Date: Wed, 5 Aug 1998 12:23:39 -0700 (PDT)
To: 2mass
Subject: IPAC 2MASS WG Meeting #159 Minutes
Cc: chas, steining, bgreen
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           IPAC 2MASS Working Group Meeting #159 Minutes

Attendees: R. Cutri, S. Van Dyk, L. Fullmer, R. Beck, D. Engler, T. Evans,
           R. Hurt, J. Fowler, G. Kopan, D. Kirkpatrick, W. Wheaton,
           H. McCallon, J. Mazzarella


1.) Testing in the south
2.) 2MAPPS 2.1
3.) 2MASS Sampler
4.) Christmas in August


1.) Testing in the south

     R. Cutri reported on testing in the southern hemisphere with the new
electronics.  Two short test scans were made at CTIO, including a focus test.  
The tests indicated problems with the new electronics, and so, the new 
electronics were taken back to UMass.  Operations are back to the old 

     A slew of engineering tests were also undertaken, including a 
cross-stepping test.  The cross-stepping tests were made on the Stone 
astrometric field.  This will allow testing of the responsivity vs. cross-scan 
position and the focal plane distortion.  These scans were made at two different
telescope positions.  A test of the PSF spatial variation was also made.

     The northern facility is still on hiatus, as monsoonal flows pound Mt.
Hopkins.  In the meantime, northern OPS are running on elvis, currently 
processing observations from 1998 January, while barney is being used to 
process data from 1997 September.

2.) 2MAPPS 2.1

     Obviously, August 3 has come and gone, and the switch on 2MAPPS 2.1 has
not yet been thrown.  This is due to two-and-a-half major issues that still need
to be resolved before southern OPS with v 2.1 can begin:

     a) The PSF variation issue needs to be rectified.  W. Wheaton reported on 
the status of PSF development for the southern data. A set of PSFs (and 
corresponding variance maps; hereafter, VMs) were made by 7/18/98 covering the 
good-seeing intervals (shape parameter sh < 1.0), which is applicable for the 
majority of the southern data.  Each PSF/VM was a weighted average of several 
selected PSF/VM's from individual calibration scans in the appropriate sh range.
Each PSF/VM used as input to the average was made by a separate run of the 
PSFMAKE program.  (PSFMAKE produces a single PSF/VM pair, each output as a 
separate FITS file using the 50 brightest stars in a single scan.) Besides eye
examination, the distance (in the sense of chi^2) of each input PSF/VM from the
final average was computed, and discrepant PSF/VMs were discarded.  Note that 
this procedure differed from the PSF/VM generation method R. Light previously 
used for the northern data, in that he had selected (unfortunately, using
criteria that are no longer precisely known) a *single* PSF/VM from PSFMAKE, 
with sh in the appropriate range, rather than averaging several together. 

The southern RTB nights (980328s, 980403s, and 980514s) were rerun using the new
PSFs, and two (at least) problems appeared.  The worst of these was that 
re-observations of the same calibration fields showed increased scatter in 
several calibration sets, causing them to fail, on 980403s.  In addition, the 
scatter plots of reduced chi^2 versus profile fit magnitude (although not 
obviously incorrect in themselves) are qualitatively quite different from those
from the northern observatory PSFs.  Because of these issues, a new set of PSFs
was created 7/24/98 by selection of single PSFMAKE PSF/VM pairs in the correct 
sh range (sh < 1.0).  The same RTB nights were then rerun last week using these
new PSFs.  Unfortunately it now appears (as discovered by T. Evans, who, as is
the case for W. Wheaton, has just returned from vacation) that the PSF select
mechanism is somehow broken for the southern data, as the PROPHOT output files 
for the new RTB nights have PSF IDs that are invalid, given the new PSFs that 
were installed 7/24/98.  This issue must be resolved before further progress is

     One important diagnostic to attack the PSF variation problem is to plot 
aperture magnitudes vs. PSF magnitudes as a function of star brightness.

     b) The other issue is the artifact tuning.  T. Evans is working with
C. Beichman to ensure, along with visual inspection, that all artifacts are 
being accounted for in the flagging.  R. Cutri reminded T. Evans not to forget 
the "crescent," or "tophat," artifact.

     So, once a) and b) are resolved, 2MAPPS 2.1 is nominally ready for use,
EXCEPT for the PSF variation across the focal plane.  We clearly need to gather
more information and learn more about this problem, with proper
parameterization.  In particular, PSF magnitude vs. aperture magnitude must be
mapped as a function of cross-scan position.  G. Kopan will be spearheading the
investigative effort.  He will likely be tapping on the doors of able bodies
and eyes that can perform various tests.  Effects, such as temperature, seeing,
focus, telescope position, must all be treated as viable parameters.  

     The "fix" for this problem will be made before calibration, by 
renormalizing the PSF magnitudes to the aperture magnitudes as a function of
cross-scan position, serving as a "Super MAPCOR".  Southern OPS will be held
off till there is a well-tested correction in place.  This may require three to
four weeks.  The target date for 2MAPPS 2.1 will now be September 1.

3.) 2MASS Sampler

     J. Mazzarella gave a brief update on efforts toward the Sampler.  The night
that will be released is 971116n.  A lot of work on the interface is proceeding.
Many details on queries, etc., were discussed briefly by J. Mazz.  He questioned
when the full operational interface should be delivered.  R. Cutri said that it
would be better to have incremental deliveries, as the final interface version 
is being readied.  J. Mazz will test the existing interface software by Friday.
The complete interface wil be ready by August 15, so that it, along with the 
dataset, can be frozen in place.

     Some discussion took place on how to provide upper limits, versus measured
star magnitudes, via the interface.  R. Cutri emphasized that it is still not
clear what will make it from the database to the online source catalog.  It is
a convoluted question how to give upper limits versus providing a measured
magnitude.  R. Cutri pointed out that this is not a working group issue, this
is a science team issue, that several variations on upper limits (1 sigma,
3 sigma, etc.) can be provided, but that a default option must be decided upon.
"The default is religion," R. Cutri reminded us all.  However, syntax-wise,
using a "greater than" or "less than" sign, either before the column entry, or
in a separate column, suits R. Cutri just fine.

     The target date for the Sampler is still September 15, which allows a month
for team members to bang hard on the interface, to ensure reliability.  At
some point during this month, the astronomical community must be made aware of
the Sampler, the mode of data acquisition, and the impending release date 
(whatever that truly winds up being).

4.) Christmas in August

     2MASS at IPAC is benefitting from some extra IPAC funds that have 
appeared.  With these funds, a new Enterprise 450 (Son of Barney) is being
purchased.  Also, new hardware for the database will be purchased as well.  R. 
Beck stated his satisfaction in having Son of Barney configured in the same way 
as Barney, but if more than 150 Gb were available in hard disk, then that would
be fine, too.  T. Evans indicated that with the new database hardware, there
could be more database loading with less impact on the group.

     Lastly, R. Cutri will be away for several days, but, in his absence, G. 
Kopan will handle matters concerning 2MAPPS development and testing, and D.
Kirkpatrick will handle matters concerning data processing and QA issues.