EndRun Meridian II, Руководство пользователя

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M e r i d i a n I I U s e r M a n u a l 132
C H A P T E R E L E V E N
133 M e r i d i a n I I U s e r M a n u a l
R E A L - T I M E I O N O S P H E R I C C O R R E C T I O N S ( R T I C )
another method, as only a high-performance cesium frequency standard is stable enough to act as a
filter for the timing errors caused by the GPS broadcast model. The following phase plot shows the
Meridian II with the RTIC option active (blue) compared to what the Meridian II performance would
have been using the GPS broadcast model (red). Throughout the 10-day test period the RTIC option
demonstrated substantial improvement to frequency and time-domain stability through real-time
ionospheric delay measurements and compensation.
Performance Verified at National Institute of Standards and Technology (NIST)
To characterize the performance gain of the RTIC Option, a Meridian II was sent to NIST in May of
2016, where its 1PPS output was monitored continuously relative to UTC(NIST) for over 30 days.
The RTIC Option was active in the Meridian II during this time. The ionospheric delay corrections
calculated using the broadcast ionospheric model, along with the real-time corrections computed
using the RTIC Option, were logged. With these logs, the NIST timing measurements were post-pro-
cessed to determine what the performance would have been if the RTIC Option had not been active,
and the broadcast model had instead been used.
The following chart shows the difference in stability between the two delay compensation methods of
the Meridian II, along with the stability of the two performance levels of HP 5071 Cesium standards
for comparison. The Meridian II stability performance with the RTIC option exceeds the standard HP
5071 Cesium at all measurement intervals and exceeds the High Performance HP 5071 after 300,000
seconds.