Summary: For the LSF and PSF calibration in the Gaia IDT/IDU we need LSF/PSF models that are both accurate and have as few free parameters as possible. General-purpose functions such as splines are not the best choice since they tend to require more parameters than strictly necessary, and have a tendency to become unstable when fitted to noisy or inhomogeneous data. Using Principal Component Analysis (PCA)...
 

Bibtex entry for this abstract:

@UNPUBLISHED{LL:LL-084,
author = {L.~Lindegren},
title={{M}inimum-dimension {L}{S}{F} modelling},
institution={Lund Observatory},
year={2009},
month={August},
url={http://www.rssd.esa.int/doc_fetch.php?id=2915742},
note={GAIA-C3-TN-LU-LL-084},
type={Technical note}
}