Proceedings PaperMicro-arcsecond measurement testbed and its relationship to the Space Interferometer Mission
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This paper describes the relationship between the Space Interferometer Mission (SIM) and the Micro-Arcsecond Measurement Testbed (MAM). MAM is necessary because differences exist between the starlight and the metrology measurements through the SIM instrument optical path. The goal of MAM is to establish the methodologies required to reduce these differences. The targeted SIM instrument performance requires these differences to be at the pico-meter level. Starlight and metrology difference errors can be grouped into two categories: field dependent and field independent errors. The field independent errors are either random (i.e., vibration) or drift (i.e., thermal mirror warping). The field dependent errors introduce differences between metrology and starlight that change as a function of 'look' angle. An example field dependent error is the different diffraction effects on the two beams as the delay line slews. SIM's fundamental error mitigation approach is to reduce the field dependent errors down to the prescribed error budget levels, then calibrate out the remaining field dependent portion. The paper describes the recipe to generate the MAM error budget. Since MAM is inherently a subset of SIM, the MAM testbed addresses a subset of the total SIM error budget. The paper describes the approach to determining the relevant MAM portion. In addition, it describes the derivation of the overall MAM error budget, including allocations for the pseudo star errors. The paper maps the SIM observing scenario to a MAM test measurement. A successful MAM measurement will be defined in terms of the actual measurements, the metric applied and its relationship to the MAM error budget.