Current and future data and services at ESA's Planetary Science Archive: from a peanut to the spherical duck

The Planetary Science Archive (PSA) of the European Space Agency (ESA) hosts all the data from ESA's Solar System missions. In addition, there are data of European instruments flown on the Indian Moon mission Chandrayaan-1 and ground based and Hubble Space Telescope observations of comet Halley (the target of ESA's first interplanetary mission Giotto) and comet Wirtanen (the originally intended target of the Rosetta mission).

Because of a launch delay, Rosetta indeed ended up at comet Churyumov-Gerasimenko (Chury for short). While Halley had already exhibited a peanut-like irregular shape, Chury turned out to be of a quite unexpected even more irregular shape that earned it the nickname ``rubber duck''. Because of the overhung areas, there are multiple points with the same longitude and latitude, and standard global map projections cannot display the complete surface. Therefore, the PSA is developing an interactive 3D view to facilitate location based data searches.

In order to nevertheless provide a global 2D view of Chury's complete surface, we have developed the Quincuncial Adaptive Closed Kohonen (QuACK) map. The self-organizing map ``learns'' the shape from randomly presented surface points. The resultant map projection is defined by a special shape model that can be unfolded into a rectangular grid. The topological equivalence with the Peirce quincuncial projection of the world makes it possible to define unambiguous generalized longitudes and latitudes. On these, any standard global map projection can be applied to display the complete surface of the comet.

Beyond merely providing a static global view, the generalized latitudinal coordinates make it possible to apply any tool originally designed exclusively for spherical bodies. In particular, hierarchical data structures like the Hierarchical Progressive Survey (HiPS) can be employed to create efficient interactive visualizations of high resolution data. We present a web based Aladin powered visualization of high resolution shape model data and images of Chury projected onto the QuACK map: the spherical duck.