Abstract

The Michelson Doppler Imager (MDI) is a spectral imaging experiment on the ESA-NASA Solar and Heliospheric Observatory spacecraft (SOHO-see Domingo et al., 1995). SOHO was launched in December, 1995, and reached its final orbit about the Earth-Sun Lagrangian point L1 in mid-February, 1996. This point, about 1.5×l0⁶ km towards the Sun, is where the Earth’s and Sun’s gravity balance, allowing a nearly stable orbit ideal for continuous observations of the Sun and solar wind. MDI is collecting the observational data for the Solar Oscillations Investigation (SOI), a study of the interior structure of the Sun as inferred from the normal modes of oscillation seen on its surface (“heliosesmology”). Since launch, MDI has been collecting images showing the Doppler velocity, continuum intensity, and magnetic field on the solar surface with high spatial and temporal resolution. SOI/MDI were developed jointly by Stanford University and Lockheed Martin Advanced Technology Center, supported by NASA (see Scherrer et al., 1995). The Principal Investigator is Prof. P. Scherrer of Stanford.

© 1996 Optical Society of America