Calibration Access and Data Handbook


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Description

This CCF component is used by the SAS. The OM flatfield response is decomposed into two components, spatial large scale and small scale sensitivity variations.

The PixToPixSens file describes the spatially high frequency throughput and sensitivity non-uniformities. In addition PixToPixSens describes the illumination pattern of the internal calibration lamps seen by the detector.
The high frequency sensitivity variations are introduced by the detector. Non-uniformities in the filter transmissions won't show up in small scale structures, as the filter wheel elements are out of focus.

The PixToPixSens file describes the inverse detector sensitivity normalized to the average sensitivity. Values less than one indicate pixels with a sensitivity higher than the average and values greater than one indicate pixels with a lower sensitivity than the average.

PixToPixSens consists of two image extension. The Image extension has a size of 2048x2048 pixel and is at full detector resolution. The extension name is PIXTOPIXSENS. The keyword CFRR specifies the average count rate (units: count/CCD frame) in the flatfield exposures used to generate the image extension.

The image extension LEDTEMPLATE holds the description of the LED illumination pattern. The illumination pattern is described as the inverse illumination level by a full resolution map (2048x2048 subpixel). Values less than one indicate pixels with a stronger illumination by the LEDs (higher than the average) and values greater than one indicate pixels with a lower illumination than the average.

The image extension in the pixtopixsens CCF component has the following structure PIXTOPIXSENS.
Image extension: PIXTOPIXSENS
keyword name keyword keyword keyword comment
  type unit value  
NAXIS Integer n.a. 2 number of data axes
NAXIS1 Integer n.a. 2048 length of data axis 1
NAXIS2 Integer n.a. 2048 length of data axis 2
CFRR Real cts/fullframe/sec varies average CFRR
AVERAGE Real n.a. varies average sensitivity of good pixels
DAVERAGE Real n.a. varies standard deviation on AVERAGE
PIXERR Real percent varies average standard deviation on
        single pixel value

The second image binary extension in the pixtopixsens CCF component is LEDTEMPLATE with the structure as follows.

Image extension: LEDTEMPLATE

keyword name keyword keyword keyword comment
  type unit value  
NAXIS Integer n.a. 2 number of data axes
NAXIS1 Integer n.a. 2048 length of data axis 1
NAXIS2 Integer n.a. 2048 length of data axis 2
AVERAGE Real n.a. varies avg. correction for nonflat illumination
DAVERAGE Real n.a. varies standard deviation on AVERAGE
PIXERR Real percent varies average single pixel deviation


next up previous contents
Next: Generation from Ground Calibration Up: PIXTOPIXSENS Previous: PIXTOPIXSENS   Contents
Michael Smith 2011-09-20