PosMan Results: 971116n V3 Pipeline Test

H.L. McCallon 12-14-00

The first pipeline test of PosMan V3 making use of Martin corrections for 971116n looks good. The global Martinizing task using all overlaps as well as Tycho-2 won't be completed for some time yet. The corrections used for this test were from prototype Martinizing of the Second Release data using overlaps and ACT (not Tycho-2) stars. PosFrm V3 preserves the relative J-band frame-to-frame differences as corrected by the Martinizing, freezes the x-scan J-band scale factor at an input value (V2 mean for hemisphere) and then solves for the remaining free parameters. This adjustment to the original plan preserves it's intent while allowing for possible small differences in the band-to-band relationships due to improvements in PSF modeling for V3. Distortion corrections are included in V3 processing, but were not used for V2.

A half dozen 971116n overlap scan pairs selected from the original V2 ACT reconstructions based on unusually large deviations are shown in detail. Note that some of the scans involved here were actually reconstructed during V2 processing using the USNOA because there weren't enough ACT stars available with the proper distribution along the scan. Each figure plots the V2 x-scan overlap differences (SNR>20) as a function of Dec in the top panel using red squares. Over that are plotted the V3 differences using black x's. Corresponding plots for in-scan differences can be seen in the bottom panel. Note the marked improvement in each case. The scan pairs illustrated include: 971116n064-971116n063, 971116n066-971116n065, 971116n067-971116n066, 971116n095-971116n094, 971116n133-971116n132 and 971116n134-971116n133

There is a significant improvement for the whole night as can be seen by the overlap histograms of x-scan and in-scan differences (SNR>20) of all 971116n survey scans. As before, red indicates V2 and black V3. The x-scan histograms are in the top panel and the in-scan histograms in the bottom panel. These normalized histograms show that V3 has tightened up the distributions considerably in both directions. Furthermore the overlap improvement was not done at the expense of the Tycho-1 residuals, as can be seen in comparative V2 and V3 Tycho-1 difference histograms.

---

http://spider.ipac.caltech.edu/staff/hlm/2mass/v3_971116n/v3_971116n.html
Comments to: Howard McCallon
Last update: 14 December 00