In this paper we describe the computer code GALAXY which calculates th
e excitation and ionization of a plasma, including the effect of the r
adiation field, whether incident on the plasma or generated internally
through the optical depth of the lines. In the absence of atomic data
provided by the user, GALAXY calculates energy levels and the electro
n collisional and radiative rates which link them, using simple scaled
-hydrogenic expressions. For relatively highly ionized systems this ap
proach is found to be sufficiently accurate to be useful in studies of
high-power laser-produced plasmas.