Athena acronym list, actively maintained by Jos de Bruijne.
Last updated 20 June 2017.
Some additions by Matthias Ehle (21 May 2018).
A : Abell
A : Acceptance (testing)
A64 : Ariane-6.4 (launcher)
AC : Alternating Current
AC : Anti-Coincidence
ACE : Advanced Composition Explorer (spacecraft)
ACO : Athena Community Office
ACSS : Athena Common Software System
AD : Analogue to Digital
ADA : Athena Data Analysis
ADC : Analogue-to-Digital Converter
ADR : Adiabatic Demagnetisation Refrigerator
ADS : Airbus Defence and Space
AFE : Analogue Front End
AFM : Atomic-Force Microscope
AFT : Abbreviated Functional Test
AGH : Akademia G\'{o}rniczo-Hutnicza
AHEAD : (Integrated) Activities in the High Energy Astrophysics Domain
AIB : Analogue Interface Board
AIT : Assembly, Integration, and Test
AIV : Assembly, Integration, and Verification
AKE : Absolute Knowledge Error
ALAT : Air Liquide Advanced Technologies
AMXP : Accretion-powered Millisecond X-ray Pulsar
AO : Announcement of Opportunity
AOB : All Other Business
APE : Absolute Pointing Error
APEC : Astrophysical Plasma Emission Code
APS : Active Phase Shift
APS : Active-Pixel Sensor
AREMBES : Athena Radiation Environment Modelling Background EStimator
ARF : Ancillary Response File
ARSE : Angular Resolution Sensitivity Exercise
ASA : Athena Science Archive
ASDC : Athena Science Data Centre
ASGS : Athena Science Ground Segment
ASI : Agenzia Spaziale Italiana
ASIC : Application-Specific Integrated Circuit
ASIE : Athena Science Impact Exercise
ASST : Athena Science Study Team
ASST : Athena Software and System Team
ATAC : Athena Time Allocation Committee
ATHENA : Advanced Telescope for High-ENergy Astrophysics
AVM : AVionics Model
AWG : Astronomy Working Group
Al : Aluminium
BB : Bread Board
BCB : BenzoCycloButene (coating)
BCG : Brightest Cluster Galaxy
BE : Background Estimate
BEE : Back-End Electronics
BESSY : Berliner ElektronenSpeicherring-gesellschaft f\"{u}r SYnchrotronstrahlung
BEUR : Billion EURo
BEaTriX : Beam Expander Testing X-ray facility
BGD : BackGrounD
BH* : Stellar-mass Black Hole
BHB : Black-Hole Binary 
BHC : Black-Hole Candidate
BKG : BacKGround
BSC : Back-SCattering
C/B : Clamp Band
CA : Conical(-approximation) Athena
CAD : Computer-Aided Design
CBK : Centrum Bada\'{n} Kosmicznych
CC : Cold Core (galaxy cluster)
CC : Cooling Chain
CC : Core Collapse (supernova)
CCCM : Channel-Cut Crystal Monochromator
CCDR : Closed-Cycle Dilution Refrigerator
CCM : Centre for Concepts in Mechatronics
CCN : Change-of-Contract Notice
CCSDS : Consultative Committee for Space Data Systems
CCU : Cryo-chain Control Unit
CDE : Cooler Drive Electronics
CDF : Concurrent Design Facility
CDFS : Chandra Deep Field South
CDM : Code-Domain Multiplexing
CDMU : Central Data Management Unit
CDR: Critical Design Review
CE : Conductive Emissivity
CEA : Commissariat à l'\'{E}nergie Atomique
CFE : Customer-Furnished Equipment
CFEE : Cold Front-End Electronics
CFI : Customer-Furnished Item
CFRP : Carbon-Fibre-Reinforced Plastic
CGH : Computer-Generated Hologramme
CLS : Canadian Light Source
CMZ : Central Molecular Zone
CN : Classical Nova
CND : CircumNuclear Disk
CNES : Centre National d'\'{E}tudes Spatiales
CORE : Cost-driven Observation Reprogramming Exercise
COSPAR : Committee On SPAce Research
CP : Calibration Plan
CPS : Counts Per Second
CR : Cosmic Ray
CR : Count Rate
CRD : Calibration Requirements Document
CS : Conductive Susceptibility
CS: Cooling System
CSL : Centre Spatial de Li\`ege
CSS : Core Science Survey
CT : Compton Thick
CTA : Cherenkov Telescope Array
CTE : Coefficient of Thermal Expansion
CTP : Core Technology Programme
CV : Cosmic Vision (programme of ESA's science directorate)
CWB : Colliding-Wind Binary
CXB : Cosmic X-ray Background
CXC : Chandra X-ray observatory Center
CXO : Chandra X-ray Observatory
CaC : Cost at Completion
CeSiC : Carbon-fiber-reinforced Silicon-Carbide
Cfg : Configuration
DAQ : Data AQuisition
DBRR : DCS Breadboarding for Risk Reduction
DCCM : Document Control and Change Manager
DCM : Double-Crystal Monochromator
DCS : Detector Cooling System
DCS : Demonstrator of the (X-IFU) Cooling System
DD : Double Degenerate
DDF : Design Definition File
DDT : Director’s Discretionary Time
DE : Detector Electronics
DEPFET : DEpleted P-channel Field-Effect Transistor
DF : De-Focusing
DJF : Design Justification File
DLL : Design Launch Load
DLR : Deutsches Zentrum für Luft- und Raumfahrt
DM : Demonstration Model
DMM : Design Maturity Margin
DN : Dwarf Nova
DR : DRain current (readout mode)
DRE : Digital Read-out Electronics
DRL : Deliverables Requirement List
DRL : Document Requirements List
DT : Discretionary Time
DTU : DTU Space (formally: National Space Institute, Danish: Institut for Rumforskning og Rumteknologi), part of the Technical University of Denmark
DoF : Degree of Freedom
E2E : End-to-End
EA : Effective Area
EAST : ESA Athena Science Team
EAST : ESO-Athena Synergy Team
ECAP : Erlangen Centre for Astro-particle Physics
ECAP : Erlangen Centre for Astroparticle Physics
EGSE : Electrical Ground-Support Equipment
EID : Experiment Interface Document
ELP : Low-Energy Proton
EM : Emission Measure
EM : Engineering Model
EM : Electrical Model
EMC : Electro-Magnetic Compatibility
EMI : Electro-Magnetic Interference
ENC : Equivalent Noise Charge
EPIC : Energetic Particles and Ion Composition
EPIC : European Photon Imaging Camera
EPS : Electrical Power System
EQM : Electrical Qualification Model
ERT : Earth Reception Time
ESA : European Space Agency
ESAC : European Space Astronomy Centre (Villafranca, Spain)
ESD : Electro-Static Discharge
ESOC : European Spacecraft Operations Centre
ESTEC : European Space research and TEchnology Centre
ESU : Energy Storage Unit
EUV : Extreme UltraViolet
EXACRAD : Experimental Evaluation of Athena Charged Particle Background from Secondary Radiation and Scattering in Optics
EoR : Epoch of Reionisation 
F2F : Face-to-Face
FAR : Flight Acceptance Review
FC : (WFI) Fast Chip (obsolete, now called FD)
FCM : Four Crystal Monochromator
FD : (WFI) Fast Detector
FDM : Frequency-Domain Multiplexing
FE : Finite Element
FEE : Front-End Electronics
FEM : Finite-Element Model
FF : Full Frame
FFT : Fast Fourier Transform
FINREF : FINancial REForm (framework for costing of ESA activities)
FL : Focal Length
FM : Flight Model
FMS : Fixed Metering Structure
FPA : Focal-Plane Assembly
FPGA : Field-Programmable Gate Array
FPM : Focal-Plane Module (obsolete, now called SIM)
FPP : Focal-Plane Platform (obsolete, now called SIP)
FR-II : Faranoff-Riley (type-2) radio galaxy
FRM : Fringe Reflection Metrology
FRT : Fringe-Reflection Technique
FS : Flight Spare Model
FW : Filter Wheel
FWA : Filter-Wheel Assembly
FY : Fiscal Year
FeKa : Iron K_\alpha (line)
FoR : Field of Regard
GBH : Galactic Black Hole
GCR : Galactic Cosmic Ray
GEANT : GEometry ANd Tracking
GEANT4 : GEometry ANd Tracking version 4
GM : Gifford-McMahon (cooler)
GO : Guest Observer
GPS : Global Positioning System
GRAS : GEANT4 Radiation Analysis for Space
GRB : Gamma-Ray Burst
GRP : Giant Radio Pulse
GS : Ground Segment
GS : Ground Station
GSE : Ground-Support Equipment
GSFC : Goddard Space Flight Center
GSTP : General Support Technology Programme
GT : Guaranteed Time
GUI : Graphical User Interface
GW : Gravitational Wave
H/R : Height over Radius (of a disk)
HDRM : Hold Down and Release Mechanism
HEAPA : High-Energy AstroPhysics Association (Japan)
HEO : High-Earth Orbit
HEW : Half-Energy Width (refers to the Point Spread Function)
HGA : High-Gain Antenna
HICP : Harmonised Index of Consumer Prices
HRDM : Misspelling of HDRM
HS : Heat Switch
HXI : Hard X-ray Imager (Hitomi)
HXT : Hard X-ray Telescope (Hitomi)
I/F : InterFace
IAAT : Institut f\"{u}r Astronomie und Astrophysik - Universit\"{a}t T\"{u}bingen
IACHEC : International Astronomical Consortium for High-Energy Calibration
IAPS : Istituto di Astrofisica e Planetologia Spaziali
IBF : Ion-Beam Figuring
IC : Instrument Chamber
ICC : Instrument Control Centre
ICM : Intra-Cluster Medium
ICPU : Instrument Control and Power-distribution Unit
ICS : Inner Cold Shield (WFI)
ICS : Ion Composition Sub-system
ICU : Instrument Control Unit
IEM : Interplanetary Electron Model
IFCA : Instituto de F\{\i}sica de CAntabria (CSIC-UC)
IGM : Inter-Galactic Medium
IMF : Initial-Mass Function
IMP : International Monitoring Platform
INAF : Istituto Nazionale di Astrofisica
INS : Isolated Neutron Star
INVAR : INVARiable, a particular Nickel–Iron alloy with 36% Nickel and 64% Iron (FeNi36 or 64FeNi)
IP : Intermediate Polar
IPC : Industrial Policy Committee
IR : InfraRed
IRAP : Institut de Recherche en Astrophysique et Plan\'{e}tologie
ISC : Instrument Science (and data) Centre
ISCO : Innermost Stable Circular Orbit
ISM : Instrument Switching (Selection) Mechanism
ISM : Iso-Static Mount
IT : Instrument Team
ITC : Instrument Team Centre
ITT : Invitation To Tender
IXO : International X-ray Observatory (obsolete)
IXPE : Imaging X-ray Polarimetry Explorer (NASA)
JASRI : Japan Synchrotron Radiation Research Institute
JAXA : Japan Aerospace Exploration Agency
JFY : Japanese Fiscal Year
JT : Joule-Thomson
JT2K : Joule-Thomson Two Kelvin (cooler)
KEK : High-Energy Accelerator Research Organisation (Japan)
KH : Kelvin-Helmholtz
KP : Key Programme (Project)
L1 : First Lagrange libration point of the Earth-Moon / Sun system
L1 : First Large mission of the ESA Cosmic Vision 2020 programme (assigned to JUICE)
L2 : Second Lagrange libration point of the Earth-Moon / Sun system
L2 : Second Large mission of the ESA Cosmic Vision 2020 programme (assigned to Athena)
L3 : Third Large mission of the ESA Cosmic Vision 2020 programme (gravitational-wave theme)
LA : (WFI) Large Array (obsolete, now called LDA)
LC : inductor (L) and capacitor (C)
LD : (WFI) Large Detector
LDA : (WFI) Large Detector Array
LEAF : Large European Acoustic Facility
LEO : Low-Earth Orbit
LFA : Lead Funding Agencies
LGA : Low-Gain Antenna
LHP : Loop Heat Pipe
LMCO : Lockheed Martin COrporation
LNA : Low-Noise Amplifier
LPA : Large Pixel Array
LPTC : Large Pulse-Tube Cooler
LSF : Line-Spread Function
LT : Laser Tracker
LTP : Long-Term Proposal (SPring-8)
LURE : Laboratoire d’Utilisation du Rayonnement \'{E}lectromagn\'{e}tique
LVA : Launch-Vehicle Adapter
L_bol : Bolometric Luminosity
L_edd : Eddington Luminosity
LoR : Level of Resources
MA : Mirror Assembly
MACS : MAssive Cluster Survey
MAD : Mirror-Assembly Demonstrator
MAIT : Manufacturing, Assembly, Integration, and Test
MAM : Mirror-Assembly Module
MAR: Mission Adoption Review
MBD : Mission Budget Document
MCP : Mirror Calibration Plan
MCR : Mission Consolidation Review (2016)
MCV : Magnetic Cataclysmic Variable
MD : Magnetic Diverter
MEKAL : Rolf Mewe, Jelle Kaastra, and Duane Liedahl
MEUR : Million EURo
MFP : Mean Free Path
MFR: Mission Formulation Review
MGSE : Mechanical Ground-Support Equipment
MIP : Movable Instrument Platform (obsolete)
ML : Multi-Layer (coating)
MLA : Multi-Lateral Agreement
MLT : Media Lario Technologies
MM : Mirror Module
MMA : Movable Mirror Assembly
MOC : Mission Operations Centre (ESA)
MOP : Mock Observation Plan
MOSFET : Metal–Oxide–Semiconductor Field-Effect Transistor
MPE : Max-Planck-Institut f\"{u}r Extraterrestrische Physik
MPG : Max-Planck Gesellschaft
MPS : Max-Planck Society
MPTC : Miniature Pulse-Tube Cooler
MPWG : Mission Performance Working Group
MRD : Mission Requirements Document
MRR : Manufacturing Readiness Review
MS : (ESA) Member State
MS : Mirror Structure
MSFC : Marshall Space Flight Center
MUSD : Million US Dollar
MUSD : Million USD
MXS : Modulated X-ray Source
MoM : Minutes of Meeting
MoS : Margin of Safety
MoU : Memorandum of Understanding 
Ms : Mega-second
NASA : National Aeronautics and Space Administration
NDA : Non-Disclosure Agreement
NED : NASA/IPAC Extragalactic Database
NFI : Narrow-Field Imaging
NGRM : Next-Generation Radiation Monitor
NHXM : New Hard X-ray Mission
NIEL : Non-Ionising Energy Loss
NIST : National Institute of Standards and Technology
NLS : Narrow-Line Seyfert (galaxy)
NS : Neutron Star
NSLS : National Synchrotron Light Source (Brookhaven National Laboratory)
NXB : Non- X-ray Background
OAB : Osservatorio Astronomico di Brera
OBDH : On-Board Data Handling
OBSW : On-Board SoftWare
OBT : On-Board Time
OCS : Outer Cold Shield (WFI)
ODF : Observation Data File
OGS : Operational Ground Segment
OGSE : Optical Ground-Support Equipment
OM : Optics Module
OSG : Observatory Science Goal
OT : Open Time
OTAC : Observation Time Allocation Committee
OU : Open University
OoM : Order of Magnitude
P/L : PayLoad
PANTER : PAntolsky Neuried TEstanlage Röntgen
PCA : Principal Component Analysis
PCOS : Physics of the COSmos (NASA)
PDD : Payload Definition/Description Document
PDR: Preliminary Design Review
PDU : Power Distribtuion Unit
PET : Photon-Event Table
PFM : Proto-Flight Model
PHA : Pulse Height Amplitude
PI : Photon Ionisation 
PL : PayLoad
PM : Progress Meeting
PPR : Performance and Process Review
PRR : Preliminary Requirements Review
PSD : Power Spectral Density
PSF : Point Spread Function
PSPC : Position Sensitive Proportional Counter
PT : Product Tree
PT : Pulse Tube
PTB : Physikalisch-Technische Bundesanstalt
PTC : Pulse-Tube Cooler
PTF : Palomar Transient Factory
PU : Partner User (SPring-8)
PV : Performance Verification
PWN : Pulsar-Wind Nebula
Q : Qualification (testing)
QLA : Quick-Look Analysis
QM : Qualification Model
QR : Qualification Review
QSL : Quasi-Static Load
R200 : Radius at which the mean mass density exceeds the critical density by a factor of 200
R500 : Radius at which the mean mass density exceeds the critical density by a factor of 500
RAL : Rutherford Appleton Laboratory
RCS : Reaction Control System
RE : Radiative Emissivity
REL : (SEPEM) Reference Event List
RFI : Request For Information
RIKEN : Rikagaku Kenkyūsho (research institute in Japan)
RMF : Redistribution (Response) Matrix File
RMXP : Rotation-powered Millisecond X-ray Pulsar
RN : Recurrent Nova
ROM : Rough, Order-of-Magnitude
RS : Radiative Susceptibility
RT : Radiative Transfer
RT : Ray Tracing
RTS : Rotating Target Source
RW : Reaction Wheel
RXTE : Rossi X-ray Timing Explorer
Rg : Gravitational (Schwarzschild) radius
S-K : Sulphur K (line)
S/C : SpaceCraft (also denoted SC)
SAST : SKA-Athena Synergy Team
SB : Super Bubble
SBT : Service des Basses Temp\'{e}ratures
SC : SpaceCraft (also denoted S/C)
SC : Steering Committee
SCI : SCIence directorate (ESA)
SCIOBJ : SCIence OBJective
SD : Single Degenerate
SD : Space Debris
SDC : Science Data Centre
SDMP : Space-Debris Mitigation Plan
SEL1 : Sun-Earth Lagrange point 1
SEL2 : Sun-Earth Lagrange point 2
SEP : Soft-Energy Proton
SEP : Solar Energetic Particle (event)
SEPEM: Solar Energetic Particle Environment Modelling
SF : Source Follow (readout mode)
SG : Science Goal
SGD : Soft Gamma-ray Detector (Hitomi)
SGO : Slumped-Glass Optics
SGS : Science Ground Segment
SIB : Science Instruments Bench
SIM : Science Instruments Module
SIMO : Science Impact (assessment) of Mass-saving Options
SIMPOSIuM : SIMulations of Pore Optics in SIlicon and Modelling
SIMPUT : SIMulation inPUT (for SIXTE)
SIP : Science Instruments Platform
SIRENA : Software IFCA for Reconstruction of EveNts for Athena X-IFU
SIXTE : SImulation of X-ray TElescopes
SKA : Square-Kilometre Array
SLAC : Stanford Linear Accelerator Center (now known as SLAC National Accelerator Laboratory)
SMBH : Super-Massive Black Hole
SME : Small or Medium(-sized) Enterprise
SMP : Science Management Plan
SN : SuperNova
SNR : Signal-to-Noise Ratio
SNR : SuperNova Remnant
SOAD : Science Operations Assumptions (Agreements) Document
SOC : Science Operations Centre (ESA)
SOLEIL : Source Optimis\’{e}e de Lumi\`{e}re d’\’{E}nergie Interm\’{e}diaire du LURE
SP : Soft Proton (from the Sun)
SPA : Small Pixel Array
SPC : Science Programme Committee (ESA)
SPENVIS : SPace ENVIronment, effects, and education System
SPEX : SPEctral X-ray (and UV modelling and analysis tool)
SPI : Star-Planet Interaction 
SPO : Silicon Pore Optics
SPORT : Silicon-Pore-Optics at Room Temperature
SPring-8 : Super Photon ring-8 GeV
SQUID : Superconducting QUantum Interference Device
SRE : Science and Robotic Exploration directorate (obsolete, now called SCI)
SRG : Spectrum - Roentgen - Gamma
SRON : Stichting Ruimte Onderzoek Nederland (Netherlands institute for space research)
SRON : Stichting RuimteOnderzoek Nederland (Netherlands Institute for Space Research)
SRR : System Requirements Review
SRS : Shock Response Spectrum
SSAC : Space Science Advisory Committee
SSC : Senior Survey Committee (for ESA's L-class missions)
SSC : Synchrotron Self Compton
SSS : Super-Soft (X-ray) Source
SST : Solid-State Telescope
STFC : Science and Technology Facilities Council
STM : Structural-Thermal Model
STR : Star TRacker
STT : Science Topic Team
SVM : SerVice Module
SWCX : Solar Wind Charge eXchange
SWG : Science Working Group
SWP : Synergy White Paper
SXI : Soft-X-ray Image (Hitomi)
SXRB : Soft X-Ray Background
SXS : Soft-X-ray Spectrometer (Hitomi)
SXT : Soft-X-ray Telescope (Hitomi)
SZ : Sunyaev-Zeldovitch
SciRD : Science Requirements Document
SiC : Silicon-Carbide
SoW : Statement of Work
T/O : Trade-Off
TAA : Technical Assistance Agreement
TAC : Time Allocation Committee
TAI : International Atomic Time
TAS : Thales Alenia Space
TAS-F : Thales Alenia Space France
TAS-I : Thales Alenia Space Italy
TB : Thermal Balance
TBC : To Be Confirmed
TBD : To Be Defined
TBW : To Be Written
TCB : Barycentric Coordinate Time
TCM : Trajectory Correction Manoeuvre
TCS : Thermal-Control Sub-system
TDA : Technology Demonstrator Activity
TDB : Barycentric Dynamical Time
TDM : Time-Domain Multiplexing
TDP : Technology Development Plan
TEC-EES : space Environments and Effects Section in ESA's TEChnical Directorate
TECNET : TEChnical NETwork
TECNET : TEChnology NETwork (ESA)
TES : Transition Edge Sensor
TID : Total Ionising Dose
TP : Technology Plan
TP : Topical Panel
TPA : Telescope Performance Assessment
TRL : Technology Readiness Level
TRoPIC : single photon counting CCD camera, eROSITA prototype camera
TT : Terrestrial Time
TTC : Telemetry and TeleCommand
TV : Thermal Vacuum
TWG : Telescope Working Group
TWTA : Travelling WaveTube Amplifier
ToF : Time of Flight
ToO : Target of Opportunity
UFO : Ultra-Fast Outflow
UKSA : United Kingdom Space Agency
ULIRG : Ultra-Luminous InfraRed Galaxy
ULX : Ultra-Luminous X-ray (source)
ULX : Ultra-Luminous X-ray source
US : United States
USD : United States Dollar
UTC : Universal Coordinated Time
VERITAS : VErsatile Readout based on Integrated Trapezoidal Analogue Shapers
VF : Vignetting Factor
VF : Vignetting Function
VG : ViewGraph
VO : Virtual Observatory
VTT : Valtion Teknillinen Tutkimuskeskus (Finland's State Technical Research Centre)
W : Window (mode)
W1 : Wolter-1 (design)
WA : Wolter(-1) Athena
WBS : Work Breakdown Structure
WDA : WFI Data Analysis (software)
WFEE : Warm Front-End Electronics
WFI : Wide-Field Imager
WFOIS : Wide-Field Optical/Infrared Surveyors
WG : Working Group
WHIM : Warm-Hot Inter-galactic Medium
WISC : WFI Science and data Centre
WP : Work Package
WPD : Work Package Description
X-COP : XMM-Newton Cluster Outskirts Project
X-IFU : X-ray Integral-Field Unit
XARM : X-ray Astronomy Recovery (Replacement) Mission (“Hitomi-2”)
XCaT : X-IFU Calibration Team
XDA : X-IFU Data Analysis (software)
XDIN : X-ray Dim Isolated Neutron star
XDS : X-ray Detector System
XEUS : X-ray Evolving-Universe Spectroscopy (obsolete)
XIFU : X-ray Integral-Field Unit
XISC : X-IFU Science and data Centre
XMM : X-ray Multi-Mirror telescope
XMS : X-ray Micro-calorimeter Spectrometer (obsolete)
XOU : X-ray Optical Unit
XPBF : X-ray Pencil-Beam Facility (at PTB)
XRCF : X-Ray and Cryogenic Facility (at MSFC; formerly known as X-Ray Calibration Facility)
XSS : X-ray Source System
dMCR : delta Mission Consolidation Review (2017)
e2ePA : end-to-end Performance Assessment
kSZ : kinetic SZ effect
ks : kilo-second
tSZ : thermal SZ effect
uTCA : micro Telecommunications Computing Architecture (connector)
um : micrometer
z : redshift
1g : Earth's gravity