Phase delay ambiguity resolution in VLBI


Method of very long baseline interferometry (VLBI) provides measurements of 4 basic observables for X (8.2GHz) and S (2.2GHz) bands: group delay, delay rate, multiband phase delay and amplitude of coherence function. Group delays are traditionally used for analysis of geodetic VLBI sessions. Precision of group delays measurements is 5-100 psec (2-30 mm). Precision of phase delay measurements is roughly 40 times better, but we can measure phase delay in contrast to group delay only up to unknown number of phase cycles. Observed phase delays at X-band have ambiguities 122 psec (3.6 cm) and phase delay at S-bands have ambiguities 451 psec (13 cm). We can use phase delay observables in LSQ adjustment procedure only after resolving phase delay ambiguity. In contrast to GPS pseudo-range observables adjacent VLBI measurements are not in general phase-connected. Tiny spacing of ambiguities puts serious difficulties before the problem of VLBI phase delay ambiguity resolution.


Intermediary reports

  1. L. Petrov "VLBI phase delay ambiguity resolution project. Preliminary report", (Unpublished). (230Kb)
    (Verbose report about the status of the project by 24-DEC-97)

  2. L. Petrov "Usage of phase delay measurements produced by VLBI for geodetic applications", Annales Geophysicae, Supp. 1 to Vol. 16, 1998, p. C399. (151Kb)
    (Full text of presentation at the General Assembly of EGS 20-24 April 1998, Nice)

  3. L. Petrov "Towards Phase Delay VLBI" (2.4Mb)
    (Viewgraphs presented at AGU Fall Meetings, December 1998, San Francisco)

  4. L. Petrov "Feasibility of using phase delays in geodetic VLBI data analysis" (28Kb)
    (Final report about investigation of feasibility of using phase delay in geodetic VLBI data analysis), 06-APR-2000


This work is being done within the framework of the project "Nutzung von Phasenmessung in der geodaetischen VLBI" (Using phase delay in geodetic VLBI) supported by DFG (Deutsche Forschungsgemeinschaft), research grant CA 92/7-1.
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This page was prepared by Leonid Petrov
Last update: 12-APR-2000 12:50:36