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How to Read Copernicus Files

This page provides information on reading the Copernicus data sets using FITS readers written in various languages. As mentioned elsewhere, all the Copernicus data sets use the FITS binary table extension format which was approved by the IAU in 1994. The raw data sets however use the variable length array facility which, although included in the original binary table proposal, was not part of the officially approved format. Users may have more trouble therefore reading the raw files than the coadded scans or spectral atlas files, although there are many publicly-available FITS readers that can read all 3 formats.


One of the best supported, and most extensive, FITS readers is the FTOOLS and FITSIO software library written in C and FORTRAN by Bill Pence from HEASARC. These programs should be able to read all the various Copernicus data sets. The suite of programs can be built as either a stand-alone package or as an IRAF subpackage. The first example shows how to convert a quick-look co-added spectrum to an ASCII table. The second example hows how to create an ASCII table containing a single scan from a raw data (.pep) file. The third example shows how to access and manipulate individual Copernicus scans in a time series of a target pep file (i.e. constituent scans of the co-added data).

IDL FITS Readers:

There are a number of FITS readers that are written using the Interactive Data Language (IDL) A number of the FITS readers are included in IDL libraries that are available for free via the WEB and run on several different platforms. (Note however that IDL must be purchased for the local computer). One such library is the IUEDAC software package, originally written for analyzing data from the International Ultraviolet Explorer (IUE) satellite project. The IUEDAC examples show how to use the program IFITSRD to read the raw, coadded scan, and spectral atlas files, and plot counts versus wavelength. More information on IFITSRD can be found in the prolog of the program.

Another widely used IDL library is the IDL Astronomy User's Library. This library contains astronomy-related programs donated by several projects and includes several IDL FITS Readers. Three of the FITS readers are described in the Astronomy Library examples. (note that the Readfits(), Fits_*, and FTAB_* routines can not read the variable length arrays used in the raw data sets, but CAN read the coadded scan and spectral atlas FITS files). Additional documentation on all the listed IDL programs can be found in the procedure prologs.