When will the Europa Orbiter get there, and how will it determine whether there is an ocean?
Launch of the Europa Orbiter mission has been delayed until perhaps 2006 or 2007. Travel time to Jupiter is about 3 years, then it takes another 2.5 years or so to drop into Europa orbit. This means arrival in 2013 or 2014. The mission itself would last only a month or two after that, but enough to make critical measurements. Europa’s tidal deformation will be determined using Doppler measurement of radio signals (to determine the fluctuating gravity field), and an altimeter will measure the rising and falling of the surface tides. If Europa is frozen solid, the daily tidal fluctuation of its icy surface would be only about 1 m, but if there is a subsurface ocean (whether shallow or deep) the tidal fluctuation would be about 30 m. The orbiter will probably have a radar sounder instrument capable of detecting subsurface pockets of water and perhaps an ocean. The orbiter would also have a camera or cameras to image most of the surface at better than 300 m/pixel resolution and spots at ab
