CDDIS Bulletin - May 1999
Volume 14 No. 4

In this issue:

• Cover: IGS Sites Providing Hourly Data to the CDDIS
• Articles:
  • International GLONASS Exepriment (IGEX-98) Workshop
  • IGEX-98 Campaign to Continue
• Data Bits and Bytes:
  • Permanent GPS Network Update
  • Recent SLR System Problems

About the cover: The map on the cover of this issue of the CDDIS Bulletin shows the IGS sites currently supplying hourly data in near real time to the CDDIS. Currently 46 sites are providing data in hourly increments.

International GLONASS Experiment (IGEX-98) Workshop Second Circular and Call for Papers

OVERVIEW

The first coordinated international campaign to collect and analyze GLONASS satellite data began on October 19, 1998 and is scheduled to terminate on April 19, 1999. This International GLONASS Experiment (IGEX-98) was jointly sponsored by the International Association of Geodesy's (IAG) Commission VIII for the International Coordination of Space Techniques for Geodesy and Geodynamics (CSTG), the Institute of Navigation’s (ION) GLONASS-GPS Interoperability Working Group, the International GPS Service (IGS), and the International Earth Rotation Service (IERS). The IGEX-98 Steering Committee, the ION and the IGS are organizing a joint workshop on September 13-14, 1999 to discuss the results of IGEX-98 and possible plans for the future. This workshop will be held in conjunction with the ION Satellite Division’s 12th International Technical Meeting GPS-99 in Nashville, Tennessee (U.S.).

The IGEX workshop will be run as a separate event prior to the GPS-99 conference. It will be held in the Nashville Convention Center, and will be the forum for this year’s meeting of the ION GLONASS-GPS Interoperability Working Group (GGIWG). A separate registration fee will be required for all attendees of the workshop as indicated below. (Workshop attendees who also wish to attend ION's GPS-99 Technical Meeting after the workshop ends will be required to pay the standard conference registration fee.)

The workshop will be an opportunity for participants to present and compare their findings, observations, and analyses resulting from the IGEX campaign. It will be a time to assess whether or not the objectives of the experiment were met and to discuss future plans for using and supporting GLONASS.

PRELIMINARY AGENDA

The workshop sessions will be held between the hours of 8:30 a.m. and 5:00 p.m. each day, with registration beginning at 8:00 a.m.

Monday, September 13, 1999

INTRODUCTION AND OVERVIEW, Chair: James Slater (NIMA)
Overview of IGEX Campaign
GLONASS Status, Performance and Plans
RECEIVER TECHNOLOGY, Chair: Ruth Neilan (JPL)
Software and Hardware Developments, Performance Analysis
NETWORK OPERATIONS, Chair: Werner Gurtner (Astronomical Inst. Univ. of Bern)
Data Collection, Data Communications, Data Archiving, Formats, Preprocessing
PANEL DISCUSSION — Technology Issues, Station and Network Operations Issues Chairs: Werner Gurtner and Ruth Neilan
EVENING RECEPTION

Tuesday, September 14, 1999
INTRODUCTION, Chair: Carey Noll (NASA GSFC)
ORBIT DETERMINATION, Chair: Robert Weber (Technical Univ. of Vienna)
Precise Orbit Computations, SLR Observations, Methodology
TIME AND TIME TRANSFER, Chair: Wlodzimierz Lewandowski (BIPM)
APPLICATIONS, Chair: TBD
Reference Frames and Datum Transformations
Geodetic Positioning
Atmospheric and Ionospheric Studies
GENERAL DISCUSSION — GLONASS-GPS Interoperability Issues Chair: Pratap Misra (M.I.T. Lincoln Laboratories)
PANEL DISCUSSION - Future Plans (IGS, Manufacturers, Navigation Users, Scientific Community), Chairs: Gerhard Beutler (Astronomical Inst. Univ. of Bern) and Pascal Willis (IGN)
SUMMARY

ABSTRACT SUBMISSION

Abstracts are requested for oral and poster presentations. Abstracts must be in English and must not exceed one page. The deadline for submission of abstracts is May 21, 1999. Authors will be notified by June 21 about the acceptance of their abstracts and whether they will be oral or poster papers.

All abstracts should be submitted electronically by connecting to one of the web sites referenced below and completing the online form. If you do not have access to the Internet, you may fax your abstract to Carey Noll at 301-614-5970 (USA). Submissions should include names and affiliations of all authors, and contact information for the responsible author including mailing address, phone and fax numbers and e-mail address.

Final manuscripts for all papers including poster paper summaries are requested by September 30, 1999 to facilitate publication in the workshop proceedings. Instructions for submission of papers will be available on the web sites shown below.

PRE-REGISTRATION REQUIREMENTS

Pre-registration is requested for all people planning to attend the workshop. A registration fee of $75.00 payable at the workshop will be required from each person attending. The pre-registration deadline is August 28, 1999. The pre-registration form can be found at the web sites listed below.

Abstract submission and pre-registration can be done at the following web sites:

IGN IGEX Web site: http://lareg.ensg.ign.fr/IGEX
ION IGEX Web site: http://www.ion.org/workgroup.html

GENERAL INFORMATION

Nashville is known as Music City, U.S.A. It is the home of countless musicians and songwriters, the Grand Ole Opry and the Country Music Hall of Fame. Bluegrass, jazz and other styles of music can also be found in Nashville. Other attractions include Belle Meade Plantation (a 19(superscript: th) century Greek revival mansion), The Hermitage (home of Andrew Jackson, seventh President of the U.S.), The Parthenon (full-scale reproduction of Greek temple), Van Vechten Art Gallery at Fisk University, and riverboat rides.

A few of the hotels in the vicinity of the Convention Center are listed below. In order to obtain the conference rates for the hotels, you must inform the hotel that you are attending the Institute of Navigation meeting.

Renaissance (Headquarters Hotel, adjacent to the Convention Center): Phone 615-255-8400; $116 single/double per night, $136 club level per night
Crowne Plaza: Phone 615-259-2000; $111 single/double per night
Doubletree Hotel: Phone 615-244-8200; $99 single per night, $109 double per night
Union Station Hotel: Phone 615-726-1001; $111 single per night, $131 double per night
ClubHouse Inn: Phone 615-244-0150

Specific information about the workshop including the meeting circulars, program details and registration procedures are available on the ION GGIWG web site under the IGEX heading at http://www.ion.org/workgroup.html and also at the IGN IGEX web site http://lareg.ensg.ign.fr/IGEX. Information about registering for the ION Satellite Division Meeting GPS-99 and general information about Nashville will be available on the ION web site at http://www.ion.org or the Nashville web site http://www.nashville.citysearch.com. Questions can be addressed to the Chair or Co-chair of the Organizing Committee.

ORGANIZING COMMITTEE:

Jim Slater, Chair
NIMA, USA
E-mail: slaterja@acq.osd.mil
Phone: 703-588-7431

Carey Noll, Co-chair
NASA GSFC, USA
E-mail: noll@cddis.gsfc.nasa.gov
Phone: 301-614-6542

Werner Gurtner, University of Berne, Switzerland (gurtner@aiub.unibe.ch)
Wlodzimierz Lewandowski, BIPM, France (wlewandowski@bipm.fr)
Pratap Misra, M.I.T. Lincoln Laboratories, U.S.A. (misra@ll.mit.edu)
Ruth Neilan, NASA Jet Propulsion Laboratory, U.S.A. (ren@cobra.jpl.nasa.gov)
Robert Weber, Technical University of Vienna, Austria (rweber@luna.tuwien.ac.at)
Pascal Willis, Institut Geographique National, France (pascal.willis@ensg.ign.fr)

IGEX-98 Campaign to Continue

The official end of the extended IGEX-98 campaign was April 19, 1999. IGEX-98 was a success beyond expectation, and there is a growing and important scientific user community, in particular in the field time and frequency transfer, urging the participants to continue with the IGEX-like activities. Therefore, the IGEX-98 steering committee has requested that the various components of the experiment continue their activities on a best-effort basis at least until the IGEX workshop in September in Nashville, TN (see previous article). It is planned that a proposal for a more permanent continuation of IGEX-98 will be presented by the steering committee. At this time, the steering committee wishes to express their sincere thanks to all individuals and institutions, who made the IGEX-98 such a great success. The IGEX-98 campaign has exceeded its initial goals and also its original duration; it is now possible to obtain precise GLONASS orbits from four different analysis groups working with three different software packages using data from the global IGEX-98 GPS/GLONASS tracking network. A questionnaire will be sent out to participants concerning their willingness to continue participation beyond the official end of the campaign. The steering committee will give a report to the IGS governing board at its meeting in June.

DATA BITS AND BYTES

This section is designed to give brief notices of special events, new data sets, or problems encountered in recent months. The CDDIS staff believes the user community should be informed of these problems in order to ensure that the best results possible are produced from data issued by the archive.

Permanent GPS Network Update

Since the February 1999 issue of the CDDIS Bulletin, the CDDIS has archived daily (Table 1) and hourly (Table 2) data from the following new GPS tracking sites:

Table 1. New GPS Tracking Sites

The CIC1 is a new monument at Ensenada (formerly CICE); the antenna was moved due to construction activity near the old site (IGSMail 2152). The DAEJ is a new mark at Taejon (formerly TAEJ); IGSMail messages 2192 and 2212 discuss the move.

Table 2. New GPS Tracking Sites Providing Hourly Data

At this time, hourly data from 46 sites are available from the CDDIS on a daily basis.

Recent SLR System Problems

MOBLAS-4: The MOBLAS 4 system (station number 7110) had a drifting epoch time bias (-0.4 to —13.9 microseconds) between November 25, 1998 at 12:00 GMT and November 26, 1998 at 15:00 GMT, inclusive. The problem was corrected by replacing the cesium. The time bias correction formula is -0.4 microseconds -12 microseconds*(fraction of day past 12:00 GMT on November 25). For example, the time bias correction at 12:00 GMT on November 25 can be calculated as: -0.4 microseconds = -0.4 —0. The time bias correction for 10:00 GMT on November 26 can be calculated as -11.4 microseconds = -0.4 - 12 *(22/24).

MOBLAS-5: The MOBLAS 5 system (station number 7090) had a -387.5 microsecond epoch time bias on December 21, 1998.

MOBLAS-7: The MOBLAS 7 system (station number 7105) had a fixed epoch time bias between March 04, 1999 at 20:15 GMT and March 10, 1999 at 19:15 GMT, inclusive. The epoch time bias correction is +201.5 microseconds.

The user can correct for any of these time bias errors as follows:

corrected time tag = normal point time tag - (time bias correction)

The SLR stations regret any inconvenience these problems may have caused the user community.