Projecte llegit
Títol: Assessment on orbit determination from optical observations at Montsec
Director/a: MASDEMONT SOLER, JOSEP JOAQUIM
Departament: MAT
Títol: Assessment on orbit determination from optical observations at Montsec
Data inici oferta: 07-09-2020 Data finalització oferta: 07-04-2021
Estudis d'assignació del projecte:
MU AEROSPACE S&T 15
| Tipus: Individual | |
| Lloc de realització: |
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| Nom del segon director/a (UPC): Jianlin Chen, NPU (Xina) | |
| Departament 2n director/a: | |
| Paraules clau: | |
| orbital motion, orbit determination, kalman filter, propagation, astrodynamics, orbital mechanics, gauss method, SGP4,TLE | |
| Descripció del contingut i pla d'activitats: | |
| The main goal o the project is to assess a precise orbit determination
of satellites optically tracked from the IEEC telescopes at Montsec. The project has three main parts to be implemented: a dynamical model, an observational model and filter adaptations for OD. The first part of the project will be devoted to the implementation and accuracy testing of the models. The second part will consider some current Kalman filter variants for the evaluation of a precise orbit determination. This second part has to be analyzed on the premises of the telescope data that can be provided by the IEEC optical facilities at Montsec. An assessment on the accuracy or divergence of the filters as a function of initial errors, the length of the sampling periods and the measurement errors are the main points to be reported. The primary focus of the project will be on the precise orbit determination for GEO satellites that could be suitable for altimetry purposes, but other classes of satellites should be also considered. An initial good knowledge on orbital dynamics is necessary. Computer codes and algorithms should be written in C language. For some advanced implementations the knowledge of C++ might be also advisable. |
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| Overview (resum en anglès): | |
| The objective of this project is to propose a passive method for orbit determination (OD) of GEO objects using observational data as position measurements. The proposed method use position measurements expressed as right ascension and declination angles, therefore no need of on-board sensors within a satellite are need it to track them using the methodology to be presented in this thesis. The OD method was split in 3 main parts. The perturbed model for the orbit propagator, the initial orbit determination (IOD) methodology to compute initial conditions and a filter algorithm for orbit estimation. We selected an orbit propagator based on state vector and a force model solved by a Runge-Kutta 7-8 numerical integrator. The acting forces considered in the perturbed model were the earth gravitational potential model EGM96 (n=m=70), the third body perturbation due to the moon and sun gravitational forces and the exerted force due to the solar radiation pressure. Since the case study of this project is focused on GEO objects, the perturbation because of atmospheric drag was neglected. Based on the constraints of our observational data, an angles-only method was necessary for the for initial orbit determination implementation. The Gauss method and the Gibbs-Herrick method are the best fit for the position and velocity vector respectively, when short separated observations are used. To achieve precise orbit determination, a estimation algorithm using a Extended Kalman Filter (EKF) method was implemented. The observational data was used as the sensing measurements and the orbit propagator as the state predictor. The results suggested that the EKF can be used to the reduced the uncertainty associated with the orbit propagator error and to avoid this uncertainty to accumulate over the time (up to 3km per day for GEO objects). Nevertheless, future works should discuss and study how to improve the estimation implementations when observations that are closely separated are used as the measurements (separated by less than 1 minute). |
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