Class lsst::meas::modelfit::DoubleShapeletPsfApproxAlgorithm

class DoubleShapeletPsfApproxAlgorithm : public lsst::meas::base::SimpleAlgorithm

An algorithm that fits a 2-component shapelet approximation to the PSF model.

This algorithm fits a similar model to the one that has been used on the HSC side for several data releases, but uses the improved optimizer in meas_modelfit instead of the one in (the now defunct) meas_extensions_multiShapelet and using moments to reduce the number of parameters in the fit. It is faster and more robust than GeneralShapeletPsfApprox, but much less flexible.

The model is not a fully general one, even for two shapelet components. We tie the ellipticities of the two components together, hold the center fixed, and keep their radii fixed at a value set in the configuration; this means we fit only one set of ellipse parameters, instead of two.