Remote sensing data are usually collected by SAR instruments on-board airplanes or satellites and many applications have been developed in a wide range of scientific subjects. Developments in technologies permit radar sensors to be miniaturized, which now allow them to be embedded on-board smaller platforms such as UAVs. ONERA is currently developing a new line of SAR instruments on-board UAV, called SAR-Light. In its first version, it is a mono-polarized (VV) SAR operating in X-band at high spatial resolution (0.25 m). This paper presents the SAR-Light instrument and describes the performance obtained during a flight tests campaign carried out in April 2021 in the South of France.