ngo =1 effect on time delay
ngo =2 effect on doppler shift
ngo =3 effect on doppler shift phase delay
changes to media made by t.m. eubanks ---nov 1976
rtrn = value of correction calculated by media
rtrn (ngo = 3) = - rtrn (ngo = 1)

prmter(60) and prmter(61) /param/ (on &nmlst1)
are defaulted to zero in prmred
prmter(60) = static plasma density in atoms/cc at 1 a.u.
good estimate = 10  atom/cc at 1 a.u.
prmter(61) = time varying part of plasma -same units
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note : prmter(60) must be set in the &nmlst1
the default of 0 makes the media correction = 0
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