Wind and surface roughness considerations for seismic instrumentation on a relocatable lander for Titan

Abstract The influence of terrain and the atmosphere on seismic measurements to be made by the Dragonfly rotorcraft lander on Saturn's moon Titan are examined. The need to relocate the vehicle leads to rather different deployment considerations from a fixed lander. Surface texture affects the tilt that the seismometer instrument (vertical-only) must tolerate on deployment: consideration of terrestrial analog terrain suggests a tolerance of 5° and legs of 1–3 ​cm should eliminate the need for a leveling mechanism at most sites. 3-axis geophones fixed to the landing gear provide omnidirectional measurements (albeit with lower sensitivity) at all sites without requiring deployment operations. Empirical and first-principles models suggest that a characteristic velocity noise of ~0.5 μm/s may be expected on the lander skids on loose ground, with values an order of magnitude smaller or larger for calm and strong wind conditions, respectively. Wind loads directly on a streamlined seismometer housing, on the tether, and on the lander via the ground all give comparable vertical noise (~10 ​nm/s) at the instrument, and thus the mechanical complexity of a separate windshield, which would need to be massive to not itself blow away, is not justified.