Impact of receiver's frequency response in GNSS reflectometers

Global Navigation Satellite System's (GNSS) opportunity signals reflected over the surface of the Earth can be used for altimetry, sea state determination… So far, GPS signals scattered over the Earth's surface have been cross-correlated with a local replica of the transmitted signal (typically the GPS available C/A code) shifted in frequency (Δƒd) and in delay (τ). However, it is not possible to achieve the full potential of these signals due to the unavailability of the large bandwidth codes. To overcome this problem, the direct and reflected signals can be cross-correlated. However, to improve the SNR high gain antennas are required and they must be steerable so as to point to the direct satellite and to the specular reflection point. Differences between the receivers' frequency responses impact the overall frequency response, and may distort the ideal observables. This work presents the analytical computation of the GNSS reflectometer observables in the above conditions and will compare them to the ideal ones, so as to be able to properly specify the receivers' frequency response.

[1]  M. Caparrini,et al.  Sea state monitoring using coastal GNSS‐R , 2004 .

[2]  Adriano Camps,et al.  New Instrument Concepts for Ocean Sensing: Analysis of the PAU-Radiometer , 2007, IEEE Transactions on Geoscience and Remote Sensing.

[3]  Cinzia Zuffada,et al.  First spaceborne observation of an Earth‐reflected GPS signal , 2002 .

[4]  James L. Garrison,et al.  Mediterranean Balloon Experiment: ocean wind speed sensing from the stratosphere, using GPS reflections , 2003 .

[5]  Stephen J. Katzberg,et al.  Wind speed measurement using forward scattered GPS signals , 2002, IEEE Trans. Geosci. Remote. Sens..

[6]  M. Martín-Neira.  A pasive reflectometry and interferometry system (PARIS) application to ocean altimetry , 1993 .

[7]  Adriano Camps,et al.  Correction of the Sea State Impact in the L-Band Brightness Temperature by Means of Delay-Doppler Maps of Global Navigation Satellite Signals Reflected Over the Sea Surface , 2008, IEEE Transactions on Geoscience and Remote Sensing.

[8]  A. Camps,et al.  PAU in SeoSAT: A proposed hybrid L-band microwave radiometer/GPS reflectometer to improve Sea Surface Salinity estimates from space , 2008, 2008 Microwave Radiometry and Remote Sensing of the Environment.

[10]  Manuel Martín-Neira,et al.  The PARIS Ocean Altimeter In-Orbit Demonstrator , 2011, IEEE Transactions on Geoscience and Remote Sensing.

[11]  C. Zuffada,et al.  5‐cm‐Precision aircraft ocean altimetry using GPS reflections , 2002 .

[12]  Martin Unwin,et al.  Detection and Processing of bistatically reflected GPS signals from low Earth orbit for the purpose of ocean remote sensing , 2005, IEEE Transactions on Geoscience and Remote Sensing.

[13]  James L. Garrison,et al.  GPS Signal Scattering from Sea Surface: Wind Speed Retrieval Using Experimental Data and Theoretical Model , 2000 .

[14]  Valery U. Zavorotny,et al.  Scattering of GPS signals from the ocean with wind remote sensing application , 2000, IEEE Trans. Geosci. Remote. Sens..