On-line Access and Visualization of Multi-dimensional FITS Data

Federl, Pavol

As astronomical data sets continue to grow in size, the challenges involved in data access and visualization increase in complexity. Obtaining entire data sets is time consuming, awkward and in many cases even impractical. Furthermore, visualization of data is traditionally accomplished off-line, requiring specialized software that is often OS/library dependent and cannot be easily installed everywhere.

We have implemented some Web-based tools for accessing and visualizing multidimensional FITS data as part of the CyberSKA Web portal. CyberSKA is a Canadian lead project aimed at developing cyberinfrastructure that will meet the evolving science needs of the Square Kilometre Array (SKA). The intent in offering on-line tools is to provide astronomers with easy access to data from any computer with a modern Web browser and Internet access. These tools are currently being used by members of the GALFACTS SKA pathfinder project for accessing and visualizing spectro-polarimetric image cube data.

The data access tool provides an interactive GUI for selecting a region of interest on a pre-generated thumbnail for the data set. Stokes parameters, spectral frequency range, and frequency width over which to average data can also be selected. The reduced data set is then generated on the server side, in a virtual machine-based Condor pool, and can eventually be downloaded to the user's computer through the browser. FITS files on the portal are automatically recognized by their MIME type, and can be viewed with a JavaScript-based visualization tool. The visualization tool currently supports interactive panning and zooming, histogram correction, color map adjustments, and displaying the data value at each pixel. Future work will involve establishing a cloud-based environment to dynamically manage the size of the Condor pool and launch other services based on user demand. We are also working on improving the scalability of the viewer to work with very large images.

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