Planetary Ephemerides Generation From Interplanetary Laser Ranging Data

Abstract

With the introduction of Interplanetary Laser Ranging (ILR), the acquired tracking measurements accuracy of planets can be improved drastically (up to a few millimeters) which can result in an improvement in planetary ephemerides of not only the planet which is the target of laser ranging but also other bodies in the solar system due to dynamical coupling between the bodies. A quantitative analysis is performed to analyze how much improvement in the current planetary ephemerides can be achieved if highly accurate laser ranging observation were to be introduced in the current planetary ephemerides generation processes. The thesis achieved this by developing an ephemerides generation model using TU Delft's Astrodynamic Toolkit (i.e TUDAT) in which planetary ephemerides are generated for two cases. Once using simulated laser ranging observations to Mars between 2020 and 2023 and once without utilizing laser ranging observations. By comparing the estimated planetary ephemerides of the two cases, it is concluded that laser ranging to Mars resulted in a more stable and close to a factor of two improvement in ephemerides uncertainty for most of planets. The ephemerides of the Mars itself sees nearly a factor of ten improvement in uncertainty which resulted in a significant improvement in the knowledge of asteroid masses. The estimated mass parameter of 11 of the most perturbing asteroids in the solar system see more than a factor of ten improvement in their uncertainty which is unprecedented. Laser ranging to Mars and its cascade effect on the orbit of Mercury resulted in providing better constraints on PPN parameter γ and Sun's oblateness parameter J₂ allowing γ to be determined with an uncertainty of 5.5 x 10^-8 which is 3 order of magnitude better than the constraints provided from Cassini experiment. An order of magnitude improvement is also observed is Sun's J₂ parameter estimating it to an uncertainty level of 2.0 x 10^-9.