Phase II Final Report - NASA's Institute for Advanced Concepts

Chapter 4.0 Entomopter Flight Operations
4.2 Rover-centric Entomopter Navigation
climbing in altitude a point at which it will be reacquired by the rover radar. Such a maneuver
would be negotiated a priori with the rover to assure that the Entomopter is not operating in the
vicinity of another Entomopter when it goes out of sight and to alert the rover that it should not
expect to see the Entomopter for a brief period.
Were a non-line-of-sight maneuver to be executed, the Entomopter would navigate with only its
altimeter and any short range obstacle detection/avoidance system normally used for terminal
flight path adjustments during landing (for example, the acoustic FMCW ranger that is inherent
to the reciprocating chemical muscle). This would allow emergency obstacle-avoidance maneuvers
to prevent a collision with an outcropping or the ground surface. Because there is risk
involved in flying without navigation cues, such a maneuver would likely be considered only if
the Entomopter were to investigate a large open space on the other side of a masking ridge, or if
the Entomopter were to descend into a large chasm or canyon.
Note that were the Entomopter to wander beyond radar detection range due to its own motions
or those of the ever-progressing rover, the navigation link would be lost. However, because the
rover's radiated signal must be sufficiently strong to elicit a skin return from the Entomopters,
the rover transmitter will serve as a useful homing beacon for a much greater range than it can
function as a radar. So if an Entomopter were to rise up from behind an obstruction to the point
that it is once again in line of sight with the rover, but the rover is unable to acquire the Entomopter,
this would immediately be evident to the Entomopter based on the lack of range, azimuth,
and elevation information updates sent to it by the rover. Basically, it would still be
receiving the “awaiting reacquisition” signal from the rover. The Entomopter would recognize
this and change its mode of behavior to one of beacon following. This will lead it back to the
rover, even apart from navigation data. At some point it will enter tracking range, and the rover
radar will reacquire the Entomopter, whereupon the navigation information stream will be reinitiated
and the Entomopter can revert to its mission plan.
Nap-of-the-surface flight is also possible during both line-of-sight and non-line-of-sight operations.
The criterion for nap-of-the-surface flight is that the flight speed must not exceed the
maneuverability of the Entomopter for its given obstacle-avoidance and altimetry-sensor range.
In summary, navigation can be achieved with a rover-centric scanning radar system that interrogates
the environment to detect obstacles as well as flying Entomopters. The distinctive Doppler
signature of the Entomopters can be exploited to easily identify and track them against the Mars
clutter background. Information gathered by the rover-borne radar, when processed, can be sent
to each Entomopter as a frequency modulation of the radar carrier. The center frequency for the
uploaded data will be above the maximum expected Doppler shift due to Entomopter radial
speed. Each Entomopter, having detected that it is being painted by the radar, will modulate its
radar cross-section using techniques similar to quantum well remodulators. This is an amplitude
modulation and will not interfere with the already impressed FM data upload, and will not be
corrupted by the much lower frequency wing-flapping-induced radar cross-section seen by the
rover. This obviates the need for long range emissions by the Entomopter, thereby saving weight
and energy. Short range altimetry emissions will require much lower power and will not conflict
with the navigation signal cues or responses. High bandwidth payload data will be stored
onboard for downloading once the Entomopter has returned to the refueling rover for replenish-
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