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Projecte llegit

Títol: Effects of the Lower Thermosphere on the Re-Entry of Space Debris

Director/a: GUTIÉRREZ CABELLO, JORDI

Departament: FIS

Títol: Effects of the Lower Thermosphere on the Re-Entry of Space Debris

Data inici oferta: 26-07-2020 Data finalització oferta: 26-03-2021

Estudis d'assignació del projecte:

GR ENG SIST AEROESP

Tipus: Individual

Lloc de realització: EETAC

Paraules clau:
thermosphere, solar activity, drag coefficient, space debris

Descripció del contingut i pla d'activitats:
Space debris are composed of inactive satellites, exhaust rocket upper stages, mission debris, and fragments caused by accidental collisions and explosions. The debris population is controlled by the drag caused thermosphere, whose density depends on the solar activity state and on the geomagnetic activity. In this work, we propose to analyse the evolution of satellites during the last phases of their re-entries, below 250 km above sea level. To do so, we will select a set of debris with a high degree of symmetry (like cubic satellites, cylindric rocket bodies, and so on) whose behaviour will be analysed by means of suitable software tools. Using historic TLE data and solar and geomagnetic activity indices, we will determine the goodness of the most often used atmospheric models (MSISE00 and Jacchia and Brown models).

Overview (resum en anglès):
Nowadays a large number of artificial satellites orbit the Earth, of which many of them have completed their mission or are fragments of satellites that travel without any purpose. These objects can pose a collision problem for other active missions, so these inactive satellites need to be tracked. The highest concentration of inactive satellites is found in LEO orbits, from where due to the effect of aerodynamic drag, a function of density, the satellite will end up re-entering the atmosphere. The density parameter is influenced by solar and geomagnetic activity. Currently, thermospheric density models are available to estimate density, necessary for orbital prediction. The aim of this project is to study how solar and geomagnetic activity changes density, and therefore the orbital evolution of the satellite in the thermosphere. The second objective is to determine the goodness of the NRLMSISE-00 thermospheric density model. For the first objective, the TLEs of satellites that are in periods of maximum solar activity have been analyzed. From the code made with Matlab these TLE files have been read and the epoch, the semi-major axis and the eccentricity have been extracted. The evolution of these last two parameters has been analyzed in the presence of solar activity, in the form of solar flare. For the second objective, to determine the goodness of the NRLMSISE-00 model, in the first place the density has been calculated from parameters obtained from the TLEs, at the same time, from the Matlab package NRLMSISE-00 the density that estimates the NRLMSISE-00 model for the same dates. Finally, results have been compared. However, the TLEs data are associated with a prediction error, which is unknown. Therefore, based on the DOPs (Precise Orbit Determination) of the GFZ-1 satellite, provided by the GFZ German Research Center for Geociences, it has been analyzed the error TLEs make in the prediction of the semi-major axis compared to the semi-axis obtained with greater precision from the DOPs.