PROBA (Project for On-Board Autonomy), renamed PROBA-1, is a Belgian satellite technology demonstration mission launched atop an Indian Polar Satellite Launch Vehicle by ISRO on 22 October 2001.

[1][2] The satellite was funded through the ESA's MicroSat and General Study Program with the objective of addressing issues regarding on-board operational autonomy of a generic satellite platform.

[3][4] This small (60×60×80 cm; 95 kg) boxlike system, with solar panel collectors on its surface, hosts two Earth Observation instruments dubbed CHRIS and HRC.

[5] On 9 March 2018, it surpassed ERS-2 as ESA's longest operated Earth observation mission of all time.

Further planned satellites in the PROBA series include the formation flying demonstration mission PROBA-3 and limb sounder ALTIUS.