ASTM E491-73(2020)
(Practice)Standard Practice for Solar Simulation for Thermal Balance Testing of Spacecraft
Standard Practice for Solar Simulation for Thermal Balance Testing of Spacecraft
ABSTRACT
This practice provides guidance for making adequate thermal balance tests of spacecraft and components where solar simulation has been determined to be the applicable method. Careful adherence to this practice should ensure the adequate simulation of the radiation environment of space for thermal tests of space vehicles. This practice also provides the proper test environment for systems-integration tests of space vehicles. However, there is no discussion herein of the extensive electronic equipment and procedures required to support such tests. This practice does not apply to or provide incomplete coverage of the following types of tests: launch phase or atmospheric reentry of space vehicles; landers on planet surfaces; degradation of thermal coatings; increased friction in space of mechanical devices, sometimes called "cold welding"; sun sensors; man in space; energy conversion devices; and tests of components for leaks, outgassing, radiation damage, or bulk thermal properties.
SCOPE
1.1 Purpose:
1.1.1 The primary purpose of this practice is to provide guidance for making adequate thermal balance tests of spacecraft and components where solar simulation has been determined to be the applicable method. Careful adherence to this practice should ensure the adequate simulation of the radiation environment of space for thermal tests of space vehicles.
1.1.2 A corollary purpose is to provide the proper test environment for systems-integration tests of space vehicles. An accurate space-simulation test for thermal balance generally will provide a good environment for operating all electrical and mechanical systems in their various mission modes to determine interferences within the complete system. Although adherence to this practice will provide the correct thermal environment for this type of test, there is no discussion of the extensive electronic equipment and procedures required to support systems-integration testing.
1.2 Nonapplicability—This practice does not apply to or provide incomplete coverage of the following types of tests:
1.2.1 Launch phase or atmospheric reentry of space vehicles,
1.2.2 Landers on planet surfaces,
1.2.3 Degradation of thermal coatings,
1.2.4 Increased friction in space of mechanical devices, sometimes called “cold welding,”
1.2.5 Sun sensors,
1.2.6 Man in space,
1.2.7 Energy conversion devices, and
1.2.8 Tests of components for leaks, outgassing, radiation damage, or bulk thermal properties.
1.3 Range of Application:
1.3.1 The extreme diversification of space-craft, design philosophies, and analytical effort makes the preparation of a brief, concise document impossible. Because of this, various spacecraft parameters are classified and related to the important characteristic of space simulators in a chart in 7.6.
1.3.2 The ultimate result of the thermal balance test is to prove the thermal design to the satisfaction of the thermal designers. Flexibility must be provided to them to trade off additional analytical effort for simulator shortcomings. The combination of a comprehensive thermal-analytical model, modern computers, and a competent team of analysts greatly reduces the requirements for accuracy of space simulation.
1.4 Utility—This practice will be useful during space vehicle test phases from the development through flight acceptance test. It should provide guidance for space simulation testing early in the design phase of thermal control models of subsystems and spacecraft. Flight spacecraft frequently are tested before launch. Occasionally, tests are made in a space chamber after a sister spacecraft is launched as an aid in analyzing anomalies that occur in space.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicabili...
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E491 − 73 (Reapproved 2020)
Standard Practice for
Solar Simulation for Thermal Balance Testing of Spacecraft
This standard is issued under the fixed designation E491; 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.
1. Scope 1.3.2 The ultimate result of the thermal balance test is to
prove the thermal design to the satisfaction of the thermal
1.1 Purpose:
designers. Flexibility must be provided to them to trade off
1.1.1 The primary purpose of this practice is to provide
additional analytical effort for simulator shortcomings. The
guidance for making adequate thermal balance tests of space-
combination of a comprehensive thermal-analytical model,
craft and components where solar simulation has been deter-
modern computers, and a competent team of analysts greatly
mined to be the applicable method. Careful adherence to this
reduces the requirements for accuracy of space simulation.
practice should ensure the adequate simulation of the radiation
environment of space for thermal tests of space vehicles. 1.4 Utility—This practice will be useful during space ve-
1.1.2 A corollary purpose is to provide the proper test hicle test phases from the development through flight accep-
environmentforsystems-integrationtestsofspacevehicles.An tance test. It should provide guidance for space simulation
accurate space-simulation test for thermal balance generally testing early in the design phase of thermal control models of
willprovideagoodenvironmentforoperatingallelectricaland subsystems and spacecraft. Flight spacecraft frequently are
mechanical systems in their various mission modes to deter- tested before launch. Occasionally, tests are made in a space
mine interferences within the complete system. Although chamber after a sister spacecraft is launched as an aid in
adherence to this practice will provide the correct thermal analyzing anomalies that occur in space.
environment for this type of test, there is no discussion of the
1.5 This standard does not purport to address all of the
extensive electronic equipment and procedures required to
safety concerns, if any, associated with its use. It is the
support systems-integration testing.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.2 Nonapplicability—This practice does not apply to or
mine the applicability of regulatory limitations prior to use.
provide incomplete coverage of the following types of tests:
1.6 This international standard was developed in accor-
1.2.1 Launch phase or atmospheric reentry of space
dance with internationally recognized principles on standard-
vehicles,
ization established in the Decision on Principles for the
1.2.2 Landers on planet surfaces,
Development of International Standards, Guides and Recom-
1.2.3 Degradation of thermal coatings,
mendations issued by the World Trade Organization Technical
1.2.4 Increased friction in space of mechanical devices,
Barriers to Trade (TBT) Committee.
sometimes called “cold welding,”
1.2.5 Sun sensors,
2. Referenced Documents
1.2.6 Man in space,
1.2.7 Energy conversion devices, and
2.1 ASTM Standards:
1.2.8 Tests of components for leaks, outgassing, radiation E259Practice for Preparation of Pressed Powder White
damage, or bulk thermal properties.
Reflectance Factor Transfer Standards for Hemispherical
and Bi-Directional Geometries
1.3 Range of Application:
E296Practice for Ionization Gage Application to Space
1.3.1 The extreme diversification of space-craft, design
Simulators
philosophies, and analytical effort makes the preparation of a
E297Test Method for Calibrating Ionization Vacuum Gage
brief, concise document impossible. Because of this, various
Tubes (Withdrawn 1983)
spacecraftparametersareclassifiedandrelatedtotheimportant
E349Terminology Relating to Space Simulation
characteristic of space simulators in a chart in 7.6.
1 2
This practice is under the jurisdiction of ASTM Committee E21 on Space For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Simulation andApplications of SpaceTechnology and is the direct responsibility of contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Subcommittee E21.04 on Space Simulation Test Methods. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2020. Published December 2020. Originally the ASTM website.
approvedin1973.Lastpreviouseditionapprovedin2015asE491–73(2015).DOI: The last approved version of this historical standard is referenced on
10.1520/E0491-73R20. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E491 − 73 (2020)
2.2 ISO Standard: 3.2.5 albedo—the ratio of the amount of electromagnetic
ISO 1000-1973SI Units and Recommendations for the Use radiation reflected by a body to the amount incident upon it.
of Their Multiples and of Certain Other Units
3.2.6 apparent source—the minimum area of the final ele-
2.3 American National Standards:
ments of the solar optical system from which issues 95% or
ANSI Y10.18-1967Letter Symbols for Illuminating Engi-
more of the energy that strikes an arbitrary point on the test
neering
specimen.
ANSIZ7.1-1967StandardNomenclatureandDefinitionsfor
3.2.7 astronomical unit (AU)—a unit of length defined as
Illuminating Engineering
the mean distance from the earth to the sun (that is,
ANSI Y10.19-1969Letter Symbols for Units Used in Sci-
149597890 6 500 km).
ence and Technology
3.2.8 blackbody (USA),Planckian radiator—a thermal ra-
diator which completely absorbs all incident radiation, what-
3. Terminology
ever the wavelength, the direction of incidence, or the polar-
3.1 Definitions, Symbols, Units, and Constants—This sec-
ization. This radiator has, for any wavelength, the maximum
tioncontainstherecommendeddefinitions,symbols,units,and
spectral concentration of radiant exitance at a given tempera-
constantsforuseinsolarsimulationforthermalbalancetesting
ture (E349).
of spacecraft. The International System of Units (SI) and
3.2.9 collimate—to render parallel, (for example, rays of
International and American National Standards have been
light).
adheredtoasmuchaspossible.TerminologyE349isalsoused
3.2.10 collimation angle—in solar simulation, the angular
andissoindicatedinthetext.Table1providescommonlyused
nonparallelism of the solar beam, that is, the decollimation
symbols.
angle. In general, a collimated solar simulator uses an optical
3.2 Definitions:
componenttoimageatinfinityanapparentsource(pseudosun)
3.2.1 absorptance (α , α ,α )—ratio of the absorbed radiant
e v
offinitesize.Theanglesubtendedbytheapparentsourcetothe
or luminous flux to the incident flux (E349)(Table 1).
finalopticalcomponentreferredtoasthecollimator,isdefined
3.2.2 absorptivity of an absorbing material—internal ab-
asthesolarsubtenseangleandestablishesthenominalangleof
sorptance of a layer of the material such that the path of the
decollimation. A primary property of the “collimated” system
radiation is of unit length (E349).
is the near constancy of the angular subtense angle as viewed
3.2.3 air mass one (AM1)—the equivalent atmospheric at- from any point in the test volume. The solar subtense angle is
tenuation of the electromagnetic spectrum to modify the solar therefore a measure of the nonparallelism of the beam. To
irradiance as measured at one astronomical unit from the sum avoid confusion between various scientific fields, the use of
outside the sensible atmosphere to that received at sea level, solar subtense angle instead of collimation angle or decollima-
when the sun is in the zenith position. tion angle is encouraged (see solar subtense angle).
3.2.4 air mass zero (AM0)—the absence of atmospheric 3.2.11 collimator—an optical device which renders rays of
attenuation of the solar irradiance at one astronomical unit light parallel.
from the sun.
3.2.12 decollimation angle—not recommended (see colli-
mation angle).
3.2.13 diffuse reflector—a body that reflects radiant energy
in such a manner that the reflected energy may be treated as if
Withdrawn.
it were being emitted (radiated) in accordance with Lambert’s
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org.
TABLE 1 Commonly Used Symbols
Symbol Quantity Definition Equation or Value Unit Unit Symbol
Q radiant energy, work, joule J
quantity of heat
−1
Φ radiant flux Φ =dQ/dt watt (joule/second) W, Js
−2
E irradiance (receiver) flux E =dΦ/dA watt per square metre W·m
density
−2
M radiant exitance (source) M =dΦ/dA watt per square metre W·m
−1
I radiant intensity (source) I =dΦ/dω watt per steradian W·sr
ω = solid angle through which flux from source is radiated
−1 −2
L radiance L =dI/(dA cosθ ) watt per steradian = W·sr ·m
square metre
θ = angle between line of sight and normal to surface dA
τ transmittance τ = Φ, transmitted/Φ, incident none
τ(λ) spectral transmittance τ(λ)= Φ(λ), transmitted/Φ(λ), incident none
ρ reflectance (total) ρ = Φ, reflected/Φ, incident none
εH emittance (total εH = M, specimen/M, blackbody
hemispherical)
α absorptance α = Φ, absorbed/Φ, incident none
α solar absorptance α = solar irradiance absorbed/solar irradiance incident none
s s
E491 − 73 (2020)
law.The radiant intensity reflected in any direction from a unit 3.2.27 integrating (Ulbrecht) sphere—part of an integrating
area of such a reflector varies as the cosine of the angle photometer. It is a sphere which is coated internally with a
between the normal to the surface and the direction of the white diffusing paint as nonselective as possible, and which is
reflected radiant energy (E349). provided with associated equipment for making a photometric
measurement at a point of the inner surface of the sphere. A
3.2.14 dispersion function (X/λ)—a measure of the separa-
screen placed inside the sphere prevents the point under
tion of wavelengths from each other at the exit slit of the
observation from receiving any radiation directly from the
monochromator, where X is the distance in the slit plane and λ
source (E349).
is wavelength. The dispersion function is, in general, different
3.2.28 intensity—see radiant intensity.
for each monochromator design and is usually available from
the manufacturer.
3.2.29 irradiance at a point on a surface E ,E;E =dΦ /
e e e
dA—quotient of the radiant flux incident on an element of the
3.2.15 divergence angle—see solar beam divergence
surface containing the point, by the area of that element
angle(3.2.60).
−2
measured in W·m (E349)(Table 1).
3.2.16 electromagnetic spectrum—the ordered array of
¯
3.2.30 irradiance, mean total (E)—the average total irradi-
known electromagnetic radiations, extending from the shortest
ance over the test volume, as defined by the following
wavelengths, gamma rays, through X rays, ultraviolet
equation:
radiation, visible radiation, infrared and including microwave
and all other wavelengths of radio energy (E349).
¯
E 5 E r,θ,z dV/ dV (1)
* ~ ! *
v v
3.2.17 emissivity of a thermal radiator ε, ε =M /
e,th
where:
M (ε = 1)—ratio of the thermal radiant exitance of the radiator
e
¯
E(r,θ,z) = total irradiance as a function of position (Table
to that of a full radiator at the same temperature, formerly
1).
“pouvoir emissif” (E349).
3.2.31 irradiance, spectral [E or E(λ)] —the irradiance at a
3.2.18 emittance (ε)—the ratio of the radiant exitance of a λ
specific wavelength over a narrow bandwidth, or as a function
specimen to that emitted by a blackbody radiator at the same
of wavelength.
temperature identically viewed. The term generally refers to a
specific sample or measurement of a specific sample. Total
3.2.32 irradiance, temporal—the temporal variation of in-
hemispherical emittance is the energy emitted over the hemi- dividual irradiances from the mean irradiance. The temporal
sphere above emitting element for all wavelengths. Normal
variations should be measured over time intervals equal to the
emittance refers to the emittance normal to the surface to the
thermal time constants of the components. The temporal
emitting body.
stability of total irradiance can be defined as:
3.2.19 exitance at a point on a surface (radiant exitance) ¯
E 56100@ ∆E 1∆E /2E# (2)
~ !
t t ~min! t ~max!
(M)—quotient of the radiant flux leaving an element of the
3.2.33 irradiance, total—the integration over all wave-
surface containing the point, by the area of that element,
−2 lengths of the spectral irradiance.
measured in W·m (E349)(Table 1).
3.2.34 irradiance, uniformity of—uniformity of total irradi-
3.2.20 field angle—not recommended (see solar beam sub-
ance can be defined as:
tense angle).
¯
E 56100@ E 1E /2E# (3)
~ !
u ~min! ~max!
3.2.21 flight model—an operational flight-capable space-
craft that is usually subjected to acceptance tests.
where:
3.2.22 flux (radiant, particulate, and so forth)—for electro-
E = uniformity of the irradiance within the test volume,
u
magnetic radiation, the quantity of radiant energy flowing per
expressed as a percent of the mean irradiance,
unit time; for particles and photons, the number of particles or E = smallest value obtained for irradiance within the
(min)
photons flowing per unit time (E349). test volume, and
E = largest value obtained for irradiance within the test
(max)
3.2.23 gray body—a body for which the spectral emittance
volume.
and absorptance is constant and independent of wavelength.
Uniformity of irradiance values must always be specified
The term is also used to describe bodies whose spectral
together with the largest linear dimension of the detector used.
emittance and absorptance are constant within a given wave-
length band of interest (E349).
3.2.35 Lambert’s law—the radiant intensity (flux per unit
solid angle) emitted in any direction from a unit-radiating
3.2.24 incident angle—the angle at which a ray of energy
surface varies as the cosine of the angle between the normal to
impinges upon a surface, usually measured between the direc-
the surface and the direction of the radiation (also called
tion of propagation of the energy and a perpendicular to the
Lambert’scosinelaw).Lambert’slawisnotobeyedexactlyby
surface at the point of impingement or incidence.
most real surfaces, but an ideal blackbody emits according to
3.2.25 inf
...
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