Over the past 10 years, several advances have been made in helicopter geophysical systems for mapping and detection of unexploded ordnance (UXO). Earlier total-field magnetometer systems for this application invoked a novel boom-mounted sensor design, which en-abled safe operation at altitudes of a few meters above ground level and permitted detection of individual small ferrous objects. The first such system, the Aerodat HM-3, had three cesium vapor magnetometers at 6-m spacing, mounted at the tips of one forward and two lateral booms (Gamey and Mahler, 1999). Subsequent improvements incorporated as many as eight magnetometers at 1.7-m spacing (Doll et al., 2003), as in the ORAGS-Hammerhead and ORAGS-Arrowhead systems. Since that time, improved magnetometer systems have been developed, and a production time-domain electromagnetic system has been introduced.