An improved target assembly is provided for use in calibrating a non-contact sensor in a sensor calibration system. The target assembly includes: a plate member; three pairs of truncated cones mounted adjacent to each other on a surface of the plate member, where one of the truncated cones in each pair is orientated inversely in relation to the other truncated cone; and at least three targets connected to the plate member for calibrating the target assembly in relation to a reference frame external to the target assembly.