Message-ID: <3C76CEAB.E756E739@jpl.nasa.gov>
Date: Fri, 22 Feb 2002 15:05:16 -0800
From: "Angelyn W. Moore" <Angelyn.W.Moore@jpl.nasa.gov>
To: igsmail@igscb.JPL.NASA.GOV
Subject: [IGSMAIL-3758]: TurboRogue L2 tracking
Sender: owner-igsmail
Precedence: bulk

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IGS Electronic Mail      22 Feb 15:05:18 PST 2002      Message Number 3758
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Author: Angelyn Moore

Dear Colleagues,

Recalling IGSMail #2071, TurboRogue receivers have been
known to experience significant degradation of L2 tracking
during times of high ionosphere.  
(http://igscb.jpl.nasa.gov/mail/igsmail/1998/msg00298.html)
This effect continues to be seen today in all TurboRogue 
stations not operating in a one-second sampling mode, and 
negatively impacts the IGS network effectiveness. 

A firmware upgrade for such receivers appears to 
correct this difficulty.  Several IGS stations have
utilized this firmware version and the L2 tracking
is seen to be restored at the time of the firmware 
installation.

I've prepared two graphs to demonstrate.
http://igscb.jpl.nasa.gov/images/aoa1_p2c1.gif shows
that tracking when P2-C1 exceeds 12m was restored
at the time of the upgrade.  (Although not too obvious
on this scale, the quantization effect for 8m<P2-C1<12m
is also removed).
http://igscb.jpl.nasa.gov/images/aoa1_l1l2.gif shows
over a few preceding days that the number of channels 
tracking dual-frequency declined to about 2 near 00:00UT 
every day (this is, predictably, near local noon). 
After the firmware upgrade, no such decrease is seen.

Similar studies for the few other stations using this
firmware corroborate.

All agencies operating TurboRogue stations are requested to 
test and install 3.2.32.11 as soon as possible, to restore these 
sites to reliable dual-frequency operation (as is required by
the IGS station guidelines!).  

Jim Holston (j_holston@aoa_gps.com; +1 805 495 8420) can be
contacted at AOA to arrange to receive the firmware.

Analysts wanting to examine the effect can check data
quality for sites that have had 3.2.32.11 installed 
before and after the firmware changes:

AOA1  y2002 d052
AOML  y2000 before d207 vs. after d229 *
DUBO  y2001 d023
HNPT  y2000 d222
SOL1  y2000 d242
USNA  y2000 d242
BRMU  y2001 before d093 vs. after d110

  * AOML was in operation between these days, but had
    an interim release of firmware during this time.

I ask that you please let us know at the CB of any relevant 
experiences in operating stations or using 3.2.32.11 data.

Please note that this firmware, while apparently restoring 
such stations to dual-frequency tracking, does not offer all 
the improvements of upgrading to a modern codeless receiver,
and agencies operating stations with cross-correlation 
receivers should continue to plan to upgrade to codeless 
receivers wherever possible.  Stations of high
importance to the IGS (for instance, ITRF sites or 
particularly remote sites with few nearby IGS stations)

Please note that this firmware, while apparently restoring 
such stations to dual-frequency tracking, does not offer all 
the improvements of upgrading to a modern codeless receiver,
and agencies operating stations with cross-correlation 
receivers should continue to plan to upgrade to codeless 
receivers wherever possible.  Stations of high
importance to the IGS (for instance, ITRF sites or 
particularly remote sites with few nearby IGS stations)
should take precedent in such planning.

Many thanks to Dave Stowers and Jim Holston for arranging
the AOA1 test and demonstration on short notice, and to all
site operators for maintaining accurate information in 
the site logs!!

With best regards,
Angie
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Angelyn W. Moore, Ph.D.              Deputy Director, IGS Central Bureau 
 JPL/Caltech                                 Angelyn.W.Moore@jpl.nasa.gov
 4800 Oak Grove Dr. MS 238-540                     voice: +1 818 354 5434 
 Pasadena CA 91109 USA   http://igscb.jpl.nasa.gov   fax: +1 818 393 6686