Agence Spatiale Europeenne

Agence Spatiale Europeene

Manuel Martin Neira

Giulio Ruffini

Adriano José Camps Carmona

Salvatore D'Addio

Petri Viljo Emil Piironen

Luis Sempere Payá

Pablo Colmenarejo Matellano

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.

Space-borne altimetry apparatus, antenna subsystem for such an apparatus and methods for calibrating the same

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.

Digital circuit for measuring the power of a signal

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.

Ocean altimetry interferometric method and device using GNSS signals

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.

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Oegstgeest, Netherlands

Manuel Martin Neira