Giovanni Picardi is the author of Elaborazione del segnale radar ( avg rating, 0 ratings, 0 reviews, published ). Abstract (en). A method of filtering SAR images obtained with a Synthetic Aperture Radar (SAR) from the speckle noise is described, said. : Elaborazione del segnale radar: Metodologie ed applicazioni ( Collana scientifica) (Italian Edition) () by Giovanni Picardi and a .
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Go to the content. Move to the navigation Go to the site search Go to the menu Contacts Accessibility. Poltronieri, Sara Determination of the orbit of Picarid from Cassini. Moreover, the Measurements Simulation part of SOSYA has been enriched the introduction of the module that creates synthetic altimetric measurements at given observation times set.
This research can be divided in four parts.
The first part gives a brief introduction of the Cassini mission and a detailed description of the RADAR instrument on board the satellite with its features and scientific purposes. RADAR is a multimode instrument that uses the five beam antenna feed assembly associated with the spacecraft high gain antenna to transmit and receive electromagnetic radiation according to different operative modes: The imaging mode is selected while the spacecraft altitude passes from km to its minimum value, then outbound observations are repeated in reverse order.
Basic concepts of the radar theory and signal modulation are presented. Radar data acquisition is a type of remote sensing technique. These techniques acquire information detecting and measuring changes that the object causes on the surrounding field potential, electromagnetic or acoustic field. In fact, radar altimetry involves bouncing microwave pulses off the surface of the target body and measuring the time it takes the echo to return to the spacecraft.
The second part is concerned with the fundamentals of orbit determination. Statistical orbit determination is the set of techniques that allows the estimation of the orbital parameters of a spacecraft or a celestial body during its motion in the Solar System. It is the problem of determining the best estimate of the orbital parameters of a spacecraft or a celestial body, whose initial state is unknown, from observations influenced by random and systematic errors, using a mathematical model that is not exact.
Then we give the detailed development of the geometrical observation model used to determine the altimetric measurement for the residuals computation at each observation time.
The third part is dedicated to the altimetric data used and to the flybys during which they were collected by the Cassini RADAR. The altimetric data have been received from CO. The total number of altimetric measurements processed is and they are not uniformly distributed in the 14 flybys: T13 and T25 have the lowest numbers of observations so they are precessed but not included in results discussion.
In order to give a description of the flybys used in the Orbit Determination process, we implemented a simple SPICE-based routine that reads the ephemeris files and gives three output files containing respectively: Then by the use of Matlab, the states have been plotted in order to visualize the entire encounters in two different ways: For each available flyby, we give its general description, as duration and the closest approach distance and time.
Moreover we give tables that summarize the distribution over time of the altimetric observation sequence. Since the altimetric observation errors were not available, we have used a constant value for the weight of 80 m for all the observations corresponding to the maximum resolution value that the instrument achieves approximatively.
The mean of all the rms values at first iteration is 4.
The global mean of residuals at the first iteration is m and it decreases to the global mean at the last iteration of?
The minimum value of standard deviation of the estimated position is m, while the maximum value is 5. e,aborazione
Elaborazione del segnale radar ( edition) | Open Library
The standard deviation of the velocity ranges from a minimum of 6. Although our estimation has been made only for Titan and yields particular and local solutions, the results are fully satisfying.
Jacobson  obtained 1- uncertainties for Ravar of 40 km along R, km along T and 50 km along N. These results come from astrometry, radiometric tracking and spacecraft imaging data and estimating all the major Saturnian satellites. The accuracy of our solution is limited by the altimetric measurement errors and by the a priori covariance matrix values applied to the initial conditions of the natural bodies integrated.
In fact we proved that the standard deviation errors effectively decrease by the use of different a priori variance matrices. In addition, the resulting accuracy of the estimation is due to the short orbital arcs considered in the orbit determination process over which the measurements are taken. Our research can be further extended to other mission scenarios in order to reach a better accuracy in the orbit determination of natural satellites by the means of altimetric data collected on board spacecrafts by radar or laser instruments.
New data sets coming from the last part of the nominal picarci and from its extended part will be included in the research dfl processed by SOSYA? ART will be enriched by the consider covariance analysis module testing the impact of the introduction of the altimetric observations on the state estimation process without having the real data.
The altimetric measurements simulation module will be improved by the introduction of the possibility of adding noise to the signal.
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Elaborazione del segnale radar