RSG1, RSG2, RSG3, etc were originally provided as spare real variables which could be ascribed values in (group 19 of) the Q1 file, and then transmitted to the solver module, EARTH, via the eardat file.
They reside in the file which is "included" in both SATELLITE and GROUND Fortran, namely: satgrd.
The common block /RSG/, which is dimensioned in main.htm has 150 elements; but, as will be seen, many of them have other names than RSGx.
These variables have, in the course of time, become PIL variables used for well-established purposes. For example,
The first 9 values have no currently-assigned purpose, and so may be safely used. However, users wishing to transmit real values to their coding in GROUND, are advised to use the RG( ) array, not any RSG value at all.