This note describes the IPP video cell photometry pipeline or "VP stage".

== VP Run ==
vpRun is the table in the IPP database that is used to manage video cell photometry (VP) processing. When a run is processed all OTAs that contain video cells are processed. A new IPP tool program vptool was written to manage the database operations. Exposures are selected for processing using the command "vptool -definebyquery". The selectors are the same as used for chip processing so a wide range of options is available.

{{{
Usage: vptool -definebyquery [<options>]

-definebyquery:
  -exp_id              search by exp_id
  -exp_name            search by exp_name
  -inst                search for camera
  -telescope           search for telescope
  -dateobs_begin       search for exposures by time (>=)
  -dateobs_end         search for exposures by time (<=)
  -exp_tag             search by exp_tag
  -exp_type            search by exp_type
  -filelevel           search by filelevel
  -filter              search for filter
  -airmass_min         search by min airmass
  -airmass_max         search by max airmass
  -ra_min              search by min RA (degrees) 
  -ra_max              search by max RA (degrees) 
  -decl_min            search by min DEC (degrees)
  -decl_max            search by max DEC (degrees)
  -exp_time_min        search by min exposure time
  -exp_time_max        search by max exposure time
  -sat_pixel_frac_min  search by min fraction of saturated pixels
  -sat_pixel_frac_max  search by max fraction of saturated pixels
  -bg_min              search by min background
  -bg_max              search by max background
  -bg_stdev_min        search by min background standard deviation
  -bg_stdev_max        search by max background standard deviation
  -bg_mean_stdev_min   search by min background mean standard deviation (across imfiles)
  -bg_mean_stdev_max   search by max background mean standard deviation (across imfiles)
  -alt_min             search by min altitude
  -alt_max             search by max altitude
  -az_min              search by min azimuth 
  -az_max              search by max azimuth 
  -ccd_temp_min        search by min ccd tempature
  -ccd_temp_max        search by max ccd tempature
  -posang_min          search by min rotator position angle
  -posang_max          search by max rotator position angle
  -sun_angle_min       search by min solar angle
  -sun_angle_max       search by max solar angle
  -object              search by exposure object
  -comment             search by comment field (LIKE comparison)
  -obs_mode            search by observation mode
  -label               search by newExp label (LIKE comparison)
  -set_label           define label
  -set_data_group      define data group
  -set_workdir         define workdir (required)
  -set_note            define note
  -set_dest_id         define destination
  -pretend             do not actually modify the database
  -unique              only queue exposures that have no previous vpRun
  -simple              use the simple output format

}}}


== videophot_process.pl ==
The ippScript videophot_process.pl processes an entire vpRun. That is all OTAS are processed by a single job. This may be contrasted with chip processing where each OTA is processed separately. Since each video cell only takes a few seconds to process this is a reasonable choice.

The actual processing is performed by the program psvideophot. The output for each video cell is a FITS table (file extension vpt).

A second fits file is created which contains the original video cell data that has been extracted from the raw data. TODO: we should make creation of this file optional since it takes up ~4MB per cell (3pi)

== vpt table ==
Each row in the vpt table contains the data for a frame. The data in the columns have 2 sources: 
 * The video_table extension created by the GPC1 camera software 
 * The results of the psvideophot analysis. These columns have names that begin with vp_

{{{
FITS table description (from header) TODO: do a proper table.
TTYPE1  = 'frame_start_time'   / label for field   1                           
TFORM1  = '1D      '           / data format of field: 8-byte DOUBLE           
TTYPE2  = 'frame_complete_time' / label for field   2                          
TFORM2  = '1D      '           / data format of field: 8-byte DOUBLE           
TTYPE3  = 'centroid_x'         / label for field   3                           
TFORM3  = '1D      '           / data format of field: 8-byte DOUBLE           
TTYPE4  = 'centroid_y'         / label for field   4                           
TFORM4  = '1D      '           / data format of field: 8-byte DOUBLE           
TTYPE5  = 'fwhm    '           / label for field   5                           
TFORM5  = '1D      '           / data format of field: 8-byte DOUBLE           
TTYPE6  = 'fwhm_x  '           / label for field   6                           
TFORM6  = '1D      '           / data format of field: 8-byte DOUBLE           
TTYPE7  = 'fwhm_y  '           / label for field   7                           
TFORM7  = '1D      '           / data format of field: 8-byte DOUBLE           
TTYPE8  = 'sky     '           / label for field   8                           
TFORM8  = '1D      '           / data format of field: 8-byte DOUBLE           
TTYPE9  = 'flux    '           / label for field   9                           
TFORM9  = '1D      '           / data format of field: 8-byte DOUBLE           
TTYPE10 = 'snr     '           / label for field  10                           
TFORM10 = '1D      '           / data format of field: 8-byte DOUBLE           
TTYPE11 = 'rowpre  '           / label for field  11                           
TFORM11 = '1J      '           / data format of field: 4-byte INTEGER          
TTYPE12 = 'cnpix1  '           / label for field  12                           
TFORM12 = '1J      '           / data format of field: 4-byte INTEGER          
TTYPE13 = 'cnpix2  '           / label for field  13                           
TFORM13 = '1J      '           / data format of field: 4-byte INTEGER          
TTYPE14 = 'vp_flux '           / label for field  14                           
TFORM14 = '1E      '           / data format of field: 4-byte REAL             
TTYPE15 = 'vp_median'          / label for field  15                           
TFORM15 = '1E      '           / data format of field: 4-byte REAL             
TTYPE16 = 'vp_stddev'          / label for field  16                           
TFORM16 = '1E      '           / data format of field: 4-byte REAL             
TTYPE17 = 'vp_sum  '           / label for field  17                           
TFORM17 = '1E      '           / data format of field: 4-byte REAL             
TTYPE18 = 'vp_x    '           / label for field  18                           
TFORM18 = '1E      '           / data format of field: 4-byte REAL             
TTYPE19 = 'vp_y    '           / label for field  19                           
TFORM19 = '1E      '           / data format of field: 4-byte REAL             

}}}

== Results Data Store ==
When a run is queued it may optionally be assigned a data store product where results filesets will be posted. See for example http://datastore.ipp.ifa.hawaii.edu/ps1-vp/o5769g0314o.369032.vp.1