IMPACT OF THE SPACE ENVIRONMENT ON DARWIN AND A LOW EARTH ORBIT (LEO) DEMONSTRATION MISSION

摘要

ESA's space interferometry mission Darwin will make use of optical delay lines (ODL) to help control the optical path differences (OPD) between the satellites to the nanometer level. In order to determine the required ODL control bandwidth, this study investigates the order of magnitude of the high-frequency ( > 1 Hz) disturbance forces, and their effects on the OPD. The internal disturbance forces are examined for the three subsystems which are believed to cause most mechanical vibrations. The frequency-dependence of the external disturbance forces is determined in LEO for a precursor interferometry demonstration mission, by Fourier-transforming the accelerometer data of the GRACE mission. These results, together with a literature survey on the space environment in L_2, lead to an overall view on the order of magnitude of the high-frequency disturbance forces that can be expected on Darwin. In addition the micrometeoroid impacts are studied. The internal disturbance forces are found to be dominating. Their high-frequency component remains small but has still the same order of magnitude as the OPD-requirement of 5 nm_(RMS), for a 1 Hz control bandwidth. Also the micrometeoroid environment shows a possible threat for Darwin.