mtf: Day Modulation Transfer Function

The Modulation Transfer Function, mtf, is a three dimensional, two-plane image generated during the GEOMPIPE subsystem of VMBICAL, consisting of a measure of the Modulation Transfer Function (mtf) in the first plane and its error in the second, for each point (minute) in a time series data set. In this file, time is along the x-axis and spatial frequency (1 / pixels) is along the y-axis. The mtf image is generated for each day of observation taken at a given network site.

The mtf is used during the MERGE pipeline stage, where the time series of the Spherical Harmonic Transform coefficients from each site are merged into one "Network Day." The mtf allows a measure of the quality of a given solar image, with respect to seeing distortions and imperfections in instrument optics. The value of the mtf is used at each data point to make corrections for seeing distortions and instrument effects; the value of the mtf and the error are used so that the contribution from that image may be weighted appropriately when the corresponding data point is merged into the network day time series.

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