HMI Filtergram Processing and Continuum Data Products Continuum

HMI Filtergram Processing and Continuum Data Products • Continuum Definition – The current observing scheme does not take a “true” continuum filtergram during the Doppler framelist and an appropriate continuum proxy needs to be defined. The current options are to use the filtergrams taken at the tuning position furthest from line center or to construct a continuum observable from all the Doppler framelist filtergrams. – A true continuum intensity filtergram should be taken as part of the daily calibration sequence which is currently set for every 12 hours. • Limb and Image Center Determination – The image limb position and image center need to be determined for all filtergrams. • Update Flat-Field Corrections – SDO offpoint maneuvers are scheduled every six months to obtain data for flat-field/gain calibrations. A standard pipeline processing module is required to generate a new set of flatfield correction needed for the standard pipeline processing. – An interim flat-field correction is anticipated approximately once a month based on experience with the MDI continuum data. These interim flat-fields corrections are determined from large scale continuum variations over a solar rotation. • Solar Shape Determination – A SDO roll maneuver is planned every six months in part to measure the solar oblateness. The processing routines to determine the solar shape from these data should be incorporated into the pipeline system to insure a consistent shape determination. JSOC for SDO MOR October 2007 Page 1