Comparison of UTC(NICT)-UTC(NMIJ) via VLBI and GPS

1. [GPS Data] Time Standard Authorities are submitting the Time-link data to BIPIM, regularly. The time comparison data is available from follwing FTP site.
   ftp://ftp2.bipm.org/pub/tai/timelinks/lkc/
   We used "NMIJ-NICT" data in the directory . Data is here
2. [VLBI Data] Precise group delay observable obtained by brodband data were used. AB baseline data have been generated from OA and OB data with closure delay relation.

Results, Data plot

• UTC(NICT)-UTC(NMIJ) Time comparison data of UTC(NICT)-UTC(NMIJ) beasured by broadband VLBI and GPS-PPP(BIPM). Vertical position of VLBI data is shifted by 31.55 nsec offset.
  
• Precision of Data To indicate the precision of each data, difference between neigbouring data are plotted for VLBI and GPS.
  　　
• VLBI-GPS Data Difference between VLBI and GPS are plotted. Timing of VLBI data sampler is not resetted by 1PPS for all these period. Since signal path calibration data on [12 May] was applied to the VLBI exepriment [09 June], then clock comparison data is continuously connected. The adata of [21 April] was not used the same calibration data, though clock comparison data shows no significant jump. We do not have definite reason of that, but clock rate difference in order of 1.2e-16 s/s were observed between VLBI and GPS-PPP, at presetnt. This need to be investigated.
  Observation signal path was changed between June and July, there is a jump in clock comparison data btween [09 June] and [03 July].
  　
• Alan Standard Deviation for [21April]-[09June] The three experiments were not donducted in same interval, then Alan standard deviation (ASD) could not be computed for long span. The ASD value was almost consistent between experiment at Nov. 2016 and these exeriment in April-June 2017.
  

  The data of VLBI-GPS are plotted by shifting 21 days to show the interval of the experiment was not equal interval.	Alan Standard Deviation computed from data April-June 2017.	Alan Standard Deviation computed from data Nov. 2016.