Analysis software

A major consideration here is in balancing currently available astronomical data analysis packages with in house software components. Given the large volume of data that will be involved, large scale image and data analysis software will be written using a low level language. C++ is the language choice because it is object oriented and allows encodeing of very complex data structures.

Software modules include:

• Utilities for basic image manipulation operations such as pixel rebinning, resampling to new coordinate systems, etc. Image classes will be developed in C++ with appropriate I/O interfaces (based on CFITSIO in the case of FITS images).
• Source extraction, measurement, and classification tools. Existing software packages include DOPHOT, DAOPHOT, and SExtractor. It would probably also be necessary to develop bespoke software to provide additional functionality - an example here would be in the construction of source catalogues merged across the different passbands.
• Astrometric and photometric calibration tools. Probably requires a combination of existing and bespoke software.
• Difference imaging tools. These would be useful for constructing emission line images derived from subtracting a broad band (e.g. K) image from a narrow band image (e.g. H2). Also useful for variability studies. We have software that can generate difference images by optimally matching the seeing on the two images involved (see http://www-wfau.roe.ac.uk/sss/halpha).
• We also plan to implement software from drawing upon our astroinformatics research. Software has been developed that allows the identification of artifacts such as satellite trails and diffraction halos in CCD images (Storkey et al. 2002, in preparation)
• Image combining software. Tools for combining CCD frames taken in overlapping regions of the sky to produce single layer image mosaics and multiple layered images derived from stacking frames. This would involve development of special classes to deal with mosaic cameras such as WFCAM.

As far as on-the-fly applications are concerned, the feasibility of manipulation of large images is questionable when they reach Gbytes in size. All of the formal science requirements will be subject to the limitations of implementation constraints and network bandwidth. However, we suggest that no user would need or expect rapid response to use cases requiring manipulation of large imaging datasets.