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From: Demetrios "N." Matsakis
Message-Id: <199812041653.QAA23492@orion.usno.navy.mil>
Subject: GeTT data
To: gpst@maia.usno.navy.mil
Date: Fri, 4 Dec 1998 16:53:25 +0000 (UTC)
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This is to announce that some USNO-applied corrections to GeTT (Geodetic
Time Transfer) data are available at ftp://tycho.usno.navy.mil/pub/gett,
and also via anonymous ftp to tycho.usno.navy.mil in the directory pub/gett.
The data are updated nightly, and the attached readme file should be self-
explanatory. Raw GeTT data are probably also available from the indicated CODE
site, but in any event Tim Springer's email address is springer@aiub.unibe.ch.
Data are corrected for TurboRogue jumps using the 1pps data and for
the link between Bldgs. 78 and 52. However, recent discoveries concerning
the shape of the 1pps pulse are not incorporated in the analysis.
The file USN3-USNB.ns.hr qualitatively agrees with GIPSY about the great
improvement resulting from the re-cabling of the USNO Bldg. 52 TurboRogue on
MJD 51037, which was conceived and carried out by Ed Powers and Jim Eler.
Postscript files are not yet available, but will be soon.
What follows is the readme file at the URL site:
************************************************************************
US Naval Observatory GeTT data analysis
Version of 21SEP98
Demetrios Matsakis
dnm@orion.usno.navy.mil
***********************************************************************
Based upon raw data extracted from CODE by anonymous ftp using
the following unix script:
#!/bin/ksh
ftp -n -v ubeclu.unibe.ch > logfile <<-EOF
user anonymous dnm
cd AIUB\$FTP.TIMTRANS.RESULTS
prompt
mget *
EOF
***********************************************************************
Site Names Used by CODE/IGS
USNO TurboRogue in Wash. DC (Bldg. 52) which contributes to the IGS effort
timing data from receiver USNO are referenced to Master Clock 3 (MC3).
A large diurnal term, due to the antenna cable, was removed on MJD 51037.
AMCT TurboRogue at AMC (U.S. Naval Observatory's alternate master clock)
in Schriver AFB, Colorado, and which contributes to the IGS effort.
USNB GeTT installed at USNO-DC (Bldg. 78)
Timing data from receiver USNB are referenced to Master Clock 2
(MC2), which is UTC(USNO).
There are unmeasured timing offsets between all these GPS carrier phasel
receivers and their associated clocks. Some information on MC3-MC2 is
available in tycho.usno.navy.mil pub/usnodc-amc.gpscv.
***********************************************************************
SITE names "made up" for this analysis only
Indicates site data which are corrected for TurboRogue receiver's
instrumental jumps, as measured by the 1pps data.
AMC1 = 1pps-corrected data from TurboRogue AMCT
USN3 = 1pps-corrected data from TurboRogue USNO with MC3 as ref.
(MC3 is the original timing reference)
USN2 = 1pps-corrected data from TurboRogue USNO with MC2 as ref.
Correction for MC3-MC2 from led link between buildings,
whose long and short term characteristics are under study.
Comparisons with a recently installed laser link show a
range of 326 ps over 2 months, and an hourly first
difference rss of 15 ps. A 100-ps diurnal term is suspected.
TurboRogue jumps for AMCT and USNO are available by anonymous ftp
from tycho.usno.navy.mil in pub/usnodc-amc.gpscv. Look for files
ending in 1pps,1pps.jumps, 1pps.smooth plus their readme file.
************************************************************************
Note that USNO in this document means one specific TurboRogue receiver ,
and not the U.S. Naval Observatory
*******************************************************************
US Naval Observatory-Generated Files
Hourly averages of timing differences between sites, in nanosec.
USN2-USNB.ns.hr
USN3-AMC1.ns.hr
USN3-AMCT.ns.hr
USN3-USNB.ns.hr
USNB-AMC1.ns.hr
USNB-AMCT.ns.hr
USNO-AMC1.ns.hr
USNO-AMCT.ns.hr
USNO-USNB.ns.hr
Hourly averages of CODE timing differences between PTB and sites, in microsec:
ptb-AMC1.us.hr
ptb-AMCT.us.hr
ptb-USN3.us.hr
ptb-USNB.us.hr
ptb-USNO.us.hr
Double-differenced time transfer data between listed sites,
double_difference.USNO-AMC1_gett-twstt
double_difference.USN3-AMC1_gett-twstt
sense is (SITE1-SITE2) as measured by GeTT minus (SITE1-SITE2)
as measured by TWSTT (Two Way Satellite Time Transfer).
**********************************************************************
CODE data format
**********************************************************************
Our data is processed with a delay of 5 days (almost 6 since it starts at
20:00 hours local time). The reason for this delay is that we wait for our
so-called "final-orbits" which are computed with a 4 to 5 day delay.
Currently we are having some problems with our computer system which is
delaying the processing significantly. However, I hope to be "back on track"
by tomorrow.
I have describe the format of the file below. Note that the units are
microseconds for both the estimates and the formal errors. However, the
formal errors are not correctly computed and therefor much to optimistic.
They reflect (to a certain extend) the PDOD.
Format of ALL*.CLK files:
-------------------------
COLUMN:
-1: Internal number of parameter type: 23 means station clock
Not very useful/important for you
-2: Internal station number. Not very useful/important because station
name is given in column 6.
-3: Epoch of estimates given in GPS time in MJD.
-4: Clock estimate. Estimated for receiver clock of station named in column 6
relative to the chosen reference clock which is normally PTB.
-5: Formal error of clock estimate. Note that the formal error is not computed
correctly. Therefore it is much to optimisted. It a more a measure of
PDOP than anything else. However, relative the are meaningful; i.e.
is you see a significantly larger value for a certain estimate than
it is based on (much) less observations (less satellites tracked).
-6: Station name. 4 character abbreviation followed by the official IERS
DOMES number (if available). The 4-character abbreviations are usually
identical with the RINEX names but there are exceptions (for instance
NYAL is actually NYA1 and USNB is our GETT terminal at USNO).
-------------------------------------------------------------------------------
COL 1 2 3 4 5 6
-------------------------------------------------------------------------------
23 1 51013.003472 0.315737 0.000030 # NYAL 10317M003
23 2 51013.003472 3.799088 0.000029 # ONSA 10402M004
23 4 51013.003472 0.233839 0.000029 # REYK 10202M001
23 5 51013.003472 -0.703608 0.000029 # WTZR 14201M010
23 6 51013.003472 -2.325062 0.000029 # ALGO 40104M002
23 7 51013.003472 0.232556 0.000028 # NRC1 40114M001
23 8 51013.003472 -0.148186 0.000028 # USNB
23 9 51013.003472 -0.229847 0.000028 # USNO 40451S003
23 10 51013.003472 -0.479388 0.000029 # WES2 40440S020
23 1 51013.006944 0.316037 0.000030 # NYAL 10317M003
23 2 51013.006944 3.799365 0.000029 # ONSA 10402M004
-------------------------------------------------------------------------------
------------------------------------------------------------------------------
Tim Springer Astronomical Institute, University of Berne
Tel: +41 31 6318592 Sidlerstrasse 5, CH-3012 Bern, Switzerland
Fax: +41 31 6313869 ftp: ubeclu.unibe.ch -or- 130.92.6.17
e-mail: springer@aiub.unibe.ch after login: cd "aiub$ftp"
www: http://www.cx.unibe.ch/aiub/
------------------------------------------------------------------------------
stations analyzed by CODE as of 8sep98
ALGO
AMCT
BRUS
GODE
NLIB
NRC1
NYAL
ONSA
PIE1
REYK
USNB
USNO
WES2
WSRT
WTZR
YELL