1. SJC - 109/29/05IRAC Calibration Workshop Status of IRAC Artifact Corrector Sean Carey

2. SJC - 209/29/05IRAC Calibration Workshop imask Files Reorder dmask flags, removing less than useful bits imask definition (tbs: to be set) –Bit 0: reserved for boolean mask of data to mask –Bit 1: reserved –Bit 2: optical ghost (post-BCD, tbs) –Bit 3: stray light (post-BCD stray light masking sets this) –Bit 4: strong saturation (donut) detection (post-BCD, tbs) –Bit 5: muxbleed (post-BCD, set in prototype code) –Bit 6: banding (post-BCD, set in prototype code) –Bit 7: column pulldown (post-BCD, set in prototype code) –Bit 8: crosstalk (set in pipeline) –Bit 9: radhit (set in pipeline) –Bit 10: latent image (set in pipeline) –Bit 11: not flat-field corrected (set in pipeline) –Bit 12: data not linear (set in pipeline) –Bit 13: saturation (set in pipeline) –Bit 14: bad or missing data (set in pipeline) Recommend using bits 3, 8-14 = 32520 in making mosaics, etc.

3. SJC - 309/29/05IRAC Calibration Workshop Muxbleed Cause: Relaxation of multiplexer after observing bright source Present only in 3.6 and 4.5  m arrays Symptom: Trail of bright pixels in read direction (every 4th column) 3.6  m 30 Doradus Muxbleed

4. SJC - 409/29/05IRAC Calibration Workshop Muxstripes Related to muxbleed Symptom: Variation in level of column segments due to very bright source Bright stars trigger and stop stripes Muxstripe ends Muxstripe starts

5. SJC - 509/29/05IRAC Calibration Workshop Column Pulldown Symptom: Bias change in column containing bright source Strongest at 3.6  m, also present at 4.5 and 5.8  m Different above and below source - Fowler sampling dependent

6. SJC - 609/29/05IRAC Calibration Workshop Banding Horizontal and vertical stripes produced by bright sources at 5.8 and 8.0  m Partially electronic, also optical Strength of banding can be different on opposite sides of triggering source Weak banding may also be present in 3.6 and 4.5  m images

7. SJC - 709/29/05IRAC Calibration Workshop Optical Banding Light scattered in array for Si:As arrays –Row and column bands –Diffuse component Verified by ground tests on spare arrays 10-20% of incident flux scattered into bands Diffuse scattering is 1.3  band flux Banding has curvature 5.8  m

8. SJC - 809/29/05IRAC Calibration Workshop Electronic Artifact Mitigation Method Artifact flagging –Cleaning up of mask files (dmask  imask) –Identification of triggering pixels –Masking of affected data Estimation of true sky under artifacts –Interpolation using nearby data –Gaussian kernel which mimics PRF Modeling of artifacts –Fit to difference between data and estimation –Fit functional forms for each artifact Correction of BCDs –Replace data with data - model –Update uncertainties

9. SJC - 909/29/05IRAC Calibration Workshop Artifact Flagging Find triggering pixels based on unsaturated fluence (number of e - ) e - = MJy/sr * GAIN * EXPTIME / FLUXCONV HDR saturations –Use short frame data to estimate fluence –Replace pixels if short > 100000 e - and long < 0.5  short Full frametime saturations –Need additional data –Can estimate from 2MASS for most sources –Tool to PRF fit in testing Muxbleed (3.6 and 4.5  m) –30000, 60000, 150000 e - at 3.6  m to mask 32, 64, 192 samples –55000, 160000, 250000 e - at 4.5  m to mask 32, 64, 128 samples Column pulldown (3.6 and 4.5  m) –30000 e - at 3.6  m –110000 e - at 4.5  m

10. SJC - 1009/29/05IRAC Calibration Workshop 3.6  m Flagging MaskBCD

11. SJC - 1109/29/05IRAC Calibration Workshop 5.8 and 8.0  m Flagging Horizontal banding: 200000 e - (5.8  m), 55000 e - (8.0  m) Vertical banding: 80000 e - (5.8  m), 200000 e - (8.0  m) 5.8  m BCD 5.8  m mask

12. SJC - 1209/29/05IRAC Calibration Workshop Sky Estimation Interpolate over masked pixels Use Gaussian kernel with FWHM of 1.44, 1.43, 1.49, 1.71 arcsec for 3.6, 4.5, 5.8, 8.0  m 3.6  m BCD 3.6  m sky estimate

13. SJC - 1309/29/05IRAC Calibration Workshop Model Fit Fit corrective functions to BCD-sky_estimate difference Banding, pulldown : DC offset on either side of triggering source –Linear fit may be appropriate for some data Muxbleed: model derived from data in AOR –Fowler sampling dependent –Scaled and filtered muxbleed instances –Optionally, smooth with a polynomial fit

14. SJC - 1409/29/05IRAC Calibration Workshop Good 3.6  m Results BCDCorrected BCD

15. SJC - 1509/29/05IRAC Calibration Workshop Poor 4.5  m Results BCDCorrected BCD

16. SJC - 1609/29/05IRAC Calibration Workshop Good 8.0  m Results BCDCorrected BCD

17. SJC - 1709/29/05IRAC Calibration Workshop Poor 8.0  m Results BCDCorrected BCD

18. SJC - 1809/29/05IRAC Calibration Workshop Photometry? BCDCorrected BCD Source should be 2.0 ± 0.2 Muxbleed source is 2.5 ± 0.5 Pulldown source is 1.5 ± 0.4

19. SJC - 1909/29/05IRAC Calibration Workshop Future Improvements Artifact thresholds as user-controlled input table Upper cutoff thresholds for artifacts Muxbleed model family as a function of triggering fluence Default muxbleed models for all frametimes Muxstripe corrector –Detection of triggering pixel –Hot pixel map to determine end of effect –Median matching of outputs in affected subimage Alternative background estimators –Morphlogical component analysis (Elad et al. 2005)