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gaia data release 3 documentation

6.4 Processing steps

6.4.2 EpochInit

This pipeline is in charge of preparing the processing batches for each trending epoch (TE) for the downstream pipelines Scatter, Calibration and FullExtraction. It works per transit and per trending epoch. It is mostly a technical pipeline with the only scientific task to estimate the electronic (uniform) bias offset as a function of time. The bias offset is measured from the prescan data (from the IDT) which are acquired every 70 minutes in bursts of 1024 samples. The uniform bias offset calibration consists of extracting the median signal from the bursts of prescan data for each CCD. These bias offsets obtained every 70 minutes are stored in a dedicated data model (RvsBiasRecord) and input to the downstream pipelines Scatter, Calibration and FullExtraction, where a linear interpolation to these data is performed to obtain the bias offset that is to be subtracted from the spectra at any time. The input data of the EpochInit pipeline are the SpectroObservation, SpectroObservationVo, Prescan, ObjectLogs, and the initial GenericTrending, containing the start and end times of each trending epoch.