Table of Contents Cosmic Origins SpectrographInstrument Handbookfor Cycle 21 Acknowledgments References and Additional Information Chapter 1: An Introduction to COS 1.1 Overview 1.2 Observing with COS 1.2.1 Target Acquisitions 1.2.2 Observing Modes: Spectroscopic and Imaging 1.2.3 Observing Modes: TIME-TAG and ACCUM 1.2.4 Typical Observing Sequences 1.3 COS Quick Reference Guide 1.4 COS FAQ 1.5 Purpose of this Handbook 1.5.1 Document Conventions Chapter 2: Special Considerations for Cycle 21 2.1 New FUV Detector Lifetime Position 2.2 Resolution of COS Observations below 1150 Å 2.3 Time-Dependent Sensitivity Changes 2.4 Non-Optimal Observing Scenarios 2.5 SNAP and TOO Programs with COS 2.6 Should I Use COS or STIS? Chapter 3: Description and Performance of the COS Optics 3.1 The Optical Design of COS 3.1.1 External Shutter 3.1.2 The Apertures and Aperture Mechanism Primary Science Aperture Wavelength Calibration Aperture Bright Object Aperture Flat-Field Calibration Aperture 3.1.3 Gratings and Mirrors: The Optics Select Mechanisms FUV Channel Optical Design OSM2 and the NUV Channel Imaging with the NUV Mirror 3.2 Size of a Resolution Element 3.3 The COS Line-Spread Function 3.3.1 Non-Gaussianity of the COS LSF 3.3.2 Quantifying the Resolution 3.3.3 Impact on Equivalent Width Measurements 3.3.4 Extended Wings of the COS LSF 3.3.5 Enclosed Energy of COS LSF Chapter 4: Description and Performance of the COS Detectors 4.1 The FUV XDL Detector 4.1.1 XDL Properties 4.1.2 XDL Spectrum Response 4.1.3 XDL Dark Rate 4.1.4 XDL Read-out Format 4.1.5 Stim Pulses 4.1.6 Pulse-height Distributions Gain Sag Detector Walk Mitigation Strategies Calcos Changes Onboard Changes 4.1.7 Non-linear Photon Counting Effects (Dead Time) 4.1.8 Spatial Variation of the Dark Rate 4.2 The NUV MAMA Detector 4.2.1 MAMA Properties 4.2.2 MAMA Spectrum Response 4.2.3 MAMA Dark Rate 4.2.4 MAMA Read-Out Format 4.2.5 MAMA Dead Time 4.2.6 Non-Gaussian Wings in the MAMA PSF Chapter 5: Spectroscopy with COS 5.1 The Capabilities of COS 5.1.1 First-Order Sensitivity 5.1.2 Sensitivity below 1150 Å 5.1.3 Second-Order Sensitivity 5.1.4 Spectroscopic Resolving Power 5.1.5 Time-Dependent Sensitivity Changes 5.1.6 Dip in Sensitivity around 1180 Å 5.1.7 Zero-Order Image 5.1.8 Internal Scattered Light 5.1.9 Spatial Resolution and Field of View 5.1.10 Photometric (Flux) Precision 5.1.11 Wavelength Accuracy 5.1.12 Vignetting of the NUV Channel 5.2 TIME-TAG vs. ACCUM Mode 5.2.1 TIME-TAG Mode Doppler Correction for TIME-TAG Mode Pulse-Height Data for TIME-TAG 5.2.2 ACCUM Mode Observing Efficiencies with ACCUM Doppler Correction for ACCUM Mode Pulse-Height Distribution Data for ACCUM Mode Observations 5.3 Valid Exposure Times 5.4 Estimating the BUFFER-TIME in TIME-TAG Mode 5.4.1 BUFFER-TIME > 110 s and BUFFER-TIME > Exposure Time 5.4.2 BUFFER-TIME > 110 s and BUFFER-TIME ≤ Exposure Time 5.4.3 80 s < BUFFER-TIME ≤ 110 s) 5.4.4 BUFFER-TIME ≤ 80 s 5.4.5 BUFFER-TIME and AUTO-ADJUST 5.5 Spanning the Gap with Multiple CENWAVE Settings 5.6 FUV Single-Segment Observations 5.7 Internal Wavelength Calibration Exposures 5.7.1 Concurrent Wavelength Calibration with TAGFLASH 5.7.2 AUTO Wavecals (when TAGFLASH is not used) 5.7.3 GO Wavecals (User-Specified) 5.7.4 No-Cal Wavecals 5.8 Fixed-Pattern Noise 5.8.1 COS Flat Fielding 5.8.2 Use of Multiple FP-POS Settings Requirements for Use of Multiple FP-POS Settings 5.9 COS Spectroscopy of Extended Sources 5.10 Wavelength Settings and Ranges Chapter 6: Imaging with COS 6.1 Introduction to COS Imaging 6.2 Sensitivity 6.3 Image Characteristics Chapter 7: Exposure-Time Calculator (ETC) 7.1 The COS Exposure Time Calculators 7.2 Imaging Observations of Red Objects 7.3 Sensitivity, Count Rate, and S/N 7.4 Detector and Sky Backgrounds 7.4.1 Detector Dark Count 7.4.2 Earthshine 7.4.3 Zodiacal Light 7.4.4 Airglow Emission 7.4.5 Tabular Sky Backgrounds 7.5 Extinction Correction 7.6 Examples 7.6.1 A Flat-Spectrum Source 7.6.2 An Early-Type Star 7.6.3 A Solar-Type Star with an Emission Line 7.6.4 A Faint QSO Chapter 8: Target Acquisitions 8.1 Introduction Bright-Object Protection 8.2 Target Acquisition Overview Please Note... 8.3 ACQ/SEARCH Acquisition Mode 8.4 ACQ/IMAGE Acquisition Mode 8.5 ACQ/PEAKXD Acquisition Mode 8.5.1 Description 8.5.2 Effects of FUV Detector Y Walk 8.6 ACQ/PEAKD Acquisition Mode 8.7 Exposure Times 8.7.1 Imaging Acquisitions 8.7.2 Dispersed-Light Acquisitions 8.8 Centering Accuracy and Data Quality 8.8.1 Centering Accuracy and Wavelength Accuracy 8.8.2 Centering Accuracy and Photometric Precision 8.8.3 Centering Accuracy and Spectroscopic Resolution 8.9 Recommended Parameters for all COS TA Modes 8.10 Special Cases 8.10.1 Early Acquisitions and Preliminary Images 8.10.2 Extended or Multiple Targets 8.10.3 Offset Target Acquisitions 8.10.4 Acquisition Failure Actions and Diagnostics Chapter 9: Scheduling Observations 9.1 Introduction 9.1.1 Phase I Proposal 9.1.2 Phase II Proposal 9.2 Generic Observatory Overheads 9.3 Spectral Element Movement Overheads 9.4 Acquisition Overheads 9.5 Science Exposure Overheads 9.6 First Exposure Overhead Adjustment 9.7 Examples of Orbit Estimates 9.7.1 Target Acquisition Using ACQ/IMAGE 9.7.2 ACQ/SEARCH plus ACQ/IMAGE Acquisition 9.7.3 FUV Acquisition plus TIME-TAG 9.7.4 FUV TIME-TAG with BOA and Multiple FP-POS 9.7.5 FUV TIME-TAG with Modified BUFFER-TIME Chapter 10: Bright-Object Protection 10.1 Introduction 10.2 Screening Limits 10.3 Screening versus Data-Rate Limits 10.4 Source V Magnitude Limits 10.5 Tools for Bright-Object Screening 10.5.1 The Bright Object Tool (BOT) 10.5.2 The Exposure Time Calculator (ETC) 10.6 Policies and Procedures 10.7 On-Orbit Protection Procedures FUV Bright Object Protection NUV Bright Object Protection Chapter 11: Data Products and Data Reduction 11.1 Overview 11.2 COS Data Files 11.3 Additional COS Files Chapter 12: The COS Calibration Program 12.1 Introduction 12.2 Ground Testing and Calibration 12.3 SMOV4 Testing and Calibration 12.4 Cycle 17 Calibration Program 12.5 Cycle 18 Calibration Program 12.6 FUV Lifetime Position Calibration Program 12.7 Cycle 19 Calibration Program 12.8 Cycle 20 Calibration Program 12.9 Cycle 21 Calibration Plans Chapter 13: Spectroscopic Reference Material 13.1 Introduction 13.2 Using the Information in this Chapter 13.2.1 Grating Parameters 13.2.2 Wavelength Ranges 13.2.3 Grating Sensitivities and Effective Areas 13.2.4 Signal-to-Noise Plots 13.3 Gratings FUV Grating G130M FUV Grating G130M with CENWAVE=1222 FUV Grating G130M with CENWAVE=1055 or 1096 FUV Grating G160M FUV Grating G140L NUV Grating G185M NUV Grating G225M NUV Grating G285M NUV Grating G230L 13.4 Spectrograph Design Parameters 13.4.1 FUV Channel 13.4.2 NUV Gratings 13.5 The Location of COS in the HST Focal Plane 13.6 The COS User Coordinate System Glossary A Glossary of Terms and Abbreviations
