code db-name sked db 5-9 used fit eps Y UT1 rd0202 $02MAR05XA 2090 1889 1704 1663 12 55 51 2.3 rd0204 $02APR03XA 2032 1952 1776 1733 11 50 50 2.2 rd0205 $02MAY15XA 1915 1035 905 877 12 70 86 4.5 rd0206 $02JUN12XA 1962 1874 1712 1671 17 83 79 3.6 rd0207 $02JUL10XA 1953 1416 1300 1275 14 80 70 2.9 rd0209 $02NOV06XA 2031 1859 1229 1180 8 68 55 2.3 rd0210 $02DEC04XA 2049 1947 1836 1787 9 52 51 2.2
code db-name sked db 5-9 used fit eps Y UT1 r1009 $02MAR04XA 4596 4240 3866 3853 21 48.6 60.2 1.8 r1013 $02APR02XA 3277 3121 2890 2856 23 62.3 67.7 2.0 r1019 $02MAY13XA 2468 2324 1928 1857 25 50.5 55.3 2.3 r1023 $02JUN10XA 2565 2425 2124 2106 29 49.0 57.7 2.4 r1027 $02JUL08XA 3596 2731 2403 2295 24 76.0 83.5 2.1 r1044 $02NOV04XA 3411 3103 2809 2793 21 65.0 69.4 2.0 r1048 $02DEC02XA 3319 3083 2916 2875 21 60.8 63.2 2.0
code db-name sked db 5-9 used fit eps Y UT1 r4010 $02MAR07XE 1325 1298 1231 1206 23 57.6 60.8 2.1 r4014 $02APR04XE 1757 1718 1575 1554 21 55.7 52.4 2.2 r4020 $02MAY16XE 744 702 648 644 21 73.5 71.0 2.9 r4024 $02JUN13XE 1432 1390 1149 1121 30 82.4 87.3 4.1 r4028 $02JUL11XE 1587 1543 1396 1370 22 55.0 62.4 3.0 r4045 $02NOV07XE 1393? 1745 1566 1554 18 57.3 60.9 2.6 r4049 $02DEC05XE 1618 1245 1141 1128 18 77.7 91.3 3.0 sked -- number of scheduled observations db -- number of correlated observations 5-9 -- number of pairs of observations with quality codes 5-9 used -- number of used observations fit -- wrms of postfit residuals in psec eps -- formal uncertainties of the estimates of nutation in obliquity (muas) Y -- formal uncertainties of Y polar motion (muas) UT1 -- formal uncertainties of UT1 estimates (musec)
--------------------|---------|---------|---------| | R&D | R1 | R4 | --------------------|---------|---------|---------| X-pole (uas) | 167.2 | 131.1 | 81.9 | Y-pole (uas) | 72.6 | 107.9 | 99.9 | --------------------|---------|---------|---------|(hint: standard deviation of the rms over 7 points is about 50% of the rms itself)
These tables show that high SNR R&D experiments give EOP with formal uncertainties not worse than R1, R4 and even better.
Investigation of IMF shows that troposphere is not the major source of errors in VLBI results. Imperfection of the geophysical models is, certainly, the factor neither. The major factor which limits precision and accuracy of VLBI is INSTRUMENTAL ERRORS. So, the main reserve in improvement of VLBI results is development of a technology which would allow us to investigate, understand and eventually reduce effect of instrumental errors. High SNR sessions are the most advantageous for this strategy: when the level of noise is reduced, instrumental effects became more visible.
High SNR experiments are inevitable in the future. How it was already shown, antennas' slewing sets the limit of the number of observations per sessions. Current R1 sessions are rather close to this limit. So observing in 1 Gb/sec mode we will not in a position to set significantly more scans than in R1 (in fact, no more than 30% than in R1). But we can increase SNR limit. The challenge is to transform high SNR in high accuracy. We tried high number of scans approach. We see it does not work. Let's try high SNR strategy. I propose to change the SNR limit in R1 sessions to 80/60 -- the same as it was in the R&D sessions.
Last update: 27-FEB-2003 18:32:48