Subject: [IGSMAIL-41] IGS Status Report, July 10, 1992
From: Gerhard Beutler
Date: 11 JUL 1992 13:37:45

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IGS Electronic Mail       11-JUL-1992 13:37:45       Message Number 41
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                   THIS FILE CONTAINS 3 MESSAGES
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From:    Gerhard Beutler
Subject: IGS Status Report, July 10, 1992
         --------------------------------

IGS Status Report, July 10, 1992
________________________________

General Remarks :

 - The IGS campaign 1992 started three weeks ago.

 - The data flow seems to be pretty well established by now. Since I
   heard no complaints I conclude that the transmission of 30 sec data
   for (more or less) the entire core network does not pose serious
   problems.

 - First results were produced by four processing centers : In the
   first IGS'92 Earth Orientation Bulletin (IGS Message No. 38) four
   processing centers, namely Code (Bern), CSR (Austin),
   JPL(Pasadena), and SIO (San Diego) presented their first sets of
   erp-s.

 - It is therefore clear that not only earth orientation parameters
   but also orbits were computed from at least four processing
   centers. On the other hand only data from one processing center
   are available in the subdirectory GPS1:[PRODUCTS].

   I INVITE ALL PROCESSING CENTERS TO DEPOSIT THEIR RESULTS AT
   CDDIS (contact Carey Noll for details, compare also Carey Noll's
   report in IGS message No. 3, message No. 16 for name conventions).

   As soon as orbits from several agencies are available at CDDIS
   Clyde Goad will start comparing them.

 - Still the processing centers have to work with a delay of about 6-8
   days between the last observation and the processing, because not
   all the data are available - as expected - within 3 days. Let us
   keep in mind that prior to the campaign we considered timeliness
   of data transfer as (one of) the vital issues.

(1) 1992 Epoch Campaign
    ___________________

 -  The 1992 Epoch Campaign will start in two weeks, the exact dates
    are:

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

 -  From the experiences gained so far we can expect that high
    precision global orbits stemming from different institutions will
    be available at CDDIS shortly after Epoch'92.

 -  I believe that for most experiments scheduled under the label
    "Epoch'92" it will be possible to perform the final analysis on
    the 0.01-0.03 ppm level without further orbit improvement (using
    precise IGS orbits).

 -  Let me remind you that Epoch'92 will deal with 30-sec-data.
    Most analysis centers dealing with Epoch'92 rely on the
    availability of 30-sec-data from the core sites too. As far as I
    can see most core sites produce 30 sec data already now. Please
    make sure that all core sites will use this sampling rate at
    least during Epoch'92).

  - I hope that the regional coordinators will give an overview of
    the activities in their spheres of influence prior to the campaign
    through IGS mail.

  - Be careful when combining receivers of different type. To avoid
    difficulties with Selective Availability (SA) all receivers should
    be synchronized with GPS time within a few milliseconds.

(2) IGS and the Ionosphere
    ______________________

  - I was approached from different sides to clarify the IGS oversight
    committee's policy concerning the ionosphere.

  - Let me mention in particular the workshop "Observing the
    Ionosphere with GPS" which took place on April 27-28 at the
    Institut f�r Erdmessung in Hannover. The purpose of the workshop
    was to stimulate/initiate a discussion between GPS experts on the
    one hand and atmosphere specialists on the other hand. Lambert
    Wanninger from Hannover wrote a summary of this informative
    meeting (L.  Wanninger, May 1992 "Workshop on Observing the
    Ionosphere with GPS", IfE-Memo WA-05/92).

    Let me try to summarize the essential information :

     - Obviously there is an increasing interest from geophysicists
       to use GPS for ionosphere studies.

     - The IGS core network with dual frequency P-code receivers is an
       excellent data set for ionosphere studies (too).

     - The Wanninger report contains a proposal to the IGS oversight
       committee to extend the list of IGS products to include
       information concerning the ionosphere. In particular site and
       even satellite specific estimates of the total electron content
       (TEC) with a high temporal resolution is requested.

  - Let me specify my personal position :

     - I am convinced that a routine analysis of the ionosphere
       should be part of the future International GPS Service.

     - I agree that the 1992 IGS campaign is a phantastic test data
       set to show the power of GPS for analyzing the ionosphere.

     - I know that some processing centers are developing tools to
       analyze the ionosphere (among them our institute).

     - On the other hand I believe that it is not possible to agree
       upon type and format of such products before the end of the
       1992 test campagn.

  - Let me therefore suggest the following :

     - We invite the geophysicists interested in the ionosphere to
       use the material of the 1992 IGS campaign for test studies.

     - Those already working with IGS data (or wishing to do so) are
       advised to coordinate their efforts with the Wanninger group.

     - At the next official IGS oversight committee meeting (scheduled
       for 15/16 October at Goddard, but not yet confirmed) this topic
       will be addressed and a solution will be sought.

  - I would like to point out that this is a suggestion. Please let me
    know your opinion. I would like to give an answer to Lambert in the
    next 2-3 weeks.

                                                 Kind regards

                                                Gerhard Beutler
                                                Tim Springer

==============================================================================

From:    Carey Noll
Subject: CDDIS GPS Data Holdings for IGS Week 2/GPS Week 651
         ---------------------------------------------------

         Current CDDIS IGS GPS Data Holdings (as of 10-Jul-92 12:07)
 1992 IGS Week 3/GPS Week 651 (June 28 thru July 04, 1992; Days 180 thru 186)

                                         1   1   1   1   1   1   1
                     Mon.                8   8   8   8   8   8   8    No.
    Site Name        Name    Receiver    0   1   2   3   4   5   6   Sites
------------------   ----   ----------   -   -   -   -   -   -   -   -----
Albert Head          ALBH   ROGUE        X   X   X   X   X   X   X       7
Algonquin            ALGO   ROGUE        X   X   X   X   X   X   X       7
Fairbanks            FAIR   ROGUE        X   X   X   X   X   X   X       7
Goldstone            DS10   ROGUE        X   X   X   X   X   X   X       7
Graz                 GRAZ   ROGUE        X   X   X   X   X   X   X       7
Hartebeesthoek       HART   ROGUE        X           X   X   X   X       5
Herstmonceux         HERS   ROGUE        X   X   X   X   X   X   X       7
Hobart               HOBA   MINIMAC          X   X   X   X   X   X       6
Kokee Park           KOKB   ROGUE            X   X   X   X   X   X       6
Kootwijk             KOSG   ROGUE        X   X   X   X   X   X   X       7
Madrid               DS60   ROGUE        X   X   X   X   X   X   X       7
Mas Palomas          MASP   ROGUE        X   X   X   X   X   X   X       7
Matera               MATE   ROGUE        X   X   X   X   X   X   X       7
McMurdo              MCMU   ROGUE        X   X   X   X   X               5
Metsahovi            METS   ROGUE        X   X   X   X   X   X   X       7
Mojave               MOJ1   MINIMAC      X   X   X   X   X   X   X       7
Ny Alesund        NYAL/NALL ROGUE        X   X   X   X   X   X   X       7
Onsala               ONSA   ROGUE        X   X   X   X   X   X   X       7
Pamate               PAMA   ROGUE        X   X       X   X   X           5
Pasadena             MESA   ROGUE        X   X   X   X   X       X       6
Penticton            DRAO   ROGUE        X   X   X   X   X   X   X       7
Pinyon Flat          PINY   ROGUE        X   X   X   X   X   X   X       7
Richmond             RCMA   MINIMAC      X   X   X   X   X   X   X       7
Saint John's         STJO   ROGUE        X   X   X   X   X   X   X       7
Santiago             SANT   ROGUE        X       X   X   X   X   X       6
Taiwan               TAIW   ROGUE        X   X   X   X   X   X   X       7
Tidbinbilla          DS40   ROGUE        X   X   X   X   X   X   X       7
Townsville           TOWN   TRIMBLE      X   X   X   X   X   X   X       7
Tromso               TROM   ROGUE        X   X   X   X   X   X   X       7
Tsukuba              TSUK   MINIMAC      X   X   X   X   X   X   X       7
Usuda                USUD   ROGUE        X   X   X   X   X   X   X       7
Victoria             PGC1   ROGUE        X   X   X       X   X   X       6
Wellington           WELL   TRIMBLE      X   X   X   X   X   X   X       7
Westford             WES1   MINIMAC      X   X   X   X   X   X   X       7
Wettzell             WETT   ROGUE        X   X   X   X   X   X   X       7
Yaragadee            YAR1   ROGUE        X   X   X   X   X   X   X       7
Yellowknife          YELL   ROGUE        X   X   X   X   X   X   X       7
Zimmerwald           ZIMM   TRIMBLE      X   X   X   X   X   X   X       7
------------------   ----   ----------  --  --  --  --  --  --  --   -----
Totals:                38 stations      36  36  36  37  38  36  36     255

==============================================================================

From:    Tom Clark, NASA/GSFC
Subject: VLBI's Plans during EPOCH 92
         ----------------------------

Several people have asked about VLBI data that will be available during
the "EPOCH 92" period in late July and early August. The following is
extracted from the Master VLBI List which we maintain here at NASA/GSFC
and contains all the 1+ day observing sessions planned by all the inter-
national groups for the period 13 July thru 20 August. The TIME column
is the experiment UTC starting time.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

  EXPERIMENT   DATE   TIME DUR STATIONS
  --------------------------------------------------------
  Pol-749      13-JUL 08:00 24h Wf-Mo-Ri-Wz-Ag-Fb (Post-Quake Special)
  PPM-S1       15-JUL 16:00 24h Fb-Ka-Ks-Ti-Sc-Cn
  NAVNET-185   16-JUL 18:00 24h Fb-Gb-Ka-Ri
  PHASE-DELAY2 16-JUL 21:00 24h Fv-Pt-La
  IRIS-P64     17-JUL 20:00 24h Fb-Ka-K4-Ta
  Pol-750      20-JUL 08:00 24h Wf-Os-Fb-Wz-Hf
  SH-S32       20-JUL 16:00 24h Ta-Hb-Sc
  GLOBAL       21-JUL 20:00 48h Wz-Sc-Fb-Wf-Ka-Ks-Ta-Hb-Cn
  HOFN-2       22-JUL 08:00 24h Hf-Ri-Os
  NAVNET-186   23-JUL 22:00 24h Fb-Gb-Ka-Ri
  HOFN-3       25-JUL 04:00 24h Hf-Wz-Os-Wf-Fb
  HOFN-4       26-JUL 06:00 24h Hf-Wz-Os-Wf-Fb
> Pol-751      27-JUL 08:00 24h Hf-Wz-Os-Wf-Fb
> NAVEX-G3     28-JUL 08:00 26h Sc-Mt-Hb-Gb-K4
> EXT-R&D-A    28-JUL 10:00 26h Fb-Ka-Wf-Wz-La-Fv
> NAVEX-G4     29-JUL 12:00 30h Sc-Mt-Hb-Gb-K4-Ag
> EXT-R&D-B    29-JUL 14:00 26h Fb-Ka-Wf-Wz-La-Fv
> NAVNET-187   30-JUL 18:00 24h Fb-Gb-Ka-Ri
> EXT-R&D-C    31-JUL 20:00 28h Fb-Ka-Wf-Wz-La-Fv
  MARK-4 Test  01-AUG  TBD  TBD Wf(or Ha)-Gf
> EXT-R&D-D    02-AUG 02:00 28h Fb-Ka-Wf-Wz-La-Fv
> Pol-752      03-AUG 08:00 24h Wf-Mo-Ri-Wz-Ag
> NAVEX-G5     04-AUG 08:00 26h Sc-Mt-Hb-Gb-K4
> EXT-R&D-E    04-AUG 10:00 26h Fb-Ka-Wf-Wz-La-Fv
> NAVEX-G6     05-AUG 12:00 30h Sc-Mt-Hb-Gb-K4-Ag
> EXT-R&D-F    05-AUG 14:00 26h Fb-Ka-Wf-Wz-La-Fv
> NAVNET-188   06-AUG 18:00 24h Fb-Gb-Ka-Ri
> EXT-R&D-G    07-AUG 20:00 28h Fb-Ka-Wf-Wz-La-Fv
> EXT-R&D-H    09-AUG 02:00 28h Fb-Ka-Wf-Wz-La-Fv
> Pol-753      10-AUG 08:00 24h Wf-Mo-Ri-Wz-Ag
> SH-S33       10-AUG 14:00 24h Ta-Hb-Sc
> NAVEX-25     10-AUG 18:00 24h Fb-Gb-Ka-Mt-K4
  XASIA-2      11-AUG 16:00 24h Wz-Hb-Ti-Ks-Cn-Ta
  TROMSO-1     12-AUG 18:00 24h Ts-Wz-Os-Wf-Fb
  NAVNET-189   13-AUG 18:00 24h Fb-Gb-Ka-Ri
  TROMSO-2     15-AUG 04:00 24h Ts-Wz-Os-Wf-Fb
  TROMSO-3     16-AUG 06:00 24h Ts-Wz-Os-Wf-Fb
  Pol-754      17-AUG 08:00 24h Ts-Wz-Os-Wf-Fb
  PHASE-DELAY3 17-AUG 16:00 24h Fv-Pt-La
  IRIS-S57     18-AUG 16:00 24h Wf-Ri-Wz-Hb-Sc
  FRAME-57     18-AUG 18:00 24h Fb-Gb-Ka-Ag
  TROMSO-5     19-AUG 18:00 24h Ts-Wz-Os-Wf-Fb
  NAVNET-190   20-AUG 18:00 24h Fb-Gb-Ka-Ri

STATION CODES:

Ag - Algonquin Park               Mt - Matera
Cn - China                        Nt - Noto
D5 - DSS15                        Nl - North Liberty/VLBA
Fb - Fairbanks                    Oh - O'Higgins
Fv - Fort Davis/VLBA              Om - Onsala (MV-2)
Gb - Green Bank 85-3              Os - Onsala
Gf - GGAO (MV-3)                  Ov - Owens Valley
Hb - HartRAO                      Pt - Pie Town
Hf - Hofn (MV-2)                  Ri - Richmond
Ho - Hohenspeissenberg (MV-2)     Sc - Santiago
Hs - Haystack                     Ta - Tasmania
Ka - Kauai                        TBD - To Be Determined
Ki - Kirschberg (MV-2)            Ti - DSS45 (Australia)
Kp - Kitt Peak                    Tr - Trysil (MV-2)
Ks - Kashima (26m)                Ts - Tromso (MV-2)
K4 - Kashima (34m)                Us - Ussuriisk
La - Los Alamos                   Wf - Westford
Ma - DSS65 (Madrid)               Wz - Wettzell
Md - Medicina                     Yk - Yellowknife
Mo - Mojave

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Pay special note of the lines beginning ">" during the July 27 - August 10
period. During this time, the NASA-sponsored Extended R&D sessions, plus
scheduled POLARIS/IRIS sessions, plus the augmented USNO NAVNET/NAVEX programs
will provide essentially continuous coverage on two simultaneous VLBI
networks. 

Concerning the R&D experiments -- in these measurements we pull out all the
stops and use the strongest network we can form with the most optimum
observing schedule we can generate. The more routine POLARIS/IRIS and 
NAVNET sessions are "operational" and are more conservative.

As a prediction of VLBI performance, a comparison of representative data,
analyzed under the assumption of perfect site and source positions, for
a 24-hour period shows the following one-sigma uncertainties:

            X-pole     Y-pole      UT1
             milliarcseconds      usec of time
   R&D       0.08       0.07        3
   IRIS      0.14       0.13        6
   NAVNET    0.17       0.18        9

If the analysis is modified to allow piecewise-linear variation of the EOP
in intervals of 4 hours so that sub-daily variations can be studied, these 
values approximately double to

   R&D       0.18       0.17        7
   IRIS      0.31       0.30       16
   NAVNET    0.35       0.40       20

(thanks to Dan MacMillan and Chopo Ma for doing the work to produce these
predictions. Marshall Eubanks indicates that his analysis of NAVNET data
shows that the sub-daily uncertainties scale approximately as 1/sqrt(t)
from 24 hours down to about 1 hour -- in this case sqrt(6) ~ 2.4 in
reasonable agreement with Dan & Chopo's result.)

We look forward to having the simultaneous GPS and VLBI data to compare
short- and long-term performance. Good Luck!

Tom Clark

P.S. Serious budget problems have forced NASA & NOAA to close down Mojave
as of September. Most of the Mojave staff have already departed. You will
note that the network we are using for the R&D measurements no longer
includes Mojave at all. This is a change from the information we had
given out earlier.