Abstract: A sensor and method for measuring an electrical potential difference are described. The sensor includes a micro-fabricated field emission device situated in a space plasma environment. The field emission device has an emitter terminal and a gate terminal. A voltage source applies a voltage across the gate and the emitter terminals to induce current to flow from the emitter terminal A first current monitor measures current flowing from the emitter in response to the applied voltage. A second current monitor measures current flowing to the gate. A control system correlates applied voltages and measured gate and emitter currents with electrical potential differences between the field emission device and the space plasma environment. The control system obtains the gate and emitter currents from the current monitors. A processor computes a value from the gate and emitter current measurements based on a predetermined functional relationship.

Abstract: A system and method for altering an orbit of a space object are described. An electrodynamic tether is deployed from an orbiting space object such that the electrodynamic tether is capable of producing electrical charge. A micro-fabricated charge-emitting device is placed at one end of the electrodynamic tether and has at least two terminals. One of the terminals is electrically connected to the tether to receive the electrical charge produced by the tether. A voltage source applies a voltage across the two terminals of the charge-emitting device to induce the charge-emitting device to emit the charge received from the tether. Depending in part upon the end at which the charge emission device is placed and upon the polarity of the charge emitted, emission of the charge raises or lowers the orbit of the space object.

Abstract: A controller for controlling an electrical potential of an object with respect to its environment is described. The controller includes a micro-fabricated charge-emitting device connected to a space object situated in a space plasma environment. The charge-emitting device has a gate and an emitter. A voltage source applies a voltage across the gate and the emitter of the charge-emitting device to induce the emitter to emit into the environment electrical charge drawn from the object. In general, the magnitude of the applied voltage can be less than 100 volts. A control system varies the voltage applied between the gate and the emitter of the charge-emitting device. Varying the voltage adjusts the amount of electrical charge that is emitted by the emitter. Thus, by controlling the voltage, the control system can control the electrical potential of the space object with respect to the space plasma environment.