The Multiview Observatory for Solar Terrestrial Science (MOST)

Understanding the emergence of magnetic flux from the solar interior through the
photosphere and its global impact on the inner heliosphere is a key scientific goal of the
heliophysics community. This white paper outlines the concept of the Multiview Observatory for
Solar Terrestrial Science (MOST) mission, which will make measurements of solar variability
from the solar interior, atmosphere, and the interplanetary (IP) medium. MOST will be a 4-
spacecraft mission with one each at L4 (MOST1) and L5 (MOST2) and the other two (MOST3
and MOST4) at variable locations along Earth orbit. MOST1 and MOST2 will each carry seven
remote-sensing and 3 in-situ instruments. All four spacecraft will carry a novel radio package
known as the Faraday Effect Tracker of Coronal and Heliospheric structures (FETCH) that will
systematically probe the magnetic content of transient IP structures including coronal mass
ejections (CMEs) and stream interaction regions (SIRs). The Faraday rotation measurements will
provide magnetic content of these structures at various heliocentric distances from the outer
corona to Earth’s vicinity. Photospheric and/or chromospheric magnetograms will cover >70%
of the solar surface providing synchronic maps needed for accurately modeling the corona and
solar wind. EUV, coronagraph, radio spectrograph, and heliospheric imager (HI) observations
from multiple viewpoints provide 3-d information on CMEs/CME-driven shocks, SIRs, and
other solar wind structures. Hard X-ray imagers will provide the flare aspects of solar eruptions
to complement the CME aspects. MOST, a 10-year mission, is well aligned with NASA’s
Heliophysics objectives and will provide an unprecedented opportunity to achieve these
objectives with broad participation from the heliophysics community.