An on-line computer has been in use at Jodrell Bank since 1964, both controlling the Mk II radio telescope and performing data processing functions in connection with it. However this system is now being superseded, and the following describes the present state of development, including some facilities that are only now being constructed.

An Argus 400 computer is associated with each of the two main telescopes. Each has 12 000 words of core store, the word length being 24-bits, and the time for obeying most functions is 12 μs. The 24-bit word length is well suited to the application since more than 16-bit accuracy is required in the coordinate transformation. This fact, and the very versatile organization of the Argus computer, makes the effective speed relatively higher when compared with faster machines of smaller word size. In addition a drum store of about 50,000 words capacity will be fitted to each machine, and CRT and graphical output devices are available. Each machine operates a permanent program, which performs a number of functions, including in the case of the Mk II telescope the control of the instrument itself. In addition, up to three “user” programs may be operated simultaneously; these may be on-line data collection, with links to the telescope control sections, or completely off-line background jobs. A wide selection of library routine, available to all programs, is permanently in the core store, and this makes the writing of programs a relatively simple matter.