CRIRES-POP

CRIRES-POP

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Contact:
Thomas Lebzelter
University of Vienna
Department of Astronomy
Türkenschanzstrasse 17
1180 Vienna / Austria
thomas.lebzelter AT univie.ac.at

How to access CRIRES data

Pipeline reduced data as well as raw data from the CRIRES spectrograph are stored as binary tables. The basic structure of the pipeline reduced data is the following.
A fits file for one wavelength setting (indicated in the file name) holds 5 parts:

Header: basic information for the whole data set.

CHIP1.INT1: a binary table with the data from the first of the four CRIRES detectors

CHIP2.INT1: a binary table with the data from the second of the four CRIRES detectors

CHIP3.INT1: a binary table with the data from the third of the four CRIRES detectors

CHIP4.INT1: a binary table with the data from the fourth of the four CRIRES detectors

Each binary table consists of 9 columns and 1024 rows. A description of the content of the 9 columns can be found in the table header. The most important ones for plotting the data are column 2, which include the flux values based on an optimized extraction, and column 8, which holds the wavelength for each data point.

For reading the binary tables, several tools exist. We give here a certainly incomplete list of possibilities:

fitsview: this is a very nice software which you can download here (NRAO website). It is available for UNIX, MacOS, and also Windows. With this software you can read, plot, display, and extract the data from the binary tables.

IDL-routines: there are two routines that can be used. We found them here:
http://idlastro.gsfc.nasa.gov/ftp/pro/fits_table/ftab_ext.pro

MIDAS also offers the possibility to read, plot and convert binary tables. Use these commands:
INDISK/FITS filename root=myfile
This will split the file filename into the four binary tables, which will get the names myfile0001.tbl to myfile0004.tbl.
SHOW/TABLE myfile0001
This shows the 9 column headers.
PLOT/TABLE myfile0001 #8 #2
This plots the extracted spectrum vs. wavelength. Note that you have to create a graph window first with the command CREATE/GRAPH.
ASSIGN/PRINT FILE myoutput.txt
PRINT/TAB myfile0001 ? output.fmt N
These two commands allow to convert a MIDAS binary table into an ASCII file. You have to create the file output.fmt first. For extracting wavelength and flux this file should include the lines:
DEFINE/FIELD 9 17 R F8.3 :Wavelength
DEFINE/FIELD 20 27 R F7.3 :Extracted_OPT

IRAF: please have a look at:
http://iraf.noao.edu/faq/FAQsec05.html

For more information on the CRIRES data format please have a look at the CRIRES webpages at ESO.

If you are aware of a further nice method, please send us details. We are happy to include it.

last modification: Oct 31 2011

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