## 5 Conclusions  
The UTM program has proven quite valuable in laying a foundation for integrating UAS into the NAS. Notable progress has been made on several fronts. UTM framework and procedures: Through much hard work on the part of NASA and the FAA, the UTM architecture is becoming well-established and has been communicated widely within the UAS and manned aviation communities, both within the US and internationally. This framework has been used as an important model for the systems being investigated by the International Civil Aviation Organization and under development with other regions and countries. While a definitive set of FAA-approved procedures has yet to be released, the extensive work performed under the NASA and FAA UTM efforts has provided much of the required ground work in identifying practical, workable, and safe practices, which will form the governing policies, regulations, and practices. UAS vehicle/sensor technologies: The UTM program has been pivotal in identifying key technologies needed to support the demanding levels of safety with respect to UAS/UTM communications, navigation, and vehicle autonomy required for high-density UAS flight within the NAS. Significant achievements have been made by the UAS test sites and their partners in several areas: (1) UAS position sensing and reporting; (2) ground-based sensors, such as radar, for tracking and GBDAA; (3) airborne sensors, such as vision-based, acoustic/ultrasonic, and lidar/radar for larger UAS; (4) automated landing/takeoff and UAS battery recharging; (5) seamless transition of UAS flight between outdoor/indoor (GNSS-denied) environments; (6) UAS vehicle health monitoring and reporting; and (7) UAS failsafe capabilities addressing lost navigation/communication (NAV/comm), lost power, and vehicle recovery after emergency landing or a crash. Much remains to be done before these systems are truly ready for the general consumer, but all issues appear to be solvable, given adequate attention and resources. UTM communications: One overarching challenge for the UTM system remains that of providing continuous, uninterrupted communications between the UAS and the UTM FIMS via a set of USS providers. These communications may be via cellular networks, WiFi/Bluetooth, or satellite systems. Availability of cellular systems varies considerably across the nation, with ample coverage found in most urban population centers and many rural communities, yet with sparse or no coverage found in more remote locations like most of Alaska. WiFi/Bluetooth and similar networks may prove suitable when operating around major metropolitan centers, business complexes, or with groups of UAS and ground entities forming ad hoc networks. Satellite systems can provide a failsafe communications channel when no other options are available but are of much lower bandwidths. All of these communications systems are generally bandwidth-limited with respect to sensor/payload data streams. WiFi may often prove suitable for transmitting medium or low-resolution video, but this depends upon the distance of the UAS to the GCS, power levels of transmitted signals,antenna design and placement, receiver capability, modulation scheme, and number of users sharing the link. Cellular signals often can support comparable data rates, but is also dependent on similar factors. While streaming a video may be supported close to cellular repeaters, this capability drops off dramatically further away from the GCS and may only support an occasional, lower resolution picture. Satellite communications for UAS are generally incapable of supporting anything but periodic positional reports/commands, and this may be at intervals of 2-10 min or more. Any of these systems, when present, may support basic UTM position-reporting/command functionality, but may not be sufficient for communications demanding immediate access or higher data bandwidths to support powerful sensors like the camera or radar data for SAA/DAA.