Table of Contents Advanced Camera for Surveys Instrument Handbook for Cycle 21 Acknowledgments Chapter 1: Introduction Chapter 2: Changes After SM4 and Considerations for Cy21 2.1 SM4 Repair of ACS 2.2 Comparison of ACS/WFC and WFC3/UVIS 2.3 Comparison of ACS/HRC and WFC3/UVIS 2.4 Dithering Considerations 2.5 CTE Considerations Chapter 3: Introduction to ACS 3.1 ACS Location in the HST Focal Plane 3.2 Instrument Capabilities 3.3 Instrument Design 3.3.1 Detectors The WFC & HRC CCDs The SBC MAMA 3.3.2 ACS Optical Design Filter Wheels Calibration-Lamp Systems 3.4 Basic Instrument Operations 3.4.1 Target Acquisitions 3.4.2 Typical ACS Observing Sequence 3.4.3 Data Storage and Transfer 3.5 ACS Quick Reference Guide Chapter 4: Detector Performance 4.1 Overview 4.2 The CCDs 4.2.1 Detector Properties WFC Properties HRC 4.2.2 CCD Spectral Response 4.2.3 Quantum Efficiency Hysteresis 4.2.4 CCD Long-Wavelength Fringing 4.2.5 Readout Format WFC HRC 4.2.6 Analog-To-Digital Conversion 4.2.7 Flat Fields WFC HRC 4.3 CCD Operations and Limitations 4.3.1 CCD Saturation: The CCD Full Well 4.3.2 CCD Shutter Effects on Exposure Times 4.3.3 Read Noise WFC HRC 4.3.4 Dark Current 4.3.5 Warm and hot pixels 4.3.6 Cosmic Rays 4.3.7 Charge Transfer Efficiency 4.3.8 UV Light and the HRC CCD 4.4 The SBC MAMA 4.4.1 MAMA Properties 4.4.2 SBC Spectral Response 4.4.3 Optical Performance 4.5 SBC Operations and Limitations 4.5.1 SBC Scheduling Policies 4.5.2 MAMA Overflow of the 16 Bit Buffer 4.5.3 MAMA Darks 4.5.4 SBC Signal-To-Noise Ratio Limitations 4.5.5 SBC Flatfield 4.5.6 SBC Nonlinearity Global Local 4.6 SBC Bright-Object Limits 4.6.1 Overview 4.6.2 Observational Limits Chapter 5: Imaging 5.1 Imaging Overview 5.2 Important Considerations for ACS Imaging 5.2.1 Optical Performance 5.2.2 CCD Throughput Comparison 5.2.3 Limiting Magnitudes 5.2.4 Signal-To-Noise Ratios 5.2.5 Saturation 5.2.6 Faint Horizontal Striping in WFC CCDs 5.3 Wide Field Optical CCD Imaging 5.3.1 Filter Set WFPC2 and Johnson-Cousins filters Sloan Digital Sky Survey filters Narrow Band filters Ramp filters Polarizer filters Grism and Prism 5.4 High-Resolution Optical and UV Imaging 5.4.1 Filter Set 5.4.2 Multiple Electron Events 5.4.3 Red Leaks 5.5 Ultraviolet Imaging with the SBC 5.5.1 Filter Set 5.5.2 Red Leaks 5.5.3 SBC Imaging Filter Shifts 5.6 ACS Point Spread Functions 5.6.1 CCD Pixel Response Function 5.6.2 Model PSFs 5.6.3 Encircled Energy 5.6.4 Geometric Distortions 5.6.5 PSFs at Red Wavelengths and the UV 5.6.6 Residual Aberrations Chapter 6: Polarimetry, Coronagraphy and Prism/Grism Spectroscopy 6.1 Polarimetry 6.1.1 Introduction 6.1.2 Performance of ACS Polarizers 6.1.3 Implementation of ACS Polarizers 6.1.4 Challenges and Limitations of ACS Polarimetry 6.2 Coronagraphy 6.2.1 Coronagraph Design 6.2.2 Acquisition Procedure and Pointing Accuracy 6.2.3 Vignetting and Flat Fields 6.2.4 Coronagraphic Performance 6.2.5 Subtraction of the coronagraphic PSF 6.2.6 The Off-Spot PSF 6.2.7 Occulting Spot Motions 6.3 Grism/Prism Spectroscopy 6.3.1 WFC G800L 6.3.2 HRC G800L 6.3.3 HRC PR200L 6.3.4 SBC PR110L 6.3.5 SBC PR130L 6.3.6 Observation Strategy 6.3.7 Extraction and Calibration of Spectra Chapter 7: Observing Techniques 7.1 Designing an ACS Observing Proposal 7.1.1 Identify Science Requirements and Define ACS Configuration Imaging Special Uses 7.1.2 Available but Unsupported Modes 7.1.3 Determine Exposure Time and Check Feasibility 7.1.4 Identify Need for Additional Exposures 7.1.5 Data Volume Constraints 7.1.6 Determine Total Orbit Request 7.1.7 Charge Transfer Efficiency 7.1.8 Image Anomalies 7.2 SBC Bright Object Protection 7.2.1 How Do You Determine if You Violate a Bright Object Limit for SBC Exposures? 7.2.2 Policy and Observers’ Responsibility in Phase I and Phase II Policy on Observations Which Fail Because they Exceed Bright-Object Limits 7.2.3 Bright-Object Protection for Solar System Observations 7.2.4 Prime and Parallel Observing with the SBC 7.3 Operating Modes 7.3.1 WFC ACCUM Mode WFC CCD Subarrays Ramp Filters 7.3.2 SBC ACCUM Mode 7.4 Patterns and Dithering 7.5 A Road Map for Optimizing Observations 7.6 CCD Gain Selection 7.7 ACS Apertures 7.7.1 WFC Apertures 7.7.2 Ramp Filter Apertures WFC Ramp Filter Apertures HRC Ramp Filter Apertures 7.7.3 The Small Filter Apertures 7.7.4 Polarizer Apertures 7.7.5 HRC Apertures 7.7.6 SBC Apertures 7.8 Specifying Orientation on the Sky 7.8.1 Determining Orientation for Phase II 7.9 Parallel Observations 7.9.1 Parallel Observing ACS Coordinated Parallels ACS Pure Parallels 7.10 Pointing Stability for Moving Targets Chapter 8: Overheads and Orbit-Time Determination 8.1 Overview 8.2 ACS Exposure Overheads 8.2.1 Subarrays 8.3 Orbit Use Determination Examples 8.3.1 Sample Orbit Calculation 1 8.3.2 Sample Orbit Calculation 2 8.3.3 Sample Orbit Calculation 3 8.3.4 Sample Orbit Calculation 4 8.3.5 Sample Orbit Calculation 5 Chapter 9: Exposure-Time Calculations 9.1 Overview 9.1.1 The ACS Exposure Time Calculator 9.2 Determining Count Rates from Sensitivities 9.2.1 Imaging Point Source Diffuse Source Emission Line Source 9.2.2 Spectroscopy Point Source 9.3 Computing Exposure Times 9.3.1 Calculating Exposure Times for a Given signal-to-noise 9.3.2 Exposure Time Estimates for Red Targets in F850LP 9.4 Detector and Sky Backgrounds 9.4.1 Detector Backgrounds 9.4.2 Sky Background Background Variations and LOW-SKY Geocoronal Emission and Shadow 9.5 Extinction Correction 9.6 Exposure-Time Examples 9.6.1 Example 1: WFC Imaging a Faint Point Source 9.6.2 Example 2: SBC Objective Prism Spectrum of a UV Spectrophotometric Standard Star 9.6.3 Example 3: WFC VIS Polarimetry of the Jet of M87 9.6.4 Example 4: SBC imaging of Jupiter’s Aurora at Lyman-alpha 9.6.5 Example 5: Coronagraphic imaging of the Beta-Pictoris Disk (The HRC is no longer available) 9.7 Tabular Sky Backgrounds Chapter 10: Imaging Reference Material 10.1 Introduction 10.2 Using the Information in this Chapter 10.2.1 Sensitivity Units and Conversions 10.2.2 Signal-to-Noise 10.2.3 Point Spread Functions WFC/F435W WFC/F475W WFC/F502N WFC/F550M WFC/F555W WFC/F606W WFC/F625W WFC/F658N WFC/F660N WFC/F775W WFC/F814W WFC/F850LP WFC/G800L WFC/CLEAR HRC/F220W HRC/F250W HRC/F330W HRC/F344N HRC/F435W HRC/F475W HRC/F502N HRC/F550M HRC/F555W HRC/F606W HRC/F625W HRC/F658N HRC/F660N HRC/F775W HRC/F814W HRC/F850LP HRC/F892N HRC/G800L HRC/PR200L HRC/CLEAR SBC/F115LP SBC/F122M SBC/F125LP SBC/F140LP SBC/F150LP SBC/F165LP SBC/PR110L SBC/PR130L 10.3 Geometrical Distortion in the ACS 10.3.1 WFC 10.3.2 HRC 10.3.3 SBC Glossary
