Determination and Analysis of the Beam Scale Factor for the LaCoste&Romberg Airborne Gravimeter

The beam scale factor(called K-factor) is one of the important parameters for the AIR-SEA gravimeter.Usually in all classical processing of marine or airborne gravity data,the K-factor is postulated to be a constant.Presumably,this is not true for the large angular deviations of the beam caused by the own movement of the boat or the aircraft.Therefore we propose an experimental procedure to determine the relation K=K(B) where B is the beam angular position.Based on this relation,the effects on the results due to different K-factor(a constant or a variable) are analyzed in detail by using the data from the test platform for gravimeter and the actual data for airborne gravimetry.Some initial conclusions can be made:① For the data from the test platform,the effects on the results due to different K-factor(a constant or a variable) are completely similar after using digital filter.The reason of this is that the changes of the beam positions are very regular.② For the actual flight data,the difference of the effects on the results due to different K-factor(a constant or a variable) is relatively large,and the standard derivation of the difference can reach 10 mGal after using digital filter,Thus it is very important to consider this difference in the real data processing.③ We use the polynomial fit to determine the relation K=K(B).There are no significant effects due to the different orders for the polynomial,and a second orders polynomial can be chosen actually.