[SUMER Emblem] The Data Cookbook

IDL-program DECOMPRESSION.PRO available here.
new: Remarks on line width estimation.
new: Remarks on line shift determination.

Imagine SUMER made a scan study and you want to visualize intensities, line shifts, line widths. You have to read one or more FITS files and produce pictures. How could you proceed?

Some IDL programs for this purpose are presented here. For a detailed description of the approach, please take a look at the Lindau Data Cookbook. - The programs are not specifically designed to deal with FITS files containing reference spectra etc., but rather to display two-dimensional images. They may not be suitable for all kinds of FITS files formats, but show some flexibility.

Step 1: Find the Study

Take a look at the SUMER Fits Files Catalogue, get the name of the file or maybe even a whole list of files.

Step 2: Get one FITS File

To get an overview, extract one FITS file with the help of program SDFITS_READONE.PRO. It uses the well-known routine FT_SUMREAD_FITS.PRO with a little dialogue around it. It gives some information on what is in the FITS file, shows images and spectra, and asks if data shall be saved in an IDL restore file. - It produces the prerequisites for Step 4.

Step 3: Get several FITS Files

To build a complete two-dimensional image of a study, use the program SDFITS_READLIST.PRO. It assumes a list of FITS files' names written to an ASCII file named DIRECT.LST. Then it does basically the same as Step 2 with a loop over all the files in that list. It is assumed, too, that all FITS files have the same north-south coordinate and that the data are ordered in east-west or west-east direction. - This also produces the prerequisites for Step 4.

Step 4: Process Image Arrays

After having restored, among other data, four two-dimensional images, namely line intensity, background intensity, line shift, and line width arrays, the program SDFITS_CORRECT.PRO can be applied. It leads through a dialogue to remove data faults in the form of vertical lines, performs a kind of flat field correction, puts the north to the top, and considers the scan direction. It also asks for the bottom and top detector pixel that you consider significant.

Step 5: Display Image Arrays

To display the pictures on screen or printer, the program SDFITS_DISPLAY.PRO can be used, together with an IDL/XDR restore file RGB.RST containing a color table for Doppler shifts. The program asks for the type of data (intensity, shift, width) to display, tries to correct the line position in a kind of de-stretching, and asks for some parameters to prepare the picture in the right scale. It does this in a dialogue, giving some hints on suitable answers. In the end, it asks whether the image shall be printed. - Please change "EAF_COLOR" to your own Postscript Color Printer if not working at the EAF in GSFC.
For questions, please contact Ingolf E. Dammasch.
IED 06.Feb.97