The desire to remove persistence and ghosts as early in the processing as possible was tempered with the decision not actually to remove these things but to flag them. "Confused" objects, i.e., objects too close to relatively bright objects, would also be flagged. The process of flagging all three types of artifacts or damaged goods was dubbed "purging", although the actual deletions would occur downstream from the production pipeline. Flagged objects would presumably not be processed as good point sources, however, i.e., they would not be calibrated, aperture-corrected, band-merged, used for pointing reconstruction, associated with existing catalogs, etc.
The Read1 merge function had been appended to PROPHOT simply because that was the logical point in the pipeline to do that task. Since the other tasks are also logically done at the same point, but since none of these tasks are especially functionally similar to PROPHOT's tasks, it was decided to remove the Read1 merge from PROPHOT and create a new subsystem to do these additional tasks.
The new subsystem was named MAPCOR (Merge And Purge & APerture CORrections [where the "AP" does double duty in the acronym]). Its input is the Read1 source list from STATS (now known as FREXAS; see item 7 below) and the Read2-Read1 source list from PROPHOT. It will be invoked by the PCP subsystem to process these lists in all three bands after PIXPHOT has finished processing the scan. Its output will be source lists in three bands, where the Read1 photometry has been merged, ghosts, persistence, and "confused" objects have been "purged", and aperture corrections have been computed and applied to the PSF-fit photometry. This will be the input to the BANDMERGE subsystem.
After this splinter meeting, another was held with T. Chester, R. Cutri, and J. Fowler, to determine a cognizant engineer candidate for MAPCOR. It became obvious that T. Evans was the logical first choice if she could accept the additional workload, because she is the cognizant engineer of the DBMAN subsystem, which depends on data structure definitions which can be made at this time by the MAPCOR cognizant engineer. In fact, DBMAN has the most drawnout schedule specifically because its design is so dependent on other subsystems' interface definitions. It is hoped that the DBMAN schedule can be compressed downstream enough to make room for MAPCOR design in the shorter term; in order to allow this, a September 1 milestone for the initial DBMAN SDS has been pushed back to May 1, 1996, in order to insert a MAPCOR SDS milestone on October 15. T. Evans accepted these challenges, and all involved wish to express our thanks to her and our confidence in her ability to accomplish these tasks.
T. Evans reported that all of the older protocam data (prior to April '95) have been completely processed through band-merging, APM and GSC association, and insertion into SyBase, and soon everything will be available via XCATSCAN.
Two improvements to the position reconstruction can be expected from this approach: (a.) frame offset corrections can be implemented at a stage where the frames themselves can be treated as "stiff", i.e., individual frames need not be effectively compressed or stretched as in the current scheme which adjusts the in-scan positions of sources without regard to frame relationships; (b.) the use of an in-scan cubic spline correction can be abandoned. The improvements for ordinary well-behaved scans might not be significant, but a worthwhile gain in robustness should result from replacing the cubic spline, which is somewhat vulnerable to astrometric catalog errors. Such errors should be more obvious in their discrepancies relative to the frame offsets. The scheme is also appealing in that it uses more of the information simultaneously rather than sequentially.
Nevertheless, this represents a serious system design change, and so a splinter session was held after the regular meeting. Most of the discussion above is based on the splinter session, which was attended by J. Fowler, G. Kopan, and H. McCallon. Howard estimated the total complexity to be about the same as before, however, and with the improved robustness and greater theoretical appeal, it was decided to adopt the modification.
This eliminates the COFF module from the STATS subsystem and the rest of the system design. Its position will be taken by POSMAN, whose old position will be taken by a POSMAN module to be named by H. McCallon. G. Kopan reported that the functions performed by STATS have gone beyond what the name implies, and that subsystem will be renamed FREXAS (FRame EXtraction And Statistics And Seeing [the "AS" does double duty in the acronym]).