WFCAM update from CASU
======================

At the last count around 160 tapes containing ~30 Tbytes of raw WFCAM data 
for 05A, 05B and 06A have been successfully received, ingested and processed.
Automatic web status pages monitor and summarise the current state-of-play
and allow access to the various quality control information generated by
the pipeline processing (see http://casu.ast.cam.ac.uk)

Raw WFCAM archives: all of the relevant raw WFCAM 06A internet transfers 
to ESO were completed by September.  The raw WFCAM data archive in Cambridge 
is up to date and has stabilised with a time-lag of ~2-3 weeks behind the 
observation date.  

WFCAM processing: all WFCAM 06A data was processed and checked by the 1st
October.  The delay over normal operations was caused by document
preparation for the VDFS UK review.  The reprocessing for 05A 
(version 3) was finished on time by the end of May and was subsequently
transfered by WFAU to Edinburgh.  Most of 06A has also been transferred.
On request from the UDS group we also reprocessed a few selected nights of 
05B data with the latest sky subtraction strategy, since the processed UDS 
data from these nights had been causing problems for deep stacking.

WFCAM photometry: as a result of discovering the correlation of the 
(extrapolated) Y- and Z-band calibration with Galactic extinction we have 
now updated the photometric calibration methodology to take account of 
Galactic extinction.  As a consequence we have made minor revisions to
the colour equations for Y and Z and also updated the JHK calibration.
This calibration has been applied to all WFCAM data for 05A, 05B, 06A
to provide a consistent internal system.  We are still awaiting 
the final offsets from the photometry working group for the Y- and Z-band 
(to ensure that A0 stars have zero colour in all WFCAM broadbands.)

WFCAM astrometry: we have recently finished investigating the bandpass
dependence of the optical distortion.  Although this feature was anticipated 
from the optical design studies, the default distortion correction used
had already satisfied the science requirements and the more stringent science
goals.  Astrometric tests using different distortion terms for each passband
show that the systematic global field distortion residuals can be reduced
to ~25mas.  Further refinement over this is also possible using residual
correction tables.  This table-based approach has now been ratified by the 
FITS WCS community and will become the standard method. The distortion 
coefficients for each passband are: 
Z  -44.0; Y  -45.0; J  -46.0; H  -50.0; K  -60.0

We have also developed and implemented, in the Cambridge pipeline, a simple 
robust variant on Maximum Likelihood centroiding.  This adds minimal overhead 
to the processing but yields up to a 50% improvement in individual object rms
astrometry, yielding close to optimal centroiding for both stars and galaxies.

Software: there have been various software upgrades (mostly minor).  Over 
the summer we finished implementing and checking the upgrades to the catalogue 
generator software to enable UDS-style stacked images to be analysed properly.
Phil Lucas reported an interesting feature of the cross-talk removal software;
namely that it does not work well in areas of bright spatially varying 
luminosity.  This was traced to a logic bug, rather than a software bug,
and a workaround is currently being sought.  Fortunately this problem only 
affects a few regions, most of which are close to the Galactic Plane.

Casuhelp: we recently introduced a casuhelp email account to enable better
monitoring and tracking of user queries.

PSF fitting: a bug in the split PSF fitting routine has finally been tracked
down and tests with simulated and real data have been successfully completed.
After some discussion it was felt that there was a need to benchmark the
PSF software with respect to other PSF fitting software. Phil Lucas has
offered to generate some test comparison data in selected GPS fields.
It is important that the WFCAM PSF routines get tested with respect
to the more manual PSF software that exists. This will provide a valuable
benchmark comparison.

Finally, as part of the previously mentioned VDFS UK review we have produced 
a draft of the WFCAM processing technical paper which will be made separately
available prior to the Board meeting.


Summary of Cambridge processing
===============================

  Version      Semester  Images       Catalogues     Calibration   Available
process|pipeline

  #1     #1     05A   stacking bug   no errors       2MASS old ce  May 2005
                                     or Petrosian                 -Jul 2005
                                     fluxes

  #2     #2     05A   fixed stacks   full standard   2MASS new ce  Aug 2005
                      better skies   parameter set                -Sep 2005
  #3     #4     05A  +cross-talk    +minor catalog  +J-Ks limits   Apr 2006 
                      removed        bug fix                      -May 2006

--------------------------------------------------------------------------

  #1     #3     05B  +cross-talk     full standard   2MASS new ce  Oct 2005  
                      removed        parameter set                -Feb 2006

  #2     #4     05B   (as above)    +minor catalog  +J-Ks limits   May 2006
                                     bug fix                      -Jun 2006

--------------------------------------------------------------------------

  #1     #4     06A   (as above)    (as above)      (as above)     May 2006
                                                                  -Sep 2006

[all version#4 processed data has updated photometric calibration based on
 a restricted J-Ks range and an empirically-derived Galactic extinction term]

===========================================================================