USNO GPS Carrier-Phase System Map and Data Source

Introduction

Our GPS CP site map begins with the phase-center of the antenna and will progress along the hardware and data path until we reach the USNO operational Master Clock known as USNO(MC2). First, the IGS keeps site information forms for all the IGS stations. The code for our Washington, DC primary Master Clock site is USNO and the code for our Alternate Master Clock site located at the home of the GPS Master Control Station near Colorado Springs, CO is AMCT.

The following is an image showing the location of our Dorne Margolin T GPS antenna on the parapet of our Building 52 in Washington, DC. The phase-center of this antenna is the reference point for all geodetic and frequency measurements currently made. Several calibration schemes for getting absolute time are currently being developed and evaluated.

(USNO Image - GIF - 167Kb)

The following is an image of our geodetic quality AOA TurboRogue SNR12 receiver located at our USNO timing facility.



(USNO Image - GIF - 87Kb)

Our USNO TurboRogue receiver has an external 5 MHz source supplied by a hydrogen maser source through an Auxiliary Output Generator (AOG) and known as USNO(MC3). USNO(MC3) is steered to our operational Master Clock on our campus which is also a hydrogen maser source through an AOG and known as USNO(MC2). USNO(MC2) is our reference source for TWSTT and other GPS timing products.

Basic system diagram for USNO TWSTT and IGS TurboRogue.


<HR>


                                       USNO

                Link to AMC(MC1)     
                                 *                               USNO
                         O       *                             GPS Ant.
                          \     *                           
                   **      \   *                            |-|-|-O-|-|-|
                     ***____** TWSTT Ant.                         | 
                           |                                      | 
                           |                                      | 
     -------------    -----|-----      -----------           -----------
     |           |    |  USNO   |      |  USNO   |   5MHz    |  USNO   |
     |  H-maser  |--->|  (MC2)  |----->|  (MC3)  |---------->|  Turbo  |
     |  Source   |    |  (AOG)  |      |  (AOG)  |           |  Rouge  |
     |___________|    |_________|      |_________|           |_________|


<HR>

Basic system diagram for USNO AMC TWSTT and IGS TurboRogue.


<HR>

                                     USNO AMC


                Link to USNO(MC2)                    
                                 *                  AMCT
                         O       *                GPS Ant.
                          \     *                 
                   **      \   *                |-|-|-O-|-|-|
                     ***____** TWSTT Ant.             | 
                           |                          | 
                           |                          | 
     -------------    -----|-----                -----------
     |           |    |   AMC   |      5MHz      |  AMCT   |
     |  H-maser  |--->|  (MC1)  |--------------->|  Turbo  |
     |  Source   |    |  (AOG)  |                |  Rogue  |
     |___________|    |_________|                |_________|

<HR>

Our AMC TurboRogue receiver has an external 5 MHz source supplied by a hydrogen maser source through an Auxiliary Output Generator (AOG)/distribution amplifier known as AMC(MC1). This clock is steered to our USNO(MC2) clock in Washington, DC using the nominal hourly experiment TWSTT data.

Description and file links

We measure at USNO the composite output 1-PPS supplied from the USNO geodetic receiver with respect to USNO(MC3). In addition, We measure at AMC the composite output 1-PPS supplied from the AMC geodetic receiver with respect to AMC(MC1). Our other high precision calibrated time transfer is done using our two-way satellite time transfer (TWSTT) systems. The TWSTT system between our USNO(MC2) and our AMC(MC1) is calibrated to be on time with our operational Master Clock to the 1-nanosecond level or better. The TWSTT data are sampled at a nominal rate of one experiment per hour. One needs to remove the small differences between our operational reference USNO(MC2) minus the geodetic reference USNO(MC3) to properly compare to our other calibrated timing references such as GPS and TWSTT. We measure local environmental data also.

Other files that you might find useful are...

  • (Hourly experiments) via TWSTT.

  • Kalman-filter smoothed estimates via TWSTT.

  • MC2 - average of USNO unsteered H-maser clocks.

  • AMC1 - average of AMC unsteered H-masers and cesium clocks.

  • Readme file which explains units and formats.

    Anonymous FTP of files

    In order to increase file transfer speeds you may wish to directly ftp to our anonymous ftp server to collect the files.

    ftp 192.5.41.239

    All these files are located under /pub/usnodc-amc.gpscp


    This page is http://tycho.usno.navy.mil/gpscp_dd.html
    (30 December 1998)

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