Helicopter Test of a Strapdown Airborne Gravimetry System.

Airborne gravimetry from a helicopter has been a feasible tool since the 1990s, with gravimeters mounted on a gyro-stabilised platform. In contrast to fixed-wing aircrafts, the helicopter allows for a higher spatial resolution, since it can move slower and closer to the ground. In August 2016, a strapdown gravimetry test was carried out over the Jakobshavn Glacier in Greenland. To our knowledge, this was the first time that a strapdown system was used in a helicopter. The strapdown configuration is appealing because it is easily installed and requires no operation during flight. While providing additional information over the thickest part of the glacier, the survey was designed to assess repeatability both within the survey and with respect to profiles flown previously using a gyro-stabilised gravimeter. The system's ability to fly at an altitude following the terrain, i.e., draped flying, was also tested. The accuracy of the gravity profiles was estimated to 2 mGal and a method for inferring the spatial resolution was investigated, yielding a half-wavelength spatial resolution of 4.5 km at normal cruise speed.