Following the launch of the first artificial satellite in 1957, geodesists refined knowledge of Earth’s flattening and used orbital drag observations from Sputnik to estimate upper atmosphere density. Since then, Precise Orbit Determination (POD)—where the satellite itself acts as a sensor through its orbital perturbations—has progressed to absolute orbit solutions at the centimeter (or sub centimeter) level to demanding long term stability on the order of 0.1 mm yr⁻¹ over decadal timescales, a prerequisite for quantitative climate change studies.

Today four Global Navigation Satellite System (GNSS) constellations are operational, and numerous Earth Observation missions rely on POD (e.g., satellite altimetry, gravimetry, InSAR, and Satellite Laser Ranging to passive spheres). Together they provide an unprecedented data set that can push orbit determination to its limits and enable new geophysical applications across the atmosphere (density and water vapor content), the ocean (sea level rise), land (large scale fluid mass redistribution and present day deformation), and the deep Earth (rheology at decadal scales).

This session aims to make the emerging challenges of orbit determination and modeling accessible to a broader community and to quantify how dynamics errors affect the many applications that depend on POD as their primary source of observations. Contributions are solicited (but not limited) to the following areas:

1. Precise orbit determination and absolute validation approaches.
2. Advances in modeling solar/terrestrial/thermal radiation pressure, atmospheric density and their interaction with space vehicles.
3. Updates on large-scale time-variable changes in the Earth’s gravity field (e.g., motion of the Earth’s center of mass relative to the crust).
4. Observational constraints on essential variables defining the status of climate change.
5. Improvements in observable modeling for all tracking systems (SLR, DORIS, GNSS) and assess their impact on POD.
6. Integration of refined clock modeling methods/space clocks into POD.
7. Studies for the co location of geodetic techniques in space (e.g., GENESIS) to strengthen the stability of future terrestrial reference frames.