The user has to give the following input:
Parameters of source:
a) source coordinates (
,
), accurate to about 
b) epoch and reference for these coordinates
c) heliocentric radial velocity of the source (-10000 to 999999 km/s).
The usual convention 
is followed, i.e. not the
relativistic formula
Parameters for each of up to 64 wavelengths to be observed with the F-P:
d) Central vacuum rest wavelength in 
m (Note: check against limits of
allowed wavelength range is done after correcting for radial velocity)
e) Velocity range to be covered (50 to 1000 km/s). Scan is centered
around central wavelength
f) Expected flux density (Jy) of the source at the observed wavelength,
i.e. the sum of continuum and line flux density.
This flux density is used to set the electronics gain, and serves as a
reference for which the required signal-to-noise ratio is to be obtained
g) Required signal-to-noise ratio per resolution element, for the expected
flux density
Parameters for each of up to 64 wavelength ranges to be observed with the
SW grating:
h) Start vacuum rest wavelength in m
i) Reference vacuum rest wavelength in m. This wavelength is used for
signal-to-noise computations (see k,m). Additionally it may be used for
additional photometric checks by frequency switching. Therefore, it should
preferably be in a region with smooth spectrum
j) End vacuum rest wavelength in m
k) Expected flux density (Jy) at the reference wavelength. Used to compute
signal-to-noise
l) Expected peak flux density (Jy) within chosen range. Used to set gain to
avoid saturation e.g. by a bright line within the range
m) Required signal-to-noise ratio at reference wavelength