## 4 Discussion
While this did take a fair amount of effort to troubleshoot and had to be set aside temporarily during the UTM data collection runs, the system was subsequently shown to operate reliably for passive and active lateral separation of aircraft and shows great promise for future efforts, both within the UTM evolutionary program and UAF mission operations. This function increased the likelihood for further automated ABDAA and GBDAA capabilities, based upon our MESA-SSR/DAA radars and IRIS Automation HCAM assets. Note: ADS-B use has since been discontinued by the FAA with the capabilities being replaced by various systems such as Remote Identification (RID). UAF's work did not include any analysis on the link reliability of the ADS-B signal. Related FAA/NASA UTM programs: At the conclusion of TCL3, NASA continued to develop technical tools and investigations of procedural techniques into UTM TCL4 with a focus on autonomous UAS operating in a high-density and highly interactive environment. During this time, the FAA developed the UTM pilot program focusing on solidifying the previous gains into a set of more operational tools and procedures. UAF's future efforts: Due to its location and inherent mission sets, UAF remains dedicated to further developing key UAS capabilities, which enables the BVLOS flight in Alaska. These areas are vital for conducting meaningful and practical missions supporting arctic research, critical infrastructure, and public service missions. * RTK GPS: Further tests of the BVLOS system need to be completed to better understand the capabilities and limitations of the RTK GPS system at different speeds and distances from the ground station, as well as the ability to handoff to secondary systems providing RTK GPS from remote locations. These capabilities are necessary for longer-distance BVLOS missions into remote locations of the state for payload delivery/retrieval and conducting of other recurring mission sets. * UAS failsafe measures: Further development is necessary for UAS safety systems designed to prevent or mitigate damage or injury due to UAS failure in flight, and to provide for enhanced airspace clearing methods in the case of high-priority missions. Example systems could include visual/auditory warnings to enhance our existing parachute recovery system or inflatable bladders designed to minimize the effects of an impact with personnel or objects. * GBDAA: Testing is needed on ADS-B or similar communication signal protocols injected into the mission planner GCS laptop as a means of generating automated GBDAA commands. One application is to demonstrate the use of the Echodyne MESA-SSR ground radar as means for generating automated GBDAA commands. The next steps would be to demonstrate the ability to use this equivalent ADS-B format message to command UAS separation via GCS/MAVLink, and finally to accomplish this function directly by the UAS. * ABDAA: The Echodyne MESA-DAA radar needs to be integrated with UAS such as the Tarot X6 hexacopter as a flight test bed. This will require the integration of new IMU sensors to accurately measure offsets of the radar with respect to the UAS, and of the UAS with respect to the coordinate system. Demonstration of the ability of the MESA-DAA airborne radar to provide automated ABDAA commands is also required.