A technique has been developed to determine the exact time a high speed projectile contacts a target to initiate an impact event. A high speed photograph is taken of the projectile just prior to impact. The time the photograph is taken is used in conjunction with the known projectile velocity and the projectile-target distance as measured from the photograph to determine initial contact time. The system is assured of being accurate within its time resolution when it operates correctly. Comparisons between this unit and more conventional impact sensors that use switch closures or impact flashes to sense impacts were made. Results indicate that the conventional sensors can be triggered improperly by finely divided debris slightly preceding the high speed projectiles.