The S2 system is no longer in use. This subsection of the recording systems section has been moved here for historical reasons.
The S2 system has been developed in Canada to support the Orbiting VLBI missions VSOP and Radioastron, in addition to ground based astronomy. It is based on VCR technology and is relatively inexpensive. It is being used in Australia on the AT and at a number of other sites around the world.
SCHED supports observations on telescopes that have S2 recorders and are controlled through the Field System (FS9.3.7 or higher). This is also done by creating a *.vex file in the VEX format (see section on MkIV).
The telescopes are characterized by RECORDER = S2 and CONTROL = VEX. Currently DAR = VLBA is completely supported (it could be possible to also implement DAR = MKIV). For any other DAR SCHED will attempt to schedule the observation with a ``standard'' S2 mode, not using any knowledge on the content of the ``user signal''.
The modes supported for DAR = VLBA can be derived from a document ``Compatibility of S2 and VSOPT recordings at S2 and VSOPT Correlators'' by R. Wietfeldt, available at ftp::s2.sgl.ists.ca:pub/s2/svlbi/s2vsop_compat_memo_v*.ps.Z.
Because the S2 recorders work in a way conceptually different from VLBA (or MkIV) recorders, the user should bear the following in mind when scheduling for S2 recorders.
Please note that no operational tests with SCHED and S2 recorders have been completed yet, except for VSOP recording. Recently (Dec 2000) it was discovered that observations that use more than 1 group of transports (thus not VSOP modes) would not switch groups. This should have been fixed.