Picometer metrology for the GAIA Mission

To measure the relative motions of GAIA's telescopes, the angle between the telescopes is monitored by an all Silicon Carbide Basic Angle Monitoring subsystem (BAM OMA). TNO is developing this metrology system. The stability requirements for this metrology system go into the pico meter and pico radian range. Such accuracies require extreme measures and extreme stability. Specific topics addressed are mountings of opto-mechanical components, gravity deformation, materials and tests that were necessary to prove that the requirements are feasible. Especially mounting glass components on Silicon Carbide and mastering the Silicon Carbide material proved to be a challenge.