System Level Modeling of the SNAP Instrument and Analysis of Reaction-Wheel-Induced Jitter

A crude, system level dynamic model of SNAP is created based on the results of initial structural design studies for some of the key telescope structures. The model is used to evaluate coupled dynamics of the SNAP spacecraft with both fixed base and free-free boundary conditions to mimic launch and on-orbit situations. The model is then used to eva luate the magnitudes of on -orbit telescope deflections induced by residual imbalances in spinning reaction wheels. It is shown that, when reaction wheel speeds are below fundamental resonances, the induced jitter is negligible or well below requirements. However, it is also found that if reaction wheel speeds are allowed to overlap structural resonances, angular mirror motions exceed requirements unless very high damping levels are present.