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

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
This system would work as follows:
• The Entomopter sends out a communication signal, which includes a header
coded with the Entomopter ID, altimetry, and time. For multiple Entomopters,
their transmitted messages will begin with an individual identification code.
• Upon receipt, each beacon determines if the message is from the Entomopter by
checking the signal ID.
• If the message is from the Entomopter, each beacon calculates the time it took the
signal to reach the beacon ∆tI based on the time of departure from the Entomopter,
which was coded in the Entomopter message header.
• The rover signal processing determines the 2D relative position (x,y) by solving
N simultaneous equations.
2
2
2 1 / 2
c ∆t
− ∆ ) = 2{( x − x ) + ( y − y ) + ( z − z ) }
Equation 4-4
(
i i
i
i
i
where c is the speed of light and i = 1, 2, …N, and z i is the Entomopter altimetry, which is
known.
This technique would require additional onboard power from the Entomopter making this
method less attractive than the monopulse technique described above. In addition, the size of the
rover will limit the distance that the transceivers can be placed from each other. A potential road
block to this technique would be that the transceivers located on the refueling rover would be
essentially co-located, and as the Entomopter range increases, the baseline for this array
becomes more point-like and the elliptical probable error (EPE) increases drastically for the x-y
dimension. This is equivalent to bad geometric dilution of precision in the GPS solution. Thus,
the concept as proposed in the NIAC Phase I report will not be considered further in this Phase
II Final Report.
4.3.2 Propogation Losses
When performing the radio link analysis, propagation losses encountered on the Mars surface
must be considered. From a radio wave propagation study for communications on and around
Mars, the gaseous atmospheric attenuations by water vapor and oxygen at the Mars surfaces
were determined and are compared to those at the Earth’s surface versus frequency in Figure 4-7
[123]. As illustrated in the plot, this attenuation is quite low relative to that on Earth, because the
Mars atmosphere has very low concentrations of uncondensed H 2 O and O 2 [123]. On the contrary,
there is a significant amount of CO 2 and N 2 , but these gases do not have electric or magnetic
dipoles and thus do not absorb electromagnetic energy from the waves. However, Ho and
Golshan indicate that these gasses may generate dipoles through collisions and interact with
waves under a high-density condition and absorb electromagnetic waves in the infrared and optical
bands [123]. For this study, the atmospheric attenuation as plotted in Figure 4-7 is considered,
and it is assumed that CO 2 and N 2 gases will not cause attenuation to radio wave
propagation. As shown in Figure 4-7, for the short ranges assumed for this mission, propagation
attenuation is negligible.
According to the same Mars propagation study, dust storms are considered the most dominant
factor in propagation attenuation. There are three supposed types of dust storms. Planet-encircling
storms are believed to encircle the planet at some latitudes; regional storms include clouds
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Phase II Final Report