The objective of this project was to construct four sensor packages for the ONR ocean bottom seismometer (OBS) system. These units augment 27 sensor packages designed and constructed under a separate ONR-supported subcontract from the Woods Hole Oceanographic Institution (WHOI). The sensor package is a semi-autonomous unit designed to be carried to the seafloor onboard the main ONR OBS frame. Upon landing the package is placed on the bottom by a deployment arm attached to the main frame; when the main instrument is retrieved the sensor unit is recovered as well. The sensor package consists of a housing, a passively gimbaled 3-component array of 1-Hz seismometers, digitally controlled variable gain preamps, and a calibration signal generator. The four sensor packages have been constructed, fully tested, and delivered to the ONR OBS Facility at WHOI.