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Projecte llegit

Títol: Orbit reconstruction using GNSS-derived state vectors

Estudiants que han llegit aquest projecte:

Director/a: GUTIÉRREZ CABELLO, JORDI

Departament: FIS

Títol: Orbit reconstruction using GNSS-derived state vectors

Data inici oferta: 15-02-2021     Data finalització oferta: 15-10-2021


Estudis d'assignació del projecte:
    GR ENG SIS TELECOMUN
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització: EETAC
 
Paraules clau:
GNNS, Astrodynamics, Orbit, Reconstruction, Thermosphere, LEO, Femtosatellites
 
Descripció del contingut i pla d'activitats:
The goal of this FDT is to explore different methods for the reconstruction of the orbit of a LEO satellite using GNSS data.
At least two methods will be explored: Least squares (LS) and Extended Kalman Filters (EKF).
Of particular interest are the methods required for orbits with partial (e.g., data obtained only during the illuminated part of the orbit) or sparse data.
 
Overview (resum en anglès):
The lower thermosphere (between 100 and 550 km of height) is known with lesser accuracy than desired. The use of spherical satellites to determine the density could result in a substantial improvement of the present situation.

The orbits of satellites at these heights are affected by drag and the inhomogeneities of the terrestrial gravitational potential (among other perturbations).

This projects has as main goal to analyse how the atmospheric drag affects the orbit of a real satellite, and then, determine the thermospheric density. Hence, it will be necessary to reconstruct the orbit accounting for the perturbations in the most accurate way possible.

Regarding the gravitational potential of the Earth, we have employed three approximations: spherical symmetry, a zonal model truncated at sixth order and a tesseral model truncated at tenth order. This last model has revealed as the most accurate.

To achieve our goal, we have analysed the telemetry gathered by one of the satellites of the FSSCat mission. Then, we have determined its orbital elements. Afterwards, we have considered two possible methods for orbit reconstruction: Non-Linear Least Squares and Extended Kalman Filter. After this analysis, we have chosen the Non-Linear Least Squares method for the purpose of orbit reconstruction.

The orbital elements determined from a physical analysis of the telemetry and the ones resulting from the non-linear least square method coincide with a remarkable accuracy.

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