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NICMOS Software at the University of Arizona

E. Stobie, D. Lytle, I. Barg, and A. Ferro NICMOS Project, University of Arizona, Tucson, AZ 85721, E-mail:




The NICMOS Software Group at the University of Arizona has built a number of software tools for processing NICMOS data. These tools have been developed entirely within IDL or have IDL interfaces to other existing software. We will describe each of these tools.

NICMOS, PSF subtraction, image registration, image deconvolution, polarimetry data reduction


The NICMOS Software Group at the University of Arizona has developed a number of software tools in IDL14.1 in support of data calibration and analysis for the NICMOS Instrument Definition Team.

Software Group

The NICMOS Software Group at the University of Arizona is composed of four members:

Programming Environment

Group members develop both batch programs and interactive programs with graphical user interfaces using IDL. In some cases, GUI's are developed for pre-existing software developed in other programming environments. All software is developed and tested under the Solaris and Linux Operating Systems. Users may retrieve any of the software in one of two ways:

Programs Available

The software tools developed within the software group at the University of Arizona may be divided into six main categories: observation planning, calibration, editing, display, analysis, and general utilities.



a graphical user interface (GUI) layered on the IRAF/STSDAS countrate task which evaluates the countrate for a given target and observing mode.


a procedure based on the IDL program, Overlay, developed by Eliot Malumuth at Goddard Space Flight Center, but has been heavily modified to our purposes at the University of Arizona. The program displays an image of the sky with an overlay of the Space Telescope apertures. The user may pick the prime aperture, orient the telescope, mark guide stars, get RA and Dec as well as Ecliptic coordinates.


an IDL GUI layered on the IRAF/STSDAS task ``simimg'', which computes simulated images for the HST imaging instruments FOC, NICMOS, STIS, and WFPC2. Simimage allows a convenient mechanism for determining the necessary parameters and provides a display of the final result as both an image and shaded surface plot. Simimage will also produce a group of dithered images across the object field.



an IDL program for building reference files from single FITS images by stitching together single-image FITS files into multi-extension FITS files. The user provides a command file that specifies the input images to be combined, the method of combination, and any keyword additions or changes that should be made to the standard NICMOS header template files that are used. The outputs of the program are NICMOS standard multi-extension FITS files that are compatible with calnica.


an IDL replication of the calnica task in IRAF/STSDAS. Its single argument is the list of files to process. The outputs are a calibrated image with associated extensions and, in the case of multiaccum data, an intermediate file with each readout fully calibrated excluding the cosmic ray rejection. If no _IMA file is desired, the user may include the command, `noima' at the beginning of the list file.


an interactive program for reviewing the bias levels from one quadrant of a NICMOS image to another and adjusting the individual quadrants. The final result may be saved to a FITS file.



an interactive program used to edit FITS header keywords in preparation for re-calibrating NICMOS data with Calnica. The display consists of a list of the calibration switch values and when appropriate their associated reference files. Both calibration switches and reference files may be modified easily using the action and radio buttons in the widget.


(FITS Header Editor ), an IDL program for editing headers of groups of FITS files. It is particularly well suited to editing FITS files with multiple image extensions. Any keyword in the primary header or any extension header (excluding the reserved FITS keywords) may be edited. Keywords may be modified, added, or deleted.


(FITS Primary Header Editor ), an IDL program designed for editing the primary headers of FITS files with image extensions. It is an optimized version of FHE which edits the headers in place and therefore will only modify the primary headers. Keywords may be modified, added, or deleted.


an interactive program used to edit bad pixel masks. The inputs are the FITS data image and the FITS mask image. There are various keywords that can be used on input to scale the image and to set the ``good pixel'' value for the mask. The program displays the data image and marks the ``bad'' pixels based on values in the mask image (bad pixels are circled). The user may then set or unset masked pixels using the mouse buttons. Finally, the new, edited, mask may be saved to a file.



an interactive program for creating a display of multiple sub-images from sections of one or more images where each sub-image has its own zoom factor and image stretch. Each sub-image may have a single line caption. The user may select the number of sub-images per row and column with the default rowsize=4 and the default colsize=6. Each of the individual sub-images may be saved to a FITS file and the entire display may be saved and restored.


(Super Display Widget), an interactive program designed to be a general purpose FITS image viewer. It allows general image display of multi-extension FITS files, zooming, bad pixel masking, log scaling, rudimentary pixel editing, min/max scaling, general IDL colormap adjustment, cursor readback, spread sheets of pixel values, header display, and access to all image extensions of a NICMOS multi-extension file.


a program for displaying and printing true color images by loading the three display color tables, red, green, and blue with separate images and overlaying the result. Each color table can be scaled individually to obtain the desired ``look''. The images may also be log scaled to bring up background detail. This program works on systems with 8-bit or 24-bit color display and produces appropriate output postscript files when the print button is pressed.



(FITS List Calculator), a program to process large groups of FITS files together by creating data lists. The program parser supports a simple command syntax including the ability to process pre-defined scripts, do-loops, and if-then-else constructs as well as arithmetic operators, native IDL commands, and operating system commands. The program has an image scan feature to view a list of images in a movie-like format, a more detailed graphics display which includes the image header, full image, single quadrant or zoomed region of the image, and the image histogram. There are also windows for editing pixels in an image and for building lists. The program supports four data types: lists, images, arrays, and scalars. The user may customize the number of each data type by editing the user definitions file. Several mathematical functions for lists are pre-defined for convenience including the computation of image statistics, pixel statistics, medians, means, and first differences. A sample display of FLC appears in Figure 1.
Figure 1: Many of the display and text windows used by FLC.


( Image Display Paradigm #3 ), a program for manipulating data images employing a powerful but easy-to-use graphical user interface. It allows the user to work with a collection of images and display one or more images in a graphics window simultaneously. Images may be individually moved, scaled, and rotated to bring image features into registration. Each image may be displayed by adding it to the composite image in the display, by subtracting it from the composite image or by one of the other various image functions (divide, XOR, average, etc.). Idp3 provides a region-of-interest pop-up tool for intensive examination of sub-regions of the main display. There are cross-section plots, masks, surface plots, statistics, spreadsheets displays and other tools at the user's disposal. Final combination images may be saved to FITS files. These output images contain descriptive headers detailing the settings in IDP3 at the time the image was written. A sample display of IDP3 appears in Figure 2.
Figure 2: Many of the display and text windows used by IDP3.


a program that generates a deconvolved image from an input image and point spread function (PSF) using the algorithm developed independently by Richardson (1972) and Lucy (1974). The widget is based on the original and accelerated algorithms with optional damping developed by White (1993) at STScI. The IDL program displays the original data as well as the result at the end of each iteration.


a quick look analysis tool for NICMOS data. The widget contains three display windows: full window, zoom window, and graphics window. Statistics may be computed for the full or zoom window. World coordinates may be overlaid on the full window and coordinates may be printed for any pixel in either the full or zoom window. Image arithmetic may be done on any of the five loaded images using arithmetic operators or IDL functions. Two images may be blinked in the full window. All commands are logged in a journal file.

Nicmosaic and Nicstikum,

tools for mosaicing NICMOS images. The inputs for Nicmosaic are a list of images to mosaic and, optionally, a table of position data previously output from ``Nicmosaic''. If no table is given, the program attempts to line up the input images as best it can based on the world coordinate information in the image headers. Image rotation and fractional pixel shifts are used to accomplish this alignment. Once the data are loaded, the user may select two of the images (called the primary and the secondary images) and blink these two images. The user may then shift and rotate the selected primary image to improve the alignment using the buttons and value fields provided. On exiting, a table of positions is written that can be used by the program ``Nicstikum'' to create a final, mosaic image.


an IDL graphical user interface wrapper for the DoPHOT stellar photometry program written by Mario Mateo, Abhijit Saha, and Paul Schechter. Nicphot provides facilities for computing the FWHM of an object, determining the image background, editing the DoPhot parameter file, executing DoPHOT, and displaying the result with detected objects removed. Since DoPHOT requires the image data as 16-bit integers Nicphot will rescale the data and create a new FITS file with extension .FITSX if the data are not 16-bit integers.

Polar and Polarplot,

two programs that have been written for the analysis of NICMOS polarization data. ``Polar'' is a program that takes three images (one from each polarizer) as input, solves the linear equations, and produces as output the ``I'', ``Q'', ``U'',``P'', and ``$\Theta$'' images. ``Polarplot'', shown in Figure 3, allows the user to overlay the polarization vectors on the intensity image. This program has many user adjustable parameters to customize the plot such as intensity image color table manipulation, axis, contour map, and polarization vector color manipulation, contour overlay, and thresholds for polarization intensity.
Figure 3: Example Polarplot display, an intensity image is shown overplotted with polarization vectors.



a batch program to delete one or more readouts (imsets) from a _raw or _ima multiaccum file.


a batch program for printing select keywords from the headers of NICMOS data files. All keyword values are taken from the primary header of the file (_raw, _ima, _cal, _mos ). If the positions option is selected the target right ascension and declination are printed in addition to the other header information. When the refiles option is selected the values of the reference file keywords are printed.


a batch program to print a table of keyword values for the specified list of files. The desired keywords are defined in a string array and the files to be read are defined in an ASCII text file. The information is printed to the user's screen and to the specified output file.


an interactive tool for querying the help files of all IDT developed software. All programs are listed and as one is selected a single line description is given. The user may display or print the entire help file.


a batch program to separate the readouts (IMSETs) of NICMOS raw (_raw) or intermediate (_ima ) multiaccum files into individual FITS files. The output files contain a single header (merging the primary and science image extension headers) and the science image. All other image extensions (ERR, DQ, SAMP, and TIME) are discarded.


a batch process to separate the readouts (IMSETs ) of multiaccum files into different files. Output files are named by replacing the last character of the IPPPSSOOT designation with the readout number. Readouts count from one to a maximum of 26 in forward time order (normal NICMOS files are in reverse time order). The inputs are an ASCII text file of filenames and an optional path parameter.

Web Interface to NICMOS Archive

In order to support our geographically diverse team members, we have developed a number of web based forms and scripts to allow them to search for and retrieve data sets. To minimize the network traffic, we have developed our own database system at the University of Arizona, which includes NICMOS data to which we have access. Via the web this database can be queried to locate specific data of interest. Authorized users can then request copies of the data via the network.

Selected proposal types (GTO/NIC, CAL, PAR, ENG, and SMOV) are monitored daily and are downloaded to a database servers at Steward Observatory. The data stored locally represents a small sub-set of the data in the HST data archive at the Space Telescope Science Institute. In addition, a database of observed and simulated (generated by the Tiny Tim program) NICMOS point spread functions (PSFs) is being developed for team use. Information about the UofA NICMOS Databases may be obtained by following the appropriate links from the web site:

We are grateful to the NICMOS Instrument Definition Team members and their Post Docs for their input and support in our software development. Their patience in testing software as it evolves is much appreciated.

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...estoration, Newsletter of STScI's Image
Restoration Project, 11

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Norbert Pirzkal