next up previous contents index
Next: 9.3 Interactive Data Processing Up: 9. Getting Started with Previous: 9.1 How to Retrieve


9.2 First Look at ISOCAM Data

As explained in Section 5.3.1, ISOCAM data products were designed to conform as much as possible to FITS standards. They are made up of a primary header plus a binary table extension containing the data. Despite that, some standard software tools for viewing and editing FITS format images, like fv (see: http://heasarc.gsfc.nasa.gov/ $\rightarrow$ Software $\rightarrow$ fv for information on this interactive FITS file editor) or SAOImage DS9 (an astronomical data visualisation application available at http://tdc-www.harvard.edu/ $\rightarrow$ SAOimage) are not able to read ISOCAM images produced by the OLP. On the other hand, IDL can easily read the OLP product files (with the mrdfits command), but an extra modification is needed in order to convert the files from 1024-element arrays to 32$\times$32-element images (using the reform command).

As an example, to read a CMAP file:


IDL> structure = mrdfits('cmap########.fits',1,header)
IDL> map = reform(structure.array,32,32,n)}

where n is the third dimension of the cube image (found when executing the mrdfits command).

For CMOS:


IDL> structure = mrdfits('cmos########.fits',1,header)
IDL> mosaic = 
reform(structure.array(*,*,0),structure.naxis1,structure.naxis2)

where structure.naxis1 and structure.naxis2 are the dimensions (in #pixels) of the mosaic image.

For a user who wants to work directly with fully reduced data, the recommended files to start with are:

Of course, tools to visualise and analyse scientifically these files are also available in CIA.

Users retrieving the so-called `browse products' (CPS files) should bear in mind that these products are essentially similar to the CMAP or CMOS (where relevant) files, with the difference that they only store the images in their extensions. The information about the image (coordinates, pfov, etc) is available in the header. However, errors are not stored. In CAM CVF observations a second CPS file contains the wavelengths for each of the planes of the cube image. The main advantage of the browse products is that they can be directly read by FTOOLS ( http://heasarc.gsfc.nasa.gov/ $\rightarrow$ Software $\rightarrow$ FTOOLS), but the recommendation is not to use them for science purposes.


next up previous contents index
Next: 9.3 Interactive Data Processing Up: 9. Getting Started with Previous: 9.1 How to Retrieve
ISO Handbook Volume II (CAM), Version 2.0, SAI/1999-057/Dc