Several of the world's large ground-based telescopes were also active during this exciting event, observing Titan before and near the Huygens encounter, within the framework of a dedicated campaign coordinated by the members of the Huygens Project Scientist Team. Indeed, large astronomical telescopes with state-of-the art adaptive optics systems allow scientists to image Titan's disc in quite some detail. Moreover, ground-based observations are not restricted to the limited period of the fly-by of Cassini and landing of Huygens. They hence complement ideally the data gathered by this NASA/ESA mission, further optimising the overall scientific return
Titan is tidally-locked to Saturn, and hence always presents the same face towards the planet. To image all sides of Titan (from the Earth) therefore requires observations during almost one entire orbital period, 16 days. The trailing hemisphere is the one we see when Titan moves away from us in its course around Saturn. The leading hemisphere is the one on the other side.