VLBI observations are unique in that we don't (can't) steer the sky frequency according to the rest frequency and object velocity. Instead, the sky frequency is held to what is dialed in manually at the receiver. To get the radial velocities right in the CLASS spectra, we put FEORGA in a mode where it modifies the object velocity so that if it could tune the receiver, it would tune it to the sky frequency that we're using for VLBI. Actually, there are two frequencies planned for the April 2002 VLBI: 147 GHz (which is very close to the CS(3-2) rest frequency) and the rest frequency of the SiO(3-2)v1 line. There's a script can be used to put FEORGA in this mode or put it back into the normal mode. Type @TEL$OBS:VLBI_FREQ CS or @TEL$OBS:VLBI_FREQ SIO or @TEL$OBS:VLBI_FREQ NONE In addition to specifying the VLBI sky frequency, the script automatically executes the appropriate LINE command. If you forget to do this script, the VLBI data will still be recorded, but the CLASS header will have the standard object velocity, so the lines will appear to be at the wrong radial velocity. If you go back to normal observing and forget to turn off the FEORGA mode, the receiver will not be tuned to the line/velocity you want. One more thing: In VLBI mode, you ought to depress the VLBI button. This disables the START button. Instead, the Start will happen when the OBSINP MEAS command is given (which is incorporated in the VLBI OBST scripts). This is meant to get the telescope to start observing at a time controlled by OBST.