Recently, there has been increased emphasis on employing reactive actions in robot task planning. The principle reasons for this change are to increase the robustness of robot action by making them sensor controlled, and to accommodate dynamic, unpredictable environments. However, in many cases, supporting reactive mechanisms requires choosing sensor inputs for the reactive procedure. This paper addresses the issue of planning the sensor required to carry out a reactive robot program. A preliminary framework for planning is presented, and sensor planning is illustrated for the problem of replacing a mechanically attached plug in a space environment.