W. Cannon
The Canadian S2-VLBI-System
 
                   ABSTRACT
 
 
The S2 VLBI System was developed in Canada as a low cost. high
preformance, 128 Mbit/sec VLBI system for use in geodesy and astrophysics.
It consists of the S2 VLBI Data Acquisition System, the S2 VLBI Data Record
System, the S2 VLBI Data Playback System, and the S2 VLBI Correlator. To date
there are approximately 55 S2 VLBI Data Record and Playback systems in use
for various astronomical purposes in more than a dozen countries. The S2 VLBI
system features a frequency agile local oscillator for geodetic applications
of group delay measurements by bandwidth synthesis (BWS) over 900 MHz as well
as a frequency agile VLBI correlator for processing frequency switched VLBI
observations. The S2 VLBI correlator also features multiple tone extractors
and pulsar gating capabilities as well as high frequency lobe rotators capable
of processing space VLBI observations with ther attendant high Doppler rates.
There are, in addition, three other ``S2 Capable'' VLBI correlators located in
Sydney Australia, Mitaka Japan, and St. Petersburg Russia, with a fourth under
development at the Astro Space Center in Moscow. These correlators are not
designed to accommodate all the features of the S2 system, in particular
frequency agile signal processing, but are nevertheless capable of processing
S2 VLBI data tapes in a subset of S2 operational modes. The Mitaka correlator
processes S2 data tapes by using S2 VLBI Data Playback Systems to copy them to
VSOP data tapes before correlation. Other S2 correlators make use of S2 VLBI
Data Playback Systems for direct input to the correlator. The Space Geodynamics
Laboratory has begun development of the S3/S4 family of VLBI Data Record and
Playback systems which will operate in the range from 1024 Mbit/sec to 4096
Mbit/sec and will feature a robotic tape changer for 24 hour unattended
operation.
 
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In Proceedings of the 13th Working Meeting on European VLBI for Geodesy
and Astrometry, Viechtach, 1999
 
Keywords: S2, VLBI terminal, recording system