Index: trunk/doc/design/ippSSDD.tex
===================================================================
--- trunk/doc/design/ippSSDD.tex	(revision 6040)
+++ trunk/doc/design/ippSSDD.tex	(revision 6041)
@@ -1,3 +1,3 @@
-%%% $Id: ippSSDD.tex,v 1.2 2006-01-19 00:04:39 eugene Exp $
+%%% $Id: ippSSDD.tex,v 1.3 2006-01-19 01:05:28 eugene Exp $
 \documentclass[panstarrs]{panstarrs}
 
@@ -2705,5 +2705,52 @@
 Here we will just address some of the basic concepts.  PSPhot may be
 used as a stand-alone program, or it may be called as a function
-within another program (such as ppImage).  In the li
+within another program (such as ppImage).  In the function form,
+psphot is passed a pmReadout structure which is populated with the
+image of interest; weight and mask elements may be supplied, or else
+constructed based on standard rules.  As a stand-alone program, psphot
+will use a structure similar to that used by ppImage to load in all of
+the image components and loop over all of the readouts, performing the
+analysis on readout-by-readout basis.  Note that for the images from
+the Static Sky or Phase 4, the readout structure is also used, though
+in that case, the readout is contained by a SkyCell, not a cell within
+an FPA heirarchy.
+
+PSPhot performs the complete object detection and analysis process,
+using the following basic outline:
+\begin{itemize}
+\item {\bf assess image} examine the image statistics; if needed and
+  desired, fit a model to the background and subtract it.
+\item {\bf detect peaks} search the image for peaks above a defined
+  threshold
+\item {\bf basic source stats} examine the peaks to determine the local
+  sky, centroid, first and second moments and other fast, simple
+  statistics.
+\item {\bf rough classification} based on the source moments,
+  determine the likely stellar sources and classify sources based on
+  their moments in relation to the stellar source moments, as well as
+  the saturation level, etc.
+\item {\bf basic deblend} identify peaks which are in the wings of
+  brighter sources, mark them for careful attention later.
+\item {\bf choose PSF} determine a PSF model from the bright possible
+  stellar sources.  PSPhot allows a wide range of possible analytical
+  PSF models, and may be set to automatically select the best one for
+  an image.  The parameters of a PSF are allowed to vary spatially.
+  Currently, pixel-based PSFs are not implemented, but can be added as
+  an upgrade.
+\item {\bf fit sources} the heart of PSPhot is the analysis of the
+  brighter sources in the image.  In this stage, each source (above a
+  certain threshold) is fitted with the PSF model, the source is
+  identified as PSF-like or not.  If not, extend source models and
+  double-PSF models are also attempted.  The best of the models is
+  kept, unless the fits fail complete, and the model is subtracted.
+\item {\bf photometry checks} curve-of-growth and aperture corrections
+  are measured and applied to the PSF photometry.
+\item {\bf output stage} as a stand-alone program, psphot will produce
+  output tables in various formats.
+
+\subsection{psastro}
+Like psphot, psastro may be run as a stand-alone program or as a
+library.  This 
+
 
 \section{Interfaces}