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Session 2 - Everything Else.
Display session, Friday, June 27
Ballroom C, Chair: Richard Canfield

[2.02] Solar Oblateness Measurements by the MDI Instrument on SOHO

R. I. Bush (Stanford University), J. R. Kuhn (NSO/ Sac Peak and Michigan State Univ.), X. Scheick (Michigan State Univ.)

The Michelson Doppler Imager instrument on the SOHO spacecraft provides high precision measurements of the solar limb brightness because of the absence of atmospheric blurring. This paper will describe the solar oblateness determined from MDI observations during a roll maneuver of the SOHO spacecraft performed on 20 March 1997. This maneuver was requested by the SOI-MDI team in order to obtain precise measurements of the solar limb and consisted of two 360 degree rolls of the SOHO spacecraft about the axis pointing to the center of the sun.. By observing the solar limb during the spacecraft roll, the static solar shape can be extracted from the distortion caused by the MDI optics.

The primary observable for this activity was the full-disk computed continuum using 1.96" pixels. The first complete roll was performed in increments of 30 degrees, and a second roll was performed in the opposite direction in increments of 90 degrees. The dwell time at each roll position was nominally 25 minutes, with about 10 minutes required to roll the spacecraft 30 degrees and precisely determine the new location. The calibration and analysis of these continuum images to determine the solar oblateness will be detailed


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