1 / 19

Status of IRAC Artifact Corrector

Status of IRAC Artifact Corrector. Sean Carey. 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)

varian
Download Presentation

Status of IRAC Artifact Corrector

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Status of IRAC Artifact Corrector Sean Carey

  2. 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. 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. Muxstripes • Related to muxbleed • Symptom: Variation in level of column segments due to very bright source • Bright stars trigger and stop stripes Muxstripe starts Muxstripe ends

  5. 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. 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. Optical Banding 5.8 m • 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

  8. 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. 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. 3.6 m Flagging BCD Mask

  11. 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. 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. 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. Good 3.6 m Results BCD Corrected BCD

  15. Poor 4.5 m Results BCD Corrected BCD

  16. Good 8.0 m Results BCD Corrected BCD

  17. Poor 8.0 m Results BCD Corrected BCD

  18. Photometry? BCD Corrected BCD Source should be 2.0 ± 0.2 Muxbleed source is 2.5 ± 0.5 Pulldown source is 1.5 ± 0.4

  19. 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)

More Related