Phase delay ambiguity resolution in VLBI
Introduction
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.
Objectives
- Investigation of accidental and systematic errors of VLBI group delay
observables.
- Development algorithms for resolving phase delay ambiguities and
verification of correctness of made phase delay ambiguity
resolution.
- Investigation of limitation of developed approaches to phase delay
ambiguity resolution. Making conclusion about feasibility of
using phase delays in routine data analysis.
- Comparison of determination of geodynamical parameters obtained using
group and phase delay measurements.
Intermediary reports
- L. Petrov "VLBI phase delay ambiguity resolution project.
Preliminary report", (Unpublished).
pharep1.ps.gz (230Kb)
(Verbose report about the status of the project by 24-DEC-97)
- L. Petrov "Usage of phase delay measurements produced by VLBI for
geodetic applications", Annales Geophysicae, Supp. 1 to
Vol. 16, 1998, p. C399.
nice.ps.gz (151Kb)
(Full text of presentation at the General Assembly of EGS 20-24
April 1998, Nice)
- L. Petrov "Towards Phase Delay VLBI"
agu98.zip (2.4Mb)
(Viewgraphs presented at AGU Fall Meetings, December 1998,
San Francisco)
- L. Petrov "Feasibility of using phase delays in geodetic
VLBI data analysis"
final_phase.ps.gz (28Kb)
(Final report about investigation of feasibility of using phase
delay in geodetic VLBI data analysis), 06-APR-2000
Acknowledgment
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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Last update: 12-APR-2000 12:50:36