Two Thermodynamics-Based Approaches to Atomic Oxygen Sensing

Impact of atomic oxygen is a main factor responsible for enhanced oxidation and fast degradation of spacecraft and satellite construction materials in low earth orbits. Thus, information concerning atomic oxygen concentration is important for spacecraft designers and manufacturers. Many sensors have been developed to perform atomic oxygen concentration measurement. However, these sensors have important disadvantages: high power consumption, low reproducibility, limited lifetime, and large mass/size parameters. In the present work two new methods based on a thermodynamic approach are proposed, employing an enhanced chemical potential of atomic oxygen. The first method is based on measurement of maximal temperature of silver oxidation in atomic oxygen, since this temperature depends on the concentration of oxygen in atmosphere. The second method is based on a Nernstian-type sensor with oxygen-conducting solid electrolyte. The electromotive force of this cell also depends on the concentration of atomic oxygen in the gas phase. Thermodynamic interpretations of sensor operation are proposed. The results of laboratory experiments on atomic oxygen pressure estimation by both methods are in good agreement. A new complex sensor using both approaches in one device is developed.