Recovery Methods Research Of The Lunar Satellite Gravity Gradiometry Technique Based On Time-wise Method

The Moon’s gravity field reflects the basic physical characteristics of the Moon’sdensity structure, mass distribution and interiors dynamics, and plays an important role inlunar explorer missions. The gravity field model with high accuracy and resolutionprovides important insight into the evolution of the Moon, and is also beneficial to theselection of the orbit and the landing site of the missions.Encouraged by the success ofSELENE and GRAIL missions, there is a great upsurge in the lunar gravity mappingmissions in the world.This paper presents the theory, method and numerical solution examples of lunargravity field recovery from satellite gradiometry, and is organized as following. InSection1, the background and significance are introduced. In Section2, the theories andmethods of gravity field recovery from satellite gradiometry are briefly discussed. Themethods mainly refer to space-wise least-squares, time-wise in the time domain andtime-wise in the frequency domain. In Section3, the error analysis equations for the lunargravity field coefficients recovery are derived by time-wise least-squares method. Theproperty of diagonal dominance of the normal matrices, instrument accuracy, orbit height,sampling rate and mission duration are also analyzed by this method. Throughcomparison of different parameters, a mission scenario with a gradiometer accuracy levelof about10mE/Hz^1/2, an orbit height of about50km, a mission duration of28days and asampling rate of5seconds is recommended. This scenario provides a lunar gravity fieldmodel with a maximum degree of335, i.e. a spatial resolution of14km. The gravityanomalies and geoids can be determined with accuracies of1.42mGal and6.77cm atdegree250, respectively. In Section4, the data of satellite orbit and the gravity gradientcomponent Vzzare simulated by applying the above mentioned parameters. Then, a lunargravity field model with the maximum degree of100is recovered based onpreconditioned conjugate gradient method, which verifies the effectiveness of time-wisein the time domain method for the Moon’s gravity field recovery.