Subject: [IGSMAIL-2136] "Fiducial" clock sites
From: Jim Ray
Date: Tue, 26 Jan 1999 10:22:40 PST

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IGS Electronic Mail      Tue Jan 26 10:22:40 PST 1999      Message Number 2136
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Author: Jim Ray
Subject: "Fiducial" clock sites

To:     Operators of the following IGS sites --

  ALGO,  BRUS,  DRAO,  FAIR,  FORT,  GODE,  GOL2,  HOB2,  IRKT,  KOKB,
  MATE,  NLIB,  NRC1,  NYAL,  ONSA,  PIE1,  TID2,  USNO,  WES2,  WTZR,
  YELL

  HRAO,  MDVO,  MEDI,  METS,  MKEA,  NOTO,  GRAZ,  MAS1,  MDO1,  TSKB,
  VILL,  YAR1

Dear Colleagues,

The IGS is in the process of expanding its set of products to include
combined estimates for the receiver clocks at the tracking stations, in
addition to the satellite clock estimates already provided in the sp3
files.  This work is being done in conjunction with the joint IGS/BIPM
timing project (see http://maia.usno.navy.mil/gpst.html for details).

As part of this effort, clock estimates from stations equipped with
high-performance frequency standards (H-masers mostly) will allow more
precise alignment of the clock solutions from the Analysis Centers
relative to one another and better relative weightings.  This was
described by Springer, Zumberge, and Kouba (1998) in their position
paper at the Darmstadt Analysis Workshop.

In order to do this, there must be a sufficient number of reliable
receiver clocks in common among the AC solutions.  A set of "fiducial
clock" stations has been developed, including primarily sites from the
47 reference frame sites which have stable frequency standards, plus
a few IGS sites at timing labs in preparation for eventually linking
the IGS clock products to TAI.  Some additional sites equipped with
H-masers but not included among the RF47 set have also be considered.
The full list of fiducial clock stations is given at the top of this
message.

The complete IGS clock analysis plan, developed among the ACs and
the Analysis Coordinator, is available at
http://maia.usno.navy.mil/gpst/anals-plan.

This message is to inform "fiducial clock" station operators about
this plan and to request your cooperation.  In particular, it would
be very helpful if you could report any change in the status of your
frequency standard or any other operational aspect that could affect
the timing performance of your station.  Changes of general interest
(such as a new frequency standard) should be reported as IGS Mail
messages.  Notification of other changes expected to affect timing
users only can be sent to me <[email-masked]> to post at
the IGS/BIPM web site.

In addition, maintaining up-to-date IGS site log files is very
important.  You are encouraged to include "Additional Information"
in the log files for such items as the model type and environmental
control for the frequency standard, and cable types, lengths, and
stability specifications.

Your assistance is greatly appreciated and valued.

Thanks and regards,

--Jim Ray, IGS/BIPM Timing Project co-chair
           http://maia.usno.navy.mil/gpst.html

[Mailed From: Jim Ray (USNO 202-762-1444) <[email-masked]>]