<i>Mit Radiation Laboratory Series</i>

Pierce, J. A.; McKenzie, A. A.; Woodward, R. H.; Hamilton, D. R.; Knipp, J. K.; Kuper, J. B. Horner; Smullin, L. D.; Montgomery, C. G.; Voorhis, S. N. Van; Ridenour, Louis N.; Pierce, J. R.

doi:10.1063/1.3066043

Cited by 1 publication

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“…Until around 1980, Loran C was widely used to monitor time at VLBI stations. Loran, an acronym for Long Range Navigation, is a system originally developed during World War II for ocean navigation (Pierce et al 1948). The transmission frequency is 100 kHz.…”

Section: Time Synchronizationmentioning

confidence: 99%

Very-Long-Baseline Interferometry

Thompson¹,

Moran²,

Swenson³

2017

Astronomy and Astrophysics Library

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In 1967, a new technique of interferometry was developed in which the receiving elements were separated by such a large distance that it was expedient to operate them independently with no real-time communication link. This was accomplished by recording the data on magnetic tape for later cross-correlation at a central processing station. The technique was called very-long-baseline interferometry (VLBI), a term recalling the earlier long-baseline interferometers at Jodrell Bank Observatory, in which the elements were connected by microwave links that had reached 127 km in length. The principles involved in VLBI are fundamentally the same as those involved in interferometers with connected elements. The tape recorder and its successor, disk storage, can be considered as an IF delay line of limited capacity with an unusually long propagation time, weeks instead of microseconds. The use of tape and disk recording media is motivated entirely by economics and places substantial limitations on the system. Satellite links have been demonstrated (Yen et al. 1977), but their high cost discourages their use.Tape recorders have been entirely replaced by compact disks. Data can also be transmitted to correlation facilities via the Internet in quasi real time. However, latency and throughput are significant issues, and data buffering is usually required.

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Section: Time Synchronizationmentioning

confidence: 99%