[IGSSTATION-4679] spurious navigation messages for PRN24/SVN24

Jake Griffiths Jake.Griffiths at noaa.gov
Tue Nov 29 11:37:01 PST 2011


Author: Jake Griffiths

Dear Colleagues,

The daily broadcast navigation (brdc) file at NASA/CDDIS is created by 
concatenating nav records collected at a set of global (IGS and non-IGS) 
tracking stations.  The Analysis Coordinator (ACC) uses the brdc file for 
various aspects of the orbit combinations. On three days in the past week, 
spurious PRN24/SVN24 records have caused ACC processes to fail. The most recent 
event happened today for yesterday's observations (i.e., brdc3320.11n).

Recall that PRN24/SVN24 was set unusable and stopped transmitting on September 
30, 2011. It was then decommissioned on Nov 4, 2011.

A search of the IGS station-specific nav files at CDDIS for year=2011 and 
doy=332 uncovered the following IGS stations (and receivers) reporting obs for 
PRN24/SVN24:

SITE  RECEIVER TYPE         FIRMWARE VERSION
---------------------------------------------
ankr  TPS E_GGD             2.6.1 Jan,10,2008
badg  JAVAD TRE_G3TH DELTA  3.2.7 May,16,2011
bzrg  LEICA GRX1200GGPRO    7.80/3.019
conz  LEICA GRX1200+GNSS    8.20/4.007
darw  LEICA GRX1200GGPRO    8.20/3.019
dlft  JPS LEGACY            2.6.1 Jan,10,2008
hers  SEPT POLARX3ETR       2.1
hofn  TPS E_GGD             2.6.1 JAN,10,2008
hueg  JPS LEGACY            2.6.1 JAN,10,2008
joz2  LEICA GRX1200GGPRO    8.20/3.019
joze  TRIMBLE 4000SSI       7.29
mac1  LEICA GRX1200+GNSS    8.10
mad2  ASHTECH Z-XII3T       1L01-1D04
maw1  LEICA GRX1200GGPRO    8.01/3.019
nano  LEICA GRX1200GGPRO    7.80/3.019
rcmn  LEICA GRX1200GGPRO    GSW
sass  JPS LEGACY            2.6.1 JAN,10,2008
str1  LEICA GRX1200GGPRO    8.20/3.019
titz  JPS LEGACY            2.6.1 JAN,10,2008
tow2  LEICA GRX1200GGPRO    8.20/3.019
wroc  LEICA GRX1200GGPRO    8.20/3.019
yar3  LEICA GRX1200GGPRO    8.20/3.019

While there are common threads in this list, it is unclear to me what may be 
causing the spurious records. If you operate a station with one of these 
receivers, perhaps refreshing the almanac would eliminate the problem. 
Otherwise, there may be firmware updates that could help. Unfortunately, I have 
no other ideas. But any progress on solving these issues would be helpful to the 
ACC.

Thanks for your time.

Best regards,

jake



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