From Bernard Thu Jul 23 09:01:21 1992 From: Bernard (Bernard) Date: 23 JUL 1992 09:01:21 Subject: [IGSMAIL-50] Epoch'92 Message-ID: *********************************************************************** IGS Electronic Mail 23-JUL-1992 09:01:21 Message Number 50 *********************************************************************** ============================================================================== THIS FILE CONTAINS 2 MESSAGES ============================================================================== >From: Bernard Minster Subject: Epoch'92 -------- 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 ============================================================================== >From: James F. Zumberge Subject: JPL analysis results -------------------- 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 starr at logos.jpl.nasa.gov): 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 jfz at edna.jpl.nasa.gov).] 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