IRAC Instrument Handbook - IRSA - California Institute of Technology

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IRAC Instrument Handbook
4.8 CALCULATION OF IRAC ZMAGS .............................................................................................................................. 50
4.9 ASTROMETRY AND PIXEL SCALES............................................................................................................................ 52
4.9.1 Optical Distortion.................................................................................................................................................. 52
4.9.2 Pixel Solid Angles.................................................................................................................................................. 52
4.10 POINT SOURCE PHOTOMET RY ................................................................................................................................... 53
4.11 EXT ENDED SOURCE PHOT OMETRY .......................................................................................................................... 55
4.11.1 Best Practices for Extended Sources............................................................................................................. 56
4.11.2 Extended Source Aperture Correction.......................................................................................................... 57
4.11.3 Low Surface Brightness Measurements and the Maximum Scaling Factors ......................................... 59
4.11.4 Caveats & Cautionary Notes.......................................................................................................................... 60
4.11.5 Faint Surface Brightness Behavior ............................................................................................................... 60
4.11.5.1 Bi nning ............................................................................................................................................................ 60
4.11.5.2 Small Scales..................................................................................................................................................... 62
4.11.5.3 Medium Scales................................................................................................................................................ 62
4.11.5.4 Large Scales..................................................................................................................................................... 62
4.11.5.5 Increasing exposure ti me................................................................................................................................ 62
4.12 POINTING PERFORMANCE .......................................................................................................................................... 64
4.12.1 Pointing Accuracy ............................................................................................................................................ 65
4.12.2 Jitter and Drift .................................................................................................................................................. 66
5 Pipeline Processing ..................................................................................................................68
5.1 LEVEL 1 (BCD) PIPELINE .......................................................................................................................................... 68
5.1.1 SANITY DATATYPE (parameter checking) ...................................................................................................... 68
5.1.2 SANITY CHECK (image contents checking) .................................................................................................... 68
5.1.3 TRANHEAD (header processing)....................................................................................................................... 68
5.1.4 INSBPOSDOM (InSb array sign flipping) ........................................................................................................ 71
5.1.5 CVTI2R4 (byte type changing) ............................................................................................................................ 72
5.1.6 Wraparound Correction: IRACWRAPDET AND IRACWRAPCORR.......................................................... 73
5.1.7 IRACNORM (Fowler sampling renormalization)............................................................................................ 74
5.1.8 SNESTIMATOR (initial estimate of uncertainty) ............................................................................................. 75
5.1.9 IRACEBWC (limited cable bandwidth correction).......................................................................................... 76
5.1.10 Dark Subtraction I: FFCORR (first frame effect correction) or LABDARKSUB (lab dark
subtraction) ........................................................................................................................................................................... 77
5.1.11 MUXBLEEDCORR (electronic ghosting correction) ............................................................................... 80
5.1.12 DARKDRIFT (``readout channel’’ bias offset correction) ....................................................................... 81
5.1.13 FOWLINEARIZE (detector linearization) ................................................................................................... 82
5.1.14 BGMODEL (zodiacal background estimation) ........................................................................................... 83
5.1.15 Dark Subtraction II: SKYDARKSUB (sky “delta-dark” subtraction)..................................................... 83
5.1.16 FLATAP (flatfielding) ...................................................................................................................................... 84
5.1.17 IMFLIPROT ...................................................................................................................................................... 84
5.1.18 DETECT-RADHIT (cosmic ray detection)................................................................................................... 85
5.1.19 DNTOFLUX (flux calibration)....................................................................................................................... 85
5.1.20 Pointing Transfer (calculation of pointing information) ........................................................................... 86
5.1.21 PREDICTSAT (HDR saturation processing)............................................................................................... 88
5.1.22 LATIMFLAG (residual image flagging)....................................................................................................... 89
5.2 THE ARTIFACT -CORRECTED BCD PIPELINE........................................................................................................... 89
5.2.1 Stray Light .............................................................................................................................................................. 89
5.2.2 Saturation................................................................................................................................................................ 90
5.2.3 Sky Background Estimation ................................................................................................................................. 91