Message-ID: <008369CA8EDAD311BE9500A0C9D854B4AEA661@naiad.usno.navy.mil>
From: powers.edward@usno.navy.mil
To: igsmail@igscb.jpl.nasa.gov
Subject: [IGSMAIL-4018]: New IGS station USN1 traceable to UTC
Date: Thu, 1 Aug 2002 16:08:37 -0400 
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IGS Electronic Mail      01 Aug 13:20:03 PDT 2002      Message Number 4018
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Author: Ed Powers
 
Dear Colleagues,
 
USNO is pleased to announce a new IGS station with the station designation
of USN1. USN1 has been specifically designed to support UTC time transfer.
Data collection for this station is handled as part of the JPL Global Real
Time data collection network and flows to the IGS in the form of high-rate
sub-hourly data, hourly data, and daily data in RINEX format.
 
USN1 is an Ashtech Z-XII3T Metronome receiver and is directly connected to
UTC(USNO), the USNO Master Clock in Washington, D.C.   The antenna is a
special DM choke ring antenna with built in active thermal controllers used
to minimize any antenna electronics sensitivity to temperature.  See IGS
LOGS for detail about the USN1 station configuration.
   
UTC(USNO) is produced from an ensemble of more than 60 high performance
cesium and 12 H-Maser clocks kept in environmental chambers at the USNO
Washington, D.C. location.  The international time standard UTC is
maintained by the Bureau International des Poids et Mesures (BIPM).  Over
the past few years UTC(USNO) has maintained agreement with UTC to within a
few nanoseconds (one sigma).   
   
Detailed analysis of environmental sensitivities of the hardware used to
construct the USN1 IGS station indicated that long term instabilities of
less than 1 nanosecond should be expected.  Absolute time calibrations of
all elements of both systems have been performed and all raw pseudo-range
data produced in the IGS RINEX data archive for USN1 have already been
adjusted to account for these time biases.  Any time solution produced
referenced to this station should be directly traceable to UTC with no
additional calibration bias corrections.
 
For additional information about the USN1 station please contact:
  
  Edward Powers
  USNO Time Service
  (202) 762-1451
  powers.edward@usno.navy.mil