One of the goals of the Virtual Astronomical Observatory (VAO) is to bring the Virtual Observatory to astronomers; that is, provide access to worldwide data sets through tools and environments that astronomers use everyday. A poster paper, reproduced below, presented by Ray Plante et al. at the recent 223rd Meeting of the American Astronomical Society (AAS) in January 2014 shows considerable progress in this area. The paper describes two command line tools developed by the VAO that are ready for deployment: PyVO and VOClient. Both these tools support the VO’s goals of seamless discovery of, and access to, distributed astronomy data. Command line tools have the obvious advantage over web interfaces of supporting bulk access to many data sets in a simple script.
Python has proved an immensely powerful language in astronomy, and there are numerous packages and environments optimized for astronomy (such as PyRAF, CASA, Sherpa and others). Py-VO is a pure Python package for querying worldwide databases. It is freely available on GitHub, and its main capabilities are:
- Find archives and catalogs based on science keywords via simple registry searches.
- Find and download for images and spectra from multiple archives.
- Search source and observation catalogs by position on the sky.
VOClient, on the other hand, supports data discovery in other languages. It is written in C, offers underlying implementation for bindings to multiple languages, and shares a common Python API with PyVO. It extends the capabilities of Py-VO, as follows:
- Provides higher-level capabilities managing data from many archives.
- Built-in SAMP support for connecting to other desktop applications; e.g. download cutout images and display them in an external viewer; and
- Provides tasking framework for accessing legacy software from Python.
The poster below describes these packages in greater detail and shows a worked example: