SCHED was originally written in about 1978 as the Caltech Package scheduling program for Mark II VLBI. Most Mark II observations done since then were scheduled with it. But the program is outlasting the system that it was designed to support. I began the process of removing Mark II from SCHED when I learned that it is still in use in some parts of the world. Therefore, it is being retained for now.
Mark II recording systems have been removed from most active VLBI stations and the main Mark II correlators are no longer operating. However, the system is not completely gone. An old Caltech correlator is being supported at Medicina and Mark II recording systems are being supported at a few places. For these reasons, the Mark II specific features of SCHED have not yet been removed.
Mark II observations typically use one of the Mark III or VLBA data aquisition system baseband converters (called video converters in the Mark III world). Therefore much of the setup information required for the wide band systems is also required for Mark II, although only for a single channel. A very few parameters are available that are only for Mark II and the descriptions of those parameters should be consulted. In the main program input, the only such parameter is TPREF which helps get the tape changes synchronized. In the tape initialization parameters, parameter TPTIME serves a similar purpose. The main schedule parameter AUTOTAPE has special meaning for Mark II observations. Other than these special cases, the parameters used for a Mark II project are essentially the same as for a wide band experiment. Of course, parameters related to control of the wide band tape systems are not needed.
Tape management for Mark II observations is simpler than for wide band observations. Normally the tapes are run continuously for 4 hours per tape and then changed, usually by hand. Correlator operators normally prefer is all tapes are changed at the same time, which can be arranged using TPREF or TPTIME. The schedule should have scan breaks at the tape change times (this will be forced by SCHED, so tape changes might be requested at odd times if scan breaks don’t occur at the nominal 4 hour intervals.
Below is an example of a simple Mark II schedule. Be warned that this aspect of SCHED is not being maintained because Mark 2 is no longer available at most stations. Also, this example is not being tested with each release.
Below is an example setup file for Mark II observations. This is the standard setup file nug6cm.set and contains the correct information for the VLBA and VLA, which no longer have Mark II recording equipment. For a real Mark II observations, the stations involved would have to be added.
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