Subject: [IGSMAIL-1918] Creation of the IGS Ionosphere Working Group
From: Joachim Feltens
Date: Mon, 8 Jun 1998 1:13:12 PDT

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IGS Electronic Mail      Mon Jun  8  1:13:12 PDT 1998      Message Number 1918
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Author: Joachim Feltens
Subject: Creation of the IGS Ionosphere Working Group

Subject: Creation of the IGS Ionosphere Working Group

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Joachim Feltens                                Darmstadt, 8 June 1998
EDS at ESOC-FDD
Robert-Bosch-Strasse 5
D-64293 Darmstadt
Germany

This is the second attempt to send this IGSmail. The first attempt on
Friday evening failed.

Best regards      Joachim
=====================================================================

Joachim Feltens                                Darmstadt, 5 June 1998
EDS at ESOC-FDD
Robert-Bosch-Strasse 5
D-64293 Darmstadt
Germany

Stefan Schaer                                      Berne, 5 June 1998
Astronomical Institute
University of Berne
Sidlerstrasse 5
CH-3012 Berne
Switzerland

Subject: Creation of the IGS Ionosphere Working Group

Dear IGS colleagues,

at the 1998 IGS Analysis Centers Workshop, 9-11 February in Darmstadt, it
was decided to establish an IGS Ionosphere Working Group (WG).

According to the working plan and time schedule set up at the Darmstadt
workshop, the IGS Ionosphere WG was formally established by the IGS
Governing Board at its meeting of May 28, 1998 in Boston.

In the WG's Terms of Reference attached below you can find a list of WG
members and of agencies contributing to that effort. Further participation
in the WG and contributions to the IGS ionosphere work (as IAAC, IACC, IAVC,
etc.) are invited and encouraged. Please contact the chairman of the IGS
Ionosphere Working Group for further information.

Background
----------

Since several years the IGS community has been well aware of the fact
that the world-wide IGS network offers a unique opportunity to extract
ionospheric information on a global scale. Already at the IGS workshops
held in Potsdam in May 1995 and in Silver Spring in March 1996,
subsessions were dedicated to the ionosphere. In order to get an idea
of the accuracies that can be achieved, an intercomparison of ionosphere
products provided by several Analysis Centers was performed. In addition
Analysis Centers (ACs) interested to contribute to an IGS ionosphere
product were identified.

Most ACs are today in a position (or close to that state) to provide
ionosphere information on a routine basis. An official format for the
exchange of ionosphere maps, called IONEX, has been developed and
approved. At the 1998 IGS Workshop in Darmstadt it was decided to start
a coordinated routine processing and a combination of IGS ionosphere
products.

The importance of an IGS engagement within the area of ionosphere
science is obvious. Since mid 1996 we are approaching the next solar
maximum. Therefore good and rapidly available information about the
ionosphere's actual state becomes increasingly important. Users of
satellite navigation systems need accurate corrections to remove signal
degradation caused by the ionosphere, information on the ionosphere's
behavior is of great importance for radio signal propagation
applications, and scientists will benefit from up-to-date and long-term
ionosphere information.

IGS Ionosphere Working Group
----------------------------

The Terms of Reference for the IGS Ionosphere Working Group is attached
to this IGS message.

First IONEX files of Ionosphere Associate Analysis Centers (IAACs) shall
be made available through the IGS Global Data Centers in June 1998. The
IGS Ionosphere Pilot Project shall then start in August 1998.

****************************************************************************
* Further participation in the WG and contributions to the IGS ionosphere  
*
* work (as IAAC, IACC, IAVC, etc.) are very much appreciated.              
*
****************************************************************************

Best regards,

Joachim Feltens and Stefan Schaer

References
----------

Feltens, J., and S. Schaer (1998): 'IGS Products for the Ionosphere', in
        Proceedings of the 1998 IGS Analysis Centers Workshop, ESOC,
        Darmstadt, Germany, February 9-11, 1998.

Schaer, S., W. Gurtner, and J. Feltens (1997): 'IONEX: The IONosphere Map
        EXchange Format Version 1', February 25, 1998, in Proceedings of
        the 1998 IGS Analysis Centers Workshop, ESOC, Darmstadt, Germany,
        February 9-11, 1998.

The Proceedings of the 1998 IGS Analysis Centers Workshop are currently in
preparation. PostScript files of the above papers are available via AIUB's
anonymous ftp server:

  ftp ubeclu.unibe.ch (130.92.6.18)
  anonymous
  "your e-mail address"
  cd aiub$ftp

The corresponding files are:

  [papers]ionopp98.ps (Position Paper)
  [ionex]ionex1.ps (IONEX Manual)
  [papers]ionowg.ps (Terms of Reference)

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

Terms of Reference for the IGS Ionosphere Working Group
-------------------------------------------------------

Stefan Schaer and Joachim Feltens
on behalf of the GPS-IONO Group

June 5, 1998

General Goals
-------------
The IGS Ionosphere Working Group is a long-term working group (WG). It
should be active at least till the end of the next solar maximum. It
exploits the permanent IGS network of stations and the IGS infrastructure
to derive global IGS ionosphere maps and IGS ionosphere models.

The most important short-term goal (to be accomplished by an IGS Pilot
Project of two years, see below) consists of the development of IGS Global
Ionosphere Maps based on a combination of ionosphere maps regularly
produced by IGS Ionosphere Associate Analysis Centers (IAACs) on which more
information is provided below.

One of the important long-term goals consists of the validation of the IGS
Ionosphere Maps. This validation may lead, in the collaboration with the
ionosphere community, to an IGS Ionosphere Model.

This charter is based on first considerations provided by Gerhard Beutler
and John Dow (e-mail from April 6, 1998).

Working Plan 1998-2000
----------------------
The following goals should be achieved in the time period mid 1998 to mid
2000 (these goals were stated in the ionosphere position paper at the
Darmstadt workshop):

- Global ionosphere maps (TEC maps) including satellite-specific
  differential code biases (DCBs) from contributing Analysis Centers are
  made available in IONEX format through the IGS Global Data Centers.

- Definition of minimum analysis and performance standards for IAACs:
  - minimum analysis standards, see recommendations of Darmstadt
    position paper,
  - ionosphere products are made available not later than the IGS
    final orbits and EOPs, i.e., 11 days after the observations.

- TEC maps and DCB values as produced by individual analysis centers are
  compared by the IGS Ionosphere Coordinating Center. A weekly report has
  to be produced.

- Individual TEC maps and DCB sets are combined into a preliminary IGS
  Combined Ionosphere Product. The weekly report contains also
  "rms-values" relative to the combined product.

- Validation of IGS Ionosphere Products using independent data and methods
  (ionosondes, TOPEX, future satellite missions, etc.). The WG has to
  define criteria and guidelines for the validation of TEC maps (absolute
  accuracy in comparison with independent ionospheric data, consistency
  between equivalent TEC maps).

- A comparison of TEC maps with TEC data derived from well-known models
  such as IRI will be useful to check both, the IONEX data as well as the
  model considered.

- Deadlines for ionosphere product delivery will be reviewed after at
  least one year of pilot service. Possibly, an IGS Rapid Ionosphere
  Product may be defined.

- Principles for the definition of an IGS Ionosphere Model are developed.

On the occasion of the solar eclipse on 11 August 1999 the WG will
organize and coordinate a special observation campaign. This event is a
unique opportunity to demonstrate the power of the GPS technique in
monitoring the ionospheric ionization. As the zone of totality crosses
Europe, the rather dense portion of the IGS network provides excellent
conditions for monitoring the eclipse. Nevertheless, non-IGS stations
should also be activated and included in the data analysis.

Structure of the Working Group and Initial membership list
----------------------------------------------------------
Representatives of those Analysis Centers which confirmed their
willingness to contribute to an Pilot IGS Ionosphere Service, namely
  Mihail Codrescu (SEC),
  Joachim Feltens (ESOC),
  Mariusz Figurski (WUT),
  Manuel Hernandez-Pajares (UPC),
  Pierre Heroux (NRCan),
  Attila Komjathy (CCAR),
  Steven Musman (NOAA),
  Stefan Schaer (CODE),
  Peter Stewart (UNB),
  Rene Warnant (ROB),
  Brian Wilson (JPL),
representatives from the ionosphere research community,
  Dieter Bilitza (GSFC),
  Norbert Jakowski (DLR),
  Reinhard Leitinger (TU Graz, not confirmed),
as IGS Analysis Center Coordinator,
  Jan Kouba (NRCan),
and as representative from the IGS CB,
  Ruth Neilan (JPL).
Further participation will be called for through an IGS-mail message.

The IGS Ionosphere Working Group consists of
- Chairperson: Joachim Feltens (ESOC).
- IGS Ionosphere Associate Analysis Centers (IAACs) generating ionosphere
  maps in the IONEX format with the defined time resolution, namely
    CODE,
    ESOC,
    JPL,
    NOAA (not yet ready),
    NRCan,
    UPC.
  All these centers confirmed their participation.
- IGS Ionosphere Associate Combination Center(s) (IACC); interest
  indicated by ESOC.
- IGS Ionosphere Associate Validation Center(s) (IAVC).
Further participation for all categories of IAACs, IACCs, and IAVCs is
fostered through IGS-Mail message.

The chairperson should be the representative of a TEC map producing center
(IAAC/IACC). The IACC(s) must be associated with one of the IAACs. The
IAVC(s) should have experience in the analysis of alternative (non-GPS)
data. IAVC candidates are:
  ESOC, using ERS data,
  ROB, using ionosonde data,
  UPC, making comparisons with IRI.

Schedule for Pilot Project
--------------------------
- Establishment of IGS Ionosphere Working Group (May 1998)
- Make IONEX files of IAACs available through IGS Global Data Centers
  (June 1998)
- Start of pilot project in August 1998 including comparisons (not yet
  combinations)
- Start of combinations, based on proposal from IACC(s)
- Start of validation, based on proposal from IAVC(s)
- First report to IGS GB (December 1998)
- Review of first year of operations (August 1999)

Accronyms
---------
CB ........ Central Bureau
CCAR ...... Colorado Center for Astrodynamics Research, Boulder,
              Colorado, U.S.A.
CODE ...... Center for Orbit Determination in Europe,
              Astronomical Institute, University of Berne, Switzerland
DCB ....... Differential Code Bias
DLR ....... Deutsche Forschungsanstalt fuer Luft- und Raumfahrt, 
              Fernerkundungsstation Neustrelitz, Germany
ESOC ...... European Space Operations Centre, Darmstadt, Germany
GB ........ Governing Board
GPS ....... Global Positioning System
GSFC ...... Goddard Space Flight Center, Greenbelt, Maryland, U.S.A.
IAAC ...... Ionosphere Associate Analysis Center
IACC ...... Ionosphere Associate Combination Center
IAVC ...... Ionosphere Associate Validation Center
IGS ....... International GPS Service
IONEX ..... IONosphere Map EXchange Format
IRI ....... International Reference Ionosphere
JPL ....... Jet Propulsion Laboratory, Pasadena, California, U.S.A.
NOAA ...... National Oceanic and Atmospheric Administration,
              Silver Spring, Maryland, U.S.A.
NRCan ..... National Resources Canada, Ottawa, Ontario, Canada
ROB ....... Royal Observatory of Belgium, Brussels, Belgium
SEC ....... Space Environment Center, Boulder, Colorado, U.S.A.
UNB ....... University of New Brunswick, Fredericton, New Brunswick, Canada
UPC ....... Polytechnical University of Catalonia, Barcelona, Spain
TEC ....... Total Electron Content
TU Graz ... Technical University Graz, Graz, Austria
WUT ....... Warsaw University of Technology, Warsaw, Poland

[Mailed From: [email-masked] (J. Feltens x2078 A239 mbp/fcsd/oad)]