Dear colleagues,<= /span>

we would like to draw your a= ttention to the session “G2.1 Precise Orbit Determination for Geodesy= and Earth Science” organized at the upcoming General Assembly of the= European Geosciences Union, taking place from 27 April-2 May, 2025. The EGU25 aims to bring together geoscientists from all= over the world to one meeting covering all disciplines of the Earth, plane= tary, and space sciences. With this session, we wish to provide a forum whe= re scientists, especially early career researchers, can present their work and discuss their ideas with ex= perts in all fields of geoscience. Especially, Precise Orbit Determination = is nowadays essential to provide observational constraints on essential met= rics defining the status of climate change, as well as a wide range of geophysical models.

G2.1 session description:

Precise orbit determination = is of central importance for many applications of geodesy and earth science= . The challenge is to determine satellite orbits in an absolute sense at th= e centimeter or even sub-centimeter level, and at the millimeter or even sub-millimeter level in a relative se= nse. Four constellations of GNSS satellites are available and numerous posi= tion-critical missions (e.g. altimetry, gravity, SAR and SLR missions) are = currently in orbit. Altogether, outstanding data are available offering new opportunities to push orbit de= termination to the limit and to explore new applications.=

This session aims to make ac= cessible the technical challenges of orbit determination and modelling to t= he wider community and to quantify the nature of the impact of dynamics err= ors on the various applications. Contributions are solicited from, but not limited to, the following areas: (1) precise o= rbit determination and validation; (2) satellite surface force modelling; (= 3) advances in modelling atmospheric density and in atmospheric gravity; (4= ) advances in modelling earth radiation fluxes and their interaction with space vehicles; (5) analysis of changes = in geodetic parameters/earth models resulting from improved force modelling= /orbit determination methods; (6) improvements in observable modelling for = all tracking systems, e.g. SLR, DORIS, GNSS, VLBI and their impact on orbit determination; (7) advances in= combining the different tracking systems for orbit determination; (8) the = impact of improved clock modelling methods/space clocks on precise orbit de= termination; (9) advances in modelling satellite attitude; (10) simulation studies for the planned co-location of= geodetic techniques in space mission GENESIS.

Please consider submitting a= n abstract to this dedicated orbit session. The deadline for abstract submi= ssion is January 15, 2025 at 13:00 CET.

We are looking forward to yo= ur contribution.

On behalf of the conveners o= f session G2.1, Alexandre Couhert

Co-conveners: Daniel Arnold, Ur= s Hugentobler, Jose van den IJssel, Frank G. Lemoine