“…To measure ejecta properties such as the dynamic volume density, areal density, and impact pressure, we fielded two types of piezoelectric probes, 2,3,10 optical shadowgraphy, 11,12 and x-ray attenuation. 12,13 Additionally, optical-heterodyne velocimetry ͑OHV͒ measured the asymptotic free-surface velocity, peak free-surface jump velocity, and shock-breakout time.…”