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

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Chapter 4.0 Entomopter Flight Operations<br />

4.3 Entomopter-borne Active Emitters <strong>for</strong> Navigation and Communication<br />

Although the majority of the scientific data will be uploaded directly to the rover, it is assumed<br />

that quick-look samples will be communicated back to the rover on a regular basis. These samples<br />

will contain only small amounts of data such as health monitoring updates, fuel level and<br />

altimetry readings.<br />

4.3.1.4 Positioning Assumptions<br />

• Spherical coverage<br />

• Maximum altitude = 10 m<br />

• Maximum range = 200 m<br />

• Minimum range ~ 10 cm<br />

• Resolution near max range ~ 1 or 2 m<br />

• Resolution at ranges < 2 or 3 m ~ 3 to 6 cm<br />

It is necessary to obtain two-dimensional (2D) positioning in<strong>for</strong>mation (azimuth and range),<br />

because the elevation will be determined by the onboard altimetry in<strong>for</strong>mation.<br />

Positioning is commonly accomplished by using global positioning satellite (GPS) solutions. In<br />

the absence of GPS it is assumed that <strong>for</strong> this application, the positioning system will be incorporated<br />

into the RF functionality of the Entomopter/rover to locate the Entomopters relative to<br />

the rover.<br />

4.3.1.4.1 Monopulse Positioning<br />

In an ef<strong>for</strong>t to conserve power, the main positioning method will use the “quick look” samples<br />

and health monitoring communication signals as described above. To do this, a quick burst<br />

encoded with the Entomopter identification, time, and altitude is needed. This can be coded into<br />

the header of these quick health monitoring signals sent from the Entomopter to the rover. When<br />

the refueling rover or other Entomopters receive the signal, the range can be calculated from the<br />

time of flight, and the azimuth can be determined using monopulse techniques where the<br />

received signal strength is compared in the azimuthal sectors of the rover’s receiving antenna.<br />

Again, an MTI type of radar placed on the refueling rover could easily discriminate between signals<br />

returned from ground clutter and the Entomopter. The azimuthal resolution is determined by<br />

the antenna beam width of each of the azimuthal sectors. Thus, the resolution could be varied<br />

during the mission by using a switching network on the antenna. The altitude can be sent in the<br />

reflected signal from the Entomopter by modulating the RCS (as described earlier), or one of the<br />

Entomopter emitters can downlink this in<strong>for</strong>mation to the refueling rover.<br />

4.3.1.4.2 UWB Geolocation System<br />

The <strong>Phase</strong> I <strong>Final</strong> <strong>Report</strong> suggested a positioning scheme based on the ultra wideband (UWB)<br />

precision geolocation system presented by Fontana in [96], where N fixed position beacons<br />

would be used to determine the 3D position of a mobile ranger--the Entomopter in this case. For<br />

this application, the N beacons would be realized by placing N transceivers on the refueling<br />

rover.<br />

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