The Earth is illuminated in the microwave frequency by a vast number of satellites that transmit signals for a broad range of applications, such as GNSS or satellite broadcast TV, among many others. The use of these signals for remote sensing purposes, different from their originally intended application, is known as remote sensing using signals of opportunity (SoOP).
Signals transmitted by Global Navigation Satellite Systems (GNSS) and acquired by low-earth orbiting satellites in Radio Occultation (RO) geometries are currently being used extensively in an operational basis, to provide humidity and density profiles of the Earth atmosphere. The resulting data is highly valuable for numerical weather predictions.
Furthermore, GNSS signals are strongly reflected off the ocean surface, the polar caps, and even land. By acquiring these reflected signals and processing them appropriately, properties of the reflecting surface can be derived, as for instance the sea surface roughness or the sea surface altitude or ice surface elevation. This is known as GNSS Reflectometry (GNSS-R).
Finally, signals transmitted at other microwave bands can also be used for different remote sensing purposes. For instance, digital satellite TV signals, can also be used for remote sensing purposes, such as the sea surface, the land or even the atmosphere.
Sketch of the polarimetric GNSS radio-occultation concept (not scaled). The GNSS circularly polarized signals are received at 2 orthogonal linear polarizations to sense the polarimetric effects induced by the heavy rain and other hydrometeors.
The Earth Observation group at the Institute of Space Sciences aims at understanding how the SoOP can be used for remote sensing of the Earth. We have three main areas of research, Radio Occultations, GNSS Reflectometry, and remote sensing using digital satellite TV signals.
We investigate which signal properties make this new way of remote sensing advantageous compared to other techniques, how they complement each other, and what are the instrumental implications for future remote sensing missions.
We achieve this by implementing our own instruments and using them in experimental campaigns, developing models and simulations tools, and by proposing and participating in GNSS-R space-borne missions, such as PARIS IoD, GEROS-ISS or G-TERN.
We are also involved in the development of new algorithms for the EUMETSAT's Radio Occultation Meteorology Satellite Application Facility (ROM-SAF).
In addition, we are researching on the possibility to retrieve heavy rain estimates using polarimetric RO, for the first time ever. This new measurement technique was conceived at the ICE, and we are leading the ROHP-PAZ experiment on-board the PAZ satellite, its proof-of-concept experiment. PAZ is scheduled to be launched towards end of 2017.
We freely provide all our campaign data for scientific use at this website, together with some software tools.
Photograph of the SPIR-UAV (Software PARIS Interferometric Receiver UAV version), a custom designed GNSS-R recording receiver with beam-forming capabilities, to be flown on-board an UAV, for remote sensing of sea ice.
Senior Institute members involved
E. Cardellach, S. Ribó, A. Rius.