The Study Of Airborne Gravity Gradiometry

As a cutting-edge technology developed at the end of 20^th Century and continuously improved in the last twenty years,airborne gravity gradiometry plays a more and more important role in mineral and hydrocarbon prospecting due to the high efficiency and distinctive spatial resolution.Nowadays,airborne gravity gradiometry is the international research hotspot.Howerver,all airborne gravity gradiometers applied in the commercial exploration were manufactured by Lockheed Martin,and the United States imposed an embargo against China.In view of the fact,airborne gravity gradiometry research started on 2006,supported by the National High Technology Research and Development Program.After more than a decade of effort,several domestic research teams made a number of key technology breakthroughs.The gravity gradient anomaly was measured in the laboratory static conditions in 2012,and the practical progress was speeded up from then on.Study on key technology breakthroughs about airborne gravity gradiometer development and data application was conducted in the paper.Firstly,a systematic technology survey of the research process,application status and development trend was carried out.Then,the operational principle and design idea of the rotating accelerometer airborne gravity gradiometer were analysed.Finally,the technical difficulties and solutions were summarized,as well as a series of technology improvements from the prototype.According to the technology investigaton,the development scheme of partial tensor airborne gravity gradiometer based on quartz flexible accelerometers?QFA?was determined in consideration of domestic technology foundation.The resolution of the accelerometer prototype was below 1×10^-8g,and the precision of the gravity gradient instrument?GGI?prototype was below 70E.The gravity gradient stabilized platform satisfied the GGI requirement,and the performance passed through the flight test.The system integration scheme and the design of shock mount and temperature control were completed.The above achievements lay the foundation for flight test and practical transformation in the 13^th Five-year.According to the airborne application and the gravity gradiometer characteristics,the measurement and study on aircraft environment parameters of Y-12 fixed-wing aircraft under typical flight conditons were fulfilled.Aircaft vibration research demonstrated that vibration energy distribution has a periodic character which concerned with the propeller rotation rate base frequency.The attitude angle variation feature and range about row and yaw under different conditions were analysed,as well as the cabin pressure,temperature and humidity variation with the flight process.A full understanding of aircraft environment characteristics may provide some advices and references for instrument range,architecture,damping,temperature control and air tightness design.For the actual application service,gravity gradient forward modeling and gravity gradient tensor transformation theory were studied in the paper.The bug leading to the analytic singular points in the existing formulae for right rectangular prism was found out by formula derivation from Newton's law of universal gravitation,and non-singularity expressions were estabilished based on the special integration method.Based on the general formula of 2D Fourier transformatioin of gravity potential derivatives,gravity gradient tensor transformation expressions for partial tensor airborne gravity gradiometer survey data were derived in frequency domain.The transformation algorithm ofU_xyy andU_{x x}-U_{y y} is designed for 2D grid data based on FFT.The influences on transformation result due to different data length and sampling interval were discussed.The transformation error caused by the frequency singular points was analysed.Then,the combined transformation method was presented,using U_xyy andU_{x x}-U_yytogether.Compared with the single tensor component transformation,the frequency singular points were eliminated,and the transformation error was depressed greatly.The combined transformation method reduced the dependent on the data length,and improved the algorithm efficiency.The transformation results for synthetic data with or without white noise demonstrated the validity and availability of the algorithm.The gravity gradient transformation software was developed based on GeoProbe Mager Platform.