11:45 AM - 12:00 PM
[G07-4-06] Solar radiation pressure acceleration acting on geodetic satellites: precise orbit determination vs surface materials
Satellite orbits are subjected to various non-gravitational forces and solar radiation pressure has been one of the major error sources in orbit determination. Solar radiation pressure acting on a satellite depends on how sunlight illuminates its surface and is reflected there. The cannonball model is widely applied for spherical geodetic satellites. In this model, the scale factor of the actual acceleration in comparison with an ideal spherical black body case is expressed by a solar radiation pressure coefficient C_R.
This study attempts to relate the behavior of the C_R solutions derived from precise orbit determination with the optical properties of the satellites' surface.
We use the geodetic analysis software “c5++" (Otsubo, 2016) to estimate the solar radiation pressure coefficients C_R of the six geodetic satellites: Ajisai LAGEOS-1, LAGEOS-2, LARES, Starlette and Stella. Satellite laser ranging data for the past 20 years are analyzed where the C_R coefficients are estimated per 30 days.
It is clearly seen that the estimated C_R values for Ajisai, 1.041 on average, are smaller than those of other satellites, ranging from 1.075 to 1.164. This is explained by the fact that the surface of Ajisai is largely covered by mirrors where the surfaces of the other satellites are covered by a metallic body and corner cube reflectors.
In addition, this study deals with time variation of solar radiation pressure. When the optical properties of the satellite's surface were completely spherical symmetry, the C_R value would be constant. Sengoku (1995) predicted that the annual variation should dominate for Ajisai. However, our C_R solutions of Ajisai from precise orbit determination show a semi-annual periodic variation much larger than the predicted annual variation. We attribute the reason to a 5-cm-height metallic ring attached to one of the pole and the detailed material distributions both of which were not considered in the previous study.
This study attempts to relate the behavior of the C_R solutions derived from precise orbit determination with the optical properties of the satellites' surface.
We use the geodetic analysis software “c5++" (Otsubo, 2016) to estimate the solar radiation pressure coefficients C_R of the six geodetic satellites: Ajisai LAGEOS-1, LAGEOS-2, LARES, Starlette and Stella. Satellite laser ranging data for the past 20 years are analyzed where the C_R coefficients are estimated per 30 days.
It is clearly seen that the estimated C_R values for Ajisai, 1.041 on average, are smaller than those of other satellites, ranging from 1.075 to 1.164. This is explained by the fact that the surface of Ajisai is largely covered by mirrors where the surfaces of the other satellites are covered by a metallic body and corner cube reflectors.
In addition, this study deals with time variation of solar radiation pressure. When the optical properties of the satellite's surface were completely spherical symmetry, the C_R value would be constant. Sengoku (1995) predicted that the annual variation should dominate for Ajisai. However, our C_R solutions of Ajisai from precise orbit determination show a semi-annual periodic variation much larger than the predicted annual variation. We attribute the reason to a 5-cm-height metallic ring attached to one of the pole and the detailed material distributions both of which were not considered in the previous study.