Table of Contents Wide Field Camera 3 Instrument Handbook for Cycle 21 Acknowledgments Chapter 1: Introduction to WFC3 1.1 Overview 1.2 Key Features of WFC3 1.3 WFC3 Quick Reference Guide 1.4 Special Considerations for Cycle 21 1.4.1 Current Instrument Status 1.4.2 Ongoing Calibration 1.4.3 New Capabilities 1.5 Sources of Further Information 1.6 The WFC3 Instrument Team at STScI Chapter 2: WFC3 Instrument Description 2.1 Optical Design and Detectors 2.2 Field of View and Geometric Distortions 2.3 Spectral Elements 2.3.1 The Filter Selection Process 2.3.2 Filter and Grism Summaries 2.3.3 Shutter Mechanism 2.4 Detector Read-Out Modes and Dithering Chapter 3: Choosing the Optimum HST Instrument 3.1 Overview 3.2 Choosing Between Instruments 3.3 Comparison of WFC3 with Other HST Imaging Instruments 3.3.1 Wavelength Coverage 3.3.2 Field of View 3.3.3 Detector Performance 3.3.4 System Throughputs and Discovery Efficiencies Chapter 4: Designing a Phase I WFC3 Proposal 4.1 Phase I and Phase II Proposals 4.2 Preparing a Phase I Proposal 4.2.1 Which WFC3 Channel(s) and Filter(s)? 4.2.2 What Exposure Times? Dithering and Mosaicking Bright Targets UVIS Exposures IR Exposures 4.2.3 What Aperture or Subarray? 4.2.4 What Overheads and How Many HST Orbits? 4.2.5 Any Special Calibration Observations? 4.2.6 What is the Total Orbit Request? Chapter 5: WFC3 Detector Characteristics and Performance 5.1 Overview of this Chapter 5.2 The WFC3 UVIS Channel CCD Detectors 5.2.1 Basics of CCD Operation 5.2.2 The WFC3 CCDs 5.3 WFC3 CCD Readout Formats 5.3.1 Full-frame Readout 5.3.2 Subarrays 5.3.3 On-Chip Binning 5.4 WFC3 CCD Characteristics and Performance 5.4.1 Quantum Efficiency 5.4.2 Multiple-Electron Events at Short Wavelengths 5.4.3 Flat Fields 5.4.4 Long-Wavelength Fringing 5.4.5 Linearity and Saturation 5.4.6 Gain 5.4.7 Read Noise 5.4.8 Dark Current 5.4.9 Bad Pixels 5.4.10 Cosmic Rays 5.4.11 Charge Transfer Efficiency 5.4.12 Crosstalk 5.5 The WFC3 IR Channel Detector 5.5.1 Overview 5.5.2 IR Detector Basics 5.6 WFC3 IR Readout Formats 5.6.1 Full-Frame Readouts and Reference Pixels 5.6.2 Subarrays 5.7 WFC3/IR Detector Characteristics and Performance 5.7.1 Quantum Efficiency 5.7.2 Dark Current 5.7.3 Read Noise 5.7.4 Flat Fields 5.7.5 Linearity and Saturation 5.7.6 Count Rate Non-Linearity 5.7.7 Detector Cosmetics 5.7.8 Crosstalk Chapter 6: UVIS Imaging with WFC3 6.1 WFC3 UVIS Imaging 6.2 Specifying a UVIS Observation 6.3 UVIS Channel Characteristics 6.4 UVIS Field Geometry 6.4.1 Field of View and Pixel Size 6.4.2 Geometric Distortion 6.4.3 Coordinate Systems 6.4.4 Subarrays and On-Chip Binning Subarrays On-Chip Binning 6.4.5 Apertures 6.5 UVIS Spectral Elements 6.5.1 Filter and Grism Summary UV Filters Ultra-Wide Filters Wide-Band Filters Medium-Band Filters Narrow-Band Filters Quad Filters Grism 6.5.2 Filter Red Leaks 6.5.3 Ghosts Window Ghosts Filter Ghosts 6.6 UVIS Optical Performance 6.6.1 PSF Width and Sharpness 6.6.2 Encircled and Ensquared Energy 6.6.3 Other PSF Behavior and Characteristics Temporal Dependence of the PSF: HST Breathing Pixel Response Function PSF Characteristics 6.7 UVIS Exposure and Readout 6.7.1 Exposure Time 6.7.2 ACCUM Mode Overscan Regions 6.8 UVIS Sensitivity 6.8.1 Limiting Magnitudes 6.9 Charge Transfer Efficiency 6.9.1 Overview 6.9.2 CTE Mitigation Before Data Acquisition: Observation Planning 6.9.3 CTE Mitigation After Data Acquisition: Post-Observation Image Corrections 6.10 Other Considerations for UVIS Imaging 6.10.1 Gain and Full-Well Saturation 6.10.2 Cosmic Rays and Hot Pixels 6.10.3 Image Persistence 6.10.4 Shutter-Induced Vibration 6.10.5 Droplets 6.10.6 Optical Anomalies 6.11 UVIS Observing Strategies 6.11.1 Dithering Strategies 6.11.2 Parallel Observations 6.11.3 Spatial Scans 6.11.4 PSF Subtraction Chapter 7: IR Imaging with WFC3 7.1 WFC3 IR Imaging 7.2 Specifying an IR Observation 7.3 IR Channel Characteristics 7.4 IR Field Geometry 7.4.1 Field of View and Pixel Size 7.4.2 Geometric Distortion 7.4.3 Coordinate Systems 7.4.4 Subarrays 7.4.5 Apertures 7.5 IR Spectral Elements 7.5.1 Filter and Grism Summary Wide-Band Filters Medium-Band filters Narrow-Band Filters Grisms 7.5.2 Filter Blue Leaks 7.5.3 Ghosts 7.6 IR Optical Performance 7.6.1 PSF Width and Sharpness 7.6.2 Encircled and Ensquared Energy 7.6.3 Other PSF Behavior and Characteristics Temporal Dependence of the PSF: HST Breathing Intra-Pixel Response Inter-Pixel Capacitance 7.7 IR Exposure and Readout 7.7.1 Exposure Time 7.7.2 MULTIACCUM Mode 7.7.3 MULTIACCUM Timing Sequences: Full Array Apertures RAPID Sequence SPARS Sequences STEP Sequences 7.7.4 MULTIACCUM Timing Sequences: Subarray Apertures 7.8 IR Sensitivity 7.8.1 Limiting Magnitudes 7.9 Other Considerations for IR Imaging 7.9.1 Gain and Full-Well Saturation 7.9.2 Cosmic Rays and Snowballs 7.9.3 On-Orbit Degradation 7.9.4 Image Persistence 7.9.5 The IR Background 7.9.6 Blobs 7.9.7 Optical Anomalies 7.10 IR Observing Strategies 7.10.1 Dithering Strategies 7.10.2 Parallel Observations 7.10.3 Exposure Strategies 7.10.4 Spatial Scans 7.10.5 PSF Subtraction Chapter 8: Slitless Spectroscopy with WFC3 8.1 Grism Overview 8.2 Slitless Spectroscopy with the UVIS G280 Grism 8.3 Slitless Spectroscopy with the IR G102 and G141 Grisms 8.3.1 IR G102 8.3.2 IR G141 8.4 Sensitivities and Exposure-Time Estimation 8.5 Extraction and Calibration of Spectra 8.6 Slitless Spectroscopy with Spatial Scanning Chapter 9: WFC3 Exposure-Time Calculation 9.1 Overview 9.2 The WFC3 Exposure Time Calculator (ETC) 9.3 Calculating Sensitivities from Tabulated Data 9.4 Count Rates (Imaging) 9.4.1 Point Source 9.4.2 Diffuse Sources 9.4.3 Emission-Line Sources 9.5 Count Rates (Slitless Spectroscopy) 9.6 Estimating Exposure Times 9.6.1 S/N Reached in a Given Exposure Time 9.6.2 Exposure Time to Reach a Given S/N 9.6.3 Exposure Time Estimates for Red Targets in F850LP 9.7 Sky Background 9.7.1 Background Variations and LOW-SKY 9.7.2 Geocoronal Emission and SHADOW 9.8 Interstellar Extinction 9.9 Exposure-Time Calculation Examples 9.9.1 Example 1: UVIS Imaging of a Faint Point Source 9.9.2 Example 2: IR Imaging of a Faint Extended Source 9.9.3 Example 3: Imaging an HII region in M83 in Hα Chapter 10: Overheads and Orbit Time Determinations 10.1 Overview 10.2 Observatory Overheads 10.3 Instrument Overheads 10.3.1 Exposure Overheads Dumping of the WFC3 Buffer UVIS Parallel Buffer Dumps IR Parallel Buffer Dumps Filter and Channel Select Overheads 10.3.2 Reducing Overheads with Subarrays and Binning 10.4 Orbit Use Examples 10.4.1 Example 1: UVIS, 1 Orbit, 1 Filter 10.4.2 Example 2: UVIS, 1 Orbit, Short Exposures 10.4.3 Example 3: IR, 1 Orbit, 2 Filters 10.4.4 Example 4: UVIS, Dithering, 2 Orbits, 1 Filter 10.4.5 Example 5: IR, 1 Orbit, Grism Appendix A: WFC3 Filter Throughputs A.1 Introduction A.2 Throughputs and S/N Ratio Data A.2.1 Sensitivity Units and Conversions A.2.2 Signal-to-Noise Ratio UVIS/F200LP UVIS/F218W UVIS/F225W UVIS/F275W UVIS/F280N UVIS/F300X UVIS/F336W UVIS/F343N UVIS/F350LP UVIS/F373N UVIS/F390M UVIS/F390W UVIS/F395N UVIS/F410M UVIS/F438W UVIS/F467M UVIS/F469N UVIS/F475W UVIS/F475X UVIS/F487N UVIS/F502N UVIS/F547M UVIS/F555W UVIS/F600LP UVIS/F606W UVIS/F621M UVIS/F625W UVIS/F631N UVIS/F645N UVIS/F656N UVIS/F657N UVIS/F658N UVIS/F665N UVIS/F673N UVIS/F680N UVIS/F689M UVIS/F763M UVIS/F775W UVIS/F814W UVIS/F845M UVIS/F850LP UVIS/F953N UVIS/FQ232N UVIS/FQ243N UVIS/FQ378N UVIS/FQ387N UVIS/FQ422M UVIS/FQ436N UVIS/FQ437N UVIS/FQ492N UVIS/FQ508N UVIS/FQ575N UVIS/FQ619N UVIS/FQ634N UVIS/FQ672N UVIS/FQ674N UVIS/FQ727N UVIS/FQ750N UVIS/FQ889N UVIS/FQ906N UVIS/FQ924N UVIS/FQ937N IR/F098M IR/F105W IR/F110W IR/F125W IR/F126N IR/F127M IR/F128N IR/F130N IR/F132N IR/F139M IR/F140W IR/F153M IR/F160W IR/F164N IR /F167N Appendix B: Geometric Distortion B.1 Overview B.2 UVIS Channel B.3 IR Channel B.4 Summary Appendix C: Dithering and Mosaicking C.1 Why Mosaicking and Dithering are Needed C.2 WFC3 Patterns Appendix D: Bright-Object Constraints and Image Persistence D.1 UVIS Channel D.2 IR Channel Appendix E: Reduction and Calibration of WFC3 Data E.1 The STScI Reduction and Calibration Pipeline E.2 The SMOV Calibration Plan E.3 The Cycle 17 Calibration Plan E.4 The Cycle 18 Calibration Plan E.5 The Cycle 19 Calibration Plan E.6 The Cycle 20 Calibration Plan Glossary
