SOHO CoRoT Kepler Picard SDO GONG
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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.
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