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Session 107 - Radio Astronomy and VLBI Instruments.
Display session, Thursday, January 16
Although today's atomic clocks deliver excellent precision over minutes and hours, all are subject to significant decreases in statistical accuracy over much longer time periods. This is problematic when such clocks are used to time-stamp experiments with long durations. An excellent example is pulsar astronomy, which often needs to compare observations having sub-microsecond precision taken years apart.
A solution to the long term drift is to maintain a number of accurate time standards and reference them to each other. (For example, the United States Naval Observatory averages roughly 30 cesium clocks to produce the standard broadcast over GPS).
The Clock Comparator System (CCS) is a hardware and software tool developed at Arecibo Observatory to assist scientists in maintaining a highly accurate time base for experiments and observations by facilitating multi-clock referencing. The CCS consists of an accurate HPIB-compatible counter combined with an external multiplexer and a PC program written in Hewlett Packard's VEE programming language.
Arecibo uses a hydrogen maser as its master clock, which it references against several other atomic and GPS clocks to monitor the performance of all of the devices and to detect any unusual behavior. The CCS automates this process by repeatedly comparing and recording the difference between the 1 pulse-per-second output of any number of timing devices. This allows scientists to notice, with a minimum of delay, any drift in their time standard.
Program listing for Thursday