Projecte llegit
Títol: Dynamical Model Design and Interferometric Precise Orbit Determina- tion for GEOSAR Missions
Director/a: NICOLÁS ÁLVAREZ, JORGE
Departament: TSC
Títol: Dynamical Model Design and Interferometric Precise Orbit Determina- tion for GEOSAR Missions
Data inici oferta: 20-01-2020 Data finalització oferta: 20-09-2020
Estudis d'assignació del projecte:
DG ENG AERO/SIS TEL
| Tipus: Individual | |
| Lloc de realització: |
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| Segon director/a (UPC): BROQUETAS IBARS, ANTONI | |
| Paraules clau: | |
| synthetic, aperture, radar, geosynchronous, GEOSAR, interferometry, optimization | |
| Descripció del contingut i pla d'activitats: | |
| Background:
Low Earth Orbit Synthetic Aperture Radars (LEOSAR) present a main drawback regarding their revisit time of several days or weeks. At most, they can only provide an image of the same area of the planet per week. To mitigate this limitation, Geosynchronous Synthetic Aperture Radars (GEOSAR) missions will be able to provide permanent monitoring over wide areas of the planet. We are working in the context of an on-going GEOSAR mission. The European Space Agency (ESA) has selected Hydroterra to compete as the tenth Earth Explorer. Hydroterra will help scientists unravel the details of the daily water cycle. In that way, in the event of a natural disaster, they would be able to predict the development of floods and emergency services will be able to safely evacuate the citizens before the water rise. GEOSAR presents a main challenge: it requires unprecedented orbit determination precision. We have to demonstrate that we can get this precision before launching any spacecraft. We have designed and built a ground interferometer in the UPC-D3 building in order to track non-cooperative geostationary telecommunication satellites. Goal: The project consists of retrieving the geostationary satellite orbits from the acquired interferometric observables. By means of estimation techniques such as Least Squares and Extended Kalman Filter, the interferometric observables are fitted to an orbital model which has to accurately reproduce the geostationary environment. The model must take into account the most notable orbital perturbations: non-spherical Earth potential and longitude evolution, solar and lunar attraction, inclination evolution, solar radiation pressure, etc. |
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| Overview (resum en anglès): | |
| Synthetic aperture radar (SAR) missions at low Earth orbit (LEOSAR) perform very well but they present a major limitation regarding their revisit time of several days or weeks. They can not provide continuous illumination over the same area of the planet.
To overcome this limitation, Geosynchronous SAR (GEOSAR) missions are introduced. They will be able to provide permanent monitoring over a wide zone of the planet. But GEOSAR presents a main challenge: it requires unprecedented orbit determination precision. This project is carried out in the context of an on-going GEOSAR mission. Hydroterra has been selected in the European Space Agency (ESA) call for its tenth Earth Explorer mission. Interferometry is the most suitable precise orbit determination technique used to reach this goal. A ground-based interferometric system (installed in the roof of D3 building in Campus Nord, Universitat Politècnica de Catalunya) will provide very precise observations which will be complemented with a precise orbital model. The precise GEO orbital model has been designed considering the most important perturbations (non-spherical Earth Potential, Moon and Sun attraction and Solar Radiation Pressure). The obtained results fit very well with the experimental data. %For orbit determination, the model must be complemented with the real time interferometric observations, that work as model readjustment. The retrieved orbit is obtained by solving an optimization problem related with the orbital model and the interferometric observations. Errors in position of about 10 km has been obtained by comparing the retrieved orbit with the TLE, a data format encoding a list of orbital elements for a given epoch. |
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