VLBI analysis technique which is being developed for three decades and it reached maturity. This means that no easy recipes for improvement precision and accuracy of results remained. Further improvement will require significant efforts. Comparison of Mark-3 experiments with the Mark-4 experiments which collected 5 times more bits, and were analyzed with technology developed in 1980s, shows only a marginal improvement at the level of 10%. This means that in order to utilize a 15-fold gain in the number of recorded bits of the Mark-5 1Gbs system we have to revise our approaches to VLBI analysis.

Prioritized list of tasks (most important first) which could improve accuracy of VLBI results:

1. Expansion analysis to the level of phases and amplitudes per channel, per accumulation period (AP), down from the level of normal points. Most important advantages: taking into account ionosphere contribution to delay at the AP-by-AP basis; solving G-code problems, computation of realistic errors of the estimates of group delays.
2. Understanding of VLBI error budget: both errors of delay estimation and errors of modeling.
3. Changes of analysis strategy from baseline-dependent approach to the station-dependent approach. Elimination of unnecessary redundancy.
4. Automation of analysis of log-files, including extraction of system temperature, post-correlator output and operational data analysis.
5. Modeling of source structure delay.
6. Development of the technology of analysis of observations of other types than 24 hour sessions of R4-type and 1.5 hour Intensive-type sessions: differential VLBI, astrometry of weak objects, space navigation, etc.
7. Improvements in troposphere modeling: IMF/VMF versus NMF2; going beyond an axial-symmetric mapping function.
8. Measurements of antennas: height calibration, measurement of antenna axis offset, direction of the fixed axis, etc.
9. Investigation of errors caused by polarization leakage and developments of methods for their calibration.
10. Application of a model of spurious signals in phase calibration for routine data analysis.

Last update: 04-FEB-2004 23:04:06
This web page was prepared by Leonid Petrov ()

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