Doppler effects on acoustic ranging uncertainties on autonomous underwater vehicles in the Beaufort Sea

Moving and depth-varying receivers, such as autonomous underwater vehicles (AUVs), provide a great tool for acoustic remote sensing applications. An array of acoustic sources can be used to provide long-range acoustic positioning for AUVs, but there are challenges in the form of subsea position uncertainties that can be exacerbated by Doppler delay shifts. During the Canada Basin Acoustic Propagation Experiment (CANAPE) two M1 Seagliders equipped with WHOI micromodem acoustic receivers were deployed during August 2017. Acting as moving receivers, the Seagliders navigated the Beaufort Sea in and around the CANAPE array, recording transmissions from the broadband acoustic sources at varying ranges and depths of 2-530 km and surface to 750 m, respectively. The sources transmitted 135-second linear frequency modulated signals with a bandwidth of 100 Hz centered around 250 Hz. This work focuses on the Doppler delay shift effects on acoustic ranging uncertainties using these signals. Using vehicle attitude measurements over the duration of the signal receptions, it was found that 91 percent of the acoustic receptions included ranging uncertainties of 10 m or more due to Doppler, with particular impact at closer ranges of 50 km or less.