With the prospects of future Mars and lunar missions improving, the autonomous capabilities required to accomplish many of the proposed missions has been given considerable attention. As a result, it has been recognized that the sensing capability of spacecraft must be enhanced, not only for interplanetary missions, but for those in Earth orbit as well. NASA began addressing many technology development issues under the Pathfinder Program. A sensor trade-off study was performed at ERIM under two subprograms of Pathfinder: the Autonomous Lander Project, and Autonomous Rendezvous and Docking Project. This paper is based on that trade-off study, using the scenario of an autonomous landing on a planetary body and the associated autonomous rendezvous and docking operations which would precede and/or follow such a landing. Several sensor concepts are analyzed, including RF-based, laser- based, and passive optical techniques. For each concept, a brief description of the sensor operating principles is provided, and the results of a performance analysis are summarized along with performance drivers, operational constraints, and a state-of-the-art assessment.