OREANDA-NEWS. Nippon Telegraph and Telephone Corporation (NTT) and Japan Aerospace Exploration Agency (JAXA) have achieved the world’s first microwave electric-field measurement with the newly developed optical electric-field sensor based on an optical fiber (fiber-optic EO probe) in plasma inside a microwave discharge ion engine for use on asteroid explorers etc.

This achievement contributed to the investigation of the plasma production mechanism in the microwave discharge ion engine during actual operation, which has been difficult thus far. This investigation will make it possible to design the ion engine with higher performance characteristics, and thus, it is expected to allow the deployment of more effective and efficient space activities, enabling future asteroid explorers with an improved ion engine to set out for even more distant asteroid and with a prolonged lifetime.

Electric-field sensors conventionally comprising metal components are widely used to measure various kinds of electromagnetic wave such as weak ones fount in nature and artificially generated high-power microwaves. Since conventional electric-field sensor can disturb radiated electromagnetic waves, it is an inherent issue when attempting to precisely measure the desired electric field. To overcome this issue, NTT has developed an EO probe employing an optical fiber which is generally used as a main tool in optical communications.

Moreover, JAXA has been promoting the research and development of the ion engine boarded on the asteroid explorers and achieving improvements in its propulsion performance. To develop an improvement mechanism, JAXA required the ability to measure the microwave electric-field distribution of the internal plasma in the ion engine during actual operation.

However, since conventional electric-field sensors can provide disturbances such as scattering the electric field and require undesired modifications to the ion engine for insertion, it is difficult to precisely diagnosis internal phenomena based on microwave electric-field measurement of the accelerated plasma in the ion engine during operation.

Thus, from the viewpoint of non-invasiveness and the high spatial resolution of the fiber-optic EO probe which has been developed by NTT based on an optical fiber, the research and development of microwave electric-field measurements in the ion engine have progressed under the collaboration of NTT and JAXA