Influence of the internal structure of Europa on the Doppler signal of an orbiter
(2009) European Planetary Science Congress — Location: Potsdam, Germany (13.September.2009)
Files
No attached file found for this publication.
Details
- Authors
- Abstract
- Europa, the second Galilean satellite starting from Jupiter, probably has a liquid ocean beneath the icy shell but the thickness of these layers is poorly known. From the values of the gravitational coefficients C20 and C22 of Europa determined by the Galileo mission, the to- tal thickness of the ice and water layer is evaluated to 80 - 170 km [1]. However, the thickness of the indi- vidual ice and water layers could not be determined, since their densities are similar. An important goal of the Europa Jupiter System Mission under study by NASA and ESA is to better constrain the ice shell and subsurface ocean of Eu- ropa. Important information on the interior structure is thought to result from observation of the tides, li- brations and obliquity of Europa. Here we assess the possibility to measure those quantities with a Radio Science instrument, which is part of the scientific core payload of the Europa orbiter of EJSM Together with the static gravity field of Europa, tides and rotation determine the orbital motion of a spacecraft around Europa. The quantities we take into account are C20, C22, the libration amplitude, the obliq- uity, the Love number k2 and its quality factor Q. For their dependence on the internal structure, see e.g. [2], [3], [4], [5], [6], [7] and [8]. ll these quantities induce perturbations (secular, long term and short period) of the orbital elements of the orbiter, thereby changing the spacecraft position and the relative radial velocity between the orbiter and a terrestrial observer (or Doppler signal). We calculate these perturbations by integration of Lagrange’s equa- tions in order to obtain an analytical expression for the Doppler signal (see [9] for a similar study for Mars). The effect of each parameter on the Doppler signal is determined for different initial orbital elements of the orbiter. To test the measurability, the effects are compared with the expected accuracy of the Doppler signal. [1] Anderson, J. D. et al. (1999) Science , 281, 2019– 2022. [2] Van Hoolst, T. et al. (2008) Icarus , 195, 386–399. [3] Van Hoolst, T. et al. (2009) Icarus , 200, 256–264. [4] Peale, S. J. et al. (1988) Mercury, University of Arizona Press , 461–493. [5] Bills, B. G. and Nimmo F. (2008) Icarus , 196, 293–297. [6] Wu, X. et al. (2001) Geophysical Research Let- ters , 28, 2245–2248. [7] Wahr, J. M. et al. (2006) JGR , 111, 12005–. [8] Lainey, V. (2005) PhD Thesis, Observatoire de Paris [9] Yseboodt, M. (2003) PhD Thesis, UCL
- Affiliations
Citations
Baland, R.-M., Yseboodt, M., Van Hoolst, T., & Dehant, V. (2009). Influence of the internal structure of Europa on the Doppler signal of an orbiter. European Planetary Science Congress, Potsdam, Germany. https://hdl.handle.net/2078.5/186622