[IGSMAIL-1900] New estimated value for GPS43 antenna phase center offset
Yoaz
Yoaz
Thu May 14 16:02:45 PDT 1998
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IGS Electronic Mail Thu May 14 16:02:45 PDT 1998 Message Number 1900
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Author: Yoaz Bar-Sever
Subject: New estimated value for GPS43 antenna phase center offset
Dear Colleagues,
I have conducted a series of experiments designed to estimate the phase
center offset of the transmit antenna on GPS43 (PRN13, the new Block IIR
GPS satellite). The estimated value puts the phase center 59 cm ABOVE the
center of mass (i.e., 59 cm along the negative spacecraft-fixed Z axis).
This value differ significantly from the previously published values
(see IGS Mail 1653). A standard deviation of 13 cm is associated with this
estimate. These results are based on daily estimates of the transmit
antenna X, Y and Z offsets, spanning 31 days in December 97 and March 98.
The estimated X and Y offsets were statistically consistent with the
published zero values.
The JPL IGS Analysis Center has employed a value of -63 cm for the phase
center offset starting with the final orbit solution of March 30. The rapid
orbit solution has employed it since April 6. (The value of -63 cm was
based on a single day estimation, at the time.)
The main impact of this modeling change is on the clock solution
for the satellite. Due to the high correlation between the satellite
clock and the radial phase center offset, biases in satellite clock
estimates are to be expected between solutions using different phase
center offsets, with magnitudes similar to the difference in the offset.
Indeed, since march 30, the large bias in the clock estimates for
GPS43 between the JPL AC solution and the solutions from other Analysis
centers has lead to increased RMS difference between the JPL solution
and the IGS combined solution.
Sincerely,
Yoaz Bar-Sever
--
Dr. Yoaz E. Bar-Sever
yeb at cobra.jpl.nasa.gov MS 238-600
voice: (818) 354-2665 office Jet Propulsion Laboratory
(626) 794-9243 home 4800 Oak Grove Dr.
FAX: (818) 393-4965 Pasadena, California 91109
[Mailed From: yeb at cobra.jpl.nasa.gov]
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