Subject: [IGSMAIL-1774] IGS/BIPM Project for Time and Frequency Comparisons
From: Jim Ray (USNO) and Claudine Thomas (BIPM)
Date: Tue, 6 Jan 1998 4:49:23 PST

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IGS Electronic Mail      Tue Jan  6  4:49:23 PST 1998      Message Number 1774
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Author: Jim Ray (USNO) and Claudine Thomas (BIPM)
Subject: IGS/BIPM Project for Time and Frequency Comparisons

     INTERNATIONAL   GPS   SERVICE   FOR   GEODYNAMICS    (IGS)
     BUREAU   INTERNATIONAL   DES   POIDS   ET   MESURES (BIPM)

                           CALL FOR PARTICIPATION

                                    IN AN

                           IGS/BIPM PILOT PROJECT

               TO STUDY ACCURATE TIME AND FREQUENCY COMPARISONS

                    USING GPS PHASE AND CODE MEASUREMENTS

Background
----------
The International GPS Service for Geodynamics (IGS) and the 
Bureau International des Poids et Mesures (BIPM) are 
establishing a joint Pilot Project for Time and Frequency 
Comparisons using GPS.  The goal of this Pilot Project is to 
investigate the use of GPS phase and code measurements to 
improve worldwide availability of accurate time and frequency.

GPS offers the opportunity for highly accurate time and 
frequency transfer among many remote sites.  In their analyses 
of GPS observations, the IGS Analysis Centers have the 
potential for determining clock differences with
uncertainties well below one nanosecond.  These results are 
comparable to those of the best techniques available.  To 
exploit this potential, however, important technical issues 
remain to be resolved, which this Pilot Project will 
investigate.

The Pilot Project is open to all relevant groups, agencies, and 
individuals. These activities are not intended to limit in any 
way the freedom of participants to engage in independent 
research.  The objective is to organize and coordinate efforts 
among groups to achieve the goals of the Project and to share 
resources, data, and experiences.  The Pilot Project will be
conducted by a Working Group formed by those responding to this 
Call for Participation.

Areas of participation
----------------------
It is expected that the goals of the Pilot Project will require 
activities in a variety of areas, including those listed below. 
Investigators are invited to participate in one or more areas.

1) Deployment of GPS receivers

   In addition to the GPS receivers already installed as part   
   of the IGS global tracking network, other receivers in       
   laboratories having accurate time standards are sought.      
   These should be high-quality geodetic receivers capable of   
   recording and rapidly transmitting dual-frequency code and
   carrier phase observations.  The station configuration and   
   data distribution should conform to IGS standards and        
   appropriate documentation must be filed with the IGS Central 
   Bureau; refer to
   http://igscb.jpl.nasa.gov/igscb/resource/newstation.txt.
   In addition, due consideration should be given to electronic 
   stability and environmental control.  Upgrading of existing  
   tracking stations for better timing performance is also      
   encouraged.

2) GPS data analysis

   Strategies for analyzing GPS phase and code observations     
   must be developed, consistent with other IGS products, to    
   allow the routine, accurate characterization of time         
   standards at a large number of independent GPS receiver      
   sites.  This work will be done in close cooperation with the
   IGS Analysis Coordinator.  It is expected that regular       
   reports will be issued by participating analysis centers,    
   analogous to those distributed by the IGS for other          
   activities; refer to
   http://igscb.jpl.nasa.gov/mail/IGSREPORT.html.

3) Analysis of instrumental delays

   In order to relate clock estimates derived from GPS data     
   analysis to external timing standards it is necessary to     
   understand the instrumental electronic delays introduced by  
   the associated hardware.  Studies are sought to characterize 
   the short-term and long-term sensitivities to
   environmental changes and to develop calibration methods.    
   Differences for the L1 and L2 frequencies must be            
   considered.  Studies of both GPS ground sites as well as the 
   GPS satellites are sought.

4) Time transfer comparisons

   Simultaneous, independent time and frequency comparison data 
   are needed to compare with the GPS-derived estimates.        
   Collaborations are sought with groups performing time        
   transfer experiments using a variety of techniques.
   Close cooperation is expected with the Consultative          
   Committee for Time and Frequency (CCTF) of the Comite        
   International des Poids et Mesures (CIPM).

Data exchange
-------------
GPS observational data should be distributed using the IGS 
hierarchy of data centers and appropriate standards and 
formats.  Analysis reports should be distributed electronically 
as part of the IGS Reports series.  In addition, an e-mail 
exploder list will be assembled to allow a free exchange of
communications among Working Group members and a World Wide Web 
site will be constructed for the Pilot Project.

Organization
------------
The Pilot Project will be conducted by the Working Group formed 
by this Call for Participation.  The operation of the Working 
Group will be self-directed through consensus of the 
participants.  Subdivision of the Working Group into topical 
sub-groups may be considered.

The Working Group will be co-chaired by:
  Dr. Jim Ray (USNO), representing IGS
     e-mail = [email-masked]
  Dr. Claudine Thomas, representing BIPM
     e-mail = [email-masked]

Schedule
--------
It is anticipated that the schedule of activities will be 
reasonably flexible. However, for planning purposes the 
following schedule is suggested:

   01 Jan. 1998 -- Call for Participation distributed
   15 Mar. 1998 -- Responses to Call for Participation due
   01 Apr. 1998 -- Establishment of Pilot Project Working Group
   01 Jun. 1998 -- Target for publication of first analysis     
                   report
      Dec. 1998 -- Interim report to IGS Governing Board
    Spring 1999 -- Report to Consultative Committee for Time    
                   and Frequency
      Dec. 1999 -- Final report to IGS Governing Board

Response form
-------------
Investigators interested in participating in this Pilot Project 
are asked to return the following reponse form by 15 March 1998 
to Jim Ray at the e-mail address: [email-masked], and 
to Claudine Thomas at the e-mail address: [email-masked].

----------------------------------------------------------------
Response to CALL FOR PARTICIPATION in an

   IGS/BIPM PILOT PROJECT TO STUDY ACCURATE TIME AND FREQUENCY  
        COMPARISONS USING GPS PHASE AND CODE MEASUREMENTS

Agency or group:

Contact person(s):

E-mail address(es):

Areas of participation:
   1) Deployment of GPS receivers:          Yes or No
   2) GPS data analysis:                    Yes or No
   3) Analysis of instrumental delays:      Yes or No
   4) Time transfer comparisons:            Yes or No
   6) Other:                                (please list)

Limitations on participation: (please list any restrictions)

Comments or suggestions:

Please return to [email-masked] and [email-masked], 
preferably by 15 March 1998
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[Mailed From: Jim Ray (USNO 202-762-1444) <[email-masked]>]