Capacitive sensing of test mass motion with nanometer precision over millimeter-wide sensing gaps for space-borne gravitational reference sensors
Mendes, L.; Madden, S.; Russano, G.; Lloro, I.; Nofrarias, M.; Grado, A.; Armano, M.; Audley, H.; Baird, J.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Cavalleri, A.; Cesarini, A.; Cruise, A. M.; Danzmann, K.; de Deus Silva, M.; Diepholz, I.; Dixon, G.; Dolesi, R.; Ferraioli, L.; Ferroni, V.; Fitzsimons, E. D.; Freschi, M.; Gesa, L.; Giardini, D.; Gibert, F.; Giusteri, R.; Grimani, C.; Grzymisch, J.; Harrison, I.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hoyland, D.; Hueller, M.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Karnesis, N.; Kaune, B.; Korsakova, N.; Killow, C. J.; Liu, L.; Lobo, J. A.; López-Zaragoza, J. P.; Maarschalkerweerd, R.; Mance, D.; Martín, V.; Martin-Polo, L.; Martin-Porqueras, F.; Martino, J.; McNamara, P. W.; Mendes, J.; Meshksar, N.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Pivato, P.; Plagnol, E.; Ramos-Castro, J.; Reiche, J.; Rivas, F.; Robertson, D. I.; Slutsky, J.; Sopuerta, C. F.; Texier, D.; Thorpe, J. I.; Vetrugno, D.; Vitale, S.; Wanner, G.; Ward, H.; Wass, P. J.; Weber, W. J.; Wissel, L.; Wittchen, A.; Zweifel, P.; Mateos, I.; Trenkel, C.; Wealthy, D.; De Rosa, R.; Di Fiore, L.; LISA Pathfinder Collaboration; Auger, G.; Bassan, M.; Brandt, N.; Caleno, M.; Dunbar, N.; Flatscher, R.; García Marirrodriga, C.; Gerndt, R.; Johlander, B.; Prat, P.; Ragnit, U.; Rozemeijer, H.; Sarra, P.; Schleicher, A.; Stanga, R.; Tröbs, M.; Zambotti, A.; Zanoni, C.; Ziegler, T.; Sumner, T. J.
Spain, Germany, France, United Kingdom, Italy, Netherlands, Switzerland, United States
Abstract
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.