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gaia data release 3 documentation

9.3 Input data treatment

9.3.3 Treatment of Sky Mapper windows


SM windows are 2D windows. The first step consists in binning the AC samples into one sample to get a 1D window with increased signal to noise. The 1D SM windows are then re-sampled using similar cubic spline interpolation as for the AF windows so that a ‘synthetic SM’ window is produced, constituted of (240 pixels AL × 1 pixel AC) with a pixel size=(19.6 mas × 2121 mas) for G > 13 mag.

Re-centring of the signal in SM windows

The SM re-sampled synthetic windows of each transit are then re-centred according to LPC values. The LPC and the maximum flux pixel position are compared as for AF windows and when the difference is >160 mas for quasars and galaxies (typical RMS of the differences over SM windows of all sources) the window is eliminated.

Filtering of samples

Each synthetic SM window is then re-binned into a 20 samples window corresponding to SM original dimensions. Considering the re-binned SM windows of all transits on a source, an iterative sigma clipping on individual samples of the window (following the same rules as for median AF windows) is applied.