The LSST and big data science

The LSST Data Management Team is designing user tools that can operate on a variety of computing systems without the need for large downloads, all based on open-source software.  Their system includes two basic types of products: those produced for nightly observing and those produced for annual science releases.

Nightly processing will subtract two exposures of the each image field to quickly highlight changes. The data stream from the camera will be pipeline processed and continuously updated in real time, with a transient alert triggered within 60 seconds of completing an image readout.

Data complied into scheduled science releases will get considerable reprocessing to ensure that all contents are consistent, that false detections are filtered and that faint signal sources are confirmed.  Reprocessing will also classify objects using both standard categories (position, movement, brightness, etc.) and dimensions derived mathematically from the data themselves. Products will be reprocessed at time intervals from nightly to annually, which means that their quality will improve as additional observations are accumulated.

Preparing the science

The LSST program includes Science Collaborations, teams of scientists and technical experts that work to grow the observatory’s science agendas. There are currently eight collaborations in such areas as galaxies, dark energy and active galactic nuclei. One of the most unique, however, is the Informatics and Statistics Science Collaboration (ISSC) which, unlike other teams, doesn’t focus on a specific astronomy topic but cuts across them all. New methods will be needed to handle heavy computational loads, to optimize data representations, and to guide astronomers through the discovery process. The ISSC focus is on such new approaches to ensure that astronomers realize the best return from the anticipated flood of new data.

“Data analysis is changing because of the volume of data we’re facing,” says Kirk Borne, an astrophysicist and data scientist with Booz Allen Hamilton, and a core member of the ISSC. “Traditional data analysis is more about fitting a physical model to observed data. When I was growing up, we didn’t have sample sizes like this. We were trying to understand a particular phenomenon with our small sample sets. Now, it’s more unsupervised. Instead of asking ‘tell me about my model,’ you ask ‘tell me what you know.’ Data become the model, which means that more is different.”  

LSST data will almost certainly expand the chances for surprise. “When we start adding different measurement domains like gravitational wave physics and neutrino astrophysics for exploration,” adds Borne, “we start seeing these interesting new associations. Ultraluminous infrared galaxies are connected with colliding starbursting galaxies, for example, but it was a discovery made by combining optical radiation with infrared. Quasars were discovered when people compared bright radio observations of galaxies with optical images of galaxies.”

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