During Apollo, the constraints placed by the design of the Lunar Module (LM) window for crew visibility and
landing trajectory were "a major problem." Lunar landing trajectories were tailored to provide crew visibility
using nearly 70 degrees look-down angle from the canted LM windows. Apollo landings were scheduled only at
specific times and locations to provide optimal sunlight on the landing site.
The complications of trajectory design and crew visibility are still a problem today. Practical vehicle designs
for lunar lander missions using optimal or near-optimal fuel trajectories render the natural vision of the crew
from windows inadequate for the approach and landing task. Further, the sun angles for the desirable landing
areas in the lunar polar regions create visually powerful,
season-long shadow effects. Fortunately, Synthetic and
Enhanced Vision (S/EV) technologies, conceived and developed in the aviation domain, may provide solutions to
this visibility problem and enable additional benefits for safer, more efficient lunar operations. Piloted simulation
evaluations have been conducted to assess the handling qualities of the various lunar landing concepts, including
the influence of cockpit displays and the informational data and formats. Evaluation pilots flew various landing
scenarios with S/EV displays. For some of the evaluation trials, an eye glasses-mounted, monochrome monocular
display, coupled with head tracking, was worn. The head-worn display scene consisted of S/EV fusion concepts.
The results of this experiment showed that a head-worn system did not increase the pilot's workload when
compared to using just the head-down displays. As expected, the
head-worn system did not provide an increase in
performance measures. Some pilots commented that the head-worn system provided greater situational awareness
compared to just head-down displays.