Space Telescope Science Institute
WFC3 Data Handbook 2.1 May 2011
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Table of Contents

WFC3 Data Handbook
Acknowledgments
Preface
How to Use this Handbook
Handbook Structure
Typographic Conventions
Visual Cues
Comments
Chapter 1: WFC3 Overview
1.1 Instrument Overview
1.1.1 The UVIS Channel
1.1.2 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 Calibration Overview
3.1.1 Image Processing Summary
3.2 Overview of calwf3
3.2.1 Structure and Processing Flow
3.2.2 UVIS Processing
3.2.3 IR Processing
3.2.4 Running calwf3
3.3 Keyword Usage
3.4 Description of Calibration Steps
3.4.1 wf3ccd
3.4.2 wf32d
3.4.3 wf3ir
3.4.4 wf3rej
3.5 Calibration of WFC3 Spectroscopic Data
3.6 When should I recalibrate my data?
3.7 Manual Recalibration of WFC3 Data
3.7.1 Requirements for Manual Recalibration
3.7.2 calwf3 Examples
Chapter 4: WFC3 Images: Distortion Correction and MultiDrizzle
4.1 WFC3 Geometric Distortion
4.1.1 The UVIS Channel
4.1.2 The IR Channel
4.2 MultiDrizzle: Distortion Correction and Dither Combination
4.2.1 Why drizzle?
4.2.2 Pipeline products
4.2.3 Documentation
4.3 MultiDrizzle Examples
4.3.1 IR MultiDrizzle example
MultiDrizzle: pipeline versus offline
Getting started: input images and distortion tables
Image registration and shift file
Key drizzling parameters
Inspecting output and iteration
Chapter 5: WFC3-UVIS Error Sources
5.1 Gain and Read Noise
5.1.1 Gain
5.1.2 Read Noise
5.2 Bias Subtraction
5.2.1 Bias Calibration Issues
5.2.2 Bias Correction for WFC3 Subarrays
5.3 Dark Current, Hot Pixels, and Cosmic Rays
5.3.1 Dark Current
5.3.2 Hot Pixels
5.4 Flat Fields
5.4.1 Ground Flats (P-flats)
5.4.2 On-orbit L-flats
5.4.3 Pipeline Flats
5.5 Image Anomalies
5.5.1 Ghosts
5.5.2 Stray 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
Chapter 6: WFC3-IR Error Sources
6.1 WFC3-IR Error Source Checklist
Checklist
6.2 WFC3 Bias Correction
6.3 WFC3 Dark Current and Banding
6.3.1 Dark Current Subtraction
6.3.2 Banding
Behavior
Mitigation
6.4 Blobs
6.5 Detector Nonlinearity Issues
6.5.1 Nonlinearity Calibrations
6.5.2 Non-Zero Zeroth Read Correction for Bright Sources
6.6 Count Rate Non-Linearity
6.7 Flat-Fielding
6.7.1 Ground Flats (P-flats)
6.7.2 On-orbit L-Flats
6.7.3 Pipeline Flats
6.7.4 Sky Flats
6.8 Pixel Defects and Bad Imaging Regions
6.8.1 Bad Pixels
6.8.2 Non-nominal Detector Regions
6.8.3 Dead Pixels
6.8.4 Bad Zeroth Read Pixels
6.8.5 Unstable Pixels
6.8.6 Snowballs
6.9 Image Persistence
6.9.1 Finding Persistence
6.9.2 Mitigating effects of Persistence
6.10 Scattered Earthlight
Chapter 7: WFC3 Data Analysis
7.1 STSDAS Software
7.2 Photometry
7.2.1 Photometric Systems, Units, and Zeropoints
7.2.2 Aperture and Color Corrections
7.2.3 Pixel Area Maps
7.2.4 CTE
7.2.5 Red Leak
7.2.6 UV Contamination
7.3 Astrometry
7.3.1 Coordinate Transformations
7.3.2 Absolute and Relative Astrometry
7.3.3 Impact of Guide Star Failure
7.4 Spectroscopy
7.4.1 Using the WFC3 Grisms
7.4.2 Pipeline Calibration
7.4.3 Slitless Spectroscopy Data and Dithering
7.4.4 Spectroscopy with the WFC3 G280 Grism
7.4.5 Spectroscopy with the WFC3 IR Grisms
7.4.6 Extracting and Calibrating Slitless Spectra
7.4.7 Reducing WFC3 grism data
7.4.8 Accuracy of Slitless Spectra Wavelength and Flux Calibration

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