Open-Source High-Fidelity Orbit Estimation for Planetary Science and Space Situational Awareness Using the Tudat Software
Authors
Luigi Gisolfi
Dominic Dirkx
Sam Fayolle
Valerio Filice
Riva Alkahal
Miguel Avillez
Tristan Dijkstra
Jonas Hener
Lars Hinüber
Marco Langbroek
Nicolò Maistri
Michael Plumaris
Alfonso Sanchez Rodriguez
Giuseppe Cimò
Kevin Cowan
Fabien Dahmani
João Encarnacao
Geoffrey Garrett
Steve Gehly
Xuanyu Hu
Marceau Jeanjean
Antonio López Rivera
Andrea Minervino Amodio
Guifre Molera Calvés
Markus Reichel
Bart Root
Martin Søndergaard
Dominik Stiller
Simon Van Hulle
Gijs Verdoes Kleijn
Rees Williams
Daan Witte
Abstract
The TU Delft Astrodynamics Toolbox (Tudat) is a free open-source software suite for research and education in astrodynamics. Initially focused on numerical simulations of orbital dynamics and state estimation, it enables combining optical and radiometric tracking data from multiple sources to estimate the dynamics and parameters of natural and artificial bodies. Recent developments have added functionality for real tracking data analysis, with applications to planetary missions and Space Situational Awareness (SSA). Tudat currently supports processing of (i) deep-space Doppler and range data from DSN and ESTRACK, (ii) Doppler and VLBI data from the PRIDE experiment, and (iii) optical astrometry from the Minor Planet Center (MPC) and Natural Satellite Data Center (NSDC). Using tracking data from the MRO and GRAIL spacecraft and astrometric data of the asteroid Eros, we present prefit residuals (from SPICE-based observables) and postfit residuals (from fitting data to the Tudat dynamical model). Postfit Doppler residuals reach 1-5 mHz for MRO and GRAIL, orbit differences are a few meters for GRAIL and about one meter for MRO, and MRO range residuals are a few meters. From eight years of Eros astrometry, we obtain an orbit difference from the JPL Horizons solution by several tens of kilometers, consistent with its 3-sigma formal error. Tudat's SSA capability is demonstrated by propagating the orbit of Kosmos 482, a Venus lander launched in 1972 that remained in Earth orbit, over 50 years, including its predicted re-entry on May 10 2025. These examples showcase Tudat's modular, flexible, high-fidelity modeling across diverse orbital regimes within a fully open-source framework. All example code is publicly available, and future Tudat analyses will be published with fully reproducible code, allowing anyone in the community to improve and expand upon our work.
