The OBS Modes

The OBS program is a general purpose command program for the interferometer. It offers 4 different operating modes, selected by the OBS $\backslash$SET MODE command

SET MODE CONFIGURE is used to specify the hardware configuration of the array. This is not an observing mode. This mode must be used to indicate any hardware configuration change. Resuming observations while in this mode can only be done using the SET $\backslash$OBSERVE command.

SET MODE OPTICAL is used for optical pointing of the telescopes. The optical pointing constants and refraction coefficients are sent to all antennas.

SET MODE TEST is used either to calibrate the correlator bandpass or for tests. No antenna motions, nor receivers are required in this mode. No delay and phase tracking is done.

SET MODE INTERFEROMETER is used for interferometric observations. It allows auto-correlation, cross-correlation and specific procedures for calibration (OBS $\backslash$CALIBRATE and OBS $\backslash$SKYDIP), pointing and focussing (commands OBS $\backslash$POINTING and OBS $\backslash$FOCUS use the correlators output).