This paper presents the in-orbit performance of the spaceborne guidance navigation and control system which enabled the AVANTI experiment, a technological demonstration conducted by the German Aerospace Center in autumn 2016. AVANTI proved the viability to perform far- to close range autonomous proximity operations with respect to a noncooperative flying object using only optical angle measurements. Within AVANTI, the Earth-observation BIROS satellite played the role of a chaser spacecraft, which autonomously approached down to circa 50 m of inter-satellite distance the BEESAT-4 picosatellite, simply using a head of its star-tracker as monocular camera.