Date: Wed, 10 Dec 1997 18:22:43 -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 #138 Minutes IPAC 2MASS Working Group Meeting #138 Minutes 12/09/97 Attendees: T. Chester, R. Cutri, D. Engler, T. Evans, J. Fowler, T. Jarrett, G. Kopan, J. Mazzarella, H. McCallon, B. Wheaton, S. Wheelock, J. White AGENDA 1.) DARKS Design Changes 2.) FREXCLEAN Redelivered 3.) Southern Observatory Status 4.) Band-to-Band Position Discrepancies 5.) 2MAPPS Version 2.0 Expectations 6.) Data Base Status DISCUSSION 1.) DARKS Design Changes A telecon was held earlier today to discuss design changes to the DARKS subsystem. The participants were R. Cutri, J. Fowler, G. Kopan, and M. Skrutskie. In the last year, a better understanding of the hardware behavior has been obtained, and some of the assumptions underlying the design of DARKS have been found to be incorrect. These mostly involve the stability of the dark-current behavior and the responsivity. Both have been observed to drift on time scales of days to months, and the J-band dark behavior exhibits sudden spontaneous jumps. The drifts will require a sliding-window averaging of the responsivity images, and the spontaneous dark jumps will require more elaborate rejection tests for dark sequences. Another change will be the freezing of the masks, which will henceforth be changeable only through human intervention; this can be done with a NAMELIST change. Different utilization of morning/evening combinations of dark and flat sequences will be made, and some quality-diagnostic output files will be modified or added. The detailed descriptions of the changes will be available in the DARKS SDS. 2.) FREXCLEAN Redelivered T. Evans reported that FREXCLEAN had been redelivered. The new version updates not only the FRX01 files (see the minutes of meeting number 137), but also the FRX02 and FRX03 files, which contain information relating to the number of detections per frame and per scan. These changes are needed by PFPREP and QUALITY. 3.) Southern Observatory Status R. Cutri reported that the southern telescope had obtained "first light" and that collimation was underway. All three chips in the camera have been swapped out, and the J chip was replaced yet again because of a bad column. When the camera was opened to make these changes, it was discovered that the mounting screws for the chips had no locking nuts, and one of the chips was actually loose enough to wobble a bit. 4.) Band-to-Band Position Discrepancies H. McCallon showed the results of some analysis based on the recently completed POSMAN summary-file processing capabilities. These related to the band-to-band alignment anomalies discussed in recent meetings. Although these results shed no light on the K anomalies, they confirmed a theory proposed some months ago that movement of the H chip was the cause of band alignment variations. POSFRM solves for the band-to-band alignment for each scan, and with the exception of two anomalous nights in which all three bands showed mutual alignment anomalies, all available data showed relatively consistent alignment between the J and K chips, both of which varied significantly with respect to H. 5.) 2MAPPS Version 2.0 Expectations Version 2.0 of 2MAPPS is due on February 2, 1998. The goal of this version is to be capable of processing all observations and generating products that satisfy the Level 1 requirements, without needing redeliveries before Version 3.0 at the end of data acquisition. To do this, it is desired for all subsystem capabilities currently in the design documentation to be implemented, tested, and tuned in Version 2.0. Because of design changes necessitated by unanticipated hardware problems, and also because of periods of temporary reassignment of 2MAPPS software developers to other projects, it does not appear feasible to have all capabilities currently in the design implemented, tested, and tuned by the nominal delivery date for Version 2.0, and so some discussion of the more significant areas of concern was held. Two main areas were identified: (a.) the POSMAN capabilities that have not yet been implemented, specifically, linear band-to- band alignment change during scan, position uncertainty model refinement, refraction modelling, and distortion modelling; (b.) PSF modelling and activities dependent upon it. There appears to be no possibility of implementing all the remaining POSMAN capabilities by next February, and the team expressed doubt that all were necessary for meeting the Level 1 requirements. Prioritization was therefore in order, and the decision was to implement the band-to-band linear alignment change first. This might be the only addition to POSMAN possible, but if time permits, the next task would be refinement of the position uncertainty model. It was noted that the lack of this refinement did not appear to be much of a threat to the Level 1 requirements, since the position uncertainties used by BANDMERGE are dominated by source-extraction position errors (for which the uncertainties appear to be reasonable for clean sources, if somewhat overestimated), and the optical-catalog association processing no longer uses the position uncertainties at all (only coarse-window matching is done). The final tests of position discrepancies with respect to the astrometric reference catalogs will provide the overall position uncertainties, and results to date indicate that the Level 1 requirements are already being safely met, which also suggests that the refraction and distortion models will contribute more to enhancing the products than to permitting the requirements to be met. [Note added in proof: subsequent discussion between H. McCallon and R. Cutri resulted in a reorder. Top priority will be refracttion and distortion, since these are the most significant effects. Second is the band-band linear fit, and, time allowing, the uncertainty modelling.] The other main area involves fully populating the PSF models. B. Wheaton reported that the goals for Dec. 1 had been met, but G. Kopan reported that a considerable amount of tuning with the full model needs to be done before the dependence of the detection thresholds on PSF FWHM will be on solid ground. The imminent arrival of data from the Southern observatory may introduce some surprises, but at the least, a lot of tuning for its peculiarities will be needed. A conflict was clearly recognized between the need for a stable version of 2MAPPS in February and the lessons of experience dictating that redeliveries will not cease to be necessary at that time. It was decided that the best way to accomodate both considerations was to have a "development pipeline" running a controlled RTB concurrently with the production pipeline. The former would have to be isolated from the latter to a sufficient degree to ensure that no accidental cross-talk would be likely, which would be easiest to guarantee if a separate machine were dedicated to this task. The RTB would have to be large enough to provide statistical likelihood that all known types of problem scans were included, but small enough to permit the entire RTB to run in a few days or about one week at most. As new problems are encountered in new data, a representative scan would be added to the RTB. This would eliminate any need to test new code in the production pipeline, but would permit full testing of all software fixes and enhancements. If fixes to the production software were to become unavoidable, thorough testing beforehand would be possible. Furthermore, considerable lead time for developing and testing Version 3.0 would be provided. Two concerns were recognized: (a.) a separate machine would be highly desirable, but resources would have to be allocated; (b.) many of the current software developers are not scheduled to be working on 2MASS even through the end of 1998, much less when version 3.0 would be delivered. The latter concern is a problem in any event; the only clear path to alleviating it is to minimize the shortcomings of version 2.0, which every effort will be made to do. 6.) Data Base Status J. Mazzarella reported that the query-by-table capability of the data base has been implemented and that the design for accessing overlapping images from different surveys has been done.