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gaia data release 3 documentation

3 Pre-processing

3.1 Introduction

This chapter presents the models and processing steps used for pre-processing the raw Gaia data before the basic observables (or astrometric elementaries, sometimes referred to as AstroElementaries) can be generated and passed on to the Gaia core astrometric solution which is discussed in Chapter 4. The input to Gaia data processing is the raw satellite telemetry and an attitude star catalogue to allow a first reconstruction of the attitude of Gaia. The astrometric calibration models are outlined in Section 3.3 including PSF/LSF models and discussions of CCD calibration challenges followed by the details of the daily and cyclic processing steps in Section 3.4. The final Section 3.5 discusses both the daily and cyclic monitoring and validation that is performed before data products are passed on to the core astrometric solution described in the next chapter.