VLBI observations require the transmission of raw data samples over very long distances. Progress is being made toward an ultimate goal of doing this in real time over fiber networks. But EVLBI, as such a system is called, is still only used for a small portion of VLBI observing and that is not likely to change in some regions until more affordable access to high bandwidth networks can be obtained.
Most VLBI relies on recording the raw data on magnetic media, and then shipping that media to a correlator where it is processed days to months after the observations are made. Managing those recordings, and the specification of the data streams to be recorded, is a major part of scheduling with SCHED. This section provides background on the various recording systems in use.
Please be aware that recording systems are a technology under rapid development. It is entirely possible that some of the sections here are not entirely up to date.