On a geodetic application of multiple-station very long baseline interferometry
L. Aardoom
Delft, 1972. 23 pagina's. ISBN-13: 978 90 6132 219 1. ISBN-10: 90 6132 219 7.
Summary
Multiple-station very long baseline interferometry (VLBI) is
considered from a geodetic point of view. An approach is outlined to
deal with relative phase delay data as obtained from measurements on
both artificial radio sources at finite range and natural sources at
infinity, observed in the simultaneous mode. The approach is basically a
range-differences method and allows a treatment in theoretically
convenient steps to which the several groups of parameters are primarily
confined. This paper deals mainly with the interstation geometry of the
VLBI-net.
Attention is drawn to the possible occurrence of singular geometric
situations of stations and sources for which no unique solution for the
interstation geometry is possible in spite of the presence of an in general
sufficient amount of measurement data. For a family of idealized model
four-station VLBI-nets a numerical estimate is made of the accuracy likely
attainable for the interstation distances, using two hypothetical
observation programmes with sources at infinity in supposedly unknown
directions. It was found that there is no unique solution if only one
natural source is used. In the other programme two natural sources are used
and variance-covariance matrices have been estimated with conventional least
squares techniques. A variety of declination differences, VLBI-net
orientations and maximum zenith distances is considered. It was found that
the ratio between estimated standard deviations of the interstation
distances and the range-difference measurements lies between 5 and 25 if 9
range-difference measurements are extracted from one pass of each of the two
sources, provided cases of marginal observability of one of the sources are
avoided and if it is assumed that the directions to the sources are not
restricted to zenith distances below 55°.
Station clocks are supposed to be perfectly synchronized.
Contents
Summary 4
1. Introduction 5
2. Interstation geometry and relative clock.offsets 6
3. Some simulation calculations 14
Acknowledgement 23
References 23