Capacitive sensing of test mass motion with nanometer precision over millimeter-wide sensing gaps for space-borne gravitational reference sensors
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We report on the performance of the capacitive gap-sensing system of the Gravitational Reference Sensor on board the LISA Pathfinder spacecraft. From in-flight measurements, the system has demonstrated a performance, down to 1 mHz, that is ranging between 0.7 and 1.8¿¿aF¿Hz-1/2. That translates into a sensing noise of the test mass motion within 1.2 and 2.4¿¿nm¿Hz-1/2 in displacement and within 83 and 170¿¿nrad¿Hz-1/2 in rotation. This matches the performance goals for LISA Pathfinder, and it allows the successful implementation of the gravitational waves observatory LISA. A 1/f tail has been observed for frequencies below 1 mHz, the tail has been investigated in detail with dedicated in-flight measurements, and a model is presented in the paper. A projection of such noise to frequencies below 0.1 mHz shows that an improvement of performance at those frequencies is desirable for the next generation of gravitational reference sensors for space-borne gravitational waves observation.
CitationAudley, H., Auger, G., Baird, J., Binetruy, P., Caleno, M., Cesarini, A., Diepholz, I., Dixon, G., Dolesi, R., Ferraioli, L., Heinzel, G., Hollington, D., Karnesis, N., Martín-Porqueras, F., Sopuerta, C. F., Texier, D., Vitale, S., Wanner, G., Ward, H., Ramos, J. Capacitive sensing of test mass motion with nanometer precision over millimeter-wide sensing gaps for space-borne gravitational reference sensors. "Physical review D", 26 Setembre 2017, vol. 96, núm. 6, p. 1-11.