Observing the Solar Photosphere from Space using the MDI and HMI Instruments

Rock I. Bush [rbush@solar.stanford.edu], Stanford University, California.

    The Michelson Doppler Imager (MDI) instrument on the Solar and Heliospheric Observatory spacecraft has been observing the Sun for almost 10 years. Full disk photospheric continuum images and line of sight magnetic fields have been measured for most of solar cycle 23. These observations have been important for modeling the relationship between active region and sunspot evolution and the total solar irradiance. In addition, these observations have provided the most accurate determination of solar radius and shape.

            The Helioseismic and Magnetic Imager (HMI) instrument is being developed as part of the Solar Dynamics Observatory spacecraft which will be launched in 2008. The HMI instrument is based on the MDI design heritage and is intended to improve the MDI observations and extend them through the next solar cycle. This poster will summarize the MDI measurements relevant to solar cycle activity and irradiance changes, and detail the improvements in these measurements anticipated with the HMI instrument.