The objective of image performance evaluations is to regularly estimate two major LSST Measures of Performance (MOP): delivered image quality (image size) and single visit ellipticity distribution across the field (image shape). Both of these MOPs are defined by the Science Requirements Document, in Table 9 (image size) and Table 13 (image shape). The model required for evaluations is integrated in the sense that it constitutes a joint simulation of optics, structure, and control. It also includes the entire system to be built and placed on the summit: the dome, telescope, and camera; it does not include post-processing of the collected data, i.e. DM.
The objective of system performance modeling is to evaluate the optical effects of various implementation imperfections and disturbances:
- By considering the specified level of imperfections and the expected level of disturbances as requirements, the modeling process can be perceived as the validation of these requirements.
- By implementing in simulations the actual imperfections and disturbances as measured or expected, system modeling provides an early verification tool showing that the overall design and particular components will enable the system to meet its requirements.
The top level objectives and plans for image performance evaluation are outlined in Document-16234 "LSST Integrated Model for Image Performance Simulations". The description and results of the first implementation of such a model is summarized in the material for the Active Optics System Review (09/2013): https://lsstcorp.org/reviews/aos/.