Appendix B: Acronyms, Abbreviations, and Symbols
Encyclopedia
Updated Feb 18, 2025
B.1 PURPOSE
This Appendix provides guidance, made available in the acronym, abbreviation, and symbol definitions listed below.
| ~ | approximately | |
| β | beta, injury risk criterion | |
| ° | degree | |
| Δ | delta (change) | |
| ΔQ | delta Q | |
| = | equal | |
| > | greater than | |
| ≥ | greater than or equal to | |
| < | less than | |
| ≤ | less than or equal to | |
| – | minus | |
| µg | microgram | |
| µ | mu, micro | |
| µm | Micrometer | |
| µPa | micropascal | |
| Ω | omega, ohm | |
| % | percent, percentile | |
| + | plus | |
| ± | plus or minus | |
| θ | theta, angle of incidence | |
| ρ | rho, density | |
| A | ampere | |
| A/m | ampere per meter | |
| AC | alternating current | |
| ACGIH | American Conference of Governmental Industrial Hygienists | |
| AF | activity factor | |
| AGARD | Advisory Group for Aerospace Research and Development | |
| ALARA | as low as reasonably achievable | |
| ANSI | American National Standards Institute | |
| APP | Applicable | |
| Ar | Argon | |
| AR | augmented reality | |
| ARS | atmosphere revitalization system | |
| ASCII | American Standard Code for Information Interchange | |
| ASA | Acoustical Society of America | |
| ASHRAE | American Society of Heating, Refrigerating, and AirConditioning Engineers | |
| +/- Ax | Eyeballs in/out | |
| +/- Ay | Eyeballs right/left | |
| +/- Az | Eyeballs down/up | |
| B/W | black and white | |
| BEI | biological exposure index (indices) | |
| BET | Blur Edge Time | |
| bpm | beats per minute | |
| BSL | biosafety levels | |
| Btu | British thermal unit | |
| c | specific heat | |
| C | Celsius | |
| cal | calorie | |
| CCP | Commercial Crew Program | |
| CCT | Correlated Color Temperature | |
| cd | candela | |
| CDO | cognitive deficit onset | |
| CFE | Contractor Furnished Equipment | |
| CFR | Code of Federal Regulations | |
| CFU | colony forming unit | |
| CGMP | Current Good Manufacturing Practices | |
| CHSIP | Commercial Human Systems Integration Processes | |
| CIE | International Commission on Illumination | |
| cm | centimeter | |
| cm2 | square centimeter | |
| CMO | Chief Medical Officer | |
| Cn | minutes of noise exposure | |
| CO2 | carbon dioxide | |
| COAS | Crew Optical Alignment System | |
| Comm | Communication | |
| COSPAR | Committee for Space Research | |
| COTS | Commercial Off-the-Shelf | |
| CP | combustion product | |
| CQS | Color Quality Scale | |
| CRI | Color Rendering Index | |
| D | noise dose | |
| dB | decibel | |
| dBA | decibels, A-weighted | |
| DC | direct current | |
| DCS | decompression sickness | |
| Deg | Degree | |
| DER | Daylight Equivalent Ratio | |
| DMS | Display Measurement Standard | |
| DNA | deoxyribonucleic acid | |
| DOT | Department of Transportation | |
| DRI | dietary reference intake | |
| DRM | Design Reference Mission | |
| E | perceptual distance between colors electric field strength | |
| EAWG | Exploration Atmospheres Working Group | |
| ECG | electrocardiogram | |
| ECLSS | Environmental Control and Life Support System | |
| EDI | Equivalent Daylight Illuminance | |
| EE | Extreme Environment | |
| EER | estimated energy requirements | |
| EES | emergency egress systems | |
| EHP | Extravehicular Activity and Human Surface Mobility Program | |
| EMU | extravehicular mobility unit | |
| ETEC | Enterotoxigenic Escherichia coli | |
| ESTV | Extraterrestrial Surface Transport Vehicle | |
| ETA | estimated time of arrival Engineering Technical Authority |
|
| EVA | extravehicular activity | |
| F | Fahrenheit | |
| f | frequency | |
| fG | frequency in gigahertz | |
| Fi | Fractional concentration of inspired oxygen | |
| fM | frequency in megahertz | |
| FFRDC | Federally Funded Research and Development Center | |
| fl | fluid | |
| fl oz | fluid ounce | |
| FOD | Foreign Object Debris | |
| FPDM | Flat Panel Display Measurements | |
| FSMA | Food Safety Modernization Act | |
| ft | foot, feet | |
| G | gravitational constant | |
| g | gram gravity (gravity equals 9.8 m/s2) |
|
| GCR | galactic cosmic ray | |
| GET | Gaussian Edge Time | |
| GFP | Government Furnished Equipment | |
| GHz | gigahertz | |
| GPS | Global Positioning System | |
| GSE | Ground Support Equipment | |
| GUI | graphical user interface | |
| +/- Gx | See +/- Ax | |
| +/- Gy | See +/- Ay | |
| +/- Gz | See +/- Az | |
| H | magnetic field strength | |
| HCD | human-centered design | |
| HDBK | Handbook | |
| He | Helium | |
| HEI | human error identification | |
| HeNe | helium-neon | |
| HEOMD | Human Exploration and Operations Mission Directorate | |
| HEPA | high efficiency particulate air | |
| HFDS | Human-System Interface Standard | |
| HIDH | Human Integration Design Handbook | |
| HIDP | Human Integration Design Processes | |
| HITL | human-in-the-loop | |
| HMTA | Health and Medical Technical Authority | |
| HQR | Handling Qualities Rating | |
| hr | hour | |
| HRL | hazard response level | |
| HSI | human systems integration | |
| HSIP | Human Systems Integration Plan | |
| HUD | head’s up display | |
| Hz | Hertz | |
| ICDM | International Committee on Display Metrology | |
| ICR | Incapacitated Crew Rescue | |
| IEC | International Electrotechnical Commission | |
| IEEE | Institute of Electrical and Electronics Engineers | |
| IES | Illuminating Engineering Society | |
| IMV | inter-module ventilation | |
| in | inch | |
| IPR | intellectual property rights | |
| IR | infrared | |
| IRD | Information Requirements Document | |
| ISO | International Organization for Standardization | |
| ISS | International Space Station | |
| IVA | intravehicular activity | |
| J | Joule | |
| JPR | Johnson Procedural Requirements | |
| JSC | Johnson Space Center | |
| K | Kelvin | |
| k | kilo thermal conductivity |
|
| kcal | kilocalorie | |
| kg | kilogram | |
| kHz | kilohertz | |
| kJ | kilojoule | |
| km | kilometer | |
| kPa | kilopascal | |
| L | liter | |
| LADTAG | Lunar Atmosphere Dust Toxicity Assessment Group | |
| lb | pound | |
| LEA | launch, entry and abort | |
| LED | light-emitting diodes | |
| LEO | low Earth orbit | |
| LIA | Laser Institute of America | |
| LiOH | lithium hydroxide | |
| Ln | sound level of a noise exposure event in dBA | |
| LN,A | A-weighted sound level of the ambient noise | |
| LOC | loss of crew | |
| logMAR | Logarithm of the Minimum Angle of Resolution | |
| LOM | loss of mission | |
| LRU | Line Replacement Unit | |
| LS,A | A-weighted sound level of the auditory annunciation or signal | |
| LSi,oct | Octave band sound pressure level corresponding to the auditory annunciation or signal | |
| LSi, 1/3oct | 1/3 octave band sound pressure level corresponding to the auditory annunciation or signal | |
| Lti,1/3oct | 1/3 octave band sound pressure level corresponding to the effective masked threshold | |
| m | meter | |
| m3 | cubic meter | |
| MΩ | megaohm | |
| mA | milliampere | |
| ma | maximum current | |
| Max | maximum | |
| MET | Mission Elapsed Time | |
| mg | milligram | |
| MHz | megahertz | |
| MI | maintenance item | |
| MIL | Military | |
| min | minute | |
| mL | milliliter | |
| mm | millimeter | |
| MH | Monomethyl hydrazine | |
| MMH | Manual Materials Handling | |
| mmHg | millimeter of mercury | |
| MMOD | Micrometeoroids and Orbital Debris | |
| MORD | Medical Operations Requirements Document | |
| MPE | maximum permissible exposure | |
| ms | millisecond | |
| MSFC | Marshall Space Flight Center | |
| N | number of noise exposure events in a 24-hour period | |
| N2 | Nitrogen | |
| N/A | not applicable | |
| NASA | National Aeronautics and Space Administration | |
| NC | noise criterion normal condition | |
| NEMA | National Electrical Manufacturers Association | |
| NHV | Net habitable volume | |
| NIOSH | National Institute for Occupational Safety and Health | |
| nm | nanometer | |
| NPD | NASA Policy Directive | |
| NPR | NASA Procedural Requirements | |
| O2 | oxygen | |
| OCHMO | Office of the Chief Health and Medical Officer octave | |
| Oct | ||
| OMB | Office of Management and Budget | |
| OSHA | Occupational Safety and Health Administration | |
| oz | ounce | |
| Pa | Pascal | |
| PA | potentially applicable | |
| PB | Ambient Barometric Pressure | |
| PDA | personal digital assistant | |
| PEL | permissible exposure limit | |
| PET | Phased Elapsed TIme | |
| PICO2 | inspired carbon dioxide partial pressure | |
| PIO2 | inspired oxygen partial pressure | |
| pp ppm | partial pressure parts per million | |
| ppCO2 | partial pressure of carbon dioxide | |
| PPE | Personal Protective Equipment | |
| ppO2 | partial pressure of oxygen | |
| psi | pound(s) per square inch | |
| psia | pound(s) per square inch absolute | |
| PWD | potable water dispenser | |
| Q | heat | |
| rad/s2 | radians per second squared | |
| REID | risk of exposure-induced death | |
| RF | radio frequency | |
| Rg | color gamut index | |
| RH | relative humidity | |
| RMS | root mean square | |
| RPE | Rating of Perceived Exertion | |
| rpm | revolutions per minute | |
| s | second | |
| S | power density | |
| SA | situational awareness | |
| SAS | space adaptation syndrome | |
| SDS | Safety Data Sheet | |
| sec | second | |
| SI | International System of Units | |
| SIL | speech interference level | |
| SMAC | spacecraft maximum allowable concentration | |
| SP | special publication | |
| SPE | solar particle event | |
| SPL | sound pressure level | |
| SRD | System Requirements Document | |
| SSP | Space Station Program | |
| STD | Standard | |
| STS | Space Transportation System | |
| SUS | system usability scale | |
| SWEG | spacecraft water exposure guideline | |
| TLV | threshold limit value | |
| TM | technical memorandum | |
| Tn | maximum noise exposure duration allowed | |
| TP | technical publication | |
| TWA | time-weighted average | |
| UDMH | unsymmetrical dimethylhydrazine | |
| UN | United Nations | |
| U.S. | United States | |
| UV | ultraviolet | |
| u’v’ | uniform-chromaticity scale (CIE 15.2, Colorimetric 2nd ed. Commission International d l’ Cellarage, Vienna Austria 1986) |
|
| V | Volt volume | |
| V/m | volt(s) per meter | |
| V1 | Volume 1 (in designating numbered requirements) | |
| V2 | Volume 2 (in designating numbered requirements) | |
| VESA | Video Electronics Standards Association | |
| VGE | venous gas emboli | |
| VOC | volatile organic compound | |
| Vu | urinary output volume | |
| W | watt | |
| WHC | waste and hygiene compartment | |
| WHO | World Health Organization | |
| W/m | watt(s) per meter | |
| W/m2 | watt(s) per meter squared | |
| xEVA | Exploration EVA | |
| y | year |
