Ears of the Dragonfly: Design of a Microphone System for Operation on Titan

Dragonfly, NASA’s 4
^th
New Frontiers mission, is a radioisotope-powered rotorcraft arriving at Saturn’s moon Titan in the 2030s which carries several payloads to explore this organic-rich ocean world. Among these payloads is a Geophysics and Meteorology package (DraGMet) which hosts a variety sensors to observe the Titan environment. Among these is a set of microphones (MICRO) mounted around the rotorcraft. These microphones will provide situational awareness, diagnosing the health of Dragonfly’s rotors, fans, and drill. The experience with the microphones on Mars 2020 demonstrates powerful scientific discovery potential, with possible measurements including sound propagation (speed and attenuation) in the Titan atmosphere, wind noise and turbulence, and saltating sand grain impact. Thus, among the few microphones ever flown to other planetary bodies, MICRO promises to make observations of interest to scientists, engineers, and everyday people alike. Titan’s cryogenic atmosphere, as well as the radiation environment of deep space and of Dragonfly itself, present challenges for the selection of electronics and materials. Following the example of Mars 2020, a commercial-off-the-shelf (COTS) microphone was chosen for its low size, weight and power (SWaP), ruggedness, and suprising compatibility with the hostile Titan environment. An extensive qualification campaign characterized the performance of several COTS microphones and op amps under the stresses of the Dragonfly mission, including radiation dosage and cryogenic temperatures. In addition, mechanical enclosures were designed in order to maximize sound acceptance, while avoiding intrusion of dust and sand. This paper provides an overview of Dragonfly’s MICRO sensor suite, including science impetus, component qualification, design, and test.