IEEE - Aerospace and Electronic Systems - March 2020 - 59

Hardgrove et al.

Figure 5.
Figure 3.
LunaH-Map Transfer Trajectory. The spacecraft trajectory (cyan)
leverages the first lunar swingby to enter a weak capture around
Earth (origin and center of frame) and target lunar orbit insertion.
The Moon's trajectory during this time span is presented in grey.

months is executed to reduce the orbital energy and eventually enter into the final science orbit. These maneuvers
will occur contiguously when the spacecraft is not in
eclipse or communicating with ground stations, and burn
updates will occur at regular intervals to ensure the transition profile is maintained. If necessary, the spacecraft may
enter a stable circular orbit during its transition to avoid
Earth eclipses before targeting the final science orbit.

Figure 4.
LunaH-Map Transition Phase. Earth-centered view of LunaHMap transition from weak lunar capture to elliptical science orbit.
Low-thrust maneuver segments are presented in red, and all other
colors are coast segments where maneuvering does not occur. The
final (smallest) lunar orbit in this figure represents the 10 km Â
3150 km altitude Science Orbit, also presented in Figure 5.

MARCH 2020

LunaH-Map Science Phase. A moon-centered view of the highly
elliptical (10 km Â 3150 km altitude) science orbits with perilune
over the Lunar South Pole. The cyan and green simply represent different halves of the orbit, and the white represents when science
observations are planned to occur.

After maneuvering for several months, the spacecraft's
orbital parameters will match those of the final desired
science orbit. An illustrated view of the transition from
weak lunar capture to elliptical science orbit is shown in
Figure 4.
An elliptical science orbit with periselene above
the lunar South Pole will then be maintained with orbit
adjustment maneuvers occurring at apolune. The periselene altitude of each pass above the South Pole will
be between 5 and 25 km, enabling productive scientific
return. This science orbit will be maintained for at
least 282 lunar orbits (46 days), with the possibility of
extending the operations and orbital maintenance if
desired. The elliptical science orbit is illustrated in
Figure 5.
Due to the uncertainty in the initial deployment
time and state, various analyses have been conducted to
analyze trajectory and orbit designs to various geometric conditions. For each different deployment state,
either a one-loop (nominal) or two-loop transfer around
the Earth can be found and used to target a lunar orbit
insertion. The transition and science orbit's right ascension of the ascending node orbital parameter is dependent on initial deployment condition and causes
different natural evolution of the other orbital parameters, none of which, however, change drastically
enough to pose a threat to the nominal maneuver and
operations cadence or warrant a constraint on the trajectory. However, in the event that contingency scenarios
prevent navigation operations from executing the baseline trajectory, there are many possible recovery

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