Global Magnetospheric Imaging from the Deep Space Gateway in Lunar Orbit

We propose to use the Deep Space Gateway (DSG) in lunar orbit as an observing platform for a magnetospheric imager that will capture the first direct global images of the interface between the incident solar wind and the Earth’s magnetosphere, and the response of the coupled magnetosphere-plasmasphere-ionosphere system to all incident solar plasmas. The optical detection of the faint magnetosphere surrounding the bright Earth is achieved using the same techniques as those used to image the faint solar corona and solar wind. This method measures the brightness of visible that is Thomson-scattered by electrons in the solar wind and magnetospheric plasmas. The Thomson scattering brightness is proportional to the line of sight column electron density. The large-scale context afforded by globally imaging the magnetosphere promises major advances in our fundamental understanding of solar wind driving of the magnetosphere. Such images would reveal how electrons in the magnetosphere and plasmasphere are redistributed in response to solar wind forcing, particularly when CMEs and CIRs interact with geospace. Global images of the magnetosphere would also be useful for proving global boundary conditions to ionospheric specification models. Our global magnetospheric imager on DSG would be implemented as an externally mounted instrument suite that would not require any crew interaction under normal operation. The instrument suite would consist of an Earth-centered geocoronagraph (analogous to a solar coronagraph) with an external occulter of radius 1.2 – 1.5 Earth radii (R_E) and a magnetospheric imager (analogous to a heliospheric imager). A geocoronagraph with an Earth-centered field of view of 25° would observe out to 26 R_E from lunar orbit. This is sufficient to observe the entire cross section of the dayside magnetosphere, including the bow shock and magnetopause, the polar cusps, and a significant portion of the tail lobes. The magnetospheric imager would have an overlapping field of view approximately 30° wide that could be pointed upstream of the magnetosphere to image solar wind structures approaching the magnetosphere or downstream of Earth to observe the dynamics of the magnetotail plasma sheet.