This paper details integration and flight testing of an automatic dependent surveillancebroadcast (ADS-B) transponder onto a small unmanned aerial system (sUAS). The sUAS broadcasts ADS-B packets on 1090 MHz and is visible to any aviation stakeholder with an ADS-B in receiver. In general, this provides a means for other observers such as air traffic control (ATC) or manned traffic to track the sUAS position. However, ADS-B relies heavily on availability of the global positioning system (GPS) and cannot function properly without reliable GPS. The work includes development of a secondary position estimation system that utilizes a local area multilateration system (LAMS) to interrogate the ADS-B transponder as a standard Mode S transponder and localize the sUAS in GPS-denied environments. The system consumes position information from both ADS-B and LAMS sources and fuses these reports into consistent estimates of the sUAS position. These fused estimates are then made available to aviation stakeholders so the situational awareness of the sUAS operator is not compromised. This allows the system to operate even if the sUAS enters into a GPS-denied environment. This paper describes the development of the fusion system as well as the flight testing and results of the integrated system.

Very low electron temperatures have been obtained in a hot-filament discharge device by having a set of conditions designed to minimize heating of the confined electrons. Heating is reduced by having the energy of primaries from the filaments sufficiently large (80 eV) that they do not become confined after ionizing collisions and that they lose little energy through Coulomb collisions. The primaries create secondary electrons at the wall with several eVs of energy which heat the confined electrons through collisions. This heating is minimized by having a liner for the vacuum system coated with colloidal graphite to reduce the emission of secondary electrons and to create a uniform boundary potential. Argon plasmas are created with plasma potentials typically less than 0.2 V. Secondary electrons from the wall are not confined by the plasma potential and have a very low density of order 105 cm−3. The confined electrons have densities of order 108 cm−3 and electron temperatures as low as 0.031 eV (360 K).

No abstract