Properties of the CCD

The purpose of this page is to describe some fundamental properties of the CCDs used in the telescope modules of eROSITA which are relevant for pipeline processing and data analysis.

CCD dimensions

NXDIM = 384 for eROSITA
NYDIM = 384 for eROSITA
PIXLEN_X = 75.0 [micron]
PIXLEN_Y = 75.0 [micron]

The framestore area is not considered (could be represented as negative Y values if needed)

CCD coordinates [pixel]

Origin: lower left when seen through the telescope onto CCD and read-out from top to bottom:

RAWX [1..NXDIM] integer values, shifted by 1 with respect to telemetry
RAWY [1..NYDIM] integer values, shifted by 1 with respect to telemetry

The RAW[X|Y] integer values refer to the centre of each detector pixel, pixel boundaries are "0.5" values (lower-left pixel from 0.5 to 1.5)

Needed for sub-pixel analysis (centre of mass of component pixel charges assigned to the main event of recombined pattern):


        SUBX I*1 (unsigned)     sub-pixel resolution: micron/2, i.e. 150 sub-pixels per detector pixel

        SUBY I*1 (unsigned)     SUB[X|Y] = 127-75...127+74; the centre of a detector pixel corresponds 
                                to the SUB[X|Y] coordinate (126.5, 126.5) i.e.,
                                real valued RAW[X|Y]_r = real(RAW[X|Y]) + real(SUB[X|Y]-126.5)/150.0; 
                                if TSCALn = 6.66666666666667D-3 and TZEROn = 8.43333333333333D-1 are set, 
                                SUB[X|Y] can be read directly as fractional RAW[X|Y] values ie., 
                                RAW[X|Y]_r = real(RAW[X|Y]) + real(SUB[X|Y])