Searchable Sky Coverage of Astronomical Observations: Footprints and Exposures

TL;DR

This paper introduces algorithms and a portable implementation for representing and manipulating complex sky coverage shapes on the celestial sphere, enhancing astronomical data indexing and accessibility.

Contribution

It presents new algorithms for generalized spherical polygons, integrated with a hierarchical mesh system, and provides a portable implementation used in major astronomical archives.

Findings

Enhanced sky coverage shape representation

Improved performance of spherical geometry routines

Integration with astronomical data archives

Abstract

Sky coverage is one of the most important pieces of information about astronomical observations. We discuss possible representations, and present algorithms to create and manipulate shapes consisting of generalized spherical polygons with arbitrary complexity and size on the celestial sphere. This shape specification integrates well with our Hierarchical Triangular Mesh indexing toolbox, whose performance and capabilities are enhanced by the advanced features presented here. Our portable implementation of the relevant spherical geometry routines comes with wrapper functions for database queries, which are currently being used within several scientific catalog archives including the Sloan Digital Sky Survey, the Galaxy Evolution Explorer and the Hubble Legacy Archive projects as well as the Footprint Service of the Virtual Observatory.