The S2 very long baseline interferometry tape recorder

The S2 is a new generation very long baseline interferometry (VLBI) tape recorder designed at the Institute for Space and Terrestrial Science (ISTS). The unique features of the S2 are its use of consumer-type videocassette transports to achieve low-cost, high data rate, high-density recordings; modularity in system design and extensive internal system self-monitor and diagnosis; and standardized record and playback interfaces for VLBI systems compatibility. The S2 sustains a maximum data rate of 128 megabits per second for up to 8.5 h, and has a maximum storage capacity of approximately 4·10¹² bits; multiple S2´s may be used for increased data rates of 512 megabits per second and beyond. This paper reviews the role of the VLBI tape recorder in the signal-processing chain of a complete VLBI system, a system in which it may be argued that the VLBI recorder has historically been the weakest link, then describes the S2 and its key features which serve to increase the reliability of the recorder in the VLBI data acquisition process at the radio telescope and the general means by which S2 recorded data may be reproduced at the VLBI correlator