Airborne Gravity 2010 - Geoscience Australia

Airborne Gravity 2010
Figure 5. Comparison of power spectral density of orientation measurements for the cryostat if it
was bolted directly to the aircraft and when installed in the motion isolation mount.
Post-processing software
There are numerous corrections made to the gravity gradiometer signal during post-processing.
Among the first of these to be applied are corrections for translational accelerations, gravity, angular
accelerations and inertial angular velocities of the instrument. This involves first collecting data from
translational and angular accelerometers which are built into the gradiometer instrument, at the same
time that the gravity gradient signal is collected. These data are then processed to estimate angular
velocities. Next, all of these data are input into an error model, which combines them with preestablished
calibration coefficients in order to estimate their contributions to various terms in the
instrument’s error model. The calibration coefficients are determined pre-flight, via a series of
calibration tests of the instrument using a customized cryostat shaker facility. Finally, these error terms
are subtracted from the measured gradiometer signal. The plot in Figure 3 shows the result of applying
this post-processing step to data collected while the instrument is “quiescent” in the laboratory. In fact,
seismic motion under these conditions results in raw gradiometer signals that are well above 1000 E. It
is only after applying corrections for effects such as translational accelerations and rotational velocities
that the result of less than 1 E RMS is obtained.
Acknowledgements
This paper contains the results of work carried out by the entire HD-AGG development team at Gedex
and the University of Maryland, supported by Gedex’s management and investors.
References
Anstie, J., Aravanis, T., Haederle, M., Mann, A., McIntosh, S., Smith, R., Van Kann, F., Wells, G., and
Winterflood, J., 2009, VK-1 - a new generation airborne gravity gradiometer: Extended Abstract,
ASEG-PESA 20th International Geophysical Conference and Exhibition.
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