[FPSPACE] Does Cassini allow to measure relativistic orbital effects in the Saturnian syst

[LARRY KLAES]

General Relativity and Quantum Cosmology, abstract
gr-qc/0605111

From: Lorenzo Iorio [view email]

Date (v1): Fri, 19 May 2006 15:49:22 GMT (24kb)

Date (revised v2): Mon, 5 Jun 2006 15:14:03 GMT (10kb)

Does Cassini allow to measure relativistic orbital effects in the Saturnian 
system of natural satellites?

Authors: Lorenzo Iorio

Comments: Latex2e, 9 pages, no figures, 3 tables, 12 references. Removed 
discussion on pericentres, focus on the mean longitudes only in view of the 
small eccentricities of the Saturnian satellites'orbits

In this paper we address the following question: do the recent advances in 
the orbit determination of the major natural satellites of Saturn obtained 
with the analysis of the first data sets from the Cassini mission allow to 
detect the general relativistic gravitoelectric orbital precessions of such 
moons?

The answer is still negative. The present-day down-track accuracy would be 
adequate for Mimas, Enceladus, Thetys, Dione, Rhea and Titan and inadequate 
for Hyperion, Iapetus and Phoebe. Instead, the size of the systematic errors 
induced by the mismodelling in the key parameters of the Saturnian 
gravitational field like the even zonal harmonics Jl are larger than the 
relativistic down-track shifts by about one order of magnitude, mainly for 
the inner satellites like Mimas, Enceladus, Thetys, Dione, Rhea, Titan and 
Hyperion. Iapetus and Phoebe are not sensibly affected by such kind of 
perturbations. Moreover, the bias due to the uncertainty in Saturn's GM is 
larger than the relativistic down-track effects for all such moons. Proposed 
linear combinations of the satellites' orbital elements would allow to 
cancel out the impact of the mismodelling in the low-degree even zonal 
harmonics and GM, but the combined down-track errors would be larger than 
the combined relativistic signature.

http://arxiv.org/abs/gr-qc/0605111