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IERS Message No. 431                                      April 21, 2021
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IAG 2021, Session 1.5 on improving consistency between TRF, CRF and EOPs


Dear Colleagues,

As you know, the IAG Scientific Assembly will soon take place from 2021
June 28th to July 2nd.

The website of the event is available at
http://www.iag2021.com/en/web/index/ .

The abstract submission deadline approaches quickly. It is April 30th.

We, the session conveners of Session 1.5, would like to draw your
attention to the session "Comparison and combination of space geodesy
techniques for improving consistency between TRF, CRF and EOPs". The
full session description is displayed below.

We are looking forward receiving your abstracts and apologize for
multiple postings.

Best regards,
Robert Heinkelmann, Chengli Huang, Zinovy Malkin and Manuela Seitz


Symposium 1, Session 5

Comparison and combination of space geodesy techniques for improving
consistency between TRF, CRF and EOPs

The international terrestrial and celestial reference frames, ITRF and
ICRF, respectively, as well as the link between them expressed by the
Earth Orientation Parameters (EOP) are key products of geodesy and
astrometry. Many scientific and practical applications rely on the
consistency of ITRF, ICRF, and EOP, and the requirements to all the
components of this triad with respect to accuracy, precision and
consistency grow steadily. Today, ITRF and ICRF are computed separately,
but are linked by cross-alignments or by fixing parameters. While the
ITRF and consistently estimated EOP series are derived from a
combination of the four space geodetic techniques VLBI, SLR, GNSS and
DORIS, the ICRF and the related EOP series are derived from VLBI
observations only. To reach a high consistency between the products, the
homogeneity of geophysical and astronomical models, of geodetic datum,
and of parameterization is necessary. The topics discussed in this
session will include the comparison and combination of EOP and TRF
solutions derived by different techniques, as well as comparison of
VLBI-only and multi-technique CRF realizations including assessing and
understanding the systematic differences between them, and their impact
on EOP estimates. A further important discussion topic will be issues
currently preventing the realization of the terrestrial and celestial
reference systems at the mm/microas level of accuracy, such as
deficiencies of the station network including station instabilities,
technological (precision) limitations of existing techniques,
incompleteness of the theory and models, not fully understood and
agreed-upon details of the processing strategy, and others. The session
solicits contributions to all these topics.

This session solicits contributions focusing on the following aspects:
* Comparison and combination of EOP solutions by different techniques.
* Comparison and combination of TRF solutions derived by different
  techniques.
* Comparison of VLBI-based and combined multi-technique CRF
  realizations.
* Unification of astronomical and geophysical modeling.

Keywords: Terrestrial Reference Frame (TRF), Celestial Reference Frame
(CRF), Earth Orientation Parameters (EOPs), space geodetic techniques,
VLBI, multi-technique CRF realization.


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