Gaia Early Data Release 3: Modelling and calibration of Gaia's point and line spread functions

Understand

Context: The unprecedented astrometric precision of the Gaia mission relies on accurate estimates of the locations of sources in the Gaia data stream.

• This is ultimately performed by point spread function (PSF) fitting, which in turn requires an accurate reconstruction of the PSF.
• Gaia Early Data Release 3 (EDR3) will, for the first time, use a PSF calibration that models several of the strongest dependences, leading to signficantly reduced systematic errors.
• Aims: We describe the PSF model and calibration pipeline implemented for Gaia EDR3, including an analysis of the calibration results over the 34 months of data.