An in-space spacecraft servicing system (10) includes a servicing spacecraft (22) and a propellant module (24). The servicing spacecraft includes a client servicing system (136), as well as navigation avionics (108) for independent flight operation and a servicing propellant tank (170). The propellant module moves the servicing module from an upper stage drop off location and releases it in proximity to a client spacecraft (16) for a servicing mission. It has a propellant tank (172) with capacity for multiple missions and is used to refill the servicing spacecraft's propellant tanks between missions. Either or both the servicing spacecraft and the propellant module may have navigation avionics. The servicing spacecraft also has a universal docking adaptor (70) for different client spacecraft, and can convert a client spacecraft from non-cooperative to cooperative.