NRCO-113: EPIC vignetting calibration: raster observation of G21.5-00.9

We propose to reobserve G21.500.9 on 9 raster positions, covering the fullrange of offaxis angles from 0 to 13 arcmin, and carefully selecting theregions on both MOS2 and PN, with no chip gaps and bad columns. We shall coverall MOS2 CCDs and in addition we add 3 more raster points in the central one.Based on the previous observations, using an exposure time of 10 ks perobservation, we shall achieve excellent statistics: expected 4000 counts in thehard band 210 keV, sufficient to allow derivation of the vignetting withsmall uncertainties. G21.500.9 has an excellent visibility for full revolutions in MarchApril2021, thus all 9 rasters could fit into one revolution. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]