Spaceflight people love their abbreviations, and although we try our utmost to avoid them on this blog if you follow any space-related activities you will undoubtedly come across some combination of letters that might not be familiar. For you, but also for us, we created this cheat sheet of Artemis and European Service Module-related acronyms.

Found any that are not in this list? Let us know in the comments and we can update it!

AcronymMeaningExplanation
AAAscent Abort     An Ascent Abort would occur if during the 8 minutes from ignition an Artemis launch is cancelled. The Launch Abort System above Orion can fire and propel the capsule and crew to safety. Later in the launch the European Service Module can also kick in for an ascent abort in three scenarios. 
AI&TAssembly, Integration, and Testing   The full process of putting all the parts for Orion together and testing them to ensure they work as planned.
APUAuxiliary Power Unit    A  power supply for the spacecraft when on Earth for testing
ASEUAft Skirt Electrical Umbilical   The electrical systems at the ‘bottom’ of the Orion spacecraft
ATLOAssembly, Test, and Launch Operations  The last assembly and testing before launch focussing on stacking the spacecraft in the rocket.
ATPAuthority to Proceed    At specific moments during the assembly of the rocket and spacecraft after testing the teams convene to assess the current situation and confirm continuation of the plan
BFSBackup Flight System    All critical hardware has backups, many have multiple backups for safety. The Backup Flight System is a computer that activates if the main flight system fails.
C&DHCommand and Data Handling   The process of sending commands and data between the systems that make up Orion.
C/OCheck Out     Testing elements of the spacecraft after assembly
CAACrew Access Arm    The bridge extension from the launch tower that allows astronauts and technicians access to the Orion spacecraft once it is ready rolled out and ready for launch.
CMCrew Module     The part of Orion where the astronauts are during flight.
CMACrew Module Adapter    The part of Orion that connects the Crew Module to the European Service Module. Together with the European Service Module, the two make up the Orion Service Module.
CMASSCrew Module Ammonia Servicing Subsystem  The central heating for Orion, using ammonia pumped through radiators to regulate temperature. 
CSCore Stage     The main stage of the rocket, for SLS this is the big orange fuel tank two side boosters and motors. 
CSMCrew and Service Module   The complete Orion spacecraft. 
CSSConsumable Storage System    The tanks that hold the fuel, air and water. 
CTCrawler Transporter     The huge machine that transports the rocket and Orion to the launchpad. 
DCRDesign Certification Review    The moment when a design for the spacecraft or element is analysed and approved.
DFATDirect Field Acoustics Test   A test where the vibrations of launch are simulated with loudspeakers. 
DRIDistant Retrograde InsertionOne of the four main engine burns that the European Service Module will initiate on Artemis I. The Distant Retrograde Insertion is initiated to stay put the spacecraft in Moon orbit.
DRDDistant Retrograde DepartureOne of the four main engine burns that the European Service Module will initiate on Artemis I. The Distant Retrograde Departure is initiated to leave the Moon’s orbit and start the voyage home.
ECLSSEnvironmental Control and Life Support System The complete system that keeps astronauts alive in space: temperature control, atmosphere, air to breathe, carbon dioxide removal, ventilation and more. Pronounced ‘ecluss’ by astronauts.
ECUEngine Controller Unit    The hardware that directs each engine to fire and for how long.
EESEmergency Egress System    The emergency exit procedure, at the top of an almost 100-m rocket, getting away quickly to safety requires its own procedures and hardware. Astronauts will zip-line to ground and drive an amoured car away. 
EGSExploration Ground Systems    The people and hardware at NASA’s Kennedy Space Center that process rockets and spacecraft until launch. 
EGSEElectrical Ground Support Equipment   All electrical equipment that is used to help build and test the spacecraft that does not fly to space.
EMI/EMCElectromagnetic Interference and Electromagnetic Compatibility  Electromagnetic waves that all electrical equipment emits that could interfere with the correct functioning of other equipment. Needs to be tested and controled. 
ESAEuropean Space Agency    The space agency responsible for the European Service Module, consisting of 22 Member States. 
ESDExploration Systems Development    Former NASA division responsible for Orion spacecraft. 
ESMEuropean Service ModuleThe powerhouse for Orion providing fuel, water, electricity and propulsion.
ESTECEuropean Space Research and Technology CentreLocated in Noordwijk, the Netherlands, ESA’s technical heart is where the European Service Module team is based as well as their mission control room.
ETEEnd to End    The complete process from start to finish.
EUSExploration Upper Stage    The high-power engine that will propel Orion from Earth orbit to the Moon in future Artemis missions from Artemis IV onwards. It is discarded after use.
FASTFinal Assembly and System Test  The hardware used to connect and test the European Service Module and the Crew Module 
FCASFlight Controller Application Software   Software used by mission control to interpret data from the spacecraft
FCVFlow Control Valve    A valve that regulates how much liquid or gas is let through, used for the engines and life support systems.
FDIRFault Detection Isolation& Recovery   Pinpointing an error in the system and finding a work-around
FEEFront-End Equipment Used in Orion for the hardware interfaces that simulate aspects of spaceflight, used for the solar array simulators in particular. 
FMFlight Model     The version of the spacecraft hardware that actually flies to space, as opposed to testing models.
FMAFinal Mission Analysis    The last analysis of a mission plan
FPGAField-Programmable Gate ArrayAn integrated circuit that is configured after manufacturing and are used everywhere, including on the European Service Modules
FRACFlight Readiness Analysis Cycle   Mission-specific information, such as mass properties, Booster burn rates, and launch window, to determine performance of the system. 
FRRFlight Readiness Review    The final review of hardware integration giving the thumbs-up for spaceflight
FSWFlight Software     The computer programmes that control the spacecraft during its mission
FWDForward      The front, in Orion’s case this is the nose cone of the Crew Module.
GFASGround/Flight Application Software    The computer programmes used on Earth to run the mission
GFASTGround/Flight Application Software Team   The people who use and make the computer programmes used on Earth to run the mission
GHeGaseous Helium     Helium gas (the lightest gas in the Universe) when not in liquid or solid form. In the European Service Module helium is used to push fuel through the guel tanks
GLSGround Launch Sequencer    The countdown to launch and sequence of events to the run-up
GN2Gaseous Nitrogen     Nitrogen gas when not in liquid or solid form. Nitrogen makes up roughly 70% of our atmosphere so humans breathe it in at all time. The European Service Module stores nitrogen in tanks to mix with oxygen for astronauts to breathe. 
GNCGuidance, Navigation, and Control   The complete system that tells Orion where it is, where it should go, and how to do it
GO2Gaseous Oxygen     Oxygen when not in liquid or solid form. Nitrogen makes up roughly 70% of our atmosphere so humans breathe it in at all time. The European Service Module stores nitrogen in tanks to mix with oxygen for astronauts to breathe. 
GR&AGround Rules and Assumptions   A large list of rules and procedures used during the mission. Think, “if this happens at this moment then we will assume it is because this happened”
GRASGreen Run Application Software   Computer programmes used to run and analyse the test-firing of the Artemis SLS rocket core stage
GRCGlenn Research Center    NASA technical expertise centre in Ohio, USA, where the European Service Module test article was put to its paces
GSEGround Support Equipment    All the equipment used on Earth to help build and test Orion, think tools, trolleys to hold the tools but also diagnostic equipment and more
HBHigh Bay     A large building that can hold a complete spacecraft or rocket for testing or integration
HOTHHouston Orion Test Hardware   Equipment used to simulate an Orion mission to train mission controllers at NASA’s
HWHardware      Equipment, anything that you can touch that helps Orion go to space
ICPSInterim Cryogenic Propulsion Stage   The large engine that boosts Orion to the Moon from Earth orbit and is discarded after use
ICPSUInterim Cryogenic Propulsion Stage Umbilical  The electronic connection between the large engine that boosts Orion to the Moon from Earth orbit and is discarded after use
IPOInitial Power On    The first time the spacecraft is provided with electrical power and switched on
ITLIntegrated Test Laboratory    Located at Lockheed Martin’s Denver, Colorado, USA, site the Integrated Test Laboratory is where the software is tested for Orion
JICBJoint Integrated Control Board   Board tri-chaired by the chief engineers from each programme (Orion, SLS, EGS), charged with maintaining the cross-programme technical baseline
JMJettison Motor     An engine that is discarded during the mission, either from the rocket or in the first Artemis missions the  Interim Cryogenic Propulsion Stage that is discarded after it boosts Orion to the Moon.
KSCKennedy Space Center    NASA centre in Florida, USA, where Orion has its final checkout, integration, placing on the rocket and launch
LASLaunch Abort System    The cone at the top of the rocket that can propel the Orion spacecraft away to safety if needed during launch
LCCLaunch Commit Criteria    The minimum situation required for a GO for launch, think wind speeds, weather, orbits etc.
LCLLatching Control LimiterSwitches in the Power Control and Distribution Units that turn power on or off and protect from overloading.
LETFLaunch Equipment Test Facility   Located at NASA’s Kennedy Space Centre this area allows technicians to test hardware before liftoff
LH2Liquid Hydrogen     Hydrogen (the lightest gas in the Universe) when not in gaseous or solid form. The gas occurs naturally as two hydrogen atoms bonded, hence the 2 in the abbreviation.
LN2Liquid Nitrogen     Nitrogen when not in gaseous or solid form. Nitrogen oocurs naturally as two nitrogen atoms bonded, hence the 2 in the abbreviation. In the European Service Module nitrogen is stored as a liquid in tanks and mixed with oxygen to create a breathable atmosphere for astronauts.
LO2Liquid Oxygen     Oxygen when not in gaseous or solid form. Occurs naturally as two oxygen atoms bonded, hence the 2 in the abbreviation. In the European Service Module nitrogen is stored as a liquid in tanks and mixed with oxygen to create a breathable atmosphere for astronauts.
LOXLiquid Oxygen     Nitrogen when not in gaseous or solid form. In the European Service Module nitrogen is stored as a liquid in tanks and mixed with oxygen to create a breathable atmosphere for astronauts.
LVSALaunch Vehicle Stage Adapter   The hardware that connects the rocket to the spacecraft and is discarded after separation.
MAFMichoud Assembly Facility    NASA facility that is part of the Marshall Space Flicht Center, New Orleans, USA, where the Artemis rocket is built.
MLMobile Launcher     The machine that carries the Artemis rocket and spacecraft to the launchpad, also known as the crawler
MPPFMulti-Payload Processing Facility    A building where many different types of spacecraft or space hardware can be prepared for launch
MPSMain Propulsion System    The large engine or engines in a rocket or spacecraft
MSFCMarshall Space Flight Center   NASA centre in New Orleans, USA, where the Artemis rocket is built
NASANational Aeronautics and Space AdministrationThe civil space agency for the United States of America and responsible for Artemis and the Orion spacecraft. 
NDENondestructive Evaluation     A test to see if something works and will not break without actually pushing it beyond its limits and breaking it.
O&COperations and Checkout    The process of assembling Orion and checking it will work
O/DOn Dock     When a spacecraft is not flying, before launch
OGVOgive Panel     Panels outside the Crew Module that protect it during launch 
OMOrbital Manoeuvres  Changes in orientation and course performed by the spacecraft.
OMRSOperations and Maintenance Requirements and Specifications The list of what is needed when working on the spacecraft and keeping it in good condition before flight.
OMS-EOrbital Maneuvering System Engine   The main engine for Orion is a repurposed Space Shuttle engine that was called OMS-E as ot was used to move once in Earth orbit
OPFOutbound Powered FlybyOne of the four main engine burns that the European Service Module will initiate on Artemis I. The Outbound Powered Flyby is initiated on first approach to the Moon.
OSAOrion Stage Adapter    The connecting hardware between the Orion spacecraft and its booster engine the ICPS 
OTCOutbound Trajectory CorrectionsThruster fires performed by the European Service Module with minor course corrections on the way to the Moon.
OTPOrion Transportation Pallet    Hardware used to transport Orion when on Earth
PBSPlum Brook Station    A facility that is part of NASA’s Glenn Research Centre where spacecraft are tested, including Orion.
PCAPressure Control AssemblyThe hardware that controls the pressure in the European Service Module fuel lines.
PCDUPower Control Distribution Unit   The hardware that controls how much of the electricity generated by the solar panels goes to each component.
PDUPower Distribution Unit    The hardware that controls how much of the electricity generated by the solar panels goes to each component.
PLIPropellant Liner Insulation    The protective compound 
PMProgram Manager     The head of a programme, in this case responsible for building the spacecraft (components)
PPEPower and Propulsion Element   The first module for the lunar Gateway that will orbit the Moon and be visited by Orion
PPSPropulsion Sub SystemThe complete system for propulsion: from fuel tanks to fuel lines and the engines.
PRAProbabilistic Risk AssessmentA method to analyse and report on how likely something will happen in the domain of engineering and hardware 
PRMPerigee Raising ManoeuvreA boost given by the Interim Cryogenic Propulsion Stage to raise Orion’s orbit around Earth after launch.
Proof cellProof Pressure CellThe Proof Pressure Cell at NASA’s Operations and Checkout building in Kennedy Space Center uses helium gas that is piped through newly-welded joints at high pressure to test their effectiveness. If the welds do not leak under increased pressure then they are fit to fly and can withstand the forces of launch and spaceflight.
QDQuick Disconnect     Connectors used to provide fast and easy connection and disconnection of fluid lines
QMQualification Motor     An engine used to test and ensure the real thing will work correctly once in space
RCSReaction Control System    The name for the 24 Airbus engines used to orient Orion
RPFReturn Powered FlybyOne of the four main engine burns that the European Service Module will initiate on Artemis I. The Return Powered Flyby is initiated to start the return to Earth.
RTCReturn Trajectory CorrectionsThruster fires performed by the European Service Module with minor course corrections on the way back to Earth from the Moon.
SARSystem Acceptance Review    NASA review  to evaluate at the end of the integration process and before integration with SLS  the Orion spacecraft and related systems for their ability to fly into space, and getting to the Moon 
SAWSolar Array WingsThe four solar panel wings that generate power for the European Service Module
SCAPESelf-Contained Atmospheric Protection Ensemble   The suits worn by technicians when fueling a rocket or spacecraft to protect them from hazardous fuel leaks
SCCSSpaceport Command and Control System  The system used to send commands to the rocket before launch
SE&ISystems Engineering and Integration   Disciplined approach for the definition, implementation, integration and operations of a system 
SILSystem Integration Lab     Avionics and Software testing facility for the SLS established at Marshall  (MSFC) which demonstrates real-time flight control of the launch vehicle during ascent.
SITFSoftware Integration Testing Facility   Avionics and Software testing facility for the SLS established at Marshall  (MSFC) which  integrates and tests software specifically for the SLS Core/Upper Stage avionics system
SLSSpace Launch System    The Artemis rocket
SMService Module     The European Service Module including Crew Module Adapter
SSCStennis Space Center    NASA centre where the Artemis rocket is built and tested. 
STAStructural Test Article    A version of a spacecraft that is similar in weight and structure but does not include all the components. Used for testing. 
SWSoftware      Yes, one word can also be abbreviated in spaceflight!
TCSThermal Control SystemThe hardware and software that are used to keep Orion and the European Service Module operating at a cozy temperature.
TCUThermal Control Unit    Hardware used to control the temperature in Orion.
TLITrans Lunar InjectionA boost from the Interim Cryogenic Propulsion Stage to send Orion off to the Moon from Earth’s orbit.
TLMTelemetry      Data sent to ground control during flight.
TPSThermal Protection System    The protective covers and raditors used to keep Orion at the correct temperature
TRRTest Readiness Review    A review to see if the hardware is ready for testing
TSMUTail Service Mast Umbilical   Provides liquid oxygen and liquid hydrogen fluid lines and electrical cable connections to the SLS core stage engine section to support propellant handling during prelaunch operations
TVCThrust Vector Control    The control mechanisms for the engine power.
V&VVerification and Validation    Checking and confirming everything works.
VABVehicle Assembly Building    The building at NASA Kennedy Space Center where the rocket is assembled and the spacecraft integrated.
VACVertical Assembly Center    Welding facility at NASA’s Michoud Assembly Facility in New Orleans, USA.
WDRWet Dress Rehearsal    A full-scale test of the rocket where fuel is pumped into the tanks and all aspects of the launch countdown are done until just a few minutes before lift-off. The big final test before a launch.