Introduction Oak Ridge National Laboratory (ORNL), in collaboration with the U.S. Army Engineering Support Center—Huntsville (USAESCH) and private sector partners, has focused effort on development and evaluation of airborne technologies for detection and characterization of unexploded ordnance (UXO) and other shallow metallic objects that are frequently of concern in engineering and environmental investigations. Airborne technologies offer the potential to bring significant cost reduction to surveys for such objects. We have developed systems that use boom-mounted sensors on helicopters to allow data acquisition at one to two meters above the ground surface. Earlier efforts led to successful development of an airborne magnetic system, the Oak Ridge Airborne Geophysical System—Hammerhead Array (ORAGS-HA). The ORAGS-HA consists of eight magnetometers at 1.75-m spacing, mounted in three booms attached to a helicopter. Three magnetometers are located in each of the two lateral booms, and two magnetometers are in the forward boom. The system uses a realtime differential GPS (RT-DGPS) receiver for navigation and data synchronization and a PC-based data acquisition system that is capable of recording eight magnetometer outputs at a 1200-Hz sample rate. Navigation is provided by a PicoDas pilot guidance system with satellite differential corrections. The ORAGS-HA system, and its successor, the ORAGS-Arrowhead system are described in Doll et al., 2001 and Gamey et al., 2002.