Subject: [IGSMAIL-50] Epoch'92
From: Bernard Minster
Date: 23 JUL 1992 09:01:21

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IGS Electronic Mail       23-JUL-1992 09:01:21       Message Number 50
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                   THIS FILE CONTAINS 2 MESSAGES
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From:    Bernard Minster
Subject: Epoch'92
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        Reply to:   Epoch '92
We are now on the eve of the EPOCH '92 experiment.  As described in the second
circular and in IGSMAIL #41 the EPOCH '92 period is:

25 July 0:00 UT to 8 August 23:59:59 UT  (1992)

One of the purposes of the experiment is to provide a quantitative test of the
usefulness of the global network, the communications systems, and the data
products disseminated during the 3 -month campaign, to support regional
deployments.  In particular, can we process regional and local data sets
without any further improvements of the IGS precise orbits.

Scientific purposes will vary from region to region.  The density and
distribution of sites in each instance is therefore likely to be
region-dependent.  The very broad participation to the experiment is good in
this respect since it allows us to test a lot of applications.  There is no
formal requirement to synchronize occupations on a global scale, but
coordination of the sessions on a regional scale is important.

EPOCH '92 will deal with 30 second data, so that it would be good if core sites
went to 30 second data during that period.  This will increase the traffic for
a while, and we (Peter Morgan?) should watch for bottlenecks.  Note the
important facts that (1) the EPOCH data do not have to be transmitted in "real
time", and in fact should not be, except of course for the core stations.  The
nominal time for processing the EPOCH campaign is 90 days.  (2) For each site
contributed to the EPOCH experiment, it is essential to identify a regional
data center and a processing center.  The commitment to process these data sets
is a critical ingredient of the experiment, without which a station may as well
not be counted.

As stated in IGSMAIL #41, receivers should be synchronized with GPS time within
a few milliseconds, in order to mitigate the effects of SA.

A preliminary list of sites participating in the experiments was included in
the second circular.  However, I have received a number of corrections and/or
queries, from T. Kato (Japan), E. Bergamini (INPE), P. Pesec (Graz), A. Termens
(Spain), and H. Fagard (IGN).  I also realize that, given the large number of
participants, there will be quite a few last-minute changes.

Since a heavily bureaucratic approach to the experiment would be most
counterproductive, I propose that we simply adopt a system in which the station
information is merely updated in response to circumstances.  I have the station
list proposed in May, and am willing to update it and to circulate these
updates through IGSMAIL.  G. Preiss has also indicated that he has setup a
database, which could be a very useful tool to sumnmarize and maintain the
information.  My proposal is that an updated list of stations be forwarded to
the appropriate regional coordinators, and I will coordinate with George Preiss
to produce a final merged list.  The goal is to produce a list of the stations
which **have** been occupied by August 8.  For each station, we need a site
name, abbreviation if it has been chosen, approximate coordinates (for map
making purposes), equipment, and recording sessions during EPOCH '92.  We also
need the data center(s) and the processing center(s), and finally a point of
contact  (i.e. a culprit) to answer questions.  

Further details will eventually be required, but this will do for a start, and
for purposes of organizing the information.  The updates to this informational
material will be verified and disseminated using electronic mail.

Any suggestions for improving the flow of information and the scientific value
of the experiment are very welcome.

Regards to all
Bernard Minster

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From: James F. Zumberge
Subject: JPL analysis results
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Submitted by

J F Zumberge, G Blewitt, M B Heflin, D C Jefferson, F H Webb

all at the Jet Propulsion Laboratory, California Institute of Technology, 
Pasadena, CA  91109.

The following files have been posted on BODHI (for access to BODHI contact
[email-masked]):

filename               contents

jpl06527.sum        This text file.
jpl06527.erp        Earth rotation parameters for GPS week 652 (Jul 05-11).
jpl06520.sp1        Precise ephemerides for 1992 Jul 05, NGS sp1 format.
jpl06521.sp1                                         06
jpl06522.sp1                                         07
jpl06523.sp1                                         08
jpl06524.sp1                                         09
jpl06525.sp1                                         10
jpl06526.sp1                                         11
jpl06520.sp3        Precise ephemerides for 1992 Jul 05, NGS sp3 format.
jpl06521.sp3                                         06
jpl06522.sp3                                         07
jpl06523.sp3                                         08
jpl06524.sp3                                         09
jpl06525.sp3                                         10
jpl06526.sp3                                         11
jpl06507.sp3        Precise ephemerides for GPS week 650, NGS sp3 format.
jpl06517.sp3                                         651

We depart from the convention of using ".eph" to identify precise ephemerides,
as we feel that ".sp1" or ".sp3" is more informative.

Because these formats require that all prns listed in the header be present at
all time tags, and because we exclude certain satellites on certain days, we
have organized the files on a daily rather than weekly basis.

[The sp3 files are the output of a sp1-to-sp3 conversion routine, with source
code by Ben Remondi. Thanks to Miranda Chin for supplying us with that code.
We would appreciate hearing from users regarding their preference for format
(sp1 or sp3; email to [email-masked]).]

Our analysis of GPS week 652 (1992 Jul 05 - Jul 11) follows the strategy de-
scribed in detail in IGS Mail Message 37 (file jpl06507.sum). For that week, 
we have determined that prn12 is unusable for Jul 05 through Jul 07, usable
on Jul 08, then unusable again on Jul 09 and Jul 10. Beginning with Jul 11 and
through Jul 15 (our most recent day of analysis), prn 12 is usable.

Unlike last week's submission, if we consider a prn to be unusable, we will
not include it in the precise orbits file. Users could use the broadcast
ephemeris if necessary for such days and prns.

WARNING: We recommend against using prn12 on Jul 05,06,07,09,10.

[For the week beginning Jul 12, we have confirmed the that prn 24 was 
unusable on Jul 14, and that prn 25 was unusable on Jul 15. These
correspond to NANU nos. 151-92196 and 155-92197 in file gpsn3.txt, retrieved
with anonymous ftp from tycho.usno.navy.mil. Curiously, we found no anomalous
behaviour with prn 18, although similar NANUs regarding it can be found.] 

Data from Fairbanks on Jul 09 from 3 hr 13 min 0 sec and continuing through
7 hr 58 min 30 sec (GPS time) were excluded from the analysis. Normally,
the receiver at Fairbanks sees 4-5 satellites throughout this period, but on
Jul 09 saw only prn 21.

The following table summarizes our daily solutions for polar motion for 11 days
beginning July 5. The week of July 5 (GPS week 652) is contained separately in
file jpl06527.erp.

JPL UTPM TABLE                                            (1992 Jul 05 - Jul 15)
  MJD       X        Y       UT1R-UTC XSIG    YSIG   UTSIG  RMS  XYC  XUC  YUC STA SAT PASS    
           ''        ''        sec     ''     ''      sec
 48808.5  -.13569   .39171   .00000  .00026  .00031  .00000  .0  .25  .00  .00  26 16  0
 48809.5  -.13406   .39399   .00000  .00023  .00028  .00000  .0  .25  .00  .00  26 16  0
 48810.5  -.13271   .39464   .00000  .00027  .00032  .00000  .0  .32  .00  .00  26 16  0
 48811.5  -.13062   .39847   .00000  .00023  .00027  .00000  .0  .34  .00  .00  26 17  0
 48812.5  -.12994   .39966   .00000  .00029  .00036  .00000  .0  .38  .00  .00  23 16  0
 48813.5  -.12868   .40264   .00000  .00028  .00035  .00000  .0  .21  .00  .00  24 16  0
 48814.5  -.12707   .40588   .00000  .00021  .00025  .00000  .0  .23  .00  .00  26 17  0
 48815.5  -.12651   .40865   .00000  .00024  .00029  .00000  .0  .31  .00  .00  25 17  0
 48816.5  -.12692   .41055   .00000  .00023  .00028  .00000  .0  .21  .00  .00  27 17  0
 48817.5  -.12580   .41290   .00000  .00025  .00029  .00000  .0  .20  .00  .00  27 16  0
 48818.5  -.12451   .41301   .00000  .00025  .00029  .00000  .0  .25  .00  .00  26 16  0
END UTPM TABLE

The following table indicates the "orbit repeatability", as defined in IGS Mail
Message 37, for GPS week 652:

JPL ORBIT REPEATABILITY TABLE                GPS week 652 (1992 Jul 05 - Jul 11)
      92  7  5   92  7  6   92  7  7   92  7  8   92  7  9   92  7 10   92  7 11
prn    rms (m)
  2       1.34       1.10       1.06       1.43       1.06       1.01       0.90
  3       0.65       0.35       0.45       0.38       0.32       0.47       0.44
 11       0.65       0.49       0.61       0.66       0.53       0.58       0.70
 12                                                                         0.7 
 13       0.81       0.86       0.55       1.13       0.86       0.74       0.64
 14       0.94       0.45       0.39       1.48       0.77       1.35       1.21
 15       1.01       0.84       1.08       1.00       1.04       1.27       0.75
 16       0.36       0.47       0.34       0.45       0.61       0.35       0.30
 17       0.82       0.96       1.03       1.01       0.67       0.85       0.48
 18       0.68       0.49       0.63       0.47       0.62       0.65       0.35
 19       0.56       0.79       0.49       0.66       0.74       0.59       0.66
 20       0.60       0.52       0.73       0.67       0.67       1.05       1.05
 21       0.45       0.61       0.50       0.53       0.72       0.82       0.74
 23       0.25       0.49       0.58       0.57       0.65       0.75       0.48
 24       0.76       0.56       0.60       0.80       0.77       0.72       0.91
 25       0.42       0.69       0.71       0.89       1.05       0.98       0.75
 28       1.08       1.40       0.91       1.15       0.59       1.00       1.36
END ORBIT REPEATABILITY TABLE

As described in IGS Mail Message 37, the following table compares the JPL
precise ephemerides with those from the broadcast ephemeris:

JPL COMPARISON OF BROADCAST NAVIGATION MESSAGE WITH PRECISE EPHEMERIDES
      92  7  5   92  7  6   92  7  7   92  7  8   92  7  9   92  7 10   92  7 11
prn    rms (m)
  2       5.8        5.2        4.9        6.3        7.1        6.2        6.3 
  3      12.5       11.8       11.2       13.5       12.4       12.4       12.4 
 11       6.7        7.7        4.8        7.6        8.9        5.0        5.2 
 12                                       24.9                             43.3 
 13       6.2        4.4        8.0        6.6        6.3        9.2        7.2 
 14       4.8        4.8        4.4        4.0        4.4        6.2        6.6 
 15       5.1        5.7        7.0        6.2        7.5        6.8        7.2 
 16       3.6        4.6        6.6        5.7        6.6        7.7        6.4 
 17       6.3        7.1        8.5        7.1        7.1        9.5        9.2 
 18       7.0        5.9        5.9        7.1        8.1        8.0        7.4 
 19       7.0        7.5        8.1        8.2        7.0        8.2        9.7 
 20       5.3        5.0        6.1        6.1        7.0        4.8        6.9 
 21       4.9        4.6        5.9        5.8        5.9        6.7        6.3 
 23       3.3        3.3        6.3        4.6        5.3        6.1        5.3 
 24      11.1       10.6        9.2        8.7        9.4       12.8       13.8 
 25       6.9        7.6        6.9       10.0       11.5       12.2       11.9 
 28       5.4        4.5        4.4        5.1        5.4        4.7        6.7 
END COMPARISON OF BROADCAST NAVIGATION MESSAGE WITH PRECISE EPHEMERIDES