Electron 1D VDFs used for cross calibration of SWA-EAS heads. Top left: VDF of solar wind electrons as a function of E, constructed from the (black) SWA-EAS 1 and (red) SWA-EAS 2 head by including only the elevation and azimuth bins closest to the +z direction in the instrument frame. The pink shadowed region marks the energy range we analyze in this study. Top right: Histogram of the ratio values of the VDF constructed from SWA-EAS 1 measurements, divided by the corresponding VDF constructed by SWA-EAS 2 measurements. Bottom left: Same as in the top left panel, but with SWA-EAS 2 measurements multiplied by 1.66. Bottom right: Corresponding ratio after the multiplication.