IPAC 2MASS Working Group Meeting #72 Minutes

IPAC 2MASS Working Group Meeting #72 Minutes, 9/12/95

Attendees: T. Chester, R. Cutri, T. Evans, J. Fowler, L. Fullmer, T. Jarrett, G. Kopan, B. Light, C. Lonsdale, H. McCallon, M. Moshir, S. Terebey, J. White


  1. Computer Maintenance
  2. Protocamera Data Product Status
  3. Twilight Flat Stability
  4. Obs/IPAC Interface Document
  5. CsFlat Divide-By-Zero Error
  6. Flowchart Report
  7. Extended Source Processing Near the Galactic Plane


  1. Computer Maintenance-- R. Cutri announced that karloff and lugosi would be unavailable for one hour on Wednesday (9/13) because of scheduled maintenance. Lugosi has been more stable ever since a number of component replacements were installed in an attempt to correct its previous tendency to turn off CPUs (apparently the new power supply was the critical ingredient).

  2. Protocamera Data Product Status-- R. Cutri reported that we appear to be on schedule for finishing the protocamera data products. This means we expect that in two weeks all data from photometric nights will have been processed for bandmerging and confirmation and will be available via XCATSCAN. The data products for the two different cameras will be stored separately but both will be accessible. T. Evans reported that a new version of XCATSCAN should be online by the end of this two-week period also, so that the data products will be accessed through the new version. This will include a 2MASS option that will require a password. A separate 2MASS version of XCATSCAN will no longer be required.

  3. Twilight Flat Stability-- R. Cutri reported that an analysis of the twilight flat stability has been performed. This involved computing a mean twilight flat for the entire observing period from the individual nights' twilight flats, and the standard deviation about the mean in each pixel was computed and viewed in image format. There was structure in the standard-deviation image, with extreme values of about 5% tending to be in the corners, where light-leak variations may have had some impact. For about 98% of the pixels, the standard deviation was 1% or less. The conclusion is that the twilight flats appear to be quite stable for this observing run.

  4. Obs/IPAC Interface Document-- J. White reported that M. Rudenko had sent comments on the Obs/IPAC Interface Document Rev. H. The suggested modifications appear useful and have low impact on 2MAPPS. J. White and J. Fowler will go over them in detail and J. White will incorporate them in the next version of the document.

  5. CsFlat Divide-By-Zero Error-- A divide-by-zero error was intercepted by the user-installed IEEE error handler in CsFlat running some April '95 J scans on karloff (CsFlat is the protocamera pipeline version of the frame flattener that uses the flattening method anticipated for 2MAPPS in the DFLAT subsystem). The handler prints a message showing the error code and (supposedly) program location and then terminates the program. Past problems with IEEE error handlers under Solaris have led to the discovery that the information passed to the handler is generally erroneous in optimized programs, and only the nature of the call is informative (e.g., in this case the divide-by-zero handling routine was called). A search of the CsFlat code had revealed that the program was vulnerable to unmasked zero pixels in the responsivity image. J. Fowler and J. White agreed to pursue this after the meeting (installing a trap for this condition subsequently revealed that there was indeed one unmasked zero pixel in the responsivity image; code was installed to mask the pixel at that point, bypass the division, and print a message identifying the fixup and the pixel involved; the set of scans then ran successfully).

  6. Flowchart Report-- J. White reported that flowcharts produced by the graphics department in Spalding were fine in hardcopy form but apparently unusable in postscript file format. J. Fowler reported that he had examined the disks and it appeared that Macintosh files had been written on DOS disks and vice versa. All attempts to view the flowcharts with ghostscript or to print them on local printers failed. This approach will therefore be abandoned.

  7. Extended Source Processing Near the Galactic Plane-- S. Terebey reported further on the extended source processing in or near the galactic plane (see last week's minutes). GALWORKS generates too many false-alarm extractions in regions of significantly varying background. It appears that the main problem is background removal under these conditions. It does not appear likely that setting thresholds differently can help sufficiently to achieve the related science goals. She and T. Jarrett will study alternative methods for handling the background.