Modeling for instrument diagnostics: Gaia non-nominal configurations impact on astrometric performance

Abstract

The Gaia payload is a highly sophisticated system and many of its instrumental behaviors will be tested at proper accuracy only during the operational phase. However simulation results are critical parts for developing system integration, as well as for understanding unexpected behavior during commissioning and operations. The data analysis procedures are sensitive to several instrument parameters, as their variation over the field and with time. We focused our dissertation on the study and analysis of non-nominal configurations effects on astrometric accuracy, putting also in evidence the level of the effects that the difference between the design data and as-built data can produce if not adequately taken into account. We identify and quantify the effects. We move from this forward analysis to look at the data and perform instrument monitoring and diagnostic procedures, an essential activity for the verification of GAIA measurements. We conducted the study in the context of the Astrometric Verification Unit.