Skip to main content
Public
Scientists
Intranet
Sitemap
Search
Main navigation
Open Menu
About
Leadership
NOIRLab Scientific staff
Scientific Acknowledgments
Acronyms
Contacts & Travel
Careers
Governance
Time Allocation Committee
User Committees
UCN
Charter
Membership
Meetings
Reports
Time-Domain Advisory Sub-committee
Data Science Advisory Sub-committee
UCM
Public Documents & Reports
Programs & Projects
Community Science & Data Center
ANTARES
Astro Data Archive
Astro Data Lab
La Serena School of Data Science
Time Allocation Committee
US National Gemini Office
Gemini Observatory
Gemini North
Gemini South
Instruments
Cerro Tololo Inter-American Observatory (MSO-CTIO)
Telescopes
Víctor M. Blanco 4-meter Telescope
Instruments Available on Blanco
Optical Properties
Basic Optical Parameters
Available Foci & Instruments
Horizon Limits
A note on Blanco pointing
TCS Format
SOAR Telescope
About SOAR
Organization
Staff
Site description
History
Strategic Planning
Board of Directors
Science Advisory Committee
Instruments
Visitor Instruments
Filters
Telescope Technical Specifications
Optical data for SOAR & Instruments
Telescope limits, overheads and efficiency
Acknowledging SOAR
News
2021
NOIRLab Transition and SOAR Interfaces
SOAR participates in study of sextuple eclipsing binary
2020
SOAR Telescope resumes science operations
SOAR Telescope suspends science operations (revised and updated)
Call for Proposals 2020B - SOAR Opportunities
2019
Warning on macOS Upgrade to Catalina
Call for Proposals 2020A - SOAR Opportunities
Automated Observing Network Inaugurated at SOAR Telescope
Start of SOAR-AEON observations for the 2019B semester
SOAR 2019B Observing Opportunities
The VISCACHA survey: deep and spatially resolved photometry of Magellanic Cloud star clusters with SAM
January 19 Earthquake (updated)
2018
SOAR Aluminizing Shutdown - Final Update
TESS Follow-Up at SOAR
Goodman Radial Velocity Measurements - Update
SOAR Projects Status
Solar System Occultations at SOAR
Release of the Goodman Spectrograph Data Reduction Pipeline
SOAR 2018B Proposals
Deep SAM AO Imaging of a distant young cluster
SOAR 2018 Summer Interns
2017
SAM using SOI Filter Wheel
SAM Fabry-Perot Call for Proposals
SOAR tracks spectroscopic evolution of historic LIGO discovery
Desierto Florido on the Road to Pachón
Punching Above Its Weight, a Brown Dwarf Launches a Parsec-Scale Jet
In Memoriam - Daniel Maturana
SIFS SV Call for Proposals; Goodman Updates; SOAR 2020 Workshop
Announcements: SAM F-P & Workshop on SOAR Science 2020
2016
Daniel Maturana retires
Goodman Spectrograph Updates (Oct 21, 2016)
Additional Information for 2017A Proposers
Early-Science call for observing time with SAM-FP
Resolved time-series photometry of Globular Clusters with SAM
Time Change in Chile
Instrumentation Update for Proposers
2015
Variable stars in globular clusters with SAM
New slit-viewing acquisition camera for the Goodman spectrograph
SOAR Hiring Data Assistant
Spring Snow Storm of Oct 14, 2015
Earthquake Impact at SOAR - updated
SOAR Instrumentation News
2015 SOAR Board Meeting
SOAR Winter Storm
First SOAR MOS observations find old Galactic globular cluster with no signatures of multiple stellar populations
SOAR observations key to identifying the densest galaxies known
SOAR held its Review Committee 2015
First Snow of 2015 at Cerro Tololo and Cerro Pachon
The SOAR Adaptive Optics Module (SAM) takes a sharp look at HH-46/47
2014
Cosmic Skidmark
Gravitational Arcs in the Galaxy Cluster Abel 370
2013
2012
2011
SOAR dome struck by laser!
SOAR Adaptive Module (SAM) Closes the Loop
Beginning of Summer Time in Chile
SOAR Adaptive Module (SAM) UV LASER Launch
SAM Commissioning
SIFS First Light
2005
Loop Closed With Real DM, CCD-39 and Software In the Lab!
SMARTS Consortium
SMARTS-GSU 1.5-meter Telescope
SMARTS-GSU 0.9-meter Telescope
SMARTS History
SMARTS Telescopes' Histories
0.9-m History
Tenant Telescopes
Instruments
Dark Energy Camera (Blanco)
Safety Precautions
Acknowledgments in Publications
The DECam User Guide
Getting Help
Exposure Time Calculator (ETC) and Overheads
Preparing Observing Scripts
Photometric Standard Stars
Setup
Taking Exposures
Afternoon Calibrations
At the Start of the Night
During the Night
At the End of the Night
How to Take the Data Home
Troubleshooting
Instrument Characteristics
Status of DECam CCDs
DECam Shutter
Known Problems
Calibration Files
Communicating DECam Exposures to Ignore
FAQ
The DECam eROSITA Survey (DeROSITAS)
NEWFIRM
NEWFIRM Manual
NEWFIRM Instrument
Detectors
Optics
Filters
NEWFIRM Observing
NEWFIRM Startup Guide
NEWFIRM Observing Guide
NEWFIRM Guider Operation
NEWFIRM Data Products and Data Reduction
NEWFIRM Data Handbook
NEWFIRM Quick Reduction Pipeline
NEWFIRM Technical Publications
TBD
NEWFIRM News
NEWFIRM Characteristics
NEWFIRM Publications
COSMOS (Blanco)
User Manual
Startup
Observing
Dispersers
Throughput
Calibration Lamp Exposure Times
Comparison-Lamp-Spectra
Contact
Goodman (SOAR)
Overview
Goodman Cheat Sheet
Instrument Characteristics
Goodman Long slits
Gratings
Blue Camera
Blue Camera Throughput
Red Camera
GACAM
Calibration Information
Arc Lamp Library
Typical Flat & Arc lamp exposure times
Typical Focus Values
Goodman HTS Manual
Introduction
Hardware
Software
Observing with Goodman
Estimating Exposure Times
Multi-Object Spectroscopy
Measuring Radial Velocities
Optimizing CCD read out
Imaging focus
Data Reduction Pipeline
Pages for Support Staff
Startup Guide
Goodman Troubleshooting
Blue Camera Cold Start
Red Camera Cold Start
Cryotiger Help Page
Naming syntax for Gratings, Slits, Filters
SAM (SOAR)
Instrument Characteristics
Performance
Filters for SAMI
Fabry-Perot module
SAM F-P Characteristics
SAM-FP Filters
SAM User Guides
Observing with SAM
Reducing SAM Images
SAM Pages for Support Staff
Uploading PAM files
Technical Manuals
Technical Publications
Instrument Documentation
Laser Safety
History & Milestones
SIFS (SOAR)
SIFS First Light
SIFS Characteristics & Performance
SOI (SOAR)
SOI Overview
SOI Introduction
SOI Hardware
SOI Software
Dome Flats Exposure Times
Fringing in SOI
Reducing SOI Images
SOI Image Reduction Guide
SOI Distances to optical elements
TSpec IR (SOAR)
Commissioning and Science Verification
Differences from Blanco
Instrument Calibration
Observing Guide
Instrument Characteristics
Startup and Shutdown Guide
History
SPARTAN IR (SOAR)
SPARTAN Cookbook
Typical Flat exposure times
Spartan Trouble-Shooting
Spartan's Frequent Asked Questions
Spartan Documentation
Visitor Instruments (SOAR)
HRCam (SOAR)
CHIRON (SMARTS-GSU 1.5-m)
CHIRON Overview
Tek2K (SMARTS 0.9-m)
Retired Instruments
ARCoIRIS (Blanco)
Instrument Characteristics
Instrument Overview
ETC and Sensitivity
On-Sky Rotator Vector
Spectral Format
Slit Assembly
Startup Guide
Calibration
Data Reduction
Contact
Acknowledgments
History
CFCCD
CFCCD Manual index
Telescope and Focus Choice
Instrument & Computer Configuration
Data Taking Procedures
Detector Characteristics
Appendix CFCCD
Hydra (Blanco)
Overview
VNC
Hydra User's Manual
A CTIO Hydra User's Manual
Preparation
Observing Environment
Calibrations
Reductions
Common Problem - Simple Solutions
Documentation
The Hydra Positioner
Hints & Tips
Temperature-Focus relationship for Hydra
Focus & Throughput
How to use the TV camera in the chimney
Knut's Hydra Notes
Software
Hydra Simulator
FOPS Guider
Starting the FOPS Guider
FOPS Alignment
The Hydra Positioner Software
Overview
Embedded Galil Software Coding Standard
Embedded Galil Software Files
Embedded Galil Software Routines
Galil Box Input assignments
Hydraassign
Source Code
Init, Status, Script and Coord Files
User Interface
IRAF Output File
GWC Variables
Trouble-shooting
Measuring Concentricities
Downloading the Galil Software
How to obtain the Hydra CTIO Simulator
Hydra Spectrograph GUI
SMC Commands
Hydra Bench Spectrograph
HBS - 229mm
HBS - 400 mm
Gratings for Hydra MOS
Calibration Lamps
Reference Spectra
Fibers
Efficiency of Aperture Types
Hydra Safety
Procedimientos & Seguridad
Using Oxygen Monitor
Engineering
Hydra Dark Current I: SITe 400mm camera (2001)
Hydra Dark Current II: Keeping the dark current low (2001)
Summary of Hydra-CTIO Maintenance Work (2001)
Hydra Report - August 2002: Eng. Run
Hydra Report - May 2002
Hydra Status Report Updated 2002
Daniel's email
Javier's email
Hydra Report - March 2004
Peter Frinchaboy & Bill Kunkel's mail
Hydra Meeting - August 23, 2004
Maintenance work between observing blocks
Gripper Fixes
ISPI (Blanco)
ISPI Overview
ISPI Mechanical Design
ISPI Optical Design
ISPI GUI
ISPI Performance
ISPI Quick reference guide
ISPI Users Guide
ISPI Start-Up Procedure
ISPI Observing Notes
ISPI Flat Fields
ISPI Linearity Correction
ISPI Data Reduction
Guiding with ISPI
ISPI Troubleshooting & known problems
ISPI Noise & noise patterns
ISPI Problems related to the TCS
Problems related to the ISPI GUI
Re-starting ISPI
ISPI contact information
ISPI Project Team
ISPI Publications
MOSAIC (Blanco)
Documentation
Cookbook
detpars
instrpars
obspars
telpars
wheel1
Historic Information for Mosaic
4-m MOSAIC II First Pictures
Mosaic II CCDs
Previous CCD test data for 16-channel mode
Previous CCD test data for 8-channel mode
MOSAIC Manual
Overview
Introduction
Hardware
Software
Images
Appendix A
Appendix B
Appendix C
Flat-Field Exposures
FEP
MOSOCS
ADC
Calibration Data
CCD test data for 16 channel mode
Photometric Zero Points & Color Terms
CCD test data for 8 channel mode
Crosstalk on the CTIO Blanco 4m
Bad Pixel Mask for 8 channel mode
Sky Rates
Known Problems
Amplifier failure
Arcon crashes
Fix Headers
Limitations in absolute timing
Problems with Absolute timing
Focusing
Temperature control
FAQ
Support Notes
Common Questions and Procedures
Glowing amp pictures
Using VNC with Mosaic
Mosaic Checklist
Standard 'SetFiles' for MosaicII (8 CCD mode)
Single Controller 'SetFile' for MosaicII
How to make OTFs
Changing Mosaic data acquisition machines
Checking and Restarting the Mosaic PVMs
Mosaic Pre-Run Checkout Procedure
Booting up and shutting down ctioa8
Problem Solving and Tricks
OSIRIS (Blanco/1.5-m/SOAR)
4.0-m R-C Spectrograph
4.0-m R-C Spectrograph Quick Reference
Comparison Atlases
R-C Basic Description
Slit/Decker
Filters for the 4m R-C Spectrograph
RC Collimators
4mRC Gratings
4mRC Camera & CCD
Loral 3K with Arcon3.5 on 4M R-C Spectrograph
Recent Developments
Instrument Control Software
4mRC Virtual Smart Motor Controller
4mRC ICS Info
4m RC Basic Optical Characteristics
1.5-m R-C Spectrograph
1.5m R-C System Efficiency plots
1.5m RC Observer Manual
Filters
DECam filters
VR filter
N662 filter
N964 filter
SOAR filters
CTIO 3x3-inch and 4x4-inch Filters
MOSAIC Filters
Hydra Filters
Echelle Mode
Schott Glass Filters
ANDICAM Filters
ISPI Filters
CCD Controllers
MONSOON
What is MONSOON
Licensing
Users
Tech docs
Torrent Tech docs
Torrent ECOs
Torrent Construction
Torrent Mechanical
Torrent Test & Calibration
Torrent Configuration Data
Torrent Hardware
Cables
Transition Module
CCD Analog Front End
CCD Flex Circuits
Local Control Board
Local Control Board Mezzanine
Power Supply Module
Torrent Software
Calibration eeprom format
Setting up a System Configuration Data Set
Standard Definitions for Sequencer Code
Torrent Firmware
Firmware Information Quick Links
Loading Firmware code to the LCB eeprom
Orange Tech docs
Orange Hardware
CCD Acquisition Board
Power Supplies
Chassis Wiring
Clock and Bias Board
Infrared Acquisition Boards
Master Control Board
Power Fan Out Board
Orange Firmware
Orange Mechanical
Orange Software
Orange System Configuration Data
DECam Tech docs
DECAM Firmware
DECAM Software
DECAM Hardware
Cables
12 Channel Acquisition Board
Clock and Bias Board
Crate Controller
Crate Wiring
Master Control Board
Heater Control Crate
Power Supply
Spares Inventory
Vacuum Interface Board
Historical
The Cassegrain Cage of the V. M. Blanco Telescope
Plate logs
The new skin of the 4.0-m dome
IMAN Image Analyzer
Filter Transmission setup
The Arcon-IRAF Interface
The Arcon-IRAF Interface: 4m R-C
Kitt Peak National Observatory (MSO-KPNO)
Telescopes
Nicholas U. Mayall 4-meter Telescope
Basic Parameters
Weights
Widefield
WIYN 3.5-meter Telescope
Overview
Technical Specifications
KPNO 2.1-meter Telescope
Basic Parameters
WIYN 0.9-meter Telescope
Overview
Tenant Telescopes
Instruments
One Degree Imager (WIYN 3.5-m)
WHIRC (WIYN 3.5-m)
News
User Information
Manuals
Checkout
Filter Plots
Report
Data reduction
Retired Instruments
Cryogenic Spectograph
Spectra of HeNeAr Source
Spectral Plots
PHOENIX
Hot News
User Information
Manuals
FLAMINGOS
Hot News
Manuals
Reports
NEWFIRM
TIFKAM/ONIS
IRIM
MOSAIC
Filters
Important Filter Information
Mosaic Filters
KPNO 4-Inch Filters
KPNO 2-Inch Filters
RC Spectrograph Filters
Echelle Spectrograph Filters
Phoenix Filters
NEWFIRM Filters
FLAMINGOS Filters
KOSMOS Filters
GoldCam Spectrograph Filters
WHIRC Filters
WIYN 0.9 Meter Filters
Fast Beam Simulations
Glass Filter Spectral Transmission Curves
Filter Loan Request Form
Vera C. Rubin Observatory
Simonyi Survey Telescope
LSST Camera
LSST survey
Rubin Auxiliary Telescope
Data Preview 0
US ELT Program
Who We Are
NOIRLab US-ELTP Team
Science
Key Science Programs
Community White Papers
Astro2020 Science White Papers
Astro2020 APC White Papers
Planetary Science and Astrobiology Decadal Survey
Snowmass 2021
Research Inclusion Initiative
News
Gallery
Projects
DES
DESI
GEMMA
NEID
Observing at NOIRLab
Telescope Schedules
Available Facilities
Available Instruments
Proposals
Call for Proposals
Time Allocation Committe (TAC)
TAC Archive (2010-2021)
2010A
2010B
2011A
2011B
2012A
2012B
2013A
2013B
2014A
2014B
2015A
2015B
2016A
2016B
2017A
2017B
2018A
2018B
2019A
2019B
2020A
2020B
2021A
2021B
Gemini TAC
Surveys
Observing with Gemini
Observing at MSO-CTIO
Observing at Cerro Tololo
Planning, Executing, Wrapping up your run at CTIO
Director's Discretionary (DD) Time
ToO Policy
ToO Data Files
CTIO Staff Responsibilities
Visitor's Computer Guidelines
Observing at Blanco
Remote Observing at Blanco
Support Staff
CTIO DECam Support Staff for 2021B
DECam Support 2016A Schedule
DECAm Support 2016B
DECam Support 2015A
DECam Support 2015B Schedule
DECam Support 2014A
DECam Support 2014B
Instrumental Setup Forms and Observing Reports
Visiting Astronomers Travel Guide
Bad weather protocol at CTIO
Observing with SOAR
SOAR Internal Resources
Proposing for SOAR
SOAR Issue Status
Targets of Opportunity
Multi-Messenger Astronomy with SOAR
AEON: Time Domain at SOAR
SOAR AEON Features
SOAR AEON Night Calendars
Goodman Live Data Pipeline
AEON pages for SOAR Staff
SOAR FILTERS
SOAR Remote Observer's Guide
SOAR Observing Efficiency
SOAR Overheads - Maximizing Efficiency
Guider & Active Optics Performance
Creating Target Lists
Observing with SMARTS
Ephemeris
CTIO 2020 Ephemeris
CTIO 2021 Ephemeris
CTIO 2022 Ephemeris
CTIO 2023 Ephemeris
CTIO 2024 Ephemeris
CTIO 2025 Ephemeris
CTIO 2026 Ephemeris
CTIO 2027 Ephemeris
CTIO 2028 Ephemeris
CTIO 2029 Ephemeris
Instrument Setup Forms & Observing Reports
README for Instrument Setup
Observing Log Forms
Reducing SOAR data
Reducing Goodman Data
Reducing SAM images
Reducing TSpec Data
SOI Image Reduction
Standard Stars
Hamuy Spectrophotometric Standards
Massey Spectrophotometric Standards
Radial Velocity Standards
Observing Statistics
Telescope schedules
Observing Calendar
Observing at MSO-KPNO
User Handbook
Important Reminders
Purpose
Telescope Schedule
Items to check in advance
Getting to and from KPNO
Shuttle Transportation Information
Motor Vehicle Operator's Identification Card Application
Accommodation at KPNO
Operating the Telescopes
Mountain environment
Data Backup
Remote Observing Information
Telescope and Instrument Documentation
Available Telescopes and Instruments
The Indo-U.S. Library of Coudé Feed Stellar Spectra
KPNO Staff contacts
Observing Run Checklist
KPNO ORP Form
KPNO ORE Form
Ephemeris for Kitt Peak (Observer's Calendar)
2035
2034
2033
2032
2031
2030
2029
2028
2027
2026
2025
2024
2023
2022
2021
2020
2019
2018
2017
AEON
Filter Database
Approved Survey Programs
Weather & Webcams
Cerro Pachón
Environmental Conditions
Cerro Tololo
Environmental Conditions
Tololo Webcams
Kitt Peak
KPNO Weather
Current KPNO Weather Data
KPNO Live Cameras
LPL Spacewatch All Sky Camera
Mayall Weather Display
WIYN-KPNO Precipitable Water Vapor
Favorite Weather Links
Historic Weather Information
Past Weather & Environment Plots
All Sky Archives
All Sky Movies on Youtube (needs updating)
NASA AllSky Fireball Network Camera
Site Data
WIYN Night Logs
Maunakea
Time-lapse Videos
Acknowledgments in Publications
Data Services
ANTARES
Astro Data Archive
Astro Data Lab
Gemini Observatory Archive
Data reduction / Software
CSDC/MSO Pipelines
The DECam Community Pipeline Instrumental Signature Removal
Major Surveys
Other NOIRLab data
News
Announcements
Newsletters
NOIRLab Mirror
NOAO Newsletter (–2019)
Gemini Focus (1992–2019)
KPNO Tenant Newsletter (2003–2012)
E-mail newsletters
e-News for the NOIRLab Community
e-News for the Gemini/NOIRLab Community
Currents (2009 - 2021)
Gemini eNewscast (2008 - 2021)
Subscribe
Meetings & Events
Conference Websites
IAU GA Session WG6: Exec WG on Dark & Quiet Sky Protection
SHPE 2024 National Convention
The First Gigayear(s)
Home
Important dates
Schedule
Participants
Accommodation Information
Registration
FAQ
EREBUS/JWST workshop
Home
Important Dates
Participants
Schedule
Rare Gems in Big Data
Home
SOC/LOC
Invited speakers
Important dates
Schedule
Registration
Abstract submission
Accommodation Information
FAQ
Participants
Recordings
Charting Quantum Horizons 2024
Home
SOC/LOC
Invited speakers
Registration and Abstract Submission
Venue & Accommodation
Agenda
Code of Conduct
Participants
ELT Science in Light of JWST
Home
SOC/LOC
Invited speakers
Venue & Accommodation
Schedule
Participants
Abstracts
Important dates
Registration
Coordinating the Next Generation of Spectroscopic Processing and Analysis Tools
Home
Lodging
Windows on the Universe
Home
White Paper Endorsements
Registration
Venue & Accommodation
SOC/LOC
Invited Speakers/Panelists
Agenda
Code of Conduct
Participants
IAU Symposium 385
NOIRLab at Conferences
AAS 245
AAS 243
CASCA 2023
AAS 242
AAS 241
List of upcoming internship opportunities at NOIRLab
NSBP 2022
AAS 240
AAS 237
Exhibitions
Conferences
Talks
Friday Scientific Lunch Talks
Gemini North Talks
NOIRLab South Colloquia
NOIRLab/Steward Colloquium
Meetings
Calendar
Library
Chile
Tucson
Services
FAQ
Collections
Publications
Astro Data Lab
CSDC
Dark Energy Camera
Acknowledgments in papers
DECam Science papers
Gemini Publications Database
Metrics
MSO
NOAO, 1987-2019
ORCID
Scientific Acknowledgments
SMARTS Consortium
Refereed
Telegrams & Conference Abstracts
US NGO
Electronic Resources
Informative External Links
Resources
Decadal Survey
Astro2010 White Papers
Astro2020 NOAO-related APC White Papers
Astro2020 Science White Paper Coordination Hub
Browse
NOAO Decadal Planning website
Topic
White papers
Documents
Images
Legacy
KAOS
SWIFT
Cost Estimates
NGOS Draft Concepts
Science Sampler
Software Tasks
Presentations
REU & PIA Programs
REU Chile Program
Program Elements
Example Research Projects
Program Information and Application Process
REU Chile Poster
Previous REU/PIA Programs
REU/PIA Projects
2005 REU/PIA Projects
2004 REU/PIA Projects
2003 REU/PIA Projects
2002 REU/PIA Projects
2001 REU/PIA Projects
2000 REU/PIA Projects
1999 REU/PIA Projects
1998 REU/PIA Projects
Former Participants
CTIO REU/PIA Alumni
2014 KPNO REU Students
2014 REU Summer Lecture Series
Final Student Reports
2013 KPNO REU Students
2013 REU Summer Lecture Series
Final Student Reports
2012 KPNO REU Students
AAS Posters
Lectures
2011 KPNO REU Students
AAS Posters
Lectures
2010 KPNO REU Students
AAS Posters
Lectures
2009 KPNO REU Students
AAS Posters
2008 KPNO REU Students
KPNO REU Students at the 213th AAS Meeting (January 2009)
2007 KPNO REU Students
AAS Posters
2006 KPNO REU Students
AAS Posters
2005 KPNO REU Students
2004 KPNO REU Students
2002 KPNO REU Students
2001 KPNO REU Students
1999 Participants
2000 KPNO Summer REU Students and RETs
PIA Program
REU/PIA FAQ
2016 CTIO Summer Student Interns
2015 CTIO Summer Student Interns
2014 CTIO Summer Student Interns
2013 CTIO REU+PIA Student Program
2012 Annual Report
CTIO REU/PIA 2012
CTIO REU/PIA 2011
CTIO REU/PIA 2010
CTIO REU/PIA 2009
CTIO REU/PIA 1998
CTIO REU/PIA 1996
CTIO REU/PIA 1995
Videos
Conduct
Safety
Arizona Safety
Lightning Safety Tips
Privacy Policy
Commitment to Diversity, Equity, and Inclusion
Where to get help?
Images
sci18068a
sci18068a
sci18068a
About the Image
Id:
sci18068a
Type:
Photographic
Release date:
May 10, 2018, 8:00 am
Size:
500 x 333 px
Image Formats
Fullsize PNG
314.3 KB
Screen PHP/SITES/DEFAULT/FILES/STYLES/SCREEN/PUBLIC/SCI18068A
