HST Data Handbook for COS

3.2 Navigating STSDAS

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The tasks in STSDAS are far too numerous and complicated to describe comprehensively in this volume. Instead, we will show you where to find the STSDAS tasks appropriate for handling certain jobs. You can refer to online help or the STSDAS User's Guide for details on how to use these tasks. Some useful online help commands are:

• apropos word - searches the online help database for tasks relating to the specified word (see Figure A.4).
• help task - provides detailed descriptions and examples of each task.
• help package - lists the tasks in a given package and their functions.
• describe task - provides a detailed description of each task.
• examples task - provides examples of each task.

3.2.1 STSDAS Structure

STSDAS is structured so that related tasks are grouped together as packages. For example, tasks used in the calibration process can be found in the hst_calib package, and tasks used for image display and plotting can be found in the graphics package. Table 3.1 shows the current STSDAS package structure. The current version of IRAF (v2.14 as of September 2007) and TABLES (v3.9 as of November 2008) must be installed on your system in order to use STSDAS. It is always a good idea to make sure you have the most recent versions of the software as they often include important code updates. Newer versions of IRAF, STSDAS, and TABLES are periodically released. Please check the following web site for the latest information:

 http://www.stsci.edu/resources/software_hardware/

Table 3.1: STSDAS Version 3.8 Package Structure.

analysis	Data analysis package.
dither	Dithered image combination.
fitting	Curve fitting tools.
fourier	Fourier analysis.
gasp	Access the HST Guide Star Catalog on CD-ROM.
isophote	Elliptical isophote image analysis.
nebular	Tasks for analyzing nebular emission lines
restore	Deconvolve or filter 1- or 2-dimensional images.
statistics	Statistical analysis software.
contrib	User-contributed software.
acoadd	Image coaddition using lLucy Method with optional acceleration
gaussfit	Least squares and robust estimation program
plucy	Multiple channel photometric image restoration
slitless	Extract a spectrum from a direct/Grism image pari
redshift	Tasks for determining redshifts and dispersions.
spfitpkg	Fitting spectra with non-linear chi-square minimization.
vla	Spectral image reduction for VLA data.
fitsio	FITS and GEIS input/output for HST data (images and tables).
graphics	Graphics and image display package.
sdisplay	Image display package for SAOImage display device.
stplot	General plotting utilities.
hst_calib	HST Science Instrument calibration package.
acs	Tasks for calibrating ACS data.
ctools	General calibration tools.
foc	Tasks for calibrating FOC data.
focprism	FOC prism package.
fos	Tasks for calibrating FOS data.
spec_polar	Tasks for reducing and analyzing FOS polarimetry.
hrs	Tasks for calibrating HRS data.
nicmos	Tasks for calibrating NICMOS data.
mstools	General-purpose tasks that handle NICMOS imsets
hstcos	Tasks for calibrating COS data.
paperprod	Tasks for generating paper products.
stis	Tasks for calibrating STIS data.
synphot	Synthetic photometry and modelling instrument response.
simulators	Synthetic photometry simulation package.
wfc3	Tasks for calibration WFC3 data
wfpc	Tasks for calibrating WF/PC-1 and WFPC2 data.
w_calib	Tasks for deriving the WF/PC-1 instrument calibration.
playpen	Miscellaneous experimental tasks.
sobsolete	Package of tasks that have been retired.
foccs	FOC calibration software package.
focgeom	FOC geometry package.
focphot	FOC photometry package.
focutility	Obsolete FOC utility package.
hsp	Tasks for calibrating HSP data.
olddither	Older version (V1.2) of dither.
registration	Compute registration parameters and resample unaligned data files.
testdata	Tools for creating artificial images.
timeseries	Time series photometry data reduction and analysis.
y_calib	Tasks supporting the FOS calibration process.
z_calib	Tasks supporting the HRS calibration process.
toolbox	General tools package.
convfile	Reformat images between VAX and Sun.
headers	Tools for modifying image headers.
imgtools	Tools for manipulating & examining images and bad pixel lists.
mstools	Tasks to handle STIS/NICMOS IMSETs.
tools	Generic data handling and utility tools.
ttools	Table manipulation tools.

3.2.2 Packages of General Interest

For Images

Both IRAF and STSDAS contain a large number of tasks that work with HST images. Some of the packages you should investigate are:

• images: This IRAF package includes general tasks for copying (imcopy), moving (imrename), deleting (imdelete), displaying (tv), and examining (imexamine) image files. These tasks operate on both the header and data portions of the image. The package also contains a number of general purpose tasks for operations such as image statistics, rotating and magnifying images, and registering and dewarping images.
• stsdas.toolbox.imgtools: This package contains tools for working with GEIS images, including tasks for working with masks, and general purpose tasks for working with the pixel data, such as an interactive pixel editor (pixedit), and gcombine for coadding GEIS images. Also of note are the tasks imcalc for performing image arithmetic, and rd2xy and xy2rd for converting between RA, Dec and x,y pixel coordinates. Many of these tasks will also work with single group or waiver FITS format files.
• stsdas.toolbox.imgtools.mstools: This package contains tools for working with FITS image files, in particular ACS, NICMOS, STIS, and WFC3 image sets (imsets). Msstatistics, for example, will print statistics on each image set (imset) in an image file. Similarly, msarith can be used for image arithmetic and uses information from the Data Quality (DQ), Error (ERR), and if available, the TIME and SAMP extensions in the calculation.
• stsdas.analysis.dither.multiDrizzle: This routine is provided as a "one-touch" interface for performing all the tasks necessary for registering dithered HST images, performing cosmic ray rejection, removing geometric distortion and performing the final image combination using "drizzle".
• stsdas.analysis: This package contains general tasks for image analysis, such as Fourier analysis (fourier), dithering (dither), and fitting.

For Tables

Several of the analysis packages in STSDAS, including calibration pipeline tasks, create output files in STSDAS table format (which is a binary row-column format) or in FITS binary table format. (ASCII-format tables are supported, but only for input.) The STSDAS User's Guide describes the STSDAS table format in detail. Tasks in the ttools package or in the external tables package can be used to read, edit, create, and manipulate tables. For example:

• tread displays a table, allowing you to move through it with the arrow keys
• tprint displays a table
• tcopy copies tables
• tedit allows you to edit a table

Many other tasks in ttools perform a variety of other functions. See the online help for details.