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LINT

Longitudinal Investigation of Non-Transparency (LINT): using flats from CCDs to find the amount of dust, debris, or other contamination present on a sensor's surface. This program uses flats from CCDs to find the amount of dust, debris, or other contamination present on a sensor's surface.

The code will:

  • Load flats (fits).
  • Subtract overscan and mask overscan regions (if overscanSubtractBOOL is "True").
  • Scale the flats to a common mean.
  • Stack the flats using a median.
  • Subtract the average sky value.
  • Multiply the values by -1 to make to make attenuation spots appear positive to photometry code.
  • Run Source Extractor on the image to detect the debris.
  • Print a detailed map of the debris locations.
  • Analyze and plot histograms showing the amount of contamination.
  • Batch process data to show the accumulation of debris over time.

Programs, packages, and wrappers:

  • Interpreter: python 3
  • PyDev: 4.5.5.201603221110
  • Numpy: 1.11.0
  • Astropy: 1.3
  • Python-dev: python-dev 2.7.5-5ubuntu3
  • Eclipse: eclipse-platform 3.8.1-5.1
  • SExtractor: 2.19.5-2
  • Matplotlib: 1.5.1-1ubuntu1

Modules:

testAstro:

  • Test for issues with your astropy installation.

loadFits:

  • Load fits files image data into a 3D array.
  • Saves data to a fits file.
  • Makes a directory for output products and move output products into it.
  • Scans the images to insure that they are all the same size dimensionally.

loadConfig:

  • Load LINT.config.

overscan:

  • Subtract and remove overscan (if overscanSubtractBOOL bool is true).

scaleAndStack:

  • Scales the images using a common mean (find the mean of all of the data and scale the data so that every image has that same baseline mean).
  • Stack the images, using a median, into a single flat field image (median the images: meaning that the resulting value in a pixel in the final image is the median of the values in that same pixel in the input images).

skyValue:

  • Subtracts the average sky value from the median stacked image.

callSExtractor:

  • Call SExtractor and send commands to process the stacked and inverted image.
  • Record the output from SExtractor.

analyzeSExOutput:

  • Performs cuts to remove objects that are not debris.
    • Flags: no gremlins in photometry.
    • Flux: only want divots in original image.
    • SNR: signal to noise ratio. Calculate the signal-to-noise ratio as FLUX_ISO / FLUXERR_ISO, that is, the isophotal flux (photometry derived from the counts above the threshold minus the background) divided by the RMS error for the isophotal flux; in other words, the signal divided by the noise.
    • FWHM: Full Width at Half Maximum. Very small values may be anomalous and not represent debris.
  • Make histograms of:
    • Area of debris.
    • Debris versus clean area.

batch:

  • Create a list that groups the fits files by date.
  • Run LINT on pre-grouped (by date) fits files.
  • Plot the debris accumulation over time as: scatter plot.

To do:

  • Add logger.
  • Add help command in optional arguments.
  • Check to see if dependencies are installed.
  • Mask bad pixel columns.
  • Test installation code.

This research makes use of:

  • Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration, 2013).
  • Bertin, E. & Arnouts, S. 1996: SExtractor: Software for source extraction, Astronomy & Astrophysics Supplement 317, 393
  • PyDev for Eclipse 4.5.5.201603221110 org.python.pydev.feature.feature.group Fabio Zadrozny
  • Hunter, J. D. Matplotlib: A 2D graphics environment. 2007

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LINT (Longitudinal Investigation of Non-Transparency): using flats from CCDs to find the amount of dust, debris, or other contamination present on a sensor's surface.

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