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A study approach used to define optical tunable filter requirements while operating as an integral part of a satellite-based earth looking IR telescope is presented. The key to the study methodology is a high fidelity, dynamic, end-to-end simulation which generates realistic mission inputs and relates these inputs to system performance as a function of the sensor/filter design parameters. A modular simulation design approach is used which permits the interface of new or existing mission data base inputs. Sensor models relate the mission inputs to the sensor output. Mission models include dynamic targets with their time-correlated spectral radiant intensity and corresponding line-of-sight spectral radiant back-ground. The apparent target spectral radiant intensity contrast and background spectral radiance are computed at the sensor. Sensor models include the optics, optical tunable filter, the staring focal plane array (FPA), point spread function/FPA convolution and detector electronics. Detail design requirements for the filter are selected by exercising the simulation under different mission conditions with different selected optical filter parameters. Analysis of these data provides the inputs for selecting the filter design requirements and an optimum control strategy which can be used for adaptable tunable filter control. Initial results show the importance of spectral agility in an optical filter. It is shown that, in addition to sensor performance dependence on filter design, the spectral band and bandwidths are sensitive not only to the mission/sensor conditions but also to the spectral region selected for the operational system. Examples of data are presented to help demonstrate the analysis procedure and include (1) impact of filter efficiency; (2) system performance vs optical filter parameters; and (3) system performance vs atmospheric conditions.
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