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Forward-scattering radars (FSRs) acquire great interest when low radar cross section (RCS) targets are willing to be detected. This type of radar provides a countermeasure to stealth technology because, here, the targets' RCS depends only on the size and the shape of their silhouette. Passive radars use transmitters of opportunity as signal source, and they are therefore attractive too, due to their inherit low cost. The advantage of considering Global Navigation Satellite System (GNSS) satellites as transmitters of opportunity is the high availability that these satellites offer. Anywhere on earth, around eight Global Positioning System (GPS) satellites are continuously in view. Due to the large number of new GNSS satellites becoming operational in the near future (American GPS, Russian GLONASS, European Galileo system, and Chinese COMPASS), more than 30 satellites are expected to be constantly in view. This provides an optimum scenario for implementation of a GNSS-FSR system. In this paper, experimental results of a GPS-FSR at different target-receiver scenarios near Nuremberg Airport are analyzed. Disturbances on the signals due to diffraction effects, which take place as the targets cross the receiver-satellite baselines, are discussed and evaluated. For these experiments, a hemispherical antenna has been used, which provides promising results for a future GNSS-FSR implementation.