The 3D Viewer Project
Introduction and Scope
The majority of present and future ESO facilities (VLT, ALMA, and the E-ELT) feature instruments which produce datacubes (i.e., 2 spatial, 1 wavelength/frequency/time dimension). In this context, the need for a viewer tool, capable of handling data-cubes, was raised and discussed. A project was set up to deliver a 3D viewer to be used by the ESO staff and community for the visualization and basic scientific exploitation of (large) 3D datasets produced by ESO instruments. This tool is presently focused on the VLT/MUSE
2nd generation instrument, but it shall include the capability of visualizing the other single field IFUs operated at the VLT. Given the limited manpower and timeframe (beta-version delivery before July 2012) available to the project, it was decided to not build the viewer from scratch but to base its development on an already existing software platform.
3D Viewer in CASA
Within CASA there exists already a quite powerful viewer (casaviewer) that already implements many of the requirements of the 3D viewer, and after an evaluation of several candidate platforms it was decided to develop the 3D viewer as part of the CASA software. Besides a short development time for the 3D viewer a strong argument was also to develop synergies between the ALMA and VLT user community.
As first steps, we have evaluated the CASA viewer and identified the requirements that still have to be implemented to meet the needs of the ESO 3D cubes . These include:
- the wavelength as a unit in the spectral dimension;
- the support of multi-extension fits images;
- a data model that contains errors and data quality information for each pixel;
- the possibility to display information from external sources, e.g. source catalogs.
The software development plan attached to this page (see attached document below) contains a detailed list of all the requirements (see attached document below) that have to be implemented. The priority of every development item was estimated by P. Ballester and H. Kuntschner and then the development plan was prepared by sorting these items according to their priorities.
- "CTYPE=WAVE" (4.4.1) implemented in December 2010 by D. Petry (r13802)
- non-zero FITS extensions can be accessed in the viewer (CASA 3.2)
- wavelength and air-wavelength values are displayed as spectral values in the viewer (CASA 3.2)
- various placement of the spectral values in the viewer (CASA 3.3)
- error values can be loaded together with the data values (CASA 3.3)
- selection of different spectral units (wavelength / frequency) in the viewer (CASA 3.3)
- extraction of the error in the spectral profiler (CASA 3.3)
- error plotting in the spectral profiler (CASA 3.3)
- different combine methods (median/average/sum) in the profiler (CASA 3.3)
- export of images (FITS and CASA image formats) from the viewer (CASA 3.4)
- export of extracted spectrum (FITS and ASCII format) in the profiler (CASA 3.4)
- interactive selection of a spectral region in the profiler (CASA 3.4)
- Collapse/Moments combination of images along the spectral axis from the profiler (CASA 3.4)
- Gauss plus Polynomial fits to the extracted spectra in the profiler (CASA 3.4)
- 2D Gaussian fit added to the region panel in the viewer (ESO release / CASA 3.5)
The project was finished at the end of July 2012. A special CASA release (bewteen 3.4 and 3.5) containing all the features described above had been created and is available for download at https://svn.cv.nrao.edu/casa/osx_distro/eso/
(MAC OSX) and at https://svn.cv.nrao.edu/casa/linux_distro/eso/
(Linux). This version of the ESO 3D Visualization Tool was presented to the ESO science community in a demo by Harald Kuntschner and Martin Kümmel on July 23rd. Together with the software a Cookbook
(12 pages) and a full Manual
(based on the corresponding chapters of the CASA User Reference & Cookbook) were released as ESO documents. Test rrocedures to ensure that the implemented features remain in CASA have been implemented. A close-out document has been prepared by Harald Kuntschner.