ASTM E491-73(2004)
(Practice)Standard Practice for Solar Simulation for Thermal Balance Testing of Spacecraft
Standard Practice for Solar Simulation for Thermal Balance Testing of Spacecraft
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 NonapplicabilityThis 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 .
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 UtilityThis 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.
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 and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E 491 – 73 (Reapproved 2004)
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope designers. Flexibility must be provided to them to trade off
additional analytical effort for simulator shortcomings. The
1.1 Purpose:
combination of a comprehensive thermal-analytical model,
1.1.1 The primary purpose of this practice is to provide
modern computers, and a competent team of analysts greatly
guidance for making adequate thermal balance tests of space-
reduces the requirements for accuracy of space simulation.
craft and components where solar simulation has been deter-
1.4 Utility—This practice will be useful during space ve-
mined to be the applicable method. Careful adherence to this
hicle test phases from the development through flight accep-
practice should ensure the adequate simulation of the radiation
tance test. It should provide guidance for space simulation
environment of space for thermal tests of space vehicles.
testing early in the design phase of thermal control models of
1.1.2 A corollary purpose is to provide the proper test
subsystems and spacecraft. Flight spacecraft frequently are
environmentforsystems-integrationtestsofspacevehicles.An
tested before launch. Occasionally, tests are made in a space
accurate space-simulation test for thermal balance generally
chamber after a sister spacecraft is launched as an aid in
willprovideagoodenvironmentforoperatingallelectricaland
analyzing anomalies that occur in space.
mechanical systems in their various mission modes to deter-
1.5 This standard does not purport to address all of the
mine interferences within the complete system. Although
safety concerns, if any, associated with its use. It is the
adherence to this practice will provide the correct thermal
responsibility of the user of this standard to establish appro-
environment for this type of test, there is no discussion of the
priate safety and health practices and determine the applica-
extensive electronic equipment and procedures required to
bility of regulatory limitations prior to use.
support systems-integration testing.
1.2 Nonapplicability—This practice does not apply to or
2. Referenced Documents
provide incomplete coverage of the following types of tests:
2.1 ASTM Standards:
1.2.1 Launch phase or atmospheric reentry of space ve-
E259 Practice for Preparation of Pressed Powder White
hicles,
Reflectance Factor Transfer Standards for Hemispherical
1.2.2 Landers on planet surfaces,
and Bi-Directional Geometries
1.2.3 Degradation of thermal coatings,
E296 Practices for Ionization Gage Application to Space
1.2.4 Increased friction in space of mechanical devices,
Simulators
sometimes called “cold welding,”
E297 Methods for Calibrating Ionization Vacuum Gage
1.2.5 Sun sensors,
Tubes
1.2.6 Man in space,
E349 Terminology Relating to Space Simulation
1.2.7 Energy conversion devices, and
2.2 ISO Standard:
1.2.8 Tests of components for leaks, outgassing, radiation
ISO 1000-1973 SI Units and Recommendations for the Use
damage, or bulk thermal properties.
of Their Multiples and of Certain Other Units
1.3 Range of Application:
2.3 American National Standards:
1.3.1 The extreme diversification of space-craft, design
ANSI Y10.18-1967 Letter Symbols for Illuminating Engi-
philosophies, and analytical effort makes the preparation of a
neering
brief, concise document impossible. Because of this, various
ANSI Z7.1-1967 Standard Nomenclature and Definitions
spacecraftparametersareclassifiedandrelatedtotheimportant
for Illuminating Engineering
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
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This practice is under the jurisdiction of ASTM Committee E21 on Space Standards volume information, refer to the standard’s Document Summary page on
Simulation andApplications of SpaceTechnology and is the direct responsibility of the ASTM website.
Subcommittee E21.04 on Space Simulation Test Methods. Withdrawn.
Current edition approved Sept. 1, 2004. Published September 2004. Originally Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
approved in 1973. Last previous edition approved in 1999 as E491–73 (1999). 4th Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 491 – 73 (2004)
ANSI Y10.19-1969 Letter Symbols for Units Used in Sci- 3.2.9 collimate—to render parallel, (for example, rays of
ence and Technology light).
3.2.10 collimation angle—in solar simulation, the angular
3. Terminology
nonparallelism of the solar beam, that is, the decollimation
3.1 Definitions, Symbols, Units, and Constants—This sec-
angle. In general, a collimated solar simulator uses an optical
tioncontainstherecommendeddefinitions,symbols,units,and
componenttoimageatinfinityanapparentsource(pseudosun)
constantsforuseinsolarsimulationforthermalbalancetesting
offinitesize.Theanglesubtendedbytheapparentsourcetothe
of spacecraft. The International System of Units (SI) and
finalopticalcomponentreferredtoasthecollimator,isdefined
International and American National Standards have been
asthesolarsubtenseangleandestablishesthenominalangleof
adheredtoasmuchaspossible.TerminologyE349isalsoused
decollimation. A primary property of the “collimated” system
andissoindicatedinthetext.Table1providescommonlyused
is the near constancy of the angular subtense angle as viewed
symbols.
from any point in the test volume. The solar subtense angle is
3.2 Definitions:
therefore a measure of the nonparallelism of the beam. To
3.2.1 absorptance (a , a ,a )—ratio of the absorbed radiant
avoid confusion between various scientific fields, the use of
e v
or luminous flux to the incident flux (E349) (Table 1).
solar subtense angle instead of collimation angle or decollima-
3.2.2 absorptivity of an absorbing material—internal ab-
tion angle is encouraged (see solar subtense angle).
sorptance of a layer of the material such that the path of the
3.2.11 collimator—an optical device which renders rays of
radiation is of unit length (E349).
light parallel.
3.2.3 air mass one (AM1)—the equivalent atmospheric
3.2.12 decollimation angle—not recommended (see colli-
attenuationoftheelectromagneticspectrumtomodifythesolar
mation angle).
irradiance as measured at one astronomical unit from the sum
3.2.13 diffuse reflector—a body that reflects radiant energy
outside the sensible atmosphere to that received at sea level,
in such a manner that the reflected energy may be treated as if
when the sun is in the zenith position.
it were being emitted (radiated) in accordance with Lambert’s
3.2.4 air mass zero (AM0)—the absence of atmospheric
law.The radiant intensity reflected in any direction from a unit
attenuation of the solar irradiance at one astronomical unit
area of such a reflector varies as the cosine of the angle
from the sun.
between the normal to the surface and the direction of the
3.2.5 albedo—the ratio of the amount of electromagnetic
reflected radiant energy (E349).
radiation reflected by a body to the amount incident upon it.
3.2.14 dispersion function (X/l)—a measure of the separa-
3.2.6 apparent source—the minimum area of the final
tion of wavelengths from each other at the exit slit of the
elementsofthesolaropticalsystemfromwhichissues95%or
monochromator, where X is the distance in the slit plane and l
more of the energy that strikes an arbitrary point on the test
is wavelength. The dispersion function is, in general, different
specimen.
for each monochromator design and is usually available from
3.2.7 astronomical unit (AU)—a unit of length defined as
the manufacturer.
the mean distance from the earth to the sun (that is,
3.2.15 divergence angle—see solar beam divergence angle
149597890 6 500 km).
(3.2.60).
3.2.8 blackbody (USA), Planckian radiator—a thermal ra-
diator which completely absorbs all incident radiation, what- 3.2.16 electromagnetic spectrum—the ordered array of
ever the wavelength, the direction of incidence, or the polar- known electromagnetic radiations, extending from the shortest
ization. This radiator has, for any wavelength, the maximum wavelengths, gamma rays, through X rays, ultraviolet radia-
spectral concentration of radiant exitance at a given tempera- tion, visible radiation, infrared and including microwave and
ture (E349). all other wavelengths of radio energy (E349).
TABLE 1 Commonly Used Symbols
Symbol Quantity Definition Equation or Value Unit Unit Symbol
Q radiant energy, work, joule J
quantity of heat
−1
F radiant flux F =dQ/dt watt (joule/second) W, Js
−2
E irradiance (receiver) flux E =dF/dA watt per square metre W·m
density
−2
M radiant exitance (source) M =dF/dA watt per square metre W·m
−1
I radiant intensity (source) I =dF/dv watt per steradian W·sr
v = solid angle through which flux from source is radiated
−1 −2
L radiance L =dI/(dA cosu ) watt per steradian = W·sr ·m
square metre
u = angle between line of sight and normal to surface dA
t transmittance t = F, transmitted/F, incident none
t(l) spectral transmittance t(l)= F(l), transmitted/F(l), incident none
r reflectance (total) r = F, reflected/F, incident none
eH emittance (total eH = M, specimen/M, blackbody
hemispherical)
a absorptance a = F, absorbed/F, incident none
a solar absorptance a = solar irradiance absorbed/solar irradiance incident none
s s
E 491 – 73 (2004)
3.2.17 emissivity of a thermal radiator e, e=M /M 3.2.31 irradiance, spectral [E or E(l)]—the irradiance at a
e,th e l
(e=1)—ratio of the thermal radiant exitance of the radiator to specific wavelength over a narrow bandwidth, or as a function
that of a full radiator at the same temperature, formerly
of wavelength.
“pouvoir emissif” (E349).
3.2.32 irradiance, temporal—the temporal variation of in-
3.2.18 emittance (e)—the ratio of the radiant exitance of a
dividual irradiances from the mean irradiance. The temporal
specimen to that emitted by a blackbody radiator at the same
variations should be measured over time intervals equal to the
temperature identically viewed. The term generally refers to a
thermal time constants of the components. The temporal
specific sample or measurement of a specific sample. Total
stability of total irradiance can be defined as:
hemispherical emittance is the energy emitted over the hemi-
¯
sphere above emitting element for all wavelengths. Normal E 56100[~DE 1DE !/2E# (2)
t t ~min! t ~max!
emittance refers to the emittance normal to the surface to the
3.2.33 irradiance, total—the integration over all wave-
emitting body.
lengths of the spectral irradiance.
3.2.19 exitance at a point on a surface (radiant exitance)
3.2.34 irradiance, uniformity of—uniformity of total irradi-
(M)—quotient of the radiant flux leaving an element of the
ance can be defined as:
surface containing the point, by the area of that element,
−2
measured in W·m (E349) (Table 1).
¯
E 56100[~E 1 E !/2E# (3)
u ~min! ~max!
3.2.20 field angle—not recommended (see solar beam sub-
tense angle).
where:
3.2.21 flight model—an operational flight-capable space-
E = uniformity of the irradiance within the test vol-
u
craft that is usually subjected to acceptance tests. ume, expressed as a percent of the mean irradi-
3.2.22 flux (radiant, particulate, and so forth)—for electro-
ance,
E = smallest value obtained for irradiance within the
magnetic radiation, the quantity of radiant energy flowing per
(min)
unit time; for particles and photons, the number of particles or test volume, and
E = largest value obtained for irradiance within the
photons flowing per unit time (E349).
(max)
test volume.
3.2.23 gray body—a body for which the spectral emittance
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-
3.2.35 Lambert’s law—the radiant intensity (flux per unit
length band of interest (E349).
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 infrared radiation—see electromagnetic spectrum
this law. This law is also satisfied (by definition) by the
(E349).
distributionofradiationfromaperfectlydiffuseradiatorandby
3.2.26 insolation—direct solar irradiance received at a sur-
the radiation reflected by a perfectly diffuse reflector. In
face, contracted from incoming solar radiation.
accordance with Lambert’s law, an incandescent spherical
3.2.27 integrating (Ulbrecht) sphere—part of an integrating
blackbody when viewed from a distance appears to be a
photometer. It is a sphere which is coated internally with a
uniformlyilluminateddisk.Thislawdoesnottakeintoaccount
white diffusing paint as nonselective as possible, and which is
any effects that may alter the radiation after it leaves the
provided with associated equipment for making a photometric
source.
measurement at a point of the inner surface of the sphere. A
screen placed inside the sphere prevents the point under
3.2.36 maximum test plane divergence angle—the angle
observation from receiving any radiation directly from the
between the extreme ray from the apparent source and the test
source (E349).
plane. This applies principally to direct projection beams
3.2.28 intensity—see radiant intensity.
whereitisequivalenttoonehalftheprojectionconeangle(see
3.2.29 irradiance at a point on a surface E,E;E =dF /
e e e Fig. 1).
dA—quotient of the radiant flux incident on an element of the
3.2.37 natural bandwidth—the width at half height of a
surface containing the point, by the area of that element
radiationsourceemissionpeak.Itisindependentofinstrumen
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