Trajectory Optimization of the JUpiter ICy moons Explorer (JUICE) spacecraft in order to reach the highest sensitivity to the tidal deformation measurement by the GAnymede Laser Altimeter (GALA)

Abstract

The main purpose of this master thesis is to evaluate under the direct influence of the orbital parameters, the possible numbers of crossover points. These points are found after an orbit reconstruction and will show the tidal deformation of Ganymede. The crossovers points are intersections of laser altimeter profiles obtained through ranging to the surface from an orbiting spacecraft. At these points, dynamical effects like tidal deformation can be measured, as the topographic signal vanishes when the height difference at the crossover point is computed. By collecting several hundred millions of range measurements during the nominal mission and analyzing range measurements, the topography of Ganymede's surface will be obtained. To evaluate the impact of the orbital parameters in the number of crossover points and the sensitivity of the tidal measurements, the Ganymede Circular Orbit (GCO-500) phase of the planetary mission Jupiter Icy moons Explorer JUICE, is used as case of study. The JUICE mission is developed by the European Space Agency ESA and has as one of its payload the Ganymede Laser Altimeter GALA, an instrument developed in collaboration with institutes and industries from Germany, Japan, Switzerland, and Spain. With the aim of improving the JUICE research, the perturbations analysis and impact in the altimeter measurements are presented and evaluated, to then continue with the calculation of the sensitivity of GALA. The direct correlation between trajectory-crossover points is reviewed, analyzing how each possible trajectory setup affects the crossovers number. With this analysis, finding the conditions that will lead to the higher tidal measurements sensitivity values of GALA, and a better selection of trajectory parameters. The analysis of the sensitivity is done taking into account the possibility of improving a second phase around Ganymede at a lower altitude. Finally, a discussion and result analysis is presented and the added value to trajectory optimization is shown.