CONGO: First GPS/GIOVE Tracking Network for Science, Research

September 1, 2009 By: André Hauschild, Oliver Montenbruck, Peter Steigenberger, Urs Hugentobler, Uwe Hessels GPS World

Editor's Note: Septentrio Navigation wishes to clarify two things mentioned in this article.

The article suggests that the GeNeRx channels can track either the data or the pilot component, but not both. This is not correct. The GeNeRx receivers do track pilot and data together. For signal experimentation purpose, the GeNeRx can also be configured to ignore the pilot component and provide measurements and data from the data component only. This mode of operation, which is apparently the mode selected in CONGO, is primarily intended for signal analysis, and we don’t recommend it.

The large bias of 270 meters has been reported to ESA and the satellite manufacturers shortly after the initial in-orbit testing. The bias originates from differential group delay in the E5 and L1 signal paths in the satellites. Both GIOVE-A and GIOVE-B suffer from this abnormally large differential group delay (see for example the Septentrio-ESA joint paper at IONGNSS 2008, "Multipath and Tracking Performance of Galileo Ranging Signals Transmitted by GIOVE-B"). The GeNeRx receiver faithfully reports that delay. One option would have been to apply a corrective bias to the pseudoranges to hide this satellite-induced effect. In the GeNeRx, we opted not to apply any non-standard correction to the measurements and to report the true state of the signal in space.