Lyman-α Observations of Comet Holmes from SORCE SOLSTICE and SOHO SWAN

Abstract

In November 2007, the Solar Wind Anisotropy (SWAN) instrument on the Solar and Heliospheric Observatory (SOHO) and the SOLar-STellar Irradiance Comparison Experiment (SOLSTICE) on the SOlar Radiation and Climate Experiment (SORCE) both made observations of comet 17P/Holmes at Lyman-α wavelengths. The intent of these observations was to compare the calibration of SWAN and SOLSTICE, rather than to study the properties of comets. The two datasets require significant processing to remove interplanetary and geocoronal backgrounds which increased the uncertainty of the result. However, both instruments measured similar Lyman-α irradiances, confirming their calibration agreement.