Transverse Velocity for Angled Probes; Estimation, Uncertainty Quantification, and Sensitivity Analysis

Consider a surface being measured by Photon Doppler Velocimetry (PDV) and Broadband Laser Ranging (BLR) using a multiplexed PDV+BLR probe. The velocity measurements from PDV and the displacement measurements from BLR can be naïvely compared through differentiation or integration, although only under strict geometric and physical circumstances are these comparisons expected to agree (all surface motion colinear with the probe axis). When the probe axis is not colinear with surface motion, transverse velocity (motion perpendicular to the probe axis) becomes non-zero. We present a dynamic surface reconstruction approach to estimation of transverse velocity (velocity parallel to the plane of the initial coupon) made possible with axis-symmetric assumptions and geometric considerations of the probe-axis/surface interaction. Distinction between transverse velocity and velocity components perpendicular to initial coupon surface is relevant because of the use of diagonal (non-orthogonal) probes. We show that diagonal probes lower uncertainty estimates in the transverse velocity by at least an order of magnitude compared to orthogonal probes. This work was done by Mission Support and Test Services, LLC, under Contract No. DE-NA0003624 with the U.S. Department of Energy.