L. Gradinarsky
Comparison of atmospheric parameters estimated from VLBI, GPS and microwave 
radiometer data
 
                   ABSTRACT
 
 
Very Long Baseline Interferometry (VLBI) is colocated with a
permanent Global Positioning System (GPS) receiver and a Water Vapour
Radiometer (WVR) at the Onsala Space Observatory (OSO). Both VLBI and
GPS data
are affected by the propagation delay of radio waves in the atmosphere,
while
the WVR is sensitive to the atmospheric emission close to the center of
the 22
GHz water vapour emission line and provides wet delay estimates. We
present a
comparison of estimated atmospheric parameters (equivalent zenith wet
delay
and linear horizontal delay gradients) derived from  an independent
analysis
of simultaneous VLBI, GPS and WVR observations. We study and compare the
estimated parameters using different elevation cut off angles for the
analysis
of VLBI data with those obtained from the GPS and the WVR data analyses.
The
parameters are estimated for 90, 180 and 360 minutes long intervals,
which
allows us to study the averaging effect on the integrated parameters of
the
turbulent atmosphere.
 
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In Proceedings of the 13th Working Meeting on European VLBI for Geodesy
and Astrometry, Viechtach, 1999
 
Keywords: wet delay, horizontal gradients, VLBI, GPS, WVR,