Date: Wed, 8 Apr 1998 09:33:06 -0700 (PDT) Message-Id: <199804081633.JAA29667@colman.ipac.caltech.edu> To: 2mass Subject: IPAC 2MASS WG Mtg #148 Minutes Cc: chas, email@example.com, stiening, bgreen Content-Length: 4204 X-Lines: 93 Status: RO IPAC 2MASS Working Group Meeting #148 Minutes 4/07/98 Attendees: R. Beck, R. Cutri, S. van Dyk, D. Engler, T. Evans, J. Fowler, L. Fullmer, T. Jarrett, D. Kirkpatrick, G. Kopan, J. Mazzarella, H. McCallon, B. Nelson, B. Wheaton, S. Wheelock, J. White AGENDA 1.) Northern Observatory Changes 2.) 2MAPPS 2.0 RTB Status DISCUSSION 1.) Northern Observatory Changes R. Cutri reported that R. Stiening will be at Mt. Hopkins next week to make several hardware and procedural changes. Some improvements to the telescope control are planned; these should make the actual pointing much closer to the reported commanded pointing at the start of each scan, providing better initial estimates for pointing reconstruction. Changes in the camera electronics are also planned which will fix a recurring problem in the readout of the first column in each array quadrant; these improvements will probably alter the dark and responsivity of the pixels in the affected columns, and so a new MRD (masks, responsivities, and darks) time period will be defined beginning when the changes are finished. In addition, shorter dark sequences are planned; dark "scans" will be 48 frames instead of 278. Twilight flat sequences will also be modified so that only every fifth frame is recorded. This will reduce data volume; it is not known whether it will significantly increase the estimation error in the responsivities, but the new five-night averaging procedure should help attenuate any loss of accuracy. It has also been suggested to take twilight flat sequences in the evening instead of the morning; this can be tried as an experiment, but there is concern that the relationship between each pixel's responsivity and the frame median when the array is saturated or has recently been saturated might be very different from observing conditions. Although it has been claimed that the arrays recover from saturation in seconds or minutes, that only relieves concern about whether the hardware is ready for science observations after being saturated by evening twilight. For the responsivity relationships to be right, all pixels would have to have identical post-saturation relaxation behavior, which seems unlikely. It was proposed that evening and morning flat sequences be taken for experimental purposes; this has been done in the past, and differences at the 10% percent level have been seen, but the differences at the 1-percentile and 99-percentile are more like 2%, which is not so far from night-to-night differences in morning flat sequences. 2.) 2MAPPS 2.0 RTB Status The team was polled for items preventing 2MAPPS 2.0 from going into production. The items identified were as follows. A.) PROPHOT has a residual problem involving the environment around very bright stars producing peak pixel' values that are very negative; these cause format problems in table-file interfaces; B. Wheaton will clip the peak pixel values and flag them to prevent this. B.) Final decisions of which hot pixels to mask in the various MRD time intervals remain to be made; R. Cutri, J. Mazzarella, and J. Fowler will form a splinter group to tie this item off. C.) H. McCallon requested acceptance of a new POSMAN delivery which will provide better diagnostics (enhancements and reduction of the main POSMAN input to the QUALITY subsystem, the QAPM file, and magnitude filtering of the spectral-combination counters to reduce noise false alarms) and allow more flexibility in accepting Tycho matches (maximum distance threshold enlargement option and access of Tycho stars from adjacent tiles to compensate a declination cosine effect in the tile geometry). These changes were found acceptable. Howard also stressed that scan overlap position discrepancy analysis was extremely useful in diagnosing problem scans (and possibly fixing them) and should be considered for pipeline inclusion in some later version of 2MAPPS, but this sort of analysis must remain offline for the present.