Abstract: A space navigation receiver (NR) comprises i) a radiofrequency processing module (PM1) tasked both with converting radio navigation signals transmitted by a satellite navigation system into digital navigation signals, and with converting auxiliary radio signals representative of navigation information about said system into auxiliary digital signals, ii) a digital processing module (PM2) tasked with periodically acquiring the digital navigation signals by sub-sampling the received radio signal, then processing the acquired signal samples (resulting from this sub-sampling) in order to produce raw measurements from these samples, from auxiliary digital signals, and from location points, and iii) a location module (LM) tasked with determining location points based on raw measurements, demodulated navigation data initially contained within the digital navigation signals in a modulated form, and orbital force models.

Abstract: A space navigation receiver (NR) comprises i) a radiofrequency processing module (PM1) tasked both with converting radio navigation signals transmitted by a satellite navigation system into digital navigation signals, and with converting auxiliary radio signals representative of navigation information about said system into auxiliary digital signals, ii) a digital processing module (PM2) tasked with periodically acquiring the digital navigation signals by sub-sampling the received radio signal, then processing the acquired signal samples (resulting from this sub-sampling) in order to produce raw measurements from these samples, from auxiliary digital signals, and from location points, and iii) a location module (LM) tasked with determining location points based on raw measurements, demodulated navigation data initially contained within the digital navigation signals in a modulated form, and orbital force models.

Abstract: In order to detect the error on the frequency of an M-PSK phase-modulated carrier, the phase .psi.(n) of the samples is restored to the interval ?-.pi., +.pi.?; .phi.(n)=mod(.psi.(n), 2.pi./M) is calculated; d(n)=mod(.phi.(n)-.phi.(n-1), 2.pi./M) is calculated; p'(n)=mod(d(n)+p(n-1), 2.pi./M) is calculated, where p(n)=mod(p*(n), 2.pi./M), where p*(n) is obtained by subtracting the current output from p'(n); d'(n)=p'(n)-p(n-1) is calculated; a parameter "tri" is defined by tri=1 if .vertline.d'(n).vertline.<S and tri=.beta. if .vertline.d'(n).vertline..gtoreq.S, where S is a threshold; det.sub.-- tri(n)=.alpha..p'(n).tri is calculated, det.sub.-- tri(n) constituting the current output, representative of the error on the frequency of the carrier.

Abstract: A method and a system for locating ground equipment transmitting signals to a geostationary satellite, the method and the system being based on identifying the arrival directions of such signals within the coverage zone of the satellite. In the method, the arrival directions of the signals are identified by using a beam-forming active-module array antenna system on board the satellite, the system being controlled to define simultaneous beams in the radiation pattern of the antenna, the beams being superposed on one another with small offsets, the superposed beams corresponding to a limited analysis zone being illuminated within the coverage zone of the satellite, the system further being associated with a digital processing program which identifies the arrival directions of the signals which are received in the analysis zone.

Abstract: The method makes it possible digitally to evaluate the phase of any carrier that has been subjected to rPSK modulation subsequent to clock recovery, sampling, and digitizing the in-phase and quadrature components of the samples, by processing that is performed in polar coordinates and that comprises reducing the range over which the phase of each sample is defined to a range of +.pi./r to -.pi./r and then seeking the center of gravity over 2.sup.N successive samples (N being an integer) by performing successive averaging calculations, each time on two values, in application of an N-stage tree structure. Each average of two values is associated with an index indicative of the degree of reliability of the average, and those averages which are associated with a small reliability index are ignored while calculating subsequent averages in the tree structure.