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 Mmin

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

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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, namelyITRF2020, 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