Fixation method with high-orientation accuracy for optical terminals in space

The LEO-Terminal of the ESA project SILEX (Semiconductor Intersateffite Link EXperiment) must provide a high pointing accuracy to be able to establish an optical inter orbit communication link. An alignment accuracy of 0.01° is required at the interface to the host satellite including the interface structure of the terminal to provide the necessary open loop pointing accuracy for acquisition of the counter terminal. Perturbations during launch, thermoelastic deformation and long term shrinking of the interface structure material CFRP are the determining sources of misalignment. The critical tilting of the interface structure can be reduced by means of slots for the fixation bolts, allowing translatoric movements at the interface fixation points in proper directions. Perpendicular movements to the selected direction (e.g. thermoelastic deformation and vibration during launch) must be strictly suppressed to avoid tilting in the plane of the attachment points at the interface satellite to terminal. Interface adapters at each connection will be used to overcome the problem of integrating the terminal with the tight toleranced fixation slots on the host satellite. One side of the adapters fixed to the terminal interface structure will provide the tight toleranced slots. The other side of the adapter will provide holes with sufficient large tolerances for the bolts used for the fixing of the terminal to the host satellite. These bolts are designed to fix the terminal rigidly under all environmental conditions by friction.