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Date: Thu, 28 Jan 1999 11:18:40 -0000 (GMT)
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To: (USNO 202-762-1444) 
Subject: PTTI paper available
Status: RO



Dear Jim,

we have prepared an URL with an on-line copy of our PTTI
paper : http://www.oma.be//KSB-ORB/D1/TIME/info.html

Kind regards


Carine Bruyninx

_________________________________________________________________________

  Bruyninx, C., P. Defraigne, J-M. Sleewaegen, and P. Paquet, Frequency
    transfer using GPS: A comparative study of code and carrier phase
    analysis results, Proc. 30th Precise Time and Time Interval Meeting,
    submitted 1998. 

  Abstract.  This paper investigates the use of GPS codes and carrier
  phases for frequency transfer applications. Three types of baselines
  have been studied. First, the noise of the code and phase methods has
  been evaluated using a zero-baseline with two geodetic GPS receivers
  driven by the same H-Maser clock, or by a Cesium and an H-Maser clock
  respectively. From the common frequency reference we were able to
  derive a frequency stability of 6.10^-16 for averaging times of one
  day. The different response of the hardware of the two receivers to
  small identical temperature variations is emphasized; the differential
  effect is about 30 ps/C. The difference between the L1 and L2 carrier
  phase delays is shown too.

  Secondly, on-site tests over a 95-m baseline allowed checking the
  influence of combining two antennae/receivers in different environments.
  In this case, the effect of the varying temperature on the hardware
  delays of the receivers and cables is shown; this effect limits the
  frequency stability to 6.10^-15 for an averaging time of one day. The
  possibility to obtain frequency stabilities of a few parts in 10^16 is
  shown; this can be reached if all the instruments are located in
  temperature stabilized rooms.

  Finally, the frequency stability obtained with different code methods
  is compared on a longer baseline (640 km) between Brussels and Wettzell.
  In particular the influence of using IGS satellite ephemerides instead
  of broadcast ephemerides is shown to be very small. The "all in view"
  methods based on the code as well as on the carrier phases are compared
  to the classic frequency transfer by common view. Preliminary results,
  using carrier phases, lead to a frequency stability of a few parts in
  10^15 for averaging times of one day. Again, the main limitations are
  the hardware delay variations due to the changes in ambient conditions.