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The HMI Observing Program to Study the Evolution of the Sun's Shape | |
Auteur | Bush Rock |
Institution | Stanford University |
Theme | Solar diameter, irradiance and activity |
| Auteur(s) supplémentaire(s) | J. Kuhn, M. Emilio, I. Scholl |
| Institution(s) supplémentaire(s) | University of Hawaii, Universidade Estadual de Ponta Grossa - Brazil |
Abstract | The Helioseismic and Magnetic Imager (HMI) instrument, which was launched in February 2010 on the Solar Dynamics Observatory (SDO) spacecraft, takes full disk solar images across the Fe absorption line at 617.3 nm with 1 arc-second resolution. The position of solar limb is measured by fitting the observed limb darkening function to determine both the apparent solar radius and the shape of the solar limb. In order to remove the instrument optical distortion from the measured shape of the solar limb, the SDO spacecraft is rotated by 360 degrees with dwells at uniformly spaced angular separations. The first two SDO roll calibration maneuvers was completed on 9 and 16 April 2010. Additional SDO roll maneuvers are scheduled at 6 month intervals in order to measure the variation of the solar shape over cycle 24. Details of the observing program and initial results will be presented. This research is supported by NASA contract NAS5-02139 at Stanford University. |