  The High Inclination Solar Mission (HISM) is a concept for an
out-of-the-ecliptic mission for observing the Sun and the heliosphere. The
mission profile is largely based on the Solar Polar Imager concept: initially
spiraling in to a 0.48 AU ecliptic orbit, then increasing the orbital
inclination at a rate of $\sim 10$ degrees per year, ultimately reaching a
heliographic inclination of $>$75 degrees. The orbital profile is achieved
using solar sails derived from the technology currently being developed for the
Solar Cruiser mission, currently under development.
  HISM remote sensing instruments comprise an imaging spectropolarimeter
(Doppler imager / magnetograph) and a visible light coronagraph. The in-situ
instruments include a Faraday cup, an ion composition spectrometer, and
magnetometers. Plasma wave measurements are made with electrical antennas and
high speed magnetometers.
  The $7,000\,\mathrm{m}^2$ sail used in the mission assessment is a direct
extension of the 4-quadrant $1,666\,\mathrm{m}^2$ Solar Cruiser design and
employs the same type of high strength composite boom, deployment mechanism,
and membrane technology. The sail system modelled is spun (~1 rpm) to assure
required boom characteristics with margin. The spacecraft bus features a
fine-pointing 3-axis stabilized instrument platform that allows full science
observations as soon as the spacecraft reaches a solar distance of 0.48 AU.
