Impact of the space environment on Darwin and a Low Earth Orbit (LEO) demonstration mission
- Paper number
IAC-05-C2.5.08
- Author
Ms. Veerle Sterken, Technical University of Delft (TUDelft), The Netherlands
- Year
2005
- Abstract
noindent The main goal of ESA’s Darwin mission is a direct detection of terrestrial exo-planets and the investigation of their atmospheric composition. This is done by means of interferometry between multiple satellites, separated by up to 500 m. The key to success is the stability of the inter-satellite distances to the centimeter-level, and nullifying the Optical Path Differences (OPD) at the nanometer-level. The latter is done using an Optical Delay Line (ODL). The ODL is a mechanism that changes the OPD by altering the position of two mirrors to the utmost precision. The presented study investigates the order of magnitude of the internal and external dynamic disturbance forces and their effects on the OPD of Darwin, especially in the high frequency range. In addition, the external forces in LEO are examined for a potential preparatory interferometry demonstration mission. The internal disturbance forces of Darwin are examined for three of its subsystems that cause mechanical vibrations: the Field Emission Electric Propulsion units (FEEPs), the Optical Delay Line and the Sorption Coolers. The external disturbance forces on Darwin in the Lagrange point L 2 have been considered. For this purpose, the space environment in L 2 has been studied in detail. Finally, for the LEO interferometry mission, the external disturbance forces are deduced by using the accelerometer data of the LEO gravity missions CHAMP and GRACE. This is determined through the fourier analysis of the satellites accelerometer data. The most critical disturbance forces have been found to be the internal disturbance forces. The results of the LEO mission study confirm this statement. However, according to the presented study, their high-frequency content remains small. As a result, the OPD can be controlled adequately by a 10 Hz control loop. This opens the possibility of looking at alternative solutions, like FEEPs, besides the ODL, for controlling the OPD.
- Abstract document
- Manuscript document
IAC-05-C2.5.08.pdf (🔒 authorized access only).
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