Appendix C : Definitions

C.1 PURPOSE

This Appendix provides guidance, made available in the definitions listed below

A

Accessibility:

A design feature referring to the ability to see and maneuver within a spatial volume for the purpose of operating, cleaning, retrieving, or maintaining parts of a subsystem.

Activity Center:

A specific location uniquely configured for a human activity such as personal hygiene, body waste, food, sleep, trash, stowage, and exercise countermeasures.

Acute Field of View:

The region of visual angle in which acuity remains at least half its maximum. It is about 3 degrees in diameter.

Advisory:

A message that indicates a safe or normal configuration, indicates safe or normal operation of essential equipment, or imparts information for routine action purposes.

Affect:

Observable behavior that represents the expression of a subjectively experienced feeling state (mood, morale). Common examples of affect are sadness, fear, joy, and anger. The normal range of expressed affect varies considerably between different cultures and even within the same culture.

All Mission Systems:

Includes terrestrial ground control centers, other spacecraft on an occupied planetary body, other orbiting spacecraft, and other locations onboard a spacecraft.

Ambient:

The portion of the atmosphere, external to buildings, to which the general public has access.

Anthropogenic:

Induced or altered by the presence of humans.

Anthropometry:

The science of measuring the human body and its parts and functional capabilities. Includes lengths, circumferences, body mass, etc.

Astronaut:

An individual selected and trained to travel into space and to monitor, operate, and control parts of, or the whole space system to complete mission objectives.

Atmospheric Conditions:

The composition of the invisible gaseous substances within the vehicle/habitat (e.g., nitrogen, oxygen, argon, carbon dioxide) as well as the pressure, temperature, humidity, particulates and contaminants, etc.

Attenuation:

Diminution in force or intensity of sound.

Automatic:

Pertaining to a function, operation, process, or device that, under specified conditions, functions without intervention by the crew.

Automation:

(1) The implementation of a process by automatic means. (2) The theory, art, or technique of making a process more automatic. (3) The investigation, design, development, and application of methods of rendering processes automatic, self-moving, or self-controlling.

Autonomous:

The combination of elements that function together to produce the capability to meet a need that under specified conditions, functions without intervention by a human. Note: the elements of an autonomous systems include all hardware, software, equipment, facilities, personnel, processes, and procedures needed to function.

B

Beam Distribution:

Represents a ¼π hemisphere or ½π spherical characterization of the intensity of light at multiple angles from the source. Typically, illuminance measurements are captured at a fixed radius at multiple angles. Beam distribution is usually reported in relative percent intensity per angle with estimated lumen output, candela per angle, or illuminance per radius per angle.

Biomechanics:

The study of the principles and relationships involved with muscular activity.

Blur Edge Time (BET):

A measure of the amount of motion blur on an electronic display, especially liquid crystal display. This metric is defined in ICDM-DMS 1.0.

Body-Referenced Interfaces:

Interfaces that are controlled by the dynamic movements of the human body such as virtual environments.

Broad Spectrum:

A spectrum or list of a sufficient number of target compounds anticipated from all expected off-nominal events.

C

Capability:

Having attributes (such as physical or cognitive) required for performance.

Catastrophic:

(1) A hazard that could result in a mishap causing fatal injury to personnel and/or loss of one or more major elements of the flight vehicle or ground facility. (2) A condition that may cause death or permanently disabling injury, major system or facility destruction on the ground, or loss of crew, major systems, or vehicle during the mission (NPR 8715.3, NASA General Safety Program Requirements).

Caution:

Notification of an event that needs attention but not immediate action.

Chromaticity:

Describes the color of an object, whether that be a surface material or light source. Chromaticity cannot be estimated without the usage of a spectrophotometer to measure the spectral power distribution of a light emitting source spectrum of a material. It is a calculated metric where the format of the units can be different depending on which standard is used.

Cleaning:

Physical removal of dust, microbes, marks, or other impurities, from the habitat/suit by washing, wiping, or disinfecting.

Clear Viewing Aperture:

The area of a window that is not covered by the window assembly frame or other structure that would block incident light rays.

Cognitive:

Pertaining to the mental processes of perception, learning, memory, comprehension, judgment, and reasoning.

Color Discrimination:

The ability to distinguish between pairs of colors that span the space of colors under standard viewing conditions. The International Commission on Illumination (CIE) has defined ∆E units that specify the perceptual distance between colors.

Color Fidelity:

Describes the ability of a light source to render the appearance of colored materials accurately. The ideal case for comparison is how the Sun renders the color of materials. Color fidelity cannot be estimated without the usage of a spectral radiance or spectral irradiance meter to measure the spectral power distribution of a light emitting source. It is a calculated metric where the format of the units can be different depending on which standard is used.

Communication Systems:

Communication systems include information provided to and from the crew by way of voice, text, video, and/or telemetry.

Consistency:

The level of similarity in visual style and operation within and among different crew interface designs. Systems that have been designed with consistency in mind require less training and feel familiar. The number of different codes and ways of operating are minimized, which reduces cognitive workload and operational errors. Cross-system consistency is achieved by incorporating threads of similarity in key components across designs. Higher levels of consistency across vehicles will decrease the risk of errors and result in a safer spacecraft environment.

Contamination:

The act of rendering unfit for use by the introduction or deposition of unwholesome or undesirable, usually foreign, elements.

Contamination control:

The practice of controlling the introduction and removal of unwanted materials that could impede the proper function of a system or component (e.g., clean rooms, visual inspection, off-gassing minimization, flushing of fluid lines). While contamination control measures often serve to reduce the risk of forward contamination for planetary production, their ultimate goal is to improve system function.

Contingency:

An off-nominal situation that is identified in the hazard analysis process and has a preplanned response to mitigate the risks to crew and/or vehicle.

Continuous Noise:

Noise that exists in a steady state for durations of more than 8 hours in a 24hour period. Typical continuous sources of noise include environmental control equipment and avionics equipment (e.g., fans, pumps, ventilation systems).

Countermeasures:

A means to offset undesirable physical, physiological, and psychological effects of spaceflight on humans.

Corrective Maintenance:

Corrective maintenance involves the repair or replacement of equipment that has stopped working or is damaged. Corrective maintenance activities include identifying, isolating, and rectifying a fault so that the failed equipment, machine, or system can be restored to an operational condition.

Crew:

Team of two or more crewmembers assigned to a mission that have been trained to monitor, operate, and control parts of, or the whole space system.

Crewmember:

An individual member of a crew.

Crew Station:

A location in a vehicle or habitat where crewmembers perform an activity.

Critical:

A condition that may cause severe injury, occupational illness, or major property damage to facilities, systems, or flight hardware (NPR 8715.3); also of essential importance, vital, or indispensable as in “critical” design parameters. Frequently used in this NASA Technical Standard to cover both “critical” (as defined above) and “catastrophic.”

D

Decompression:

The act or process of reduction of pressure, as occurs when releasing compressed air from a vehicle or habitat to the vacuum of space.

Decompression Sickness:

A sickness induced by too rapid a decrease in atmospheric pressure sufficient to cause bubbles to form from gases (normally nitrogen [N2]) dissolved in blood and other body tissues.

Deconditioned Crew (deconditioning):

Decreased functionality of physiological systems, e.g., musculoskeletal, cardiovascular, vestibular, and nervous systems, related to adaptation to reduced gravity.

Dedicated Equipment Work Volume:

Volume that cannot have multi-use but must be associated full-time with the equipment (such as interior volume of glove box, etc).

Depressurization:

Reducing the pressure of air or gas within a suit, chamber, or vehicle.

Dexterity:

The skill in performing tasks, especially with the hands whether suited or unsuited.

Diffusion/Diffusor:

A material designed to scatter or redirect light that passes through it. Alternatively, a rough surface that light impacts and scatters multiple directions from.

Diffuse Reflectance:

The fraction of incident electromagnetic radiation such as light or other type of wave within a specified wavelength band that is reflected from a surface uniformly in all directions, regardless of the angle of incidence of the incident waves or rays. A truly diffusely (Lambertian) reflective surface has the same luminance (appears to have the same brightness) from all viewpoints, regardless of the direction of the source relative to the surface. This type of reflection is associated with matte or “flat” surface treatments on objects and is contrasted with specular reflectance. Most surfaces exhibit a combination of specular and diffuse reflectance.

Display:

Anything that provides visual, auditory, and/or haptic information to crewmembers, e.g., label, placard, tone, or display device. The term “display” includes text-based user interfaces, as well as Graphical User Interfaces (GUIs).

Display Device:

The hardware used to present visual, aural, and tactile information to the crew or ground operations personnel. Display devices include computer monitors and Personal Digital Assistants (PDAs).

Doors:

A moveable physical barrier that acts to provide physical separation between areas or to provide privacy. Examples of doors include enclosures for an unpressurized payload bay, or a privacy divider for a personal crew quarter or hygiene area.

Doorway:

The opening, the area of the vehicle, that houses the doors.

Drag Through:

Any item that inhibits hatchway function by interfering with the clear passage through the hatchways including, but not limited to, cargo, cables, and wires.

E

ECLS System:

Environmental Control and Life Support (ECLS) Systems designed to distribute air and remove contaminants. The elements include all hardware, software, equipment, facilities, personnel, processes, and procedures needed for this purpose.

Effective Masked Threshold:

The level of auditory danger signal just audible over the ambient noise, taking account of the acoustic parameters of both the ambient noise in the signal reception area and the listening deficiencies (hearing protection, hearing loss, and other masking effects). The method for calculating the masked threshold is given in ISO 7731:2003(E) Annex B.

Emergency:

Time-critical event that requires immediate action and procedures to prevent loss of crew/loss of mission (LOC/LOM).

Emergency Equipment:

A set of components (hardware and/or software) used to mitigate or control hazards, after occurrence, which present an immediate threat to the crew or crewed spacecraft. Examples include fire suppression systems and extinguishers, emergency breathing devices, and crew escape systems (NPR 8705.2).

Emergency Only Controls:

Controls that are only used during emergencies, e.g., eject, abort.

Environmental Conditions:

Nominal or off-nominal conditions within the vehicle that includes air, water, contamination, acceleration, acoustics, vibration, radiation, temperature, atmosphere, pressure, humidity, ppO2, ppCO2, etc.

Equipment:

Items such as tools used to accomplish a task or activity. Equipment is a type of hardware, and therefore this term is sometimes used interchangeably with hardware.

EVA Spacesuit System:

Any spacesuit system designed to allow astronauts to perform tasks outside of a spacecraft or habitat. Performance of spaceflight EVA consists of placing a human in a micro-environment that has to provide all the life support, nutrition, hydration, waste, and consumables management function of an actual space vehicle, while allowing crewmembers to perform mission tasks. EVA spacesuits are designed to be used for durations of less than a day due to potential human and suit system constraints. This includes all suited phases (e.g., prebreathe, leak checks, airlock depress, repress).

Exercise:

Any bodily activity that enhances or maintains physical fitness and overall health and wellness. Exercise is used to maintain or minimize loss of crew muscle mass and cardiovascular fitness, to maintain muscle mass and strength/endurance, for recovery from strenuous tasks and confined postures, to rehabilitate minor muscle injuries, and to maintain bone mass. Exercise also has behavioral health benefits.

Extraterrestrial:

To be from outside Earth or its atmosphere (moon, planetary, asteroid, etc.).

Extravehicular Activity:

Operations performed by suited crew outside the pressurized environment of a flight vehicle or habitat (during spaceflight or on a destination surface). Includes contingency operations performed inside unpressurized vehicles or habitats.

F

Fatigue:

Weariness, exhaustion, or decreased attention related to labor, exertion, or stress. May also result from lack of sleep, circadian shifts, depression, boredom, or disease. May result in decreased ability to perform mental or physical tasks.

Fault:

An undesired system state and/or the immediate cause of failure (e.g., maladjustment, misalignment, defect, or other). The definition of the term “fault” envelopes the word “failure,” since faults include other undesired events such as software anomalies and operational anomalies (Source – MIL-STD-721C). Faults at a lower level could lead to failures at the higher subsystem or system level.

Field of Regard:

The solid angle that can be seen by an observer with eye and head movements.

Field of View:

The solid angle that can be seen at one time by the stationary eye. It is about 150 degrees horizontally by 125 degrees vertically. When the two eyes operate together, the horizontal extent enlarges to about 190 degrees.

Field of View for Windows:

All points through a window that can be viewed directly by at least one eye, given the combination of achievable eye, head, and body movement. The field of view is restricted by obstructions imposed by the facial structure around the eye and/or placed in front of the eye such as the crewmember’s helmet if worn, mullions, structure, and/or other equipment. Achievable movement varies for different flight phases and operational tasks and is dependent on any constraints to movement that are extant such as being suited, seated, and/or restrained, and any g-loads present. With respect to line-of-sight phenomena such as contamination deposition and pluming, any point outboard of the window that is above the plane of the outer surface of the outermost pane of the window port is considered within the field of view of the window.

Food System:

The interconnected network of activities and resources involved in providing nutrients for human nourishment and sustaining life. A food system includes the production, aggregation, processing, packaging, distribution, consumption, and disposal of food. In spaceflight to date, the food system can be defined as all foods, beverages, vitamins, supplements, and associated packaging and utensils, as well as support for preparation such as water dispensers and food warmers.

G

Gaussian Edge Time (GET):

A measure of the amount of motion blur on an electronic display, especially a liquid crystal display. This metric is defined in ICDM-DMS 1.0.

Glare:

A property that describes various problems in human perception of light and the interaction of light with surfaces and materials within an operational environment. Distracting glare is an “annoyance” where, because of reflection and refraction, it creates visual artifacts making it harder to see and resolve an object. Discomforting glare is caused by bright, directed, and reflected light that makes it hard to look at the object because of the brightness level. Disabling glare causes objects to appear to have lower contrast because of scatter inside the eye. Blinding glare is caused by a direct or indirect light source and is so bright that the observer cannot see or is visually compromised.

Ground Support Personnel:

Human team of one or more members supporting a mission from the ground during preflight, in-flight, surface, and post flight operations.

Ground Support Operations:

Operations and tasks performed by ground personnel utilizing spaceflight systems, hardware, and equipment at times other than during spaceflight such as before launches and after landings.

H

Habitability:

The state of being fit for occupation or dwelling. Meeting occupant needs of health, safety, performance, and satisfaction.

Habitat:

A type of spacecraft, not normally mobile, that has the conditions necessary to sustain the life of the crew and to allow the crew to perform their functions in an efficient manner.

Habitable Atmosphere:

The composition of the breathable environment within the Habitable Volume.

Habitable Volume:

The measure of space livable and functionally usable to crew within a pressurized volume after accounting for all installed hardware and systems.

Hardware:

Individual components of equipment, including but not limited to, fasteners, panels, plumbing, switches, switch guards, and wiring. This term is sometimes used interchangeably with equipment.

Hatch:

An operable, sealable cover that separates two adjoining environments and allows physical passage of people and/or material from one environment to the other. Hatches can maintain pressurized environments. Hatches may function as ingress/egress points for crew prior to launch, postlanding, and for EVAs, and may also serve as connections between modules in a spacecraft.

Hatch Cover:

A protective encasement that protects the hatch from unwanted exposure.

Hatchway:

The opening, the area of the vehicle that houses the hatch.

Heat Storage:

Related to the human body as the balance of heat gains and heat losses; heat in minus heat out.

Human Error:

Either an action that is not intended or desired by the person or a failure on the part of the person to perform a prescribed action within specified limits of accuracy, sequence, or time that does not produce the expected result and has led or has the potential to lead to an unwanted consequence.

Human Factors:

The scientific discipline concerned with the understanding of interactions among humans and other elements of a system and the profession that applies theory, principles, data, and other methods to design to optimize human well-being and overall system performance.

Human-Rating Certification:

Human-Rating Certification is the documented authorization granted by the NASA Administrator that allows the program manager to operate the space system within its prescribed parameters for its defined reference missions. Human-Rating Certification is obtained prior to the first crewed flight (for flight vehicles) or operational use (for other systems).

I

Impulse Noise:

A burst of noise, which exists for 1 second or less, that is at least 10 dB above the background noise.

Information Management:

The act of performing functions with electronic data, including data input, organization, internal processing, storage, distribution, saving, and disposal of information about the system. Information management functions are typically performed by crew and ground personnel using displays on display devices.

Interpretable:

Capable of being explained or told the meaning of; translated into intelligible or familiar language or terms.

Ionizing Radiation:

Any combination of electromagnetic radiation or particles that deposits enough kinetic energy to create ionization events when interacting with matter. Ionizing radiation energy absorption damages biological systems that may lead to clinical illness or contribute to human health and performance decrements.

In-Mission:

Covers all phases of the mission, from launch, through landing on a planetary body and all surface activities entailed, up to landing back to earth and post-landing activities.

Intravehicular Activity:

Operations performed by crew within the pressurized environment of a spacecraft during a mission.

Intermittent Noise:

Noise that is generated for operational durations of 8 hours or less in a 24hour period. Typical intermittent sources of noise are waste control system components (pumps, fans, separators, valves), exercise equipment (treadmill, cycle ergometer), galley fans, personal hygiene station components (pumps, fans, valves), and pressure regulators.

L

Lambertian Reflectance:

An ‘ideal’ reflectance property where incident light is reflected and scattered with equal energy at all angles from the surface (2π steradians). The appearance of such a material is described as diffuse or matte in finish.

LEA/IVA Spacesuit System:

Any spacesuit system designed for use during launch, entry, and abort phases of spaceflight, primarily to protect against toxic exposure, ebullism, hypoxia, and decompression sickness in the event of an unplanned cabin depressurization or toxic release into the cabin. It may also be worn during other dynamic phases of flight such as rendezvous and docking during which there is an increased risk of cabin depressurization due to cabin leaks. The duration for which LEA spacesuits are designed to operate will depend on mission scenarios and may range from a few hours to several days per use.

Linear Acceleration:

The rate of change of velocity of a mass, the direction of which is kept constant.

Local Vertical:

Achieved by a consistent arrangement of vertical cues within a given visual field to provide a definable demarcation at the crew station boundary within the visual field. A consistent local vertical within modules is highly desirable.

M

Maintainability:

Maintainability is a quality that reflects the speed and ease with which an operational system can be retained in, or restored to, a specified condition (Department of Defense (DoD), 1997). (Reference: Department of Defense. (1997). Designing and Developing Maintainable Products and Systems (Report No. MIL-HDBK-470A)).

Maintenance:

All actions necessary for retaining material in (or restoring it to) a serviceable condition. Maintenance includes servicing, repair, modification, modernization, overhaul, inspection, condition determination, corrosion control, and initial provisioning of support items (MIL-HDBK-1908B, Definitions of Human Factors Terms).

Mission:

A major activity required to accomplish an Agency goal or to effectively pursue a scientific, technological, or engineering opportunity directly related to an Agency goal. Mission needs are independent of any particular system or technological solution.

Mission Duration:

The total time the crew is away from the surface of Earth, measured from launch of the Earth launch vehicle to landing or splashdown of the Earth return spacecraft. If the crew transfers between multiple spacecraft during this mission, except where indicated otherwise in these technical requirements, every spacecraft the crew inhabits is subject to the requirements identified for the mission duration.

Mobility:

The ability to move or be moved freely and easily whether suited or unsuited.

Monitoring:

Includes checking for quality or fidelity; testing to determine if a signal comes within limits; watching and observing for a specific signal or purpose; keeping track of, regulating, or controlling.

N

Net Habitable Volume (NHV):

The functional volume left available on a spacecraft after accounting for the loss of volume caused by deployed equipment, stowage, trash, and any other items that decrease the functional volume.

Noise:

Sound in the auditory range (15 Hz to 20,000 Hz) that is hazardous, undesired, and/or inappropriate to the intended use of the space. In this NASA Technical Standard, the word “noise” is used interchangeably with “sound” and is not intended to convey any relative or absolute degree of hazard or other acoustical characteristic.

Nominal:

Within expected, acceptable operational limits or in accordance with planned operational concepts; normal, satisfactory (aerospace usage).

Non-Habitable Volume:

The portion of Pressurized Volume taken up by fixed outfitting, equipment, stowage, and dedicated equipment work volumes.

Non-Ionizing Radiation:

Includes three categories of electromagnetic radiation: RF radiation, lasers, and incoherent electromagnetic radiation.

O

Off-Nominal:

Outside of expected, acceptable operational limits or not in accordance with planned operational concepts; anomalous, unsatisfactory (aerospace usage).

Operation:

An activity, mission, or maneuver, including its planning and execution.

P

Perception:

The process of acquiring knowledge about environmental objects and events by extracting and processing the information received through the senses.

Personal Protective Equipment (PPE):

Equipment that is worn to minimize exposure to a variety of hazards. Examples of PPE include such items as gloves, foot and eye protection, hearing protection devices (earplugs, muffs), hard hats, respirators, and full body suits.

Planetary Protection:

The practices of reducing biological forward contamination that could affect astrobiological investigations on other celestial bodies and backward contamination that might have adverse impacts on Earth’s biosphere.

Potable Water:

Water that is suitable, safe, or prepared for drinking.

Pressurized Volume:

The total volume within a pressure shell.

Preventive Maintenance:

Preventive maintenance is maintenance that is regularly performed on a system to lessen the likelihood of it failing. Preventive maintenance can be schedule- or timebased, meaning the maintenance is performed routinely on a fixed schedule, or condition-based, meaning the maintenance is performed, on contingency, depending upon the condition of the equipment or system.

Privacy:

Having an acceptable level of control over the extent of sharing oneself (physically, behaviorally, or intellectually) with others. Acceptable level is dependent upon an individual’s background and training.

Program:

A strategic investment by a Mission Directorate or Mission Support Office that has a defined architecture and/or technical approach, requirements, funding level, and a management structure that initiates and directs one or more projects. A program defines a strategic direction that the Agency has identified as critical.

Project:

A spaceflight project is a specific investment identified in a Program Plan having defined requirements, a life-cycle cost, a beginning, and an end. A project also has a management structure and may have interfaces to other projects, agencies, and international partners.

Psychomotor:

Of or relating to muscular action believed to ensue from conscious mental activity.

R

Reflectance:

The fraction or percentage of incident electromagnetic radiation such as light or other type of wave at a specified wavelength that is reflected from a surface. (See also “specular reflectance” and “diffuse reflectance.”)

Reflectance/Reflector (Light):

The property of a material to reflect and scatter light. Reflectance of surface materials is an important lighting system property as it impacts how humans and cameras observe the environment and the efficiency of lighting systems to illuminate surfaces to sufficient levels to create the desired luminous contrast. Reflectance can be considered part of the architecture and can be used as a tool in the form of a reflector.

Regolith:

Unconsolidated residual or transported material that overlies the solid rock on the Earth, Moon, or a planet.

Risk:

Outcomes of programmatic decisions, proposed implementation, pursuit of standards/requirements deviations, and/or waivers that do not change the overall likelihood and consequence of the health, medical, and human performance risks baselined by Chief Health and Medical Officer (CHMO) for a particular program or project. In the context of mission execution, risk is operationally defined as a set of Triplets:

1. The scenario(s) leading to degraded performance with respect to one or more performance measures (e.g., scenarios leading to injury, fatality, destruction of key assets; scenarios leading to exceedance of mass limits; scenarios leading to cost overruns; scenarios leading to schedule slippage).
2. The likelihood(s) (qualitative or quantitative) of those scenarios.
3. The consequence(s) (qualitative or quantitative severity of the performance degradation) that would result if those scenarios were to occur.
4. Uncertainties are included in the evaluation of likelihoods and consequences.

Rotational Acceleration:

The rate of change of angular velocity.

S

Safe:

Freedom from those conditions that can cause death, injury, occupational illness, damage to or loss of equipment or property, or damage to the environment.

Scheduling:

Arranging, controlling, and optimizing work and workloads to facilitate crew timeline of activities.

Sensory:

The information-gathering abilities of humans to see, hear, touch, smell, and taste. Includes temperature, pain, kinesthesia, and equilibrium.

Shielding:

A barrier between a source of radiation and a potential recipient (e.g., the astronaut); shielding can be solid, liquid, or gas which absorbs the energy of the radiation.

Situational Awareness:

Comprehension of information about an environment, evaluating the current situation with respect to goals, and projecting the evolution of the situation into the future.

Solid Angle:

The volumetric angular section from a unit sphere, analogous to the trigonometric concept of the unit circle. Units are in steradians (sr). An entire sphere equals 4π sr.

Sound Quality:

Those features of a sound that contribute to the subjective impression made on a listener, with reference to the suitability of the sound for a particular set of design goals. It is meant particularly to account for aspects of communication systems that are not quantifiable by intelligibility measurements.

Space System:

The collection of all space-based and ground-based systems (encompassing hardware and software) used to conduct space missions or support activity in space, including, but not limited to, the crewed space system, space-based communication and navigation systems, launch systems, and mission/launch control. Also referred to as “system” in the technical requirements.

Spacecraft:

A habitable vehicle or device, including, but not limited to, orbiters, capsules, modules, landers, transfer vehicles, surface transport vehicles, EVA suits, and habitats designed for travel or operation outside Earth’s atmosphere.

Spaceflight:

A process that begins when the crew has boarded the spacecraft on Earth and the hatch is closed and terminates when the spacecraft has returned to Earth, and all of the crew have egressed the spacecraft and are in the care of ground personnel. In the event of a launch abort, spaceflight continues until all crew have been returned to the care of ground personnel.

Spatial Contrast Sensitivity:

Defined by the inverse of the smallest contrast of a spatial sinusoidal luminance grating that can be detected, at each spatial frequency, under standard viewing conditions. Peak contrast sensitivity is about 500, and the highest frequency visible is about 60 cycles/deg.

Spectral Irradiance:

Radiometric unit, analogous to illuminance, representing the radiant flux per surface area per wavelength. Units are in watts/meter^2/nanometer (W/m^2/nm).

Spectral Power Distribution:

Waveform representing energy (absolute or relative) emitted per a range of wavelengths. All light sources have a unique spectral power distribution.

Spectral Radiance:

Radiometric unit, analogous to luminance, representing the radiant flux per surface area per wavelength. Units are in watts/steradian/meter^2/nanometer (W/sr/m^3/nm).

Specular Reflectance:

The perfect, mirror-like reflection of an incident wave or ray such as light from a surface, in which the wave or ray from a single incoming direction is reflected into a single outgoing direction as described by Snell’s Law (θi (theta i) = θr (theta r)). Diffuse reflection, on the other hand, refers to light that is reflected in a broad range of directions. (See “diffuse reflectance.”) The most familiar example of the distinction between specular and diffuse reflection in the case of light waves would be glossy and matte paints or photo prints. While both finishes exhibit a combination of specular and diffuse reflectance, glossy paints and photo prints have a greater proportion of specular reflectance, and matte paints and photo prints have a greater proportion of diffuse reflectance. Anti-reflection coatings reduce the amount of light that is reflected from a given surface. Reflectance for an uncoated glass surface is ~4%, which yields ~8% for the two surfaces of a single “pane.” Anti-reflective coatings can reduce the total reflectance to ~2% or less.

Standard:

The definition of a “standard” is described as follows:
a. The term “standard,” or “technical standard,” includes all of the following:
(1) Common and repeated use of rules, conditions, guidelines or characteristics for products or related processes and production methods, and related management systems practices;
(2) The definition of terms; classification of components; delineation of procedures; specification of dimensions, materials, performance, designs, or operations; measurement of quality and quantity in describing materials, processes, products, systems, services or practices; test methods and sampling procedures; formats for information and communication exchange; or descriptions of fit and measurements of size or strength; and,
(3) Terminology, symbols, packaging, marking or labeling requirements as they apply to a product, process, or production method.
b. “Performance standard” is a standard that states requirements in terms of required results, but without stating the methods for achieving required results; may define the functional requirements for the item, operational requirements, and/or interface and interchangeability characteristics; also may be viewed in juxtaposition to a prescriptive standard.
c. “Non-government standard” is a standard as defined above that is in the form of a standardization document developed by a private sector association, organization, or technical society that plans, develops, establishes, or coordinates standards, specifications, handbooks, or related documents.

Standardize:

To make uniform.

Stereoscopic Depth Perception:

The ability to distinguish objects at different depths as a result of their different positions (disparities) in the two eyes.

Stowage/Storage:

The action or method of storing something for future use.

Suited:

Wearing clothing that is designed to protect the crewmember from differences in environment such as pressure, atmosphere, acceleration, or temperature. “Suited” can refer to both pressurized and unpressurized pressure suits.

Surface:

The outside part or uppermost layer of an object. This can include the inner surfaces of items, like the suit.

Sustained Accelerations:

Events, linear or rotational, with a duration of greater than 0.5 seconds.

System:

The combination of elements that function together to produce the capability to meet a need. The elements include all hardware, software, equipment, facilities, personnel, processes, and procedures needed for this purpose. (Source: NPR 7120.7, NASA Information Technology and Institutional Infrastructure Program and Project Management Requirements.)

T

Tactility:

The responsiveness to stimulation of the sense of touch whether suited or unsuited.

Tailoring:

The process by which requirements are derived for a specific system. This process involves two steps:
a. Selecting applicable requirements – Not all requirements within a Standard may apply to all systems. Systems are defined by parameters such as the number of crewmembers, mission duration and operations, gravity environment, and EVA activities. Some requirements apply to only some parameters. For example, mission duration may influence the volume dedicated for certain crew functions such as crew sleep and hygiene. Or the operational gravity environment may influence which requirements are applicable such as a lunar surface transport vehicle would not have met the microgravity requirements.
b. Creating requirements that can be verified – Some requirements use general terms such as “effective.” When tailoring for a specific system, these terms are then defined with values that are objective and measurable. The tailored requirement has to comply with the intent of the general requirement. For example, analysis of a specific system may show that a critical task has to be performed in less than 20 seconds. In the tailoring process, the word “effective” would be replaced by words that limit critical task performance times to 20 seconds.

Task:

A specific type, piece, or amount of work; a subset of an activity or job that is called out in a procedure.

Team:

A collection of individuals who are assigned to support and achieve a particular mission. This can encompass both the spaceflight crew and ground support for a particular mission.

Temporal Contrast Sensitivity:

A measure of the sensitivity to contrast (i.e., modulation depth) as a function of time. This can be achieved by presenting stimuli that vary sinusoidally over time; it is like presenting a grating pattern in time instead of space.

Thermesthesiometer:

A device designed to measure the depth of burn injuries.

Time-to-Effect:

Time between when a hazard or failure occurs and the effects are manifested (NASA, 2021; Kennedy Space Center Office of Safety and Mission Assurance, 2015).

Time-to-Effect Margin:

Time between when a hazard or failure occurs and the effects are manifested (NASA, 2021; Kennedy Space Center Office of Safety and Mission Assurance, 2015).

Toxic Exposure:

Contact with agents or substances that can affect the health and performance of the astronauts.

Training:

The act of undertaking a course of instruction in skills, knowledge or fitness that relate to specific competencies needed for spaceflight missions. Training has specific goals of improving an individual or team’s capability, capacity, and performance.

Transient Accelerations:

Events, linear or rotational, with a duration of less than or equal to 0.5 seconds.

Transilluminated:

Luminous indicator, label, or button, that is made luminous by placing a colored or translucent material in front of light source or lamp.

Transmittance:

The fraction or percentage of incident electromagnetic radiation such as light at a specified wavelength that passes through a medium.

U

Uniformity:

A property that is typically applied for surface illumination but can also be applied to the light emitting face of light sources. Uniformity is usually defined in the form of ratios such as maximum/minimum, and average/minimum with a defined sampling grid size. Uniformity is an important safety and usability metric to minimize human error due to uneven illumination. Uniformity is achieved through a combination of beam distribution design, lamp placement, and understanding of reflective surfaces for the operational area.

Unit of Equipment:

A unit of equipment is an assemblage of items that may include modules, components, and parts that are packaged together into a single hardware package (FAA HFSTD-001-B, 2016).

Unsuited:

Wearing the type of clothing that is ordinarily worn in the interior of a spacecraft, especially a habitat, and as might be worn on Earth.

V

Vehicle/Habitat:

A mobile or static spacecraft with a pressurized atmosphere appropriate for sustained, unsuited survival and crew operations. The vehicle is a container, generally composed of multiple elements, used to transport persons or things to/from a location outside of Earth’s atmosphere. (See “habitat” as defined above.) Includes all hardware and equipment within or attached to the pressurized environment.

Validation:

Proof that the product accomplishes the intended purpose. May be determined by a combination of test, analysis, and demonstration.

Visual Accommodation:

Defined by the change in optical power of the eye to bring objects at different distances into focus. In young observers, average accommodative power is about 15 diopters but declines to 0 by the age of 60.

Visual Acuity:

Defined by the smallest letters that can be identified under standard viewing conditions. An average acuity for young adults is about -0.1 logMAR but declines with age.

Voluntary Consensus Standards:

A type of standard developed or adopted by voluntary consensus standards bodies, through the use of a voluntary consensus standards development process defined in the definition of voluntary consensus standards bodies in this section. These bodies often have intellectual property rights (IPR) policies that include provisions requiring that owners of relevant patented technology incorporated into a standard make that intellectual property available to implementers of the standard on a non-discriminatory and royalty-free or reasonable royalty terms (and to bind subsequent owners of standards essential patents to the same terms). A standard that includes patented technology needs to be governed by such policies, which should be easily accessible, set out clear rules governing the disclosure and licensing of the relevant intellectual property, and take into account the interests of all stakeholders, including the IPR holders and those seeking to implement the standard. (Source: OMB Circular No. A-119.)

Voluntary Consensus Standards Body:

A type of association, organization, or technical society that plans, develops, establishes, or coordinates voluntary consensus standards using a voluntary consensus standards development process that includes the following attributes or elements:

1. Openness: The procedures or processes used are open to interested parties. Such parties are provided meaningful opportunities to participate in standards development on a nondiscriminatory basis. The procedures or processes for participating in standards development and for developing the standard are transparent.
2. Balance: The standards development process should be balanced. Specifically, there should be meaningful involvement from a broad range of parties, with no single interest dominating the decision making.
3. Due process: Due process shall include documented and publicly available policies and procedures, adequate notice of meetings and standards development, sufficient time to review drafts and prepare views and objections, access to views and objections of other participants, and a fair and impartial process for resolving conflicting views.
4. Appeals process: An appeals process shall be available for the impartial handling of procedural appeals.
5. Consensus: Consensus is defined as general agreement, but not necessarily unanimity. During the development of consensus, comments and objections are considered using fair, impartial, open, and transparent processes. (Source: OMB Circular No. A-119).

W

Waiver:

A written authorization allowing relief from a requirement.

Warning:

Notification of an event that requires immediate action.

Wavefront:

The surface joining all adjacent points on a wave that have the same phase, particularly light that travels as an electromagnetic wave.

Wavefront Error:

The total optical path difference induced into a wavefront with respect to the wavelength of light, usually referenced to a helium-neon (HeNe) laser wavelength of 632.8 nm. For planar waves, wavefront error occurs when the wavefront is distorted such that an individual wavefront is no longer in phase. This occurs when different parts of the wavefront travel different optical path lengths. In an ideal window, a planar wave will pass through it such that the optical path length at each point on the window is the same, and the wavefront retains the same phase. Wavefront error is aperture dependent. In an imperfect window, the wavefront is distorted, i.e., the phase is not maintained. Wavefront error can be distorted by surface imperfections (the window is not “flat”) or by material inhomogeneities (the index of refraction varies across the window).

Window:

A non-electronic means for direct through-the-hull viewing using a transparent material; the same as and used interchangeably with window port and window assembly.

Window Assembly:

The same as and used interchangeably with window and window port.

Window Cover:

An internal non-pressure-containing, transparent sheet or pane, usually of a different material than the windowpanes such as acrylic or other material intended to protect the underlying window pressure and/or protective pane(s) from incidental crew contact. A window cover is normally not an integral part of the window assembly and has the characteristics as specified in section 8.6, Windows, of the HIDH. Non-integral protective panes can be considered temporary, i.e., replaceable after some period of time, after which their optical quality has degraded below the category level for which they were designed. External window protection devices are referred to as shutters.

Window Filter:

An internal, non-pressure-containing, transparent sheet or pane, usually of a different material than the windowpanes such as polycarbonate or other material intended to filter non-ionizing radiation hazards to safe levels. A window filter is not considered an integral part of the window assembly. Window filters are easily removed and reinstalled without the use of tools by one crewmember. A window filter may also serve as a window cover.

Window Port:

The finished assembly, including the frame structure (includes all gaskets, bolts, spacers, and other such parts) and all windowpanes that would normally be used at a specific location with any protective panes, permanent coatings, plastic films, or laminates applied or in place; the same as and used interchangeably with window and window assembly.

Window Shade:

Usually, an internal, non-pressure-containing, opaque sheet intended to block external light from entering the interior of a crew cabin. A window shade may or may not be an integral part of the window assembly. Non-integral window shades are easily removed and reinstalled without the use of tools by one crewmember. Window shades that are an integral part of the window assembly can also act as window shutters.

Window Shutter:

An internally and remotely operable external cover intended to prevent natural and induced environmental degradation, e.g., contamination, erosion, and impacts, of the outboard-most windowpane with open and close indicators that are readable from the remote operating location. Window shutters can be operated through their full range of motion in less than 10 seconds and can serve as window shades.

Workload:

The amount of work expected in a unit of time. Physical workload refers to the number of individual physical activities that are conducted simultaneously or in close succession. Similarly, mental or cognitive workload refers to the number of mental operations or activities that are conducted simultaneously or in close succession.

Worksite:

Area defined as the operational space for a task to be performed. This can be as small as the area immediately in front of a work stand and can also encompass a large operational area that has the same task performance constraints