B increased amplitude • Tip A cooled down JRD - Bremen

45. MOPITT OPTICS Cooler B Cooler A JRD - Bremen

46. MOPITT Anomalies • July 5th onwards • MOPITT in SCIENCE mode • Operating normally on channels 5-8 only • Channels 1-4 are off with detectors unpowered and tip at slightly above room temperature. • Long calibration was initiated to retrieve calibration baseline • Cooler sub-system exhibiting more amplitude wander than previously observed, but this is not impacting operations JRD - Bremen

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48. MOPITT Anomalies • On August 7 Chopper 3 motor drive current fell to zero • Not a flagged condition • no danger to instrument • Subsequent investigation showed that power feed to the chopper had failed at (nearly) the same time • Some indications of high current draw in the few seconds before failure • No indication in previous telemetry of any problem • Symptoms are exactly the same as for an unverified fuse failure pre-launch JRD - Bremen

49. MOPITT Anomalies • Channels 5 and 6 are affected • Analysis of science telemetry indicates that the chopper has failed completely open • Chopper is “loose” in the instrument • Maneuvers in the roll direction are the most likely to cause the chopper to close • Algorithms are being developed to utilise Channel 5 and Channel 6 data without the chopper closed information • Initial indications are that this might be successful • Space view is being used as a substitute for the chopper closed • Some instrument optimisation results in improved signals JRD - Bremen

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