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IERS Message No. 428                                      April 07, 2021
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IAG 2021, Session 1.1 "International Terrestrial Reference Frame ..."


Dear Colleagues,

We would like to draw your attention to the "International Terrestrial
Reference Frame: strengths, weaknesses and strategies for future
improvements" session (1.1) of the next scientific assembly of the
International Association of Geodesy virtual meeting (June 28-July 2,
2021). Please consider submitting an abstract to this session. Please
see http://www.iag2021.com/en/web/index/1646_140108 for this and other
Symposium 1 sessions.

Abstract submission deadline: 30th April, 2021
(http://www.iag2021.com/en/web/index/1646_802946).

We are looking forward to your contributions. With apologies for
cross-postings.

Best regards,
Xavier Collilieux, Ryan Hippenstiel, Zhiping Lu, Anthony Memin


Session 1.1: International Terrestrial Reference Frame: strengths,
weaknesses and strategies for future improvements

The Terrestrial Reference Frame is fundamental for monitoring Earth
rotation in space and for all geoscience applications that require
absolute positioning and precise orbit determination of artificial
satellites. The International Terrestrial Reference Frame (ITRF) series
are determined using geodetic data from Doppler Orbitography and
Radiopositioning Integrated by Satellite (DORIS), Global Navigation
Satellite Systems (GNSS), Satellite Laser Ranging (SLR) and Very Long
Baseline Interferometry (VLBI). Their overall accuracy depends on data
modeling strategies, on the precision of the relative position of
geodetic instruments at co-location sites (local tie survey) and on the
combination strategy in the final data adjustment.

A new release of the International Terrestrial Reference Frame, namely
ITRF2020, is currently under preparation. The objective of this session
is to discuss any advancement that could lead to an improvement of the
next Terrestrial Reference Frames in terms of accuracy of the frame
parameters and station coordinates. The following topics are of specific
importance:

- Recent space geodetic data modeling updatesand mitigation of technique
  systematic errors.

- New local tie determination and challenges.

- Impact of nonlinear stationmotions (loading effects, post-seismic
  deformation, etc.) and their modeling on the terrestrial reference
  frame.

- Combination strategies for the ITRF determination.

Keywords: International Terrestrial Reference Frame (ITRF), DORIS, GNSS,
SLR, VLBI, multi-technique combination, frame estimation, local ties,
secular/non-secular station motions, GIA, loading effects


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