Improved Measurement of Ejection Velocities From Craters Formed in Sand

A typical impact crater is formed by two major processes: compression of the target (essentially equivalent to a footprint in soil) and ejection of material. The Ejection-Velocity Measurement System (EVMS) in the Experimental Impact Laboratory has been used to study ejection velocities from impact craters formed in sand since the late 1990s. The original system used an early-generation Charge-Coupled Device (CCD) camera; custom-written software; and a complex, multicomponent optical system to direct laser light for illumination. Unfortunately, the electronic equipment was overtaken by age, and the software became obsolete in light of improved computer hardware. Experience obtained from years of operating the EVMS has resulted in the design of a new, simplified, and streamlined version. The equipment has been upgraded, LabVIEW has taken the place of the custom computer code, and EVMS v.2 is now up and running. It is a much more robust system, with all of the major components integrated into a single, modular assembly, a straightforward change that greatly improves the process of aligning the optics and camera. A schematic drawing of the system that illustrates the main components is shown in figure 1.