[IGSMAIL-0875] TurboRogue V3.0 Software Bug Discovered

[Ulf]

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IGS Electronic Mail      Wed Feb  8  8:04:12 PST 1995      Message Number 0875
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Author: Ulf J. Lindqwister/JPL
Subject: TurboRogue V3.0 Software Bug Discovered

We were recently informed by several investigators performing regional GPS
campaigns that they were unable to perform carrier phase ambiguity resolution
(bias fixing) with any TurboRogue data since about November (the V3.0
distribution date). After looking into the matter during the last couple of
days, the software engineers for the TurboRogue discovered that, in fact, the
V3.0 tracking loop software incorrectly formats the 30 second cross-correlation
L2 phase data type. This error in formatting results in a "random" fractional
bias being added to every L2 phase value during a track. Bias-free results are
evidently OK.

The bias is different for each satellite track (and receiver) so it will
not difference out. Presently there does not seem to be a way to remove the bias
in post-processing. We believe the error has been fixed in the latest software
version (V3.2), but we are awaiting results from zero baseline analysis to
confirm this. The new TurboRogue software version will be released as soon as we
have confirmed the recent fix. Thanks to Yehuda Bock, Tom Herring, Greg Lyzenga,
and Andrea Donnellan for help pointing us in the right direction towards
discovering the problem.  Please direct specific follow-up questions regarding
the bug to Tom Meehan in the receiver development group at JPL.

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Ulf J. Lindqwister                 Telephone:   (818) 354 1734
GPS Networks & Operations Group    FAX:         (818) 393 4965
Jet Propulsion Laboratory          Email:       ujl at logos.jpl.nasa.gov
4800 Oak Grove Dr.
Pasadena, CA 91109
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[Mailed From: Keith F. Stark <stark at cobra.jpl.nasa.gov>]