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stisnoise stis



stisnoise -- Remove fixed pattern noise from STIS images.


stisnoise input


input [string]
The name of the input image. It can be either a raw or flat-fielded image.
(exten = 1) [integer]
FITS extension to be read
(outfile = "") [string]
The name of the filtered output image.
(freq = 0.) [real]
Output parameter for the frequency of the maximum peak.
(ampl = 0.) [real]
Output paramter for the amplitude of the maximum peak.
(fwhm = 0.) [real]
Output paramter for the FWHM of the maximum peak.
(boxcar = ) [integer]
The width of the boxcar smoothing (in frequency bins) to be applied.
(wipe = ) [string]
A 3-element array (e.g. "0.0 0.05 0.0"), specifying how to modify the data in frequency space. If set, the image is converted to a 1-D time series, fourier transformed to frequency space, modified, inverse transformed back to time space, and converted back to a 2-D image. The first and second elements specify the range in frequencies to be scaled (in hz), and the third element specifies the scaling factor (should be 0-1).
(window = ) [string]
A 3-element array (e.g. "0.5 0.5 0.1"), specifying how to modify the data in frequency space. The first element is the center of the window (in hz). The second element is the width of the window (in hz). The third element controls the tapering of the window - it is the scale (in hz) of the tapering width. Specifically, a square bandstop is convolved with a gaussian having the FWHM given by the third parameter.
(dc = yes) [boolean]
The power in the first freq bin is set to zero for better plotting of the power spectrum.
(verbose = yes) [boolean]
Set to 0 if you do not want brief information about each image.


Computes an FFT on STIS CCD frames to evaluate fixed pattern noise. Fixed pattern noise is most obvious in a FFT of bias frames from side the B electronics. Optional filtering to correct the fixed pattern noise is provided through keywords boxcar, wipe, and window. The freq, ampl, and fwhm parameters return information about the maximum peak in the FFT and can be used for filter the data. Filtered data can be saved as an output file.


1. Find frequency, amplitude, and FWHM of domimant peak in FFT of image.

        --> stisnoise o6ib01010_raw.fits
        Target: NGC5139, Amp: D, Gain: 4
        FFT Results: max freq: 0.0433,  max ampl: 0.4094,  fwhm: 0.0867


In my code?


IDL task written by T. Brown (STScI)
IRAF task written by P. Barrett (STScI)

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