Rewrite task docstring

python/lsst/cp/pipe/makeBrighterFatterKernel.py

@@ -198,10 +198,43 @@ def makeDataRefList(self, namespace):
 
 
 class MakeBrighterFatterKernelTask(pipeBase.CmdLineTask):
-    """Bright-fatter effect coefficient calculation task.
-
-    See http://ls.st/ldm-151 Chapter 4, Calibration Products Production for further details
-    regarding the inputs and outputs.
+    """Brighter-fatter effect correction-kernel calculation task.
+
+    A command line task for calculating the brighter-fatter correction
+    kernel from pairs of flat-field images (with the same exposure length).
+
+    The following operations are performed:
+
+    - The configurable isr task is called, which unpersists and assembles the
+      raw images, and performs the selected instrument signature removal tasks.
+      The appropriacy of the selected isr components is checked.
+
+    - The gain of the each amplifier in the detector is calculated using
+      the PTC method and used to correct the images so that all calculations
+      are done in units of electrons, and so that the level across amplifier
+      boundaries is continuous. Outliers in the PTC are iteratively rejected
+      before fitting, with the nSigma rejection level set by
+      config.nSigmaClipRegression. Individual pixels are masked from
+      the image based on config.nSigmaClipGainCalc
+
+    - Each image is then cross-correlated with the one it's paired with
+      (with the pairing defined by the --visitPairs command line argument),
+      which is done either the whole-image to whole-image,
+      or amplifier-by-amplifier, depending on the config.level.
+
+    - Once the cross-correlations have been calculated for each visit pair,
+      these are used to generate the correction kernel.
+      Outlier values in these cross-correlations are rejected by using a
+      pixel-wise sigma-clipped thresholding to each cross-correlation in
+      the visitPair-length stack or cross-correlations.
+      The number of sigma clipped to is set by config.nSigmaClipKernelGen.
+      The maximum lag used, in pixels, and hence the size of the half-size
+      of the kernel generated, is given by config.maxLag,
+      i.e. a value of 10 will result in a kernel of size 2n-1 = 19x19 pixels.
+
+    - Once DM-15277 has been completed, a method will exist to calculate the
+      empirical correction factor, config.biasCorr.
+      TODO: DM-15277 update this part of the docstring once the ticket is done.
     """
 
     RunnerClass = MakeBrighterFatterKernelTaskRunner