  Direct-sampling observations of interstellar neutral gas, including hydrogen
and deuterium, have been performed for more than one cycle of solar activity by
IBEX. IBEX viewing is restricted to directions perpendicular to the
spacecraft--Sun line, which limits the observations to several months each
year. This restriction is removed in a forthcoming mission Interstellar Mapping
and Acceleration Probe. The IMAP-Lo instrument will have a capability of
adjusting the angle of its boresight with the spacecraft rotation axis. We
continue a series of studies of resulting science opportunities. We adopt a
schedule of adjusting the boresight angle suggested by Kubiak et al. 2023 and
focus on interstellar hydrogen and deuterium during solar maximum epoch. Based
on extensive set of simulations, we identify the times during calendar year and
elongation angles of the boresight needed to measure the abundance of D/H at
the termination shock and unambiguously observe interstellar H without
contribution from interstellar He. Furthermore, IMAP-Lo will be able to resolve
the primary and secondary populations, in particular to view the secondary
population with little contribution from the primary. We show that the expected
signal is sensitive to details of radiation pressure, particularly its
dependence on radial speed of the atoms, and to details of the behavior of the
distribution function of the primary and secondary populations at the
heliopause. Therefore, IMAP-Lo will be able to provide observations needed to
address compelling questions of the heliospheric physics, and even general
astrophysics.
