New Space and Tech

The Elliptical Uranian Relativity Orbiter (EURO) Mission

By Keith Cowing
Status Report
March 3, 2023
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The Elliptical Uranian Relativity Orbiter (EURO) Mission
Orbital geometry of EURO for a 2 000 × 100 000 km orbit oriented with respect to the ICRF according to Equations (46)–(47). The Uranian spin axis, in yellow, is oriented as per Equations (20)–(21) with respect to the CE. — astro-ph.IM

Recent years have seen an increasing interest in sending a mission to Uranus, visited so far only by Voyager 2 in 1986.

EURO (Elliptical Uranian Relativity Orbiter) is a preliminary mission concept investigating the possibility of dynamically measuring the planet’s angular momentum S by means of the Lense-Thirring effect affecting a putative Uranian orbiter.

It is possible, at least in principle, to separate the relativistic precessions of the orbital inclination I to the Celestial Equator and of the longitude of the ascending node Ω of the spacecraft from its classical rates of the pericentre ω induced by the multipoles Jℓ,ℓ=2,3,4,… of the planet’s gravity field by adopting an orbital plane containing the planet’s spin axis k̂ , perpendicular to the Celestial Equator, and whose position in the latter is the same as of the projection of k̂ on to it.

For a wide and elliptical 2000×100000km orbit, the gravitomagnetic signatures amount to tens of milliarcseconds per year, while, for a suitable choice of the initial conditions, the peak-to-peak amplitude of the range-rate shift can reach the level of ≃1.5×10−3 millimetre per second in a single pericentre passage of a few hours. By lowering the apocentre height to 10000km, the Lense-Thirring precessions are enhanced to the level of hundreds of milliarcseconds per year. The uncertainties in the orientation of k̂ and in I are major sources of systematic bias; it turns out that they should be determined with accuracies as good as ≃0.1−1 and ≃1−10 milliarcseconds, respectively.

Lorenzo Iorio, Athul P. Girija, Daniele Durante

Comments: LaTex2e, 38 pages, 7 figures, no tables
Subjects: General Relativity and Quantum Cosmology (gr-qc); Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Space Physics (
Cite as: arXiv:2303.00812 [gr-qc] (or arXiv:2303.00812v1 [gr-qc] for this version)
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Submission history
From: Lorenzo Iorio
[v1] Wed, 1 Mar 2023 20:28:17 UTC (603 KB)

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