X-ray Spectroscopic Determination of Electrostatic Potential and Material Composition for Spacecraft: Experimental Results

摘要

Remote surface potential determination for nearby objects in space is an enabling technology for a range of space mission concepts, from improved rendezvous capabilities to touchless debris remediation with the electrostatic tractor concept. One concept is to use a nearby servicing spacecraft which fires electrons at the target. These electrons generate bremsstrahlung X-rays, and the resultant X-ray spectrum can be used to determine the landing energy of the electrons. By knowing the initial energy of the electrons, such as those emitted from an electron gun, the relative potential of the target can be inferred. The use of electron-induced X-rays to determine the electrostatic potential of a surface has previously been investigated theoretically, but this work demonstrates it experimentally. Accuracy is found to correlate to the angle between the detector and the target, and investigation of this relationship is a topic of future work. The mean error in landing energy is found to be approximately 1%, and the mean error in estimated plate voltage is found to be within the uncertainty of the high voltage power supply. Material determination is successfully demonstrated, using characteristic X-rays to identify elements that make up less than 0.5% by mass of the target sample. Several possible means of improving landing energy accuracy are discussed.