The Solar Mass Ejection Imager (SMEI) viewed nearly the whole sky in visible light to a high photometric accuracy. When the appropriate background contributions are subtracted, SMEI provides Thomson-scattering data that are directly related to the solar wind density flowing outward from the Sun. SMEI launched on January 6th, 2003 into an Earth-terminator, Sun synchronous, 840 km polar orbit. It provides an effective means for tracking interplanetary disturbances, following them well past the sky coverage of near-Sun coronagraph observations, out to beyond Earth and typically out to ~3 AU. SMEI was deactivated on September 28th, 2011.
SMEI data allow the 3D tomographic reconstruction of coronal mass ejections (CMEs) and other heliospheric structures such as corotating interaction regions (CIRs) as they move outward from the Sun, with a 102-minute cadence, at resolutions of 0.05 AU in height and 1o x 1o in latitude and longitude. These UCSD tomographic techniques currently incorporate a purely kinematic model that also includes the ground-based interplanetary scintillation (IPS) data provided by Solar Terrestrial Environment Laboratory (STELab), Nagoya University, Japan. The STELab velocity data are a particularly valuable input to this 3D reconstruction technique.
SMEI is a joint project of UCSD, Boston College, the University of Birmingham (UK), and the Air Force Research Laboratory. Prior to launch UCSD was responsible for the overall design and preliminary development of the instrument baffle, CCD selection and testing, the optics construction and calibration, and early development of SMEI analysis algorithms.