MLS Research

Instrument Science and Calibration

Contact Robert Jarnot

Good Aura MLS science quality is dependent upon accurate calibration knowledge in three key areas: radiometric, spectral and field-of-view responses. To achieve this required careful attention to instrument design and fabrication, careful pre-launch performance verification, and comprehensive pre-launch calibrations.

In-orbit tests are performed periodically to monitor such important calibration data as the radiance differences between cold space views via the Switching Mirror and Antenna. In over 5 years of operation these tests have shown remarkable stability, with overall changes typically smaller than 20 mK in all bands.

Another valuable in-orbit calibration has come from the brief opportunities during which MLS can scan across the Moon. These measurements have sometimes required coordinated spacecraft maneuvers to allow the relatively narrow MLS field-of-views to scan across the appropriate portion of the lunar disk, and have significantly lowered the uncertainties on the pre-launch measurements of boresight (pointing) differences between the various radiometers, as well as indicated that the shapes of the antenna FOV's have remained stable.

Another area in which in-orbit data has added to our knowledge of measurement accuracy is in the area of standing waves on radiometric calibration views. Tracking (as opposed to scanning) the lunar disk has provided quantitative information on the impact of standing waves on radiometric calibration accuracy that was not available from pre-launch calibration data.

Signal levels seen when observing cold space via the main GHz antenna indicate no significant changes to the reflectivity or emissivity of the 3 antenna mirrors. The observed positions of atmospheric spectral lines as seen by the 30+ spectrometers on MLS indicate the absence of frequency drifts within the instrument.

The one area in which signals have been changing for the duration of the mission is that the signal powers to the nineteen 25-channel spectrometers have steadily decreased. These decreases arise from radiation effects on low-dropout voltage regulators that were added to the spectrometers late in the instrument fabrication phase.

The dropping signal levels have been periodically compensated by changes to programmable attenuator settings, and the regular in-orbit radiometric calibration sequences completely compensate for these small drifts. Extrapolating the declining signal levels indicates that these degradations are unlikely to be a life-limiting factor for the data from any measurement band.

MLS publications related to instrument science

  1. Tang, A., S. Khanal, G. Virbila, N. Livesey, F. Werner, G. Chattopadhyay and M. Chang
    A 2.0 GS/s Two-Stage Quad-Channel Digital Downconverter for a 380 GHz Spaceborne Atmospheric H2O Monitoring Instrument
    IEEE Transactions on Circuits and Systems--II: Express Briefs doi:10.1109/tcsii.2022.3205848, 2022
  2. Livesey, N., W. Read, L. Froidevaux, A. Lambert, M. Santee, M. Schwartz, L. Millán, R. Jarnot, P. Wagner, D. Hurst, K. Walker, P. Sheese and G. Nedoluha
    Investigation and amelioration of long-term instrumental drifts in water vapor and nitrous oxide measurements from the Aura Microwave Limb Sounder MLS and their implications for studies of variability and trends
    Atmos. Chem. Phys. doi:10.5194/acp-21-15409-2021, 2021
  3. Dolgii, S., A. Nevzorov, A. Nevzorov, Y. Gridnev and O. Kharchenko
    Temperature Correction of the Vertical Ozone Distribution Retrieval at the Siberian Lidar Station Using the MetOp and Aura Data
    Atmosphere doi:10.3390/atmos11111139, 2020
  4. Bourassa, A., C. Roth, D. Zawada, L. Rieger, C. McLinden and D. Degenstein
    Drift-corrected Odin-OSIRIS ozone product: algorithm and updated stratospheric ozone trends
    Atmospheric Measurement Techniques doi:10.5194/amt-11-489-2018, 2018
  5. Lee, C., G. Jee, J. Kim and I. Song
    Meteor echo height ceiling effect and mesospheric temperature estimation from meteor radar observations
    Annales Geophysicae 10.5194/angeo-36-1267-2018, 2018
  6. Millán, L., N. Livesey, M. Santee and T. von Clarmann
    Characterizing sampling and quality screening biases in infrared and microwave limb sounding
    Atmos. Chem. Phys. doi:10.5194/acp-18-4187-2018, 2018
  7. Wing, R., A. Hauchecorne, P. Keckhut, S. Godin-Beekmann, S. Khaykin and E. McCullough
    Lidar temperature series in the middle atmosphere as a reference data set – Part 2: Assessment of temperature observations from MLS/Aura and SABER/TIMED satellites
    Atmospheric Measurement Techniques 10.5194/amt-11-6703-2018, 2018
  8. Ochiai, S., P. Baron, T. Nishibori, Y. Irimajiri, Y. Uzawa, T. Manabe, H. Maezawa, A. Mizuno, T. Nagahama, H. Sagawa, M. Suzuki and M. Shiotani
    SMILES-2 Mission for Temperature, Wind, and Composition in the Whole Atmosphere
  9. Yee, J.H., J. Gjerloev, D. Wu and M.J. Schwartz
    First Application of the Zeeman Technique to Remotely Measure Auroral Electrojet Intensity from Space
    Geophys. Res. Lett. doi:10.1002/2017gl074909, 2017
  10. Höpfner, M., C.D. Boone, B. Funke, N. Glatthor, U. Grabowski, A. Günther, S. Kellmann, M. Kiefer, A. Linden, S. Lossow, H.C. Pumphrey, W.G. Read, A. Roiger, G. Stiller, H. Schlager, T. von Clarmann and K. Wissmüller
    Sulfur dioxide (SO2) from MIPAS in the upper troposphere and lower stratosphere 2002-2012
    Atmos. Chem. Phys. 10.5194/acp-15-7017-2015, 2015
  11. Kaufmann, M., J. Blank, T. Guggenmoser, J. Ungermann, A. Engel, M. Ern, F. Friedl-Vallon, D. Gerber, J.U. Grooss, G. Guenther, M. Höpfner, A. Kleinert, E. Kretschmer, T. Latzko, G. Maucher, T. Neubert, H. Nordmeyer, H. Oelhaf, F. Olschewski, J. Orphal, P. Preusse, H. Schlager, H. Schneider, D. Schuettemeyer, F. Stroh, O. Suminska-Ebersoldt, B. Vogel, C.M. Volk, W. Woiwode and M. Riese
    Retrieval of three-dimensional small-scale structures in upper-tropospheric/lower-stratospheric composition as measured by GLORIA
    Atmospheric Measurement Techniques doi:10.5194/amt-8-81-2015, 2015
  12. Meyer, J., C. Rolf, C. Schiller, S. Rohs, N. Spelten, A. Afchine, M. Zöger, N. Sitnikov, T.D. Thornberry, A.W. Rollins, Z. Bozóki, D. Tátrai, V. Ebert, B. Kühnreich, P. Mackrodt, O. Möhler, H. Saathoff, K.H. Rosenlof and M. Krämer
    Two decades of water vapor measurements with the FISH fluorescence hygrometer: a review
    Atmos. Chem. Phys. doi:10.5194/acp-15-8521-2015, 2015
  13. Pumphrey, H.C., W.G. Read, N.J. Livesey and K. Yang
    Observations of volcanic SO2 from MLS on Aura
    Atmospheric Measurement Techniques doi:10.5194/amt-8-195-2015, 2015
  14. Siegel, P.
    Terahertz Pioneer: Joe W. Waters "THz Meets Gaia"
    IEEE Trans. THz Sci. Technol. doi:10.1109/tthz.2015.2480857, 2015
  15. Clarisse, L., P.F. Coheur, N. Theys, D. Hurtmans and C. Clerbaux
    The 2011 Nabro eruption, a SO2 plume height analysis using IASI measurements
    Atmos. Chem. Phys. doi:10.5194/acp-14-3095-2014, 2014
  16. Fromm, M., G. Kablick III, G. Nedoluha, E. Carboni, R. Grainger, J. Campbell and J. Lewis
    Correcting the record of volcanic stratospheric aerosol impact: Nabro and Sarychev Peak
    Journal of Geophysical Research: Atmospheres doi:10.1002/2014JD021507, 2014
  17. Hurst, D.F., A. Lambert, W.G. Read, S.M. Davis, K.H. Rosenlof, E.G. Hall, A.F. Jordan and S.J. Oltmans
    Validation of Aura Microwave Limb Sounder stratospheric water vapor measurements by the NOAA frost point hygrometer
    Journal of Geophysical Research: Atmospheres doi:10.1002/2013JD020757, 2014
  18. Wu, D.L., A. Lambert, W.G. Read, P. Eriksson and J. Gong
    MLS and CALIOP Cloud Ice Measurements in the Upper Troposphere: A Constraint from Microwave on Cloud Microphysics
    Journal of Applied Meteorology and Climatology doi:10.1175/JAMC-D-13-041.1, 2014
  19. Hoppel, K.W., S.D. Eckermann, L. Coy, G.E. Nedoluha, D.R. Allen, S.D. Swadley and N.L. Baker
    Evaluation of SSMIS Upper Atmosphere Sounding Channels for High-Altitude Data Assimilation
    Monthly Weather Review doi:10.1175/MWR-D-13-00003.1, 2013
  20. Kenea, S.T., G.M. Tsidu, T. Blumenstock, F. Hase, T. von Clarmann and G.P. Stiller
    Retrieval and satellite intercomparison of O3 measurements from ground-based FTIR Spectrometer at Equatorial Station: Addis Ababa, Ethiopia
    Atmospheric Measurement Techniques doi:10.5194/amt-6-495-2013, 2013
  21. Nedoluha, G.E., R.M. Gomez, H. Neal, A. Lambert, D. Hurst, C. Boone and G. Stiller
    Validation of long-term measurements of water vapor from the midstratosphere to the mesosphere at two Network for the Detection of Atmospheric Composition Change sites
    J. Geophys. Res. doi:10.1029/2012JD018900, 2013
  22. Stähli, O., A. Murk, N. Kämpfer, C. Mätzler and P. Eriksson
    Microwave radiometer to retrieve temperature profiles from the surface to the stratopause
    Atmospheric Measurement Techniques doi:10.5194/amt-6-2477-2013, 2013
  23. Straub, C., P.J. Espy, R.E. Hibbins and D.A. Newnham
    Mesospheric CO above Troll station, Antarctica observed by a ground based microwave radiometer
    Earth System Science Data doi:10.5194/essd-5-199-2013, 2013
  24. Wang, L. and C. Zou
    Inter-comparison of SSU Temperature Data Records with Lidar, GPS RO, and MLS Observations
    J. Geophys. Res. doi:10.1002/jgrd.50162, 2013
  25. Millan, L., N.J. Livesey, L. Froidevaux, D. Kinnison, R. Harwood, I.A. MacKenzie and M.P. Chipperfield
    New Aura Microwave Limb Sounder observations of BrO and implications for Bry
    Atmospheric Measurement Techniques doi:10.5194/amt-5-1741-2012, 2012
  26. Pumphrey, H.C., M.L. Santee, N.J. Livesey, M.J. Schwartz and W.G. Read
    Microwave Limb Sounder observations of biomass-burning products from the Australian bush fires of February 2009
    Atmos. Chem. Phys. doi:10.5194/acp-11-6285-2011, 2011
  27. Wu, D.L., J.H. Jiang, W.G. Read, R.T. Austin, C.P. Davis, A. Lambert, G.L. Stephens, D.G. Vane and J.W. Waters
    Validation of the Aura MLS Cloud Ice Water Content (IWC) Measurements
    J. Geophys. Res. doi:10.1029/2007JD008931, 2008
  28. Mueller, E.R., R. Henschke, W.E. Robotham Jr., L.A. Newman, L.M. Laughman, R.A. Hart, J. Kennedy and H.M. Pickett
    Terahertz local oscillator for the Microwave Limb Sounder on the Aura Satellite
    Appl. Opt. doi:10.1364/AO.46.004907, 2007
  29. Cofield, R.E. and P.C. Stek
    Design and field-of-view calibration of 114-660 GHz optics of the Earth Observing System Microwave Limb Sounder
    IEEE Trans. Geosci. Remote Sensing doi:10.1109/TGRS.2006.873234, 2006
  30. Cofield, R.E., W.A. Imbriale and R.E. Hodges
    Instrument Packages
    Spaceborne Antennas 2006
  31. Jarnot, R.F., V.S. Perun and M.J. Schwartz
    Radiometric and spectral performance and calibration of the GHz bands of EOS MLS
    IEEE Trans. Geosci. Remote Sensing doi:10.1109/TGRS.2005.863714, 2006
  32. Pickett, H.M.
    Microwave Limb Sounder THz Module on Aura
    IEEE Trans. Geosci. Remote Sensing doi:10.1109/TGRS.2005.862667, 2006
  33. Schoeberl, M.R., A.R. Douglass, E. Hilsenrath, P.K. Bhartia, J. Barnett, R. Beer, J. Waters, M. Gunson, L. Froidevaux, J. Gille, P.F. Levelt and P. DeCola
    Overview of the EOS Aura Mission
    IEEE Trans. Geosci. Remote Sensing doi:10.1109/TGRS.2005.861950, 2006
  34. Waters, J.W.
    Observations for Chemistry (Remote Sensing): Microwave
    Encyclopedia of Atmospheric Sciences 2003
  35. Gaidis, M.C., H.M. Pickett, C.D. Smith, S.C. Martin, R.P. Smith and P.H. Siegel
    A 2.5-THz Receiver Front End for Spaceborne Applications
    IEEE Trans. Microwave Theory and Techniques doi:10.1109/THZ.1998.731652, 2000
  36. Woodard, S., R. Lay, R. Jarnot and D. Gell
    Experimental investigation of spacecraft in-flight disturbances and dynamic response
    Jnl. of Spacecraft and Rockets 1997
  37. Jarnot, R.F., R.E. Cofield, J.W. Waters, G.E. Peckham and D.A. Flower
    Calibration of the Microwave Limb Sounder on the Upper Atmosphere Research Satellite
    J. Geophys. Res. doi:10.1029/95JD03792, 1996
  38. Lau, C.L., G.E. Peckham, R.A. Suttie and R.F. Jarnot
    Characterisation of MLS 1/f noise parameters
    Int. Jnl. Remote Sensing 1996
  39. Barath, F.T., M.C. Chavez, R.E. Cofield, D.A. Flower, M.A. Frerking, M.B. Gram, W.M. Harris, J.R. Holden, R.F. Jarnot, W.G. Kloezeman, G.J. Klose, G.K. Lau, M.S. Loo, B.J. Maddison, R.J. Mattauch, R.P. McKinney, G.E. Peckham, H.M. Pickett, G. Siebes, F.S. Soltis, R.A. Suttie, J.A. Tarsala, J.W. Waters and W.J. Wilson
    The Upper Atmosphere Research Satellite Microwave Limb Sounder Instrument
    J. Geophys. Res. doi:10.1029/93JD00798, 1993
  40. Waters, J.W.
    Microwave Limb Sounding
    Atmospheric Remote Sensing by Microwave Radiometry 1993
  41. Waters, J.W.
    Microwave limb-sounding of Earth's upper atmosphere
    Atmos. Res. 1989
  42. Waters, J.W., J.C. Hardy, R.F. Jarnot, H.M. Pickett and P. Zimmermann
    A balloon-borne microwave limb sounder for stratospheric measurements
    J. Quant. Spectrosc. Radiat. Transfer 1984