A helicopter time-domain EM system applied to mineral exploration: system and data

David Fountain, Richard Smith, Tom Payne, and Jean Lemieux (Fugro Airborne Surveys) describe recent progress in developing helicopter systems for time-domain airborne electromagnetic surveys, once the ‘domain’ of fixed-wing aircraft. The first operational fixed-wing airborne electromagnetic (AEM) system was introduced in 1948 and was followed by the first operational helicopter AEM system in 1955 (Fountain, 1998; Fountain and Smith, 2003). There has been parallel development of both fixedwing and helicopter AEM since that time and, up to the early 1960s, all these systems were frequency-domain. However, since the late 1970s, fixed-wing AEM systems have been primarily time-domain while the helicopter systems remained primarily frequency-domain. With the new millennium, and especially since 2002/ 2003, there has been significant development and introduction of helicopter time-domain AEM systems (Boyko, et al., 2001; Balch et al., 2003; Eaton et al., 2004; Sorenson and Auken, 2004; Vrbancich and Fullagar, 2004; Witherly et al., 2004). The pace of introduction has been such that, today, the number of time-domain systems in use is equal to the number of frequency-domain systems. Fugro Airborne Surveys and its predecessor companies have been leaders in the continuing development of fixedwing AEM systems, including the introduction of the GEOTEM, MEGATEM, and TEMPEST systems (Smith and Annan, 1997; Lane et al., 2000; Smith, Fountain and Allard, 2003). By the same token, Fugro has been involved in the continuing development of helicopter frequency-domain AEM systems including DIGHEM and RESOLVE. Based upon this combined experience and seeing the need for a broader band, high power helicopter time-domain AEM system, Fugro has introduced the HeliGEOTEM system in 2005. This system brings together the proven GEOTEM/ MEGATEM technology with the greater operational flexibility and improved lateral resolution of helicoptermounted AEM systems.