subroutine prdset - j.f.chandler - 1982 march
based on code from subroutine nrmict - m.e.ash, oct 1969
determine pointers for observation series and fill bernum common
called from nrmict or prdict

determine klans1 for a second observed body (ncodf.gt.20)
(see also below statements label=1400 and label=1500)
klans1 is largely a flag to indicate tape reading
for a second object - the object itself is nps1