Issue 37 Unmanned Systems Technology April/May 2021 Einride next-gen Pod l Battery technology l Dive Technologies AUV-Kit l UGVs insight l Vanguard EFI/ETC vee twins l Icarus Swarms l Transponders l Sonobot 5 l IDEX 2021 report

82 Focus | Transponders 70 km away using only 0.025 W of power, while ADS-B transponders could be tracked at 40 km with 1 W. Such technology could enable effective UTM while greatly reducing the power consumption – on the ground and in the air – and is gaining popularity in several countries, particularly in Germany, Poland, Latvia and the Netherlands. The development of ACAS and UTM systems is also spurring airborne interrogator devices, which like their ground-based predecessors are being designed largely to enable UAVs to send requests (over 1030 MHz) for ADS-B Out information from other aircraft nearby. Based on that information, UAVs will be able to alter their altitude or heading to minimise collision risks. A key problem with ADS-B though is that it can easily be spoofed. Some developers therefore anticipate that specialised interrogators for validating the integrity of ADS-B transponder signals will be required in the future, particularly for IFF checks of UAVs operating near military bases or high-value aircraft. The interrogators might also be SWaP-optimised for installation in UAVs carrying expensive cargo or payloads, so that they can autonomously interrogate approaching UAVs without a ground station in the loop. Packaging these systems together with transponders could one day enable turnkey ACAS products to have fully automated UTM in the sky. Terrain awareness and warning systems (TAWSs) might also be potentially critical in future requirements. TAWSs were mandated for air transport craft in 2005, and work by using a database of global terrain with airports and towers overlaid on top, against which an aircraft can measure its own GNSS and altimeter measurements to determine the risk of collisions with ground features such as mountains or skyscrapers. Alerts are sent out on the basis of that risk. Like transponder modes, TAWS standards are established and recognised worldwide for their safety-critical requirements in aircraft operations. How they can be adapted for UTM applications is not yet certain though. Certainly, the growing sector of medium-mile UAVs, carrying between 10 and 1000 kg of cargo over a range of 50-100 km, could benefit from TAWSs. As such systems are increasingly adopted, these UAVs’ routes will become more congested, so at that point, alerts or alternative routes for avoiding geographical features will be critical, alongside autonomous ACAS technology. On the other hand, many other UAVs (as well as urban air taxis) are likely to be intentionally flown in cities or near the ground for the foreseeable future, so they may not need to know where ground features are. However, a much higher resolution database of TAWS, featuring a city’s streetlights, power lines and trees to centimetre-level accuracy could improve the safety of aircraft and civilians immensely, while also enabling urban aircraft to make better use of their available airspace. Future considerations Military Mode 5 IFF Level 2B could be rolled out within the next two years, at which point the uptake of ADS-B In and Out components can be expected to accelerate even further. Once all military and civilian UAVs have adopted ADS-B, however, there remains the question of how to deal with those few that are not cooperating, be it owing to malfunctioning avionics, human error during systems integration or illicit activities for example. One suggested approach is that EO/ IR and radar sensors on board UAVs might be designed to detect and define uncooperative aircraft from a distance, or to algorithmically determine the best route for avoiding them and transmit that to the operator or autopilot. Further in the future, transponders can be expected to advance in ways that enable autonomous detect & avoid capabilities. Increased networking capabilities akin to those of the new UAS remote ID requirements at low altitudes will probably be widely adopted for higher altitudes and urban April/May 2021 | Unmanned Systems Technology It is critical that GCS software can display ADS-B Out and In information clearly and intuitively (Courtesy of UAV Navigation)