Another major and pioneering experimental effort at Bates involved the Out-Of-Plane Spectrometer (OOPS). OOPS was a special version of coincidence measurements with magnetic spectrometers. Prior to OOPS coincidence events from electron scattering were carried out with both spectrometers supported in the horizontal plane. This was the case because the problem of detecting one of the particles in an arbitrary direction required a more complicated support system for the spectrometers. The OOPS Collaboration decided that the additional important information that one could gain made the challenging engineering effort worthwhile.
OOPS took data successfully for a few years, and provided important new information on the structure and reaction mechanisms of nuclei.