Cross-Calibration of Far UV Spectra of Solar System Objects and the Heliosphere

Volume 13 of the series ISSI Scientific Report Series pp 163-175


Lyman-α Models for LRO LAMP from MESSENGER MASCS and SOHO SWAN Data

  • Wayne R. PryorAffiliated withCentral Arizona CollegeLASP, University of Colorado and Space Environment Technologies
  • , Gregory M. HolsclawAffiliated withLaboratory for Atmospheric and Space Physics, University of Colorado
  • , William E. McClintockAffiliated withLaboratory for Atmospheric and Space Physics, University of Colorado
  • , Martin SnowAffiliated withLaboratory for Atmospheric and Space Physics, University of Colorado
  • , Ronald J. VervackJr.Affiliated withApplied Physics Laboratory, The Johns Hopkins University
  • , G. Randall GladstoneAffiliated withSouthwest Research Institute
  • , S. Alan SternAffiliated withSouthwest Research Institute
  • , Kurt D. RetherfordAffiliated withSouthwest Research Institute
  • , Paul F. MilesAffiliated withSouthwest Research Institute

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From models of the interplanetary Lyman-α glow derived from observations by the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) interplanetary Lyman-α data obtained in 2009–2011 on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft mission, daily all-sky Lyman-α maps were generated for use by the Lunar Reconnaissance Orbiter (LRO) LAMP Lyman-Alpha Mapping Project (LAMP) experiment. These models were then compared with Solar and Heliospheric Observatory (SOHO) Solar Wind ANistropy (SWAN) Lyman-α maps when available. Although the empirical agreement across the sky between the scaled model and the SWAN maps is adequate for LAMP mapping purposes, the model brightness values best agree with the SWAN values in 2008 and 2009. SWAN’s observations show a systematic decline in 2010 and 2011 relative to the model. It is not clear if the decline represents a failure of the model or a decline in sensitivity in SWAN in 2010 and 2011. MESSENGER MASCS and SOHO SWAN Lyman-α calibrations systematically differ in comparison with the model, with MASCS reporting Lyman-α values some 30 % lower than SWAN.