ASTRO enables to prepare the line observations with the Plateau de Bure
interferometer by plotting the frequency coverage of the line correlator for a
given rest frequency. The LINE command should be entered as in
OBS on Plateau de Bure. The syntax is:
LINE name frequency band Lock Center Harm
(only the first four arguments are mandatory). The coverage of
the line backend for both upper and lower sidebands is drawn if option
/SPECTRAL is present. Markers may be drawn for
a few by giving the option /MOLECULES file with the specification
for a text file containing, in the first column, the frequencies in GHz,
and in the second column, the line names to be used by GreG
(between single quotes; use of GreG control codes is possible).
The default file name for /MOLECULES is GAG_MOLECULES.
The Doppler correction for the last used object is used in the calculations. This is of some importance since Doppler tracking is correct only in the signal side band. The Doppler scale is exact in the image side band when the frequency is loaded in OBS, but subsequent tracking is computed for the signal side band only. The tracking error in the image side band is 0.04 km/s at 86 GHz, in the worst case (see the document on Frequency Setup, by S. Guilloteau).