WFC3 Data Handbook v.4
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Table of Contents

WFC3 Data Handbook
Acknowledgments
Current Members of the WFC3 Team:
Former Members of the WFC3 Team:
Thanks
Preface
How to Use this Handbook
Handbook Structure
Typographic Conventions
Visual Cues
Comments
List of Acronyms
Chapter 1: WFC3 Instruments
1.1 Instrument Overview
1.2 The UVIS Channel
1.3 The IR Channel
Chapter 2: WFC3 Data Structure
2.1 Types of WFC3 Files
2.1.1 Data Files and Suffixes
2.1.2 Auxiliary Data Files
2.2 WFC3 File Structure
2.2.1 UVIS Channel File Structure
2.2.2 IR Channel File Structure
2.2.3 Contents of Individual Arrays
2.3 Data Storage Requirements
2.4 Headers and Keywords
Chapter 3: WFC3 Data Calibration
3.1 The calwf3 Data Processing Pipeline
3.1.1 Where to Find calwf3
3.1.2 Running calwf3
3.1.3 Keyword Usage
3.1.4 Using CRDS To Update Reference Files
3.2 UVIS Data Calibration Steps
3.2.1 Correction For Charge Transfer Efficiency
3.2.2 Error Array Initialization
3.2.3 Data Quality Array Initialization
3.2.4 Correct for Analog-to-Digital Conversion Errors
3.2.5 Overscan Bias Correction
3.2.6 Bias Structure Correction
3.2.7 Sink Pixel Detection and Marking
3.2.8 Post-flash Correction
3.2.9 Dark Current Subtraction
3.2.10 Flat-field Correction
3.2.11 Shutter Shading Correction
3.2.12 Photometry Keywords Calculation
3.2.13 Flux normalization for UVIS1 and UVIS2
3.2.14 Cosmic-ray Rejection
3.2.15 UVIS Image Statistics Calculation
3.3 IR Data Calibration Steps
3.3.1 Data Quality Initialization
3.3.2 IR Zero-Read Signal Correction
3.3.3 Bias Correction
3.3.4 IR Zero-read Image Subtraction
3.3.5 Error Array Initialization
3.3.6 Detector Non-linearity Correction
3.3.7 Dark Current Subtraction
3.3.8 Photometry Keywords
3.3.9 Conversion To Signal Rate
3.3.10 Up-the-ramp Fitting and Cosmic Ray Identification
3.3.11 Flat-field Correction
3.3.12 Image Statistics Calculation
3.3.13 Cosmic-ray rejection
3.4 Pipeline Tasks
3.4.1 wf3cte
3.4.2 wf3ccd
3.4.3 wf32d
3.4.4 wf3ir
3.4.5 wf3rej
3.5 Manual Recalibration of WFC3 Data
3.5.1 Requirements for Manual Recalibration
3.5.2 calwf3 Examples
Chapter 4: WFC3 Images: Distortion Correction and AstroDrizzle
4.1 WFC3 Geometric Distortion
4.1.1 The UVIS Channel
4.1.2 The IR Channel
4.2 Distortion Corrections and Image Combination
4.2.1 AstroDrizzle in the Pipeline
4.2.2 Manual AstroDrizzle Reprocessing
4.2.3 AstroDrizzle Documentation
4.3 References
Chapter 5: WFC3-UVIS Sources of Error
5.1 Gain and Read Noise
5.1.1 Gain
5.1.2 Read Noise
5.2 Bias Subtraction
5.2.1 Bias Calibration
5.2.2 Bias Correction for WFC3 Subarrays
5.3 Dark Current and Hot Pixels
5.3.1 Dark Current
5.3.2 Hot Pixels
5.4 UVIS Flat Fields
5.4.1 Ground Flats
5.4.2 On-orbit Corrections
5.4.3 Chip-Dependent Flats
5.5 Image Anomalies
5.5.1 Ghosts
5.5.2 Dragon’s Breath and Scattered Light
5.5.3 Cross Talk
5.6 Generic Detector and Camera Properties
5.6.1 Full Well Depth
5.6.2 Linearity at Low to Moderate Intensity
5.6.3 Linearity Beyond Saturation
5.6.4 Shutter Stability
5.6.5 Fringing
5.7 UVIS Photometry Errors
5.8 References:
Chapter 6: Charge Transfer Efficiency (CTE) in WFC3/UVIS
6.1 Overview
6.2 CTE Losses And Background
6.3 The Nature Of CTE Losses
6.4 The Pixel-Based Model
6.5 Empirical Corrections
6.6 Dealing With CTE Losses In WFC3/UVIS Images
6.7 Sink Pixels
6.8 References
Chapter 7: WFC3/IR Sources of Error
7.1 WFC3/IR Error Source Overview
7.2 Gain
7.3 WFC3/IR Bias Correction
7.4 WFC3 Dark Current and Banding
7.4.1 Dark Current Subtraction
7.4.2 Banding
7.5 Blobs
7.6 Detector Nonlinearity Issues
7.6.1 Nonlinearity Calibrations
7.6.2 Non-Zero Zeroth Read Correction for Bright Sources
7.7 Count Rate Non-Linearity
7.8 IR Flat Fields
7.8.1 Ground Flats (P-flats)
7.8.2 On-orbit Test of the Ground Flats
7.8.3 On-orbit L-flats from Sky Observations.
7.8.4 Pipeline Flats
7.9 Pixel Defects and Bad Imaging Regions
7.9.1 Bad Pixels
7.9.2 Off-nominal Detector Regions
7.9.3 Dead Pixels
7.9.4 Bad Zeroth Read Pixels
7.9.5 Unstable Pixels
7.9.6 Snowballs
7.10 Time Variable Background Contamination
7.10.1 Scattered Earthlight
7.10.2 Metastable Helium 1.083 μm Emission Line
7.10.3 Time-variable IR Background Mitigation Strategies
7.11 IR Photometry Errors
7.12 References
Chapter 8: Persistence in WFC3/IR
8.1 Image Persistence
8.2 Evaluating the Amount of Persistence in Science Images
8.3 Mitigating the Effects of Persistence
8.4 References
Chapter 9: WFC3 Data Analysis
9.1 Photometry
9.1.1 Photometric Systems
9.1.2 Photometric Zero Points
9.1.3 UVIS Chip-Dependent Calibration
9.1.4 UV Photometry
9.1.5 UVIS QUAD Filter Photometry
9.1.6 IR Photometric Calibration
9.1.7 Image Photometry Reference Table
9.1.8 Aperture Corrections
9.1.9 Color Corrections
9.1.10 Pysynphot Examples
9.1.11 Pixel Area Maps
9.1.12 CTE
9.1.13 Red Leak
9.1.14 UV Contamination
9.2 Astrometry
9.2.1 Coordinate Transformations
9.2.2 Absolute and Relative Astrometry
9.2.3 Impact of Guide Star Failure
9.3 Spectroscopy
9.3.1 Using the WFC3 Grisms
9.3.2 Pipeline Calibration
9.3.3 Slitless Spectroscopy Data and Dithering
9.3.4 Spectroscopy with the WFC3 G280 Grism
9.3.5 Spectroscopy with the WFC3 IR Grisms
9.3.6 Extracting and Calibrating Slitless Spectra
9.3.7 Reducing WFC3 grism data
9.3.8 Accuracy of Slitless Spectra Wavelength and Flux Calibration
9.4 STSDAS and STSCI_PYTHON Software
9.5 Specific Tools for the Analysis of WFC3
9.5.1 wfc3tools
9.5.2 Standalone Fortran routines for CTE correction
9.5.3 Cross-talk correction software
9.5.4 Grizli: Grism redshift & line analysis software for space-based slitless spectroscopy
9.5.5 PandExo: A community tool for transiting exoplanet science with JWST & HST
9.5.6 IDL procedures for simulating trajectories of multi-lined spatial scans
9.5.7 Satellite Trails Detection
9.5.8 LINEAR: IDL and C tools for grism spectroscopy
9.5.9 Code for mitigation of variable IR background
9.6 References
Chapter 10: WFC3 Spatial Scan Data
10.1 Analysis of Scanned Data
10.2 IR Scanned Data
10.2.1 IR Scanned Spectra
10.3 UVIS Scanned Images
10.3.1 Astrometry using UVIS Scanned Observations
10.3.2 Photometry of Bright Targets using UVIS Scanned Observations
10.4 References

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