The Deployment of the Seismometer to Investigate Ice and Ocean Structure (SIIOS) in Northwest Greenland: An experiment to study icy ocean world seismic deployments

Abstract

In anticipation of future spacecraft missions to icy ocean worlds, the Seismometer to Investigate Ice and Ocean Structure (SIIOS) was funded by NASA 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 deployment included one Trillium 120 s Posthole (TPH) broadband seismometer, thirteen Silicon Audio flight-candidate seismometers, five Sercel L28 4.5 Hz geophones, and one HTI 60-min hydrophone. Seismometers were buried 1 m deep in the firn in a cross-shaped array centered on a co-located TPH, hydrophone, 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 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 ten 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 0.01-10 Hz. For future icy ocean world missions, a deck-coupled seismometer would perform similarly to a ground-based deployment.