Speaker
Description
Jupiter’s moon Europa is a target of high scientific interest to the planetary science and astrobiology community due to its liquid-water ocean beneath a many kilometers-thick ice shell [1,2]. Future ice shell penetrating missions aiming to investigate the potentially habitable under-ice environment require SWAP-limited (Size Weight and Power) technology and auxiliary systems. Potential mission architectures include a hybrid melting and drilling vehicle that unspools a fiber optic tether in its wake for primary communications (comms) as well as integrated signal repeaters as a backup wireless data transfer system. The wireless system must have a small form factor (< 30 cm ⌀) and be robust to water/ice mixtures, brine pockets, and/or salt deposits within the ice [3]. One potential solution for the repeaters are wireless acoustic devices that have a small footprint. Acoustic communication has heritage in both water and ice in polar environments, achieving extremely long range communication underwater [4, 5]. Within the ice, acoustic communication has the potential added benefit of characterizing the ice. Simple acoustic signals have been sent through >1km of ice [6], and recent experiments have successfully transmitted modulated data through ice-water mixtures using hydrophones (3-6kHz) [7, 8]. While acoustics provide an inherently lower data rate than RF, the lower power requirements and robust nature of low frequency signals could provide valuable communication needs not only for outer planet missions, but for similarly constrained endeavors on Earth, such as Autonomous Underwater Vehicle/Remote Operated Vehicle polar exploration under ice. Due to ice-cover, real-time correctional updates via GPS or RF are limited and minimizing navigational drift is an open area of research. In this environment, long-lasting wireless acoustic pucks may offer a waypoint solution for navigational correction when placed near the ice-ocean interface or within an ice shelf.
While acoustic frequency signaling has been used in the target environment, models for estimating and optimizing data transfer for through-ice communication in this frequency range have not been found in the literature. To accomplish this task I developed an acoustic-attenuation-through-ice model and integrated it with GNU Radio, which has provided a realistic signal chain for the addition of modulation. Custom blocks for attenuative parameters (salt concentration, scattering, geometric loss, directionality, etc) allow the user to model propagation based on estimates (or known values) of the environment’s in-ice properties, along with custom blocks for seawater absorption. The calculations for each block are based on empirical equations from in-situ experiments, and show an increase in attenuation with frequency; current estimates for optimized frequency ranges fall between 10-30kHz [9]. Here, I present the custom attenuation blocks coupled with an FSK modulation scheme. Ice attenuation parameters will be characterized in the lab to verify the model, and flowgraphs will be integrated into a Raspberry Pi-based custom acoustic modem for real-world testing using commercial acoustic transducers.
- Pappalardo, R. T., et al. “Geological Evidence for Solid-State Convection in Europa’s Ice Shell.” Nature, vol. 391, no. 6665, 6665, Jan. 1998, pp. 365–68. www.nature.com, https://doi.org/10.1038/34862.
- McKinnon, William B. “Convective Instability in Europa’s Floating Ice Shell.” Geophysical Research Letters, vol. 26, no. 7, 1999, pp. 951–54. Wiley Online Library, https://doi.org/10.1029/1999GL900125.
- Schmidt, B. E. “Vertical Entry Robot for Navigating Europa (VERNE): An Ice- and Ocean-Profiling Thermomechanical Subsurface Mission to Search for Life on Europa.” In Revision, 2021.
- Sánchez, Antonio, et al. “An Ultra-Low Power and Flexible Acoustic Modem Design to Develop Energy-Efficient Underwater Sensor Networks.” Sensors, vol. 12, no. 6, May 2012, pp. 6837–56. DOI.org, https://doi.org/10.3390/s120606837.
- Semburg, Benjamin. “HADES - Hydrophone for Acoustic Detection at South Pole.” Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, vol. 604, no. 1–2, June 2009, pp. S215–18. arXiv.org, https://doi.org/10/fdd75w.
- Abbasi, R., et al. “Measurement of Acoustic Attenuation in South Pole Ice.” Astroparticle Physics, vol. 34, no. 6, Jan. 2011, pp. 382–93. ScienceDirect, https://doi.org/10/dssjz6.
- Han, Xiao, et al. “Cross-Ice Acoustic Communication by Ice-Mounted Geophones: An Initial Experimental Demonstration.” Applied Acoustics, vol. 150, July 2019, pp. 302–06. ScienceDirect, https://doi.org/10/gk6jd4.
- Yin, Jingwei, et al. “Cross-Ice Acoustic Communication: Cascade Acoustic Channel Model and Experimental Results.” China Communications, vol. 18, no. 2, Feb. 2021, pp. 228–40. IEEE Xplore, https://doi.org/10/gmskck.
- Lishman, Ben, et al. “Assessing the Utility of Acoustic Communication for Wireless Sensors Deployed beneath Ice Sheets.” Annals of Glaciology, vol. 54, no. 64, ed 2013, pp. 124–34. Cambridge University Press, https://doi.org/10/gf2zcx.
| Talk Length | 15 Minutes |
|---|---|
| Acknowledge | Acknowledge In-Person |
