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Títol: Interferometric Precise Orbit Determination of Geostationary Satellite Missions


Director/a: NICOLÁS ÁLVAREZ, JORGE

Departament: TSC

Títol: Interferometric Precise Orbit Determination of Geostationary Satellite Missions

Data inici oferta: 20-07-2020     Data finalització oferta: 20-03-2021



Estudis d'assignació del projecte:
    GR ENG SIS TELECOMUN
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització:
UPC
    Departament: TSC - Campus Nord (D3)
 
Segon director/a (UPC): BROQUETAS IBARS, ANTONI
 
Paraules clau:
interferometry, precise orbit determination, remote sensing, GEOSAR
 
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. 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.

The student will work in the context of some on-going remote sensing missions:

The European Space Agency (ESA) has selected Hydroterra in the call for its 10th Earth Explorer. Hydroterra will help scientists unravel the details of the daily water cycle. 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.

NASA Jet Propulsion Laboratory (JPL) has a keen interest in the presented technique and has contacted us to join their team in an emerging snow remote sensing mission.

Goal: The project consists of retrieving geostationary satellite orbits from experimental interferometric measurements. The student will code an Extended Kalman Filter in Python in order to estimate the satellite position. They will work with different datasets of observables: single-
satellite and three-satellite tracking. Finally, the uncertainty of the estimated solution with respect to the true position of the satellite must be determined.
 
Overview (resum en anglès):
Geosynchronous orbits have the unique characteristic that their orbital period is equal to one sidereal day. This configuration does provide coverage on a regional scale. This is a potential advantage in terms of system usage as the demand for some satellite services is concentrated in certain regions of the globe. However, the orbit is not 100 \% determined since different perturbations appear (e.g. asphericity and non-homogeneity of Earth, the action of third bodies) and degrade the GEO orbit trajectory.

The aim of Geostationary Synthetic Aperture Radar (GeoSAR) missions is to obtain daily images of short-period events that take place over the Earth¿s surface. Some of them are critical to monitor (e.g. land stability control, natural risks prevention, or accurate numerical weather prediction models from water vapor atmospheric mapping) since their fast evolution is not observable with current Low Earth Orbit (LEO) based systems.
The aim of the project is the development of an orbit estimation software based on Extended Kalman Filtering in order to process experimental interferometric observations. Kalman Filtering consists on a recursive predictive filter that estimates the state variables of a dynamic linear system, based on a prediction-correction algorithm to produce the estimation of unknown variables. Extended Kalman filter (EKF) is the nonlinear version of the Kalman filter which linearizes about an estimate of the current mean and covariance.
The activity of this project takes place in the context of the new ESA¿s 10th Earth Explorer pre-selected Geosynchronous Radar mission G-CLASS/Hydroterra, with the aim of reducing the satellite revisit times from minutes to hours with respect to LEO missions.


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