The Deployment of the Seismometer to Investigate Ice and Ocean Structure (SIIOS) in Northwest Greenland: An Analog Experiment for Icy Ocean World Seismic Deployments

Abstract

Abstract In anticipation of future spacecraft missions to icy ocean worlds, the Seismometer to Investigate Ice and Ocean Structure (SIIOS) was funded by National Aeronautics and Space Administration, to prepare for seismologic investigations of these worlds. During the summer of 2018, the SIIOS team deployed a seismic experiment on the Greenland ice sheet situated, approximately, 80 km north of Qaanaaq, Greenland. The seismometers deployed included one Trillium 120 s Posthole (TPH) broadband seismometer, 13 Silicon Audio flight-candidate seismometers, and five Sercel L28 4.5 Hz geophones. Seismometers were buried 1 m deep in the firn in a cross-shaped array centered on a collocated TPH and Silicon Audio instrument. One part of the array consisted of Silicon Audio and Sercel geophones situated 1 m from the center of the array in the ordinal directions. A second set of four Silicon Audio instruments was situated 1 km from the center of the array in the cardinal directions. A mock-lander spacecraft was placed at the array center and instrumented with four Silicon Audio seismometers. We performed an active-source experiment and a passive-listening experiment that lasted for, approximately, 12 days. The active–source experiment consisted of 9–12 sledgehammer strikes to an aluminum plate at 10 separate locations up to 100 m from the array center. The passive experiment recorded the ice-sheet ambient background noise, as well as local and regional events. Both datasets will be used to quantify differences in spacecraft instrumentation deployment strategies, and for evaluating science capabilities for single-station and small-aperture seismic arrays in future geophysical missions. Our initial results indicate that the flight-candidate seismometer performs comparably to the TPH at frequencies above 0.1 Hz and that instruments coupled to the mock-lander perform comparably to ground-based instrumentation in the frequency band of 0.1–10 Hz. For future icy ocean world missions, a deck-coupled seismometer would perform similarly to a ground-based deployment across the most frequency bands.