Date: Fri, 9 Oct 1998 19:44:57 -0700 (PDT)
To: 2mass
Subject: IPAC 2MASS WG Meeting #168 Minutes
Cc: chas, stiening, bgreen
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           IPAC 2MASS Working Group Meeting #168 Minutes

Attendees: R. Cutri, G. Kopan, S. Van Dyk, R. Beck, T. Evans, R. Hurt, 
           J. Fowler, H. McCallon, S. Wheelock, R. Tam, W. Wheaton, 
           T. Jarrett, L. Fullmer


1.) Project Update 

2.) New and Standing Action Items 


     R. Cutri began the proceedings by showing the 2MASS Picture of the Week,
of IC 443.  The mosaic was constructed by G. Kopan.

1.) Project Update 

     The northern electronics will be replaced with the Leach electronics
sometime in mid-November.  This may require a week of intense testing after the
replacement has been done.  A new operator, E. Bennett, has been hired for the
northern facility.

     The H-band array in the north has new holes.  There are six dead pixels in
phase with the step size, leading to a one-pixel hole every ~80 arcseconds.
The pixels are likely really dead, after the thermal cycle.  It remains to be
seen how bad are these pixels and how to eliminate the pixel holes.  The
possibilities are to shorten the scan step size, or to swap out the H array for
a new one.  Whichever is chosen, it will be very time-expensive.  If the array
is replaced, this could lead to a couple weeks of downtime, as well as time to
recharacterize the array.

     H. McCallon presented a plan to use information from the database to 
compute position differences needed to: 1) derive position variance corrections
using a global least-squares technique attempting to drive the chi-squares in 
scan-segment (12 segments/scan) overlaps to one; 2) derive position corrections
at the scan-segment level using a global least-squares technique considering 
scan-segment overlaps, ACT residuals as well as differences between adjacent
segments within each scan; and, 3) rederive position variances assuming position
corrections have been applied.  There was considerable discussion concerning 
options for getting these corrections back into the database and/or catalog 
releases.  R. Cutri summed up the discussion with the realization that we cannot
promise uniformity in the first processing, and that more work and exploration 
of options are necessary.  H. McCallon will put out a memo in the near future 
discussing the position refinement technique, as well as options for its use.  

      S. Wheelock presented the latest status on DMAGCOR, specifically, 
deriving the correction for cal scans by interpolating across adjoining sci
scans.  The bottom line is that a 5 to 6% effect is being reduced to a 1 to 2%
one, so the interpolation may be a viable correction mode.  R. Cutri stated that
we must come to closure on this problem sometime next week, since the number of
processed southern nights is growing.  Swift action is necessary.  No feedback 
has been received from the Calibration Committee, and this is therefore 
interpreted as tacit approval to use aperture photometry in the south cal scans
to derive the photometric zeropoint.

      A new set of artifacts is being seen in southern data: one is splotchy
in appearance, the other looks like a flare or comet tail, to the north of a
bright star.  Both likely result from the star being near the northern edge of
the array.

2.) New and Standing Action Items

%                                                      %
%                 ACTION ITEMS                         %
%                                                      %

      R. Cutri will be gone over the next several days, through next Tuesday.
It is up to G. Kopan whether or not a meeting next week is necessary.

(Standing Action Items:)

a) However, Team members are expected to email to R. Cutri by next Wednesday 
their wishlist associated with their particular pipeline tasks for 2MAPPS v3.0.

b) Team members should continue testing the IRSA tools.

c) Team members should still contemplate the sci-staff structure proposals and 
voice their opinions.