== Summary of the WISE -> DVO interpretations ==

(Up to [wiki:DVO_TopLevel DVO Top Level]) 

This page describes the translation between data fields in the WISE Preliminary Release (Apr 2011) and the DVO data fields, primarily in the 'measure' table.

Some useful links:

 * [http://wise2.ipac.caltech.edu/docs/release/prelim/expsup/sec2_2a.html the WISE data format]
 * [source:trunk/Ohana/src/libautocode/def/measure.d Measure table description]
 * [source:trunk/Ohana/src/addstar/src/loadwise_star_full.c Code which implements the definitions below]

In the WISE Preliminary Data Release, all sources are described by the equivalent of a single database row, with separate fields in the row for W1-W4 specific measurements, and some fields common to all three filters.  For example, the coordinates and observing time are all given as a single value for all three filters.  In the conversion to the DVO representation, each measurement of an object is converted to a separate DVO measurement entry.  All WISE sources are guaranteed to have all four measurements instantiated, but in some cases the measurements may be upper limits (non-detections in those filters).  Below, we list the relationship between the WISE information on the left side of the -> and the DVO measurement field on the right side.  Values which are defined for the 4 bands separately use the short cut 'w?value' to mean W1 value, W2 value, etc.  Each measurement has one of the 4 WISE photcodes, as appropriate (

 * '''ra, dec''' : recorded using the DVO standard of delta RA,DEC relative to the object's average RA,DEC location.
 * '''sigra, sigdec''' -> dXccd, dYccd : ''''note that these are defined for perfect 1 arcsec pixels, not the real WISE pixels.  -- the values of pltscale and posangle are defined to be 1.0 and 0.0 respectively''''

 * '''w?mpro'''  -> M
 * '''w?sigmpro''' -> dM
 * '''w?rchi2m''' -> psfChisq
 * '''wx, wy''' -> Xccd, Yccd : see the note above about dXccd, dYccd.  These are '''not''' on the same system.

 * the measure.t (time) value is set to the midpoint of the WISE preliminary data release time period, since no epoch information is supplied (and the measurements are derived from a stack of multiple exposures in any case).  This date is 2010/03/07,12:00:00 (JD = 2455263.0).  

===  The following WISE values are used to set bits in the phot_flags field: ===

 * '''ph_qual:'''

  A = 0x0000.0001  Source is detected in this band with a flux signal-to-noise ratio w?snr>10.

  B = 0x0000.0002  Source is detected in this band with a flux signal-to-noise ratio 3<w?snr<10.

  C = 0x0000.0004  Source is detected in this band with a flux signal-to-noise ratio 2<w?snr<3..

  U = 0x0000.0008  Upper limit on magnitude. Source measurement has w?snr<2. The profile-fit magnitude w?mpro is a 95% confidence upper limit.

  X = 0x0000.0010   profile-fit measurement was not possible at this location possible in this band. The value of w?mpro and w?sigmpro will be "null" in this band.

  * '''cc_flag:'''

  p,P = 0x0001.0000  Persistence. Source may be a spurious detection of or contaminated by a latent image left by a bright star.

  h,H = 0x0002.0000  Halo. Source photometry may be a spurious detection of or contaminated by the scattered light halo surrounding a nearby bright source

  o,O = 0x0002.0000  Optical ghost. Source may be a spurious detection of or contaminated by an optical ghost image caused by a nearby bright source ('''note bit is overloaded''')

  d,D = 0x0004.0000  Diffraction spike. Source may be a spurious detection of or contaminated by a diffraction spike from a nearby bright star on the same image.

  Note that the UPPER case entries are thought to be spurious sources and are also flagged with the value 0x0008.0000 in the phot_flags field.  Lower case entries are thought to be real source, though affected by the contaminating feature.

 * '''saturation''' : w?sat > 0.0 -> 0x0000.0100  At least one saturated pixel in W?

 * '''deblending''' : 
   * nb > 1 and na = 0 -> 0x0010.0000 : more than 1 PSF fitted, passively deblended
   * nb > 1 and na = 1 -> 0x0020.0000 : more than 1 PSF fitted, actively deblended

 * '''extendedness''' : if ext_flg == 1 -> 0x0100.0000 (source is thought to be extended)

 * '''variability''' : for var_flg of:
    * 1-4 -> 0x1000.0000 : probably not variable
    * 5-7 -> 0x2000.0000 : possibly variably
    * 8-9 -> 0x4000.0000 : likely variable