HST data can be manipulated with several different software packages. In this section we introduce a few of the software language options.
STSDAS is an
IRAF package developed by STScI for the reduction and analysis of
HST data. The package contains
tasks that perform a wide range of functions supporting the entire data analysis process, from reading tapes, through reduction and analysis, to producing final plots and images. Sections 3.2 through 3.7 introduce the basics of
STSDAS, illustrating how to display
HST data, presenting some simple data manipulations, and pointing you towards more sophisticated tasks.
STSDAS is layered on top of the
Image Reduction and Analysis Facility (
IRAF)
software developed at the National Optical Astronomy Observatory (NOAO). Any task in
IRAF can be used in
STSDAS, and the software is portable across a number of platforms and operating systems. To exploit the power of
STSDAS, you need to know the basics of
IRAF. If you are not already familiar with
IRAF/
PyRAF, consult the
IRAF/
PyRAF Primer in
Chapter 4 before reading further.
PyRAF is a command language for
IRAF that is based on Python. It has a number of advantages over the
IRAF CL. Most importantly, with few exceptions, it allows use of exactly the same syntax as the
IRAF CL. Some of the advantages that it provides are:
Since PyRAF is so highly compatible with the
IRAF CL, virtually all of the examples shown in this handbook will work the same for
PyRAF. Minor differences include the user prompt and the graphics windows appearance.
Python is used for astronomical data reduction applications. It is a freely available, general-purpose, dynamically-typed interactive language that provides modules for scientific programming and is used for astronomical data reduction application. These modules include:
Python is a very powerful language that is well suited to writing programs to solve many needs beside scientific analysis. Tools are available to read (but currently not write) GEIS files.
Python can make use of PyRAF to allow access to
IRAF tasks. Tutorials are available which illustrate the use of Python for interactive data analysis in astronomy (in much the same style as is now popular with IDL). The initial focus of these tutorials is the use of interactive tasks for the novice user. The more advanced tutorials focus on teaching the details of Python programming. The tutorials can be downloaded from:
STScI is developing most of its new calibration and data analysis software in Python. More information on the use of Python to analyze
HST data can be obtained from:
IDL is an array-based, interactive programming language that provides many numerical analysis and visualization tools. It is typically much easier to develop new analysis and visualization applications and utilities in IDL than in Fortran or C. As a result, it is very popular in the astronomical community with many astronomers using it for their analysis of
HST data.
It can be obtained from ITT Visual Information Solutions (
http://www.ittvis.com/idl/), for a fee. Libraries for reading
HST data are part of the freely available ASTRON library (
http://idlastro.gsfc.nasa.gov) which has links to other IDL astronomy libraries.
This library does not support GEIS format directly so users will need to use the waivered FITS format obtained from the archive and manually extract the needed information.
