Ultrasonic Altimeter for Titan Landers

With the advent of rotorcraft on extraterrestrial bodies, such as the recent Ingenuity helicopter and forthcoming Dragonfly mission, there is both an interest in and benefit to adapting ranging technologies used by terrestrial drones to meet positional sensing requirements demanded for autonomous flight This paper presents the preliminary design and analysis of an ultrasonic altimeter for proximity (<10 m) operations in the unique Titan environment - an approximately 95-K nitrogen and methane atmosphere. Titan environmental parameters relevant to ultrasound propagation and reflection are explored Corresponding environmental testing for functionality and performance was conducted on several piezoelectric and electrostatic transducers. A hardware and FPGA implementation for an ultrasonic altimeter utilizing a candidate sensor is presented with accompanying analysis of link budget and FPGA utilization. Ranging error was determined for a rock distribution representative of the Titan surface at locations of interest to Dragonfly as an example.