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The 'Deglitcher' window is dominated by the data display,
framed on the right hand side by display options and
access to manual de-/selection, and on the bottom by
the parameter interface for the deglitcher routine itself.
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The data points shown in the display are the pairwise
differences of subsequent readouts of the pixel selected.
A brief listing of different colors and symbols is given below.
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red square
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valid data point
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blue square
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data point taken during spacecraft slews
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green square
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patched data point
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yellow cross
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invalid data point
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blue cross
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invalid data point taken during spacecraft slews
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dotted vertical line
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borderline between chopper sweeps
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The right panel of buttons on the deglitcher window controls the display and selection of data. |
 
These buttons are always active and enable the user to navigate through the dataset. The original display can be restored by hitting the 'Free' button in the 'Scaling' section. |
Up
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Moves the view box 1/3 of the total display area upwards, i.e. the data appears to move downwards.
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Left
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Moves the view box 1/3 of the total display area to the left, i.e. the data appears to move
to the right.
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Right
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Moves the view box 1/3 of the total display area to the right, i.e. the data appears to move
to the left.
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Down
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Moves the view box 1/3 of the total display area downwards, i.e. the data appears to move upwards.
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Zoom In
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Magnifies the rectangular area marked/opened with the left mouse button and sets
the scaling to 'fix'. More than one data point needs to be selected for a reasonable result.
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Zoom Out     
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Compresses the data set along the time-(x-)axis by 50%.
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This panel controls the magnification/scaling of the data on the display. |
Free
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Scales the data set to fully cover the display.
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Fix
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Fixes the scaling in case of 'Zoom In'.
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With this panel the display can be customized, i.e. selection of data type, plot symbols and errorbars. |
All    (default option)
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Displays all data points.
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Valid Only
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Shows only valid data points.
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Dots
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Data points are displayed as dots.
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Symbols
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Data points are displayed with squares.
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No Errorbars
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Errorbars are not plotted.
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Errorbars
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Errorbars are plotted for each data point.
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Data points are marked with the mouse. Opening a rectangle from the lower left corner to the upper right corner while holding the left mouse key down selects the area around the desired data points, after having pressed one of the following buttons. |
Select
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The data points within the marked area are flagged to be valid data points.
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Deselect
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The data points within the marked area are flagged to be invalid data points.
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The deglitcher window cannot be active simultaneously with other windows of the P32 package. It has to be closed if one wants to proceed with P32 Tools. |
Quit
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Closes the window, discarding all changes.
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Exit
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Closes the window, accepting all modifications.
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Deglitching of the data is essential, especially in maps with overall low flux and extended structures. In the initial map making process, the data is run through a so called 'spike detector' that identifies potential glitches. This deglitcher interface allows more sophisticated glitch removal, based on the initial results of the spike detector. |
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The basic functionality is illustrated in Figure 6. The lower part shows the data and the result from the deglitcher, the upper part schematically shows thresholds, spikes and glitch tails. The parameters of the deglitching routine are described below. |
Fraction bad readouts
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Controls the maximum amount of data that can be flagged bad because of deglitches.
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Time const. spike tails |
Varies the time constant for the glitch tail.
It determines how many seconds after the glitch detection the data are still affected.
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Spike inclusion Threshold |
Controls which events are marked as spikes.
Glitch candidates above this threshold are considered further.
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Spike clipping Threshold |
This parameter determines at what signal level after the spike the signal is considered back to normal.
I.e. when the value of the data points after
the spike is supposed to match more or less the average value at that
time/position within the measurement.
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Patch |
In the process of deglitching, a lot of data points can be deselected leaving
significant gaps in the data set. Part of these possible gaps can be patched
with data points from other chopper sweeps of the
same sky position. The patching is necessary to ensure a continuous illumination
history as basis for the drift fitting.
After activating 'Patch', the 'deglitch' button needs to be pressed again.
The patched data points will be shown as green squares.
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