Implementation of LARES spin model and its analysis

다국어 초록 (Multilingual Abstract)

This paper presents processes of Satellite Laser Ranging (SLR) observation data processing to obtain spin information of Laser Relativity Satellites (LARES), spin dynamic composition, and spin model development and verification. LARES is a fully passive geodetic satellite, designed for testing relativistic effects such as the frame-dragging effect, in a low Earth orbit. Spin information is necessary to improve the accuracy of Precise Orbit Determination (POD) data and in measuring frame-dragging effects on a satellite. The spin model of geodetic satellites is required to calculate non-gravitational perturbations for frame-dragging effect measurement. In order to obtain spin information from observation, we have to calculate the range residual of full-rate data from the kHz SLR observation with high order polynomial curve fitting. After a sigma filtering to remove residual outliers, we used the Lomb-Scargle algorithm to recognize repetitive signals caused by the rotation of Corner Cube Reflectors (CCRs) on the satellite’s surface. Spin rate and spin period can be obtained from this frequency analysis. The initial spin period of LARES was 11.58 second and it increased exponentially. In order to develop a LARES spin model, The Spin Model of LARES (SMOL) has been investigated. SMOL consisted of a three-external torques: Magnetic, solar radiation pressure and air drag torque. The magnitude of the magnetic torque on LARES was ？10？^3？？10？^5 times larger than other two torques. Spin rate can be calculated from angular velocity and angular momentum which can be obtained from the external torque integration. The equation of the spin period calculated from SMOL was P=11.8592e^0.002909d (where d is days from launch) and Root Mean Square (RMS) was 0.6638 seconds.Since the LARES has a simple inner structure compare to other geodetic satellites, such as Laser Geodynamics Satellites (LAGEOS), SMOL can calculate the magnetic torque of LARES without taking the inner structure into account. Therefore, SMOL can calculate and predict the spin period of LARES more accurately than a LAGEOS Spin Axis Model (LOSSAM)-based model. RMS of the LOSSAM-based model is 0.7822 seconds and this result shows that SMOL is a more correct spin model for LARES’ spin calculation and as such, it can allow us to calculate more accurate spin information.