IPAC 2MASS Working Group Meeting #88 Minutes, 3/05/96

Attendees: T. Chester, R. Cutri, T. Evans, J. Fowler, L. Fullmer, T. Jarrett, D. Kirkpatrick, G. Kopan, B. Light, H. McCallon

AGENDA

1. Monthly Activity Reports
2. PS CDR Agenda

DISCUSSION

1. Monthly Activity Reports --
   • J. Fowler: reported that he has been working on BANDMERGE.

   • B. Light: reported that he has run aperture photometry code using FREXAS-type input on the ultrasparc loaner, clone4. A 42-frame test case that took 53 CPU seconds on karloff and 50 CPU seconds on lugosi took only 29 CPU seconds on clone4, and a large part of that is believed to be due to other CPU-intensive tasks running at the same time (clone4 has a single CPU). When compiled on clone4 and run when clone4 was drier, the run took 16 CPU seconds; this version was compiled with standard high optimization but not ultrasparc-peculiar optimization.

     He also reported on a study of the dependence of the differences between PSF-fit photometry and aperture photometry on whether the aperture photometry is done on coadded images versus KAMPhot's internal method. The behavior of the mean difference as a function of magnitude appears the same for the two cases; the dispersion is quite different, but in the cases examined, the dispersions were computed differently for the two methods and have different interpretations. Bob will look into providing more comparable dispersions. In any case, going from the protopipeline method to the 2MAPPS method does not appear to introduce anomalies. During this discussion it became apparent that whereas KAMPhot has code to break a single detection into multiple extractions if doing so improves the fit, this code has never been activated; this had not been the understanding of some members of the working group. Apparently all multiple detections with "blend" flags that have come out of KAMPhot resulted from multiple close detections going in rather than splitting up of single detections.

   • G. Kopan: reported that he has been working on PIXPHOT and PICMAN. The latter is now capable of using a Weinberg kernel or a KAMPhot PSF for smoothing, and studies of the effects of different kernels will be discussed by T. Jarrett (see below and also last week's minutes). In fact, arbitrary smoothing kernels can be read in via FITS files.

     He also has been running tests on clone4. With standard optimization, clone4 appears to be faster than karloff and lugosi by a factor equal to the ratio of clock speeds. With ultrasparc-peculiar optimization, additional speed advantages are seen on clone4. The user CPU variation observed when identical tasks are run repeatedly on karloff and lugosi (see last week's minutes) were not seen on clone4.

   • T. Evans: reported that she has been working mostly on IRTS but is now returning to 2MASS to continue working on the MAPCOR SDS and SIS's. A design change in the persistence removal has occurred and will be described in the next version of the SDS.

   • L. Fullmer: reported that she has been working on the QUALITY SDS. All subsystem developers are requested to consider what kinds of boiled down information their subsystems can transmit to QUALITY to enter into an overall evaluation of scan quality. Such information will be transmitted via ASCII files. An example that was suggested is the mean trimmed average standard deviation from DFLAT.

   • R. Cutri: reported that he has been working on the point source WSDB format (see last week's minutes). Several responses to his emailed format proposal have been received from team members, but much discussion clearly remains.

   • D. Kirkpatrick: reported that he has completed some spectroscopic observations on the 200-inch, where the targets were selected from 2MASS protocamera data products. The wavelength range covered was 3500-9500 Angstroms. The targets included some late M dwarfs, some brown dwarf candidates, and some color selected objects picked out by C. Lonsdale and R. Cutri that appear to be both nonstellar and very interesting.

   • H. McCallon: reported that he has been working on the demo of his proposed position reconstruction technique for the PS CDR (since returning from IRTS). At this point, the code uses a single band and no Read1 detections but does include in-scan/cross-scan coupling. Expansion to multi-band and Read1 input will not affect the basic formulation and should only strengthen the argument that the method is fundamentally sound. The code solves for offsets and scale factors for in-scan and cross-scan coordinates and a rotational error. It has been tested with a simulation based on protocamera data. It has worked well for the frame-to-frame offsets and absolute reference solutions.

   • T. Chester: reported that he attended the WIRE review and has been working with T. Jarrett on the study of the effect of various smoothing kernels on galaxy processing.

   • T. Jarrett: reported that a narrower smoothing kernel (H = 0.4, where H is a parameter in the Weinberg smoothing formulation) works better than the broader one used previously (H = 0.6 was used for the study reported in last week's minutes). Fewer false detections were found, while faint galaxies were still detectable. For galaxy processing (as studied so far using Coma scans), this smoothing kernel is preferable to either the bilinear or area overlap kernels, as it provides better star-galaxy discrimination. It is worth investigating whether it has an impact on point source processing.

2. PS CDR Agenda -- R. Cutri reported that a conference call had been held to discuss the agenda for the Point Source Critical Design Review to be held March 21 (this is a change from the previous schedule; March 21 was to be the science team meeting, and the CDR was to be March 22; the two activities have been interchanged on the schedule). A more detailed list will be distributed soon, but in the meantime, the following speakers and topics were identified: J. Fowler will describe the bandmerging algorithm design; H. McCallon will present an overview of the POSMAN algorithm and discuss the testing performed up to that time; T. Chester will discuss position reconstruction in general; R. Cutri will discuss flat fielding and sky subtraction; S. Wheelock will present studies of completeness and reliability, including the implications of using the DAOFIND algorithm on coadds versus KAMPhot's detection algorithm applied to its internally filtered frame averaged representation; J. Fowler will discuss the status of the 2MAPPS point source software design and coding and the SDS signoffs.

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