ASTM E349-06(2014)
(Terminology)Standard Terminology Relating to Space Simulation
Standard Terminology Relating to Space Simulation
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Designation: E349 − 06 (Reapproved 2014)
Standard Terminology Relating to
Space Simulation
This standard is issued under the fixed designation E349; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
These definitions pertain to technologies related to space environment simulation. Where possible,
existing international and national standard definitions have been used.
ELECTROMAGNETIC RADIATION TERMS
considered in this vocabulary, only optical radiations, that is, electromag-
FUNDAMENTAL CONCEPTS
netic radiations (photons) of wavelengths lying between the region of
absorption, n—transformation of radiant energy to a different
transition to X-rays (1 nm) and the region of transition to radio waves (1
mm).
form of energy by interaction with matter.
reflection, n—return of radiation by a surface without change
complex radiation, n—radiation composed of a number of
offrequencyofthemonochromaticcomponentsofwhichthe
monochromatic radiations.
radiation is composed.
diffusion, n—change of the spatial distribution of a beam of
refraction, n—change in the direction of propagation of
radiation when it is deviated in many directions by a surface
radiation determined by change in the velocity of propaga-
or a medium.
tion in passing from one medium to another.
emission, n— release of radiant energy.
spectrum of radiation, n—(1) spatial display of a complex
infrared radiation, n—radiation for which the wavelengths of
radiation produced by separation of its monochromatic
the monochromatic components are greater than those for
components.
vissible radiation, and less than about 1 mm.
(2) composition of a complex radiation.
NOTE 1—The limits of the spectral range of infrared radiation are not
transmission, n—passage of radiation through a medium
welldefinedandmayvaryaccordingtotheuser.CommitteeE-2.1.2ofthe
without change of frequency of the monochromatic compo-
CIE distinguishes in the spectral range between 780 nm and 1 mm:
nents of which the radiation is composed.
IR-A 780 to 1400 nm
IR-B 1.4to3µm
ultraviolet radiation, n—radiation for which the wavelengths
IR-C 3µmto1mm
ofthemonochromaticcomponentsaresmallerthanthosefor
visible radiation and more than about 1 nm.
irradiation, n—application of radiation to an object.
NOTE3—Thelimitsofthespectralrangeofultravioletradiationarenot
monochromatic radiation, n—radiation characterized by a
welldefinedandmayvaryaccordingtotheuser.CommitteeE-2.1.2ofthe
single frequency. By extension, radiation of a very small
CIE distinguishes in the spectral range between 100 and 400 nm:
range of frequency or wavelength that can be described by
UV-A 315 to 400 nm
stating a single frequency or wavelength.
UV-B 280 to 315 nm
UV-C 100 to 280 nm
radiation, n—(1)emissionortransferofenergyintheformof
visible radiation, n—any radiation capable of causing a visual
electromagnetic waves or particles.
sensation.
(2) the electromagnetic waves or particles.
NOTE 4—The limits of the spectral range of visible radiation are not
NOTE 2—In general, nuclear radiations and radio waves are not
well defined and may vary according to the user. The lower limit is
generallytakenbetween380and400nmandtheupperlimitbetween760
−9
and 790 nm (1 nanometer, nm=10 m).
These definitions are under the jurisdiction ofASTM Committee E21 on Space
Simulation and Applications of Space Technology and are the direct responsibility
QUANTITIES
of Subcommittee E21.04 on Space Simulation Test Methods.
Current edition approved April 1, 2014. Published April 2014. Originally
absorptance, n—ratiooftheabsorbedradiantorluminousflux
approved in 1968. Last previous edition approved in 2006 as E349–06. DOI:
10.1520/E0349-06R14. to the incident flux. Symbol: α , α , α.
e v
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E349 − 06 (2014)
NOTE 5—In general, the value of the absorptance depends upon the
internal transmission density, n—logarithm to the base 10 of
modeofirradiation,thespectralcomposition,andthestateofpolarization
the reciprocal of the internal transmittance. Symbol: D,
i
of the incident radiation.
D =−log τ.
i 10 i
absorptivity of an absorbing material, n—internal absorp-
NOTE 10—See Note 12 of internal transmittance.
tance of a layer of the material such that the path of the
NOTE 11—In German, the symbol E is still in use and the natural
radiation is of unit length. logarithm is also used sometimes instead of the common logarithm; the
corresponding quantity is then called “natürliches Absorptionsmass.”
diffuse reflection, n—diffusion by reflection in which, on the (=In 1/τi).
macroscopic scale, there is no regular reflection.
internal transmittance of a homogeneous nondiffusing
plate, n—ratio of the radiant or luminous flux reaching the
diffuse transmission, n—transmission in which diffusion oc-
exit surface of the plate to the flux which leaves the entry
curs independently, on the macroscopic scale, of the laws of
surface.
refraction.
NOTE 12—For a given plate, the internal transmittance is a function of
directional emissivity of a thermal radiator, n—ratio of the
the path length of the radiation in the plate and thus of the angle of
thermalradianceoftheradiatorinagivendirectiontothatof
incidence. The fundamental concept is “spectral internal transmittance”
a full radiator at the same temperature. Symbol: ε(θ, φ); ε(θ,
τ(λ).
φ)= L (θ,φ)/L .
e,th e(ε=1)
irradiance at a point on a surface, n—quotient of the radiant
emissivity of a thermal radiator, n—ratio of the thermal flux incident on an element of the surface containing the
radiantexitanceoftheradiatortothatofafullradiatoratthe
point by the area of that element. Symbol: E , E; E =dΦ /
e e e
−2
same temperature. Symbol: ε, ε= M /Me(ε=1). dA; Unit: Watt per square metre, W·m .
e,th
NOTE 13—In ultraviolet radiation therapy and photobiology, this
NOTE 6—Formerly “pouvoir émissif” (fr.).
quantityiscalleddoserate(InternationalPhotobiologyCommittee,1954).
frequency, n—reciprocal of the period. Symbol; f, ν.
linear absorption coefficient of an absorbing medium,
NOTE 7—When the independent variable is time, the unit of frequency
n—quotient of the internal absorptance of a path element
−1
isthehertz.Symbol:Hz(1Hz=1s ).(Thisunitisalsocalled“cycleper
traversed by the radiation, by the length d of this element.
second,” c/s.)
−1
Symbol: a;−dΦ= aΦdl; Unit: m ; al=ln10D.
i
full radiator: blackbody (USA), Planckian radiator,
NOTE 14—The linear absorption coefficient is also the part of the linear
n—thermal radiator that absorbs completely all incident
attenuation coefficient that is due to absorption.
radiation, whatever the wavelength, the direction of
NOTE 15—In German practice, a linear absorption coefficient is also
incidence, or the polarization. This radiator has, for any defined for a homogeneous medium of finite thickness d, as the quotient
of the “Absorptions-mass” (logarithm of the reciprocal of the internal
wavelength, the maximum spectral concentration of radiant
transmittance), by the thickness d of the layer. According to whether the
exitance at a given temperature.
natural logarithm or the logarithm to the base 10 is used, one may
distinguish the “natürliche Absorptionskoeffizient” (m ) quotient of the
n
goniophotometer, n—photometer for measuring the direc-
“natürliche Absorptionsmass” (see Note 2, internal transmission den-
tional light distribution characteristics of sources, lighting
sity) by the thickness d of the layer traversed by the radiation, and the
fittings, media, and surfaces.
“dekadischeAbsorptionskoeffizient”(m)quotientoftheinternaltransmis-
sion density by the thickness d of the layer.
NOTE 8—A goniophotometer for measuring the spatial distribution of
NOTE 16—a/ρ, where ρ is the density of the medium, is called “mass
luminous intensity is also called a distribution photometer.
absorption coefficient.”
gray body, n—nonselective radiator whose spectral emissivity
linear attenuation (extinction) coefficient of an absorbing
is less than one.
and diffusing medium, for a collimated beam of radiation,
n—quotientoftherelativedecreaseinspectralconcentration
integrating (Ulbrecht) sphere, n—part of an integrating
ofradiantorluminousfluxofacollimatedbeamofradiation
photometer. A sphere that is coated internally with a white
during traversal with normal incidence of an infinitesimal
diffusing paint as nonselective as possible and is provided
layer of the medium by the thickness of that layer. Symbol:
with an associated equipment for making a photometric
−1
µ;−dΦ=µΦdl; Unit: m .
measurement at a point of the inner surface of the sphere.A
screen placed inside the sphere prevents the point under NOTE17—Thisconceptonlyappliesstrictlytoslightlydiffusingmedia.
NOTE18—µ/ρ,whereρisthedensityofthemedium,iscalledthe“mass
observation from receiving any radiation directly from the
attenuation coefficient.”
source.
mixed reflection, n—partly regular and partly diffuse reflec-
internal absorptance of a homogeneous nondiffusing plate,
tion.
n—ratio of the radiant or luminous flux absorbed between
the entry and exit surfaces of the plate to the flux which NOTE 19—The irradiance or illuminance received from a point source
after regular (diffuse) reflection varies inversely as the square of the
leaves the entry surface. Symbol: a , a +τ =1.
i i i
distance to the source (diffuser).
NOTE 9—For a given plate, the internal absorptance is a function of the
mixed transmission, n—partly regular and partly diffuse
path length of the radiation in the plate and thus of the angle of incidence.
The fundamental concept is spectral internal absorptance. a(λ). transmission.
i
E349 − 06 (2014)
NOTE 20—The irradiance or illuminance received from a point source,
radiant efficiency of a source of radiation, n—ratio of the
after regular (diffuse) transmission, varies inversely as the square of the
radiant flux emitted to the power consumed. Symbol: η , η.
e
distance to the source (diffuser).
NOTE 23—The radiant efficiency of a source in a limited region of the
nonselective radiator, n—thermal radiator whose spectral
spectrum may also be considered, that is, the ratio of the radiant flux
emissivity is independent of wavelength over the range
emitted in this spectral region to the power consumed.
considered.
radiant energy, n—energy emitted, transferred, or received as
opaque body, n—body that transmits practically no light. radiation. Symbol: Q , Q; Unit: joule J (1 J=W·s).
e
period, n—size of the minimum interval of the independent NOTE 24—In ultraviolet radiation therapy and photobiology, this
quantity is called “integral dose” (International Photobiology Committee,
variable after which the same characteristics of a periodic
1954).
phenomenon recur.
radiant exposure at a point on a surface, n—surface density
NOTE 21—In radiation, the independent variable is the time and the
of the energy received. Symbol: H , H; H =dQ /dA=∫ E
corresponding quantity is the periodic time: Symbol: T; Unit: second (s). e e e e
−2
dt; Unit: joule per square metre, J·m .
photometer, n—instrument used for measuring photometric
NOTE 25—Formerly “irradiation.”
quantities.
NOTE 26—Equivalent definition: Product of an irradiance and its
photometry, n—measurement of quantities referring to duration.
NOTE 27—In ultraviolet radiation therapy and photobiology, this
radiation, evaluated according to the visual effect which it
quantity is called dose (International Photobiology Committee, 1954).
produces, as based on certain conventions.
radiant exitance at a point on a surface, n—quotient of the
radiance (in a given direction, at a point on the surface of a
radiant flux leaving an element of the surface containing the
source or receptor or at a point in the path of a beam), ,
point,bytheareaofthatelement.Symbol: M , M; M =dΦ /
e e e
n—quotientoftheradiantfluxleaving,arrivingat,orpassing
−2
dA=∫ L cos θdω. Unit: Watt per square metre, W·m .
2 e
throughanelementofsurfaceatthispointandpropagatedin
directions defined by an elementary cone containing the
NOTE28—Thenameradiantemittancepreviouslygiventothisquantity
is abandoned because it has given rise to confusion. Thus, the term
given direction by the product of the solid angle of the cone
“emittance”hasbeenusedtodesignateeitherthefluxperunitarealeaving
and the area of the orthogonal projection of the element of
a surface (whatever the origin of the flux), the flux per unit area emitted
surface on a plane perpendicular to the given direction.
by a surface (flux originating in the surface), or, principally, in certain
Symbol: L , L; L =d Φ (dω dA cos Θ); Unit: Watt per
circles in the United States of America, a quantity without dimensions
e e
−1 −2
steradian and per square metre, W·sr m . similar to “emissivity,” but applicable only to a specimen.
NOTE 29—The expression “self-radiant exitance” (M ) indicates that
e,s
NOTE 22—Three special cases may be noted:
the flux considered does not include reflected or transmitted flux.
Case 1—At a point on the surface of a source, in a given direction,
The expression “thermal-radiant exitance” (M ) indicates that the flux
e,th
radiance is also the quotient of the radiant intensity in the given direction
considered is produced by thermal radiation. These same adjectives (self,
of an element of the surface at this point, by the area of the orthogonal
thermal) are equally applicable to other quantities, such as radiance, and
projection of this element on a plane perpendicular to this direction
so forth.
(radiant intensity per unit projected area). L =dI /(dA cos Θ).
e e
NOTE 30—In the case of a full radiator (blackbody), the radiance L is
e
Case 2—At a point on the surface of a receptor, in a given direction,
uniform in all directions. In consequence, when the solid angle is
radiance is also the quotient of the irradiance that is received at this point
measured in steradians, the radiant exitance has the numerical value
on a surface perpendicular to the given direction by the solid angle of the
M =πl .
e e
elementaryconecontainingthisdirectionandsurroundingthebeamwhich
produces this irradiance (perpendicular irradiance per unit solid angle). radiant flux: radiant power, n—poweremitted,transferred,or
L =dE /dω.
e e
received as radiation: Symbol: Φ , Φ, P; Φ =dQ /dt; Unit:
e e e
Case 3—On the path and in the direction of an element of a beam, in
Watt (W).
a nondiffusing, nonabsorbing medium, the radiance is also the quotient of
the radiant flux dΦ which transports the beam, by the geometric extent
e
radiant
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