Date: Mon, 27 Oct 1997 16:52:49 -0800 (PST) From: firstname.lastname@example.org To: email@example.com Cc: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Subject: 2MASS WG Mtg #134 Minutes IPAC 2MASS Working Group Meeting #134 Minutes 10/21/97 Attendees: R. Beck, R. Cutri, T. Evans, J. Fowler, L. Fullmer, D. Kirkpatrick, G. Kopan, J. Mazzarella, B. Nelson, S. Wheelock, J. White AGENDA 1.) MAPCOR Tuning 2.) Optical Catalog Association Parameters 3.) Telescope and Camera Status 4.) Science Team Meeting Agenda 5.) Quality Assessment Issues 6.) Minor Planet Processing 7.) Sample Data Base DISCUSSION 1.) MAPCOR Tuning R. Cutri reported that the top-priority parameter tuning target at this time is MAPCOR. The current persistence rejection is very good, but considerable work needs to be done on glints, diffraction spikes, and fractured bright sources. 2.) Optical Catalog Association Parameters J. Fowler reported that a study of the IAU Colloqium 179 poster writeup "The OPTID Database: Deep Optical Identifications to the IRAS Faint Source Survey" (Lonsdale et. al., August 1996) suggests that the likelihood ratio parameter defined therein would not be appropriate for use as one of the 2MASS optical-catalog association parameters. The main reason is that the paper states that this parameter follows very different distributions for different classes of objects (e.g., bright stars vs. faint galaxies), requiring some prior knowledge of the object type for interpretation. Furthermore, the parameter was used in a way that is dissimilar to the 2MASS context, namely multiple matches were retained, with a full set of identification parameters for each possible match, whereas the 2MASS associations will retain a single match as an association. The two contexts are quite dissimilar primarily because the IRAS objects had position uncertainties large enough to permit multiple associations under source-density conditions that would be considered sparse by 2MASS standards. Since the number of catalog objects within the coarse window (nominally 3 arcsec radius) will be an association parameter, and since the radial separation (and orientation angle) are also included, the group decided that sufficient match-quality and confusion indicators were included in the current design. 3.) Telescope and Camera Status R. Cutri reported that the southern-hemisphere telescope had been damaged in shipment. The mirror is OK, but the mounting needs significant repair work. The possibility that the repairs can be performed at a machine shop in La Serena is being pursued as the most desirable course of action. There is a chance that shipment back to the U.S. or replacement hardware will be needed. All repair and shipping costs should be covered by insurance. [Note added in proof: a new part will have to be fabricated in the U.S. and air-freighted to Chile.] The lab data tape for the southern camera has arrived at IPAC and will be run through the DARKS subsystem. There is concern that the K array will need to be replaced, so the results of timely IPAC analysis of these data are needed at UMASS. 4.) Science Team Meeting Agenda The Science Team meeting in Boston on November 5-6 (not 4-5, as stated in last week's minutes) will include presentations by all 2MAPPS cognizant scientists on the parameter tuning status of their respective subsystems. A splinter group will discuss photometric acceptance criteria. 5.) Quality Assessment Issues R. Cutri reported that the desire for a boiled-down two-or- three-numbers quality characterization for each scan still exists, and work on designing this will continue. Offline analysis will also pursue the relationship between the "pfrac" parameter and PSF FWHM. The pfrac parameter is computed for each band-scan by the FREXAS module; it characterizes the fraction of light from a point source contained within a single pixel. The smaller this number is, the larger the azimuthally averaged PSF is, but the exact relationship has not been calibrated in detail. Doing so is desirable in general and would be used in MAPCOR and for interpreting GALWORKS results. 6.) Minor Planet Processing J. Fowler reported that the MPCAT (Minor Planet Catalog) subsystem is now activated in the 2MAPPS pipeline. Several asteroids have been matched, and resulting analysis has revealed some residual bugs in the association program MPFIND. It also became clear that additions to the MPC03 SIS were desirable, specifically, the addition of the RA and Dec offsets between the 2MASS point source and the predicted minor planet position. This change has been made. 7.) Sample Data Base T. Evans reported that most of the 11-night sample data base has been generated. Scans with about 5000 point sources require about 45 seconds to load into the data base, whereas scans with about 30,000 sources require about 15 minutes. The complete data base contains about 6 million sources, with duplicated entries for multiply scanned regions (mostly calibration scans). There are 15 indexes per source, and each index takes about 25 minutes to be generated. Unindexed queries take about 30 minutes; currently indexed queries take the same time because of a bug that is not yet found.