Abstract: A method of performing radio occultation for inferring physical properties of a portion of atmosphere includes receiving, at a receiver, a first signal from a satellite at a first timing; receiving, at the receiver, a second signal from the satellite at a second timing different from the first timing; correlating the first signal with the second signal; and determining a first quantity indicative of a path delay between the first signal and the second signal resulting from at least one of the first signal and the second signal having passed through the portion of atmosphere between transmission by the satellite and reception at the receiver, based on a result of the correlation. The application further relates to a system for performing radio occultation for inferring physical properties of a portion of atmosphere.

Abstract: A method of performing radio occultation for inferring physical properties of a portion of atmosphere includes receiving, at a receiver, a first signal from a satellite at a first timing; receiving, at the receiver, a second signal from the satellite at a second timing different from the first timing; correlating the first signal with the second signal; and determining a first quantity indicative of a path delay between the first signal and the second signal resulting from at least one of the first signal and the second signal having passed through the portion of atmosphere between transmission by the satellite and reception at the receiver, based on a result of the correlation. The application further relates to a system for performing radio occultation for inferring physical properties of a portion of atmosphere.

Abstract: The present invention is directed to a space-borne altimetry apparatus having a first receiving antenna, pointing to outer space, for receiving at least one signal emitted by a remote satellite emitter via a direct path; a second receiving antenna, pointing to the Earth, for receiving said signal via an indirect path including a reflection from the Earth surface; and a signal processing means for computing a distance of the apparatus from a specular reflection point of the signal on the Earth surface by cross-correlating the signals received by said first and second antennas; wherein both the first and second receiving antennas are high-gain steerable antennas; and wherein the apparatus may also include antenna control means for steering at least one receiving lobe of the first antenna toward the remote satellite emitter, and at least one receiving lobe of the second antenna toward a specular reflection point on the Earth surface.

Abstract: The present invention is directed to a space-borne altimetry apparatus having a first receiving antenna, pointing to outer space, for receiving at least one signal emitted by a remote satellite emitter via a direct path; a second receiving antenna, pointing to the Earth, for receiving said signal via an indirect path including a reflection from the Earth surface; and a signal processing means for computing a distance of the apparatus from a specular reflection point of the signal on the Earth surface by cross-correlating the signals received by said first and second antennas; wherein both the first and second receiving antennas are high-gain steerable antennas; and wherein the apparatus may also include antenna control means for steering at least one receiving lobe of the first antenna toward the remote satellite emitter, and at least one receiving lobe of the second antenna toward a specular reflection point on the Earth surface.

Abstract: The invention relates to a digital circuit making it possible to measure the effective voltage of a signal, comprising at least one module exhibiting a sampler stage exhibiting an output generating an output logic signal which, for each given sampling period, exhibits a level representing the value of the voltage of the signal with respect to a given threshold (A), characterized in that it comprises a circuit (CIRC) for calculating a value representative of said effective voltage as a function of the difference between the number of times the output logic signal indicates that the voltage of the signal is above the given threshold (A) and the number of times the output logic signal indicates that this value is below said given threshold (A) over a duration corresponding to N given sampling periods.

Abstract: The invention relates to a digital circuit making it possible to measure the effective voltage of a signal, comprising at least one module exhibiting a sampler stage exhibiting an output generating an output logic signal which, for each given sampling period, exhibits a level representing the value of the voltage of the signal with respect to a given threshold (A), characterized in that it comprises a circuit (CIRC) for calculating a value representative of said effective voltage as a function of the difference between the number of times the output logic signal indicates that the voltage of the signal is above the given threshold (A) and the number of times the output logic signal indicates that this value is below said given threshold (A) over a duration corresponding to N given sampling periods.

Abstract: A method for performing Earth altimetry comprising the steps of: receiving by an upward-looking antenna onboard a platform above the Earth surface, direct signals having at least two different carrier frequencies transmitted by GNSS satellites in view of the upward-looking antenna, receiving by a downward-looking antenna onboard the platform signals reflected by the Earth surface and having the at least two different carrier frequencies, comparing carrier phases of the direct signals and received reflected signals, at the carrier frequencies, and determining from the phase comparisons a surface height.

Abstract: An aperture synthesis radiometer operating in fully polarimetric mode. The measuring receivers are connected selectively to the polarization ports of the array elements following selected switching sequences thereby to provide the required cross-correlations that allow fully polarimetric operation. The polarization switching scheme used enable measurements to be performed with a minimum degradation in sensitivity using single channel receivers.

Abstract: A method for performing Earth alimetry comprising the steps of: receiving by an upward-looking antenna onboard a platform above the Earth surface, direct signals having at least two different carrier frequencies transmitted by GNSS satellites in view of said upward-looking antenna, receiving by a downward-looking antenna onboard said platform signals reflected by the Earth surface and having said at least two different carrier frequencies, comparing carrier phases of said direct signals and received reflected signals, at said carrier frequencies, and determining from said phase comparisons a surface height.

Abstract: An aperture synthesis radiometer operating in fully polarimetric mode. The measuring receivers are connected selectively to the polarization ports of the array elements following selected switching sequences thereby to provide the required cross-correlations that allow fully polarimetric operation. The polarization switching scheme used enable measurements to be performed with a minimum degradation in sensitivity using single channel receivers.

Abstract: A radiometry system including an aperture synthesis antenna array type, including plural antenna elements, distributed in an antenna plane relative to at least one axis, according to a determined law. Each antenna element includes first and second coupling probes sensitive to hyper-frequency electromagnetic signals with dual linear polarization in quadrature (arbitrarily referred to as horizontal and vertical polarizations). The probes are connected two by two with electric receiving circuits to create a synthetic aperture. The horizontal (fH1-fH4) and vertical (fV1-fV4) coupling probes of successive antenna elements (eA1-eA4) are oriented in the antenna plane (At′), along each of the axes (&Dgr;), such that at least one of the horizontal or vertical probes (fH1-fH4, fV1-f4) presents a 180° phase shift from one antenna element to the other (eA1-eA4), with the phase shift obtained by a sequential 90° rotation of those probes (fH1-fH4, fV1-fV4).

Abstract: The invention concerns an interferometric hyperfrequency radiometry system comprising an antenna being subject to a rotation movement around the vertical direction, with a boresight axis forming an angle with a nadir direction so as to obtain a conical scanning. The antenna is a planar array antenna, of an interferometric type with distributed elements, such that the instantaneous field of vision consists of pixels, along at least one axis perpendicular to the conical scanning for an unidimensional interferometric antenna, and along two axes for a bidimensional interferometric antenna. The elements of the interferometric antenna furthermore are connected into sub-arrays.

Abstract: An altimetry method uses one or more sources of opportunity, for example transmitters on satellites of the "GPS" satellite navigation system. One or more receivers on board an aircraft or a satellite in low Earth orbit are used. Multiple correlation is applied between the direct signal received from the transmitter and the reflected signal. The coordinates of the point of specular reflection are derived from the measured delay achieved by said multiple correlation and comparison with a theoretical model of the terrestrial sphere. The device for implementing the method includes a signal processor, a variable delay circuit, a discrete delay line, a bank of correlators and detectors. A specific application of the method and device is ocean altimetry.