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

Chapter 4.0 Entomopter Flight Operations
4.1 Entomopter Navigation and Communications on Mars
Chapter 4.0 Entomopter Flight Operations
4.1 Entomopter Navigation and Communications on
Mars
There are presently no global navigation systems on Mars to support an Entomopter-based aerial
survey mission. Although such a network may be established in the future, it is not really essential
to the Entomopter navigation function. Because Entomopters are designed to return to the
rover base for refueling, their operations are necessarily rover-centric. For this reason, all navigation
cues can (and probably should) be referenced to the refueling rover's position, which
from the Entomopter's perspective is decoupled from any Mars coordinate system. All the Entomopters
need to know is where they are relative to the refueling rover. The refueling rover, on
the other hand, should have an awareness of its global position, but this position is largely irrelevant
to the Entomopters. This is particularly true because Entomopter missions are planned to be
local to the rover. Due to endurance constraints, the Entomopters are not envisioned as striking
out across the Mars landscape to investigate points hundreds of kilometers distant.
This section will present two approaches to Entomopter navigation and communication. The two
differ in terms of architecture- basically, where emitters are located. In one case, most of the
emitters are carried by the refueling rover, and except for a short distance low-power ranging
device to aid in landing, the Entomopters are free from the weight burden of this support equipment.
The other option presented places various emitters on the Entomopters, the advantage
being that longer range operation is possible and non-line-of-sight flight (relative to the refueling
rover) is simplified. The price to be paid for this increase in performance is decreased science
payload capacity in terms of weight and volume when both emitters and their supporting
energy source are considered. The particular science mission goal will dictate which method is
preferred.
4.2 Rover-centric Entomopter Navigation
Because the refueling rover (by definition) is replete with fuel and is therefore not energy constrained
to the degree that a flying vehicle would be, it has the luxury of emitting relatively high
power radio frequency (RF) radiation (a costly behavior due to emitter inefficiencies). As such,
the rover can support a radar system capable of detecting and tracking objects within a hemispherical
volume centered about the rover.
The Entomopter has a distinctive radar cross-section (RCS) that involves both high frequency
local motions and translational motions. Doppler target acquisition and tracking radar on the
rover would easily identify Entomopters in flight based on their motion as distinguished from
the stationary Mars landscape. The wingbeat would provide a high frequency (10s of Hz) modulation
of the RCS in terms of amplitude, while the flight speed of the Entomopter would provide
a Doppler shift of magnitude and sign that depends upon angle of approach or departure. Additionally,
the elevation of the Entomopters would be a discriminator most of the time as well, so
long as they were operating in the general vicinity of the rover.
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