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i

NASA/TM—2010–216445

Generation of Requirements 

for Simulant Measurements

C.M. Schrader, and J.E. Edmunson

BAE Systems, Huntsville, Alabama

D.L. Rickman

Marshall Space Flight Center, Marshall Space Flight Center, Alabama

September 2010

National Aeronautics and

Space Administration

Marshall Space Flight Center • MSFC, Alabama 35812
ii

Available from:

NASA Center for AeroSpace Information

7115 Standard Drive

Hanover, MD 21076 –1320

443–757–5802

This report is also available in electronic form at

<https://www2.sti.nasa.gov>
iii

TABLE OF CONTENTS

1. INTRODUCTION ............................................................................................................. 1

2. OBJECTIVES AND REQUIREMENTS ........................................................................... 3

2.1 Requirement 1: Verify and Validate Simulant Performance Versus Lunar Regolith ...... 3

2.2 Analysis One ................................................................................................................ 3

2.3 Analysis Two ................................................................................................................ 5

2.4 Assumptions ................................................................................................................. 6

3. DETERMINATION OF MEASUREMENTS .................................................................. 9

3.1 Important Factors ........................................................................................................ 11

3.2 Additional Considerations ............................................................................................ 15

4. SPECTROSCOPY .............................................................................................................. 16

4.1 Addendum of May 30, 2010 ......................................................................................... 16

REFERENCES ....................................................................................................................... 17
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LIST OF FIGURES

1. Model of the mineral gypsum (CaSO4⋅2H2O) ............................................................. 10

LIST OF TABLES

1. NASA simulant objectives ........................................................................................... 3

2. Design considerations for measurements ..................................................................... 4

3. Average proportion of particles in lunar highlands regolilth from Apollo 16 core

64001/64002 ................................................................................................................. 9
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LIST OF ACRONYMS

ASTM American Society for Testing and Materials

CaSO4∙2H2O gypsum

EM electromagnetic

FoM figure of merit

Mg2SiO4 forsterite
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1

TECHNICAL MEMORANDUM

GENERATION OF REQUIREMENTS FOR SIMULANT MEASUREMENTS

1. INTRODUCTION

This Technical Memorandum (TM) presents a formal, logical explanation of the parameters selected for the figure of merit (FoM) algorithm. The FoM algorithm is used to evaluate lunar 

regolith simulant. The objectives, requirements, assumptions, and analysis behind the parameters 

are provided in this TM. 
2
3

2. OBJECTIVES AND REQUIREMENTS

An analysis of NASA objectives for lunar regolith simulants was used to establish the FoM 

evaluation criteria. The FoM criteria are a series of measurements. These measurements compare 

quantitatively to a sample of regolith and a sample of simulant. This TM provides a historical view 

of why the measurements in the FoM criteria were selected, why others were not selected, and the 

consequences of the selection to specific problems of interest for engineering applications. Table 1 

identifies the current simulant objectives that NASA has determined.

Table 1. NASA simulant objectives.

Objective No. Objective

1

2

3

4

Reproduce characteristics of lunar regolith using simulants.

Produce simulants as cheaply as possible.

Produce simulants in the amount needed.

Produce simulants to meet users’ schedules.

This TM only deals with the first NASA simulant objective; that is, to reproduce characteristics of lunar regolith using simulants. Thus, requirement 1 is yielded.

2.1 Requirement 1: Verify and Validate Simulant Performance Versus Lunar Regolith

Analysis of this requirement implied a direct comparison of measurements taken on lunar 

regolith and measurements on simulant. Simplicity and a desire for high confidence strongly recommended that the same measurements be taken on regolith and simulant. This approach was 

adopted in the following specification:

•	 Specification 1: Requirement 1 shall be satisfied by comparison of measurements taken the 

same way on both regolith and simulants.

2.2 Analysis One

It should be noted that using identical measurements on regolith and simulant is not a 

necessity. This is a design choice and, as such, is subject to trade analysis. Permitting the use of 

nonidentical measurements permits greater flexibility. As an example, Apollo program Surveyor 

scoop measurements might be used to provide a lunar geotechnical value; however, a different 

method must be used to evaluate the same value with lunar regolith simulant. Scientifically, this 

is a common technique that allows one to take advantage of all the available data in a data-poor 

situation.
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A primary difficulty with this approach is that one needs to have a high degree of confidence 

that the two different measurements are functionally equivalent within the tolerance of the 

application. 

To meet the stated objectives is a very difficult constraint. The regolith is not a material 

with which we have a lot of engineering experience, and the abundant scientific measurements are 

focused on features that are not perfectly translatable to engineering needs. Defending or understanding the equivalence of two different measurements can be difficult, especially for the 

nonexpert.

Further, there is a general paucity of geotechnical and engineering measurements on the 

regolith, especially for measurements taken on the Moon. The amount of published data 

pertaining to geology dwarfs the geotechnical and engineering data.

Finally, there is no single sample for which all or even a majority of the desired measurements were obtained. This is a major consideration. Even the most casual survey of the lunar 

literature shows the regolith varies rapidly and substantially as one moves from any given point. 

It is a truism that the concept of “average” is useful, but what is processed is always a specific sample. It can be useful to test with average material, but exclusively doing so for an innovative 

design placed in a high-risk environment is probably not prudent. However, if there is no single 

sample of the regolith that was measured for all the properties, some concept of average or typical 

is all that can be used. It was thus concluded that using different measurement techniques on 

regolith and on simulants was an inherently risky option.

2.2.1 Basic Data

Having stated the requirement, examined the conceptual options, and selected an approach, 

there are many technical points to be considered. Table 2 identifies the design considerations 

for measurements.

Table 2. Design considerations for measurements.

Consideration Design Consideration Description

A The individual 

measurements 

must be:

i. Agreed on.

ii. Practical to make on both simulant and regolith.

iii. Reproducible.

iv. Of properties that process controls can affect consistently.

v. Functionally or physically meaningful.

vi. Taken in a uniform, standardized manner.

B Measurements should be as few as technically defensible.

C The phenomena measured should be independent.

D The phenomena measured should have maximal explanatory power.
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It is desirable for the measurements and underlying phenomena to have intuitive meaning and direct applicability to the users’ needs, but this is a design choice and not a demand of the 

requirement. There is no requirement to provide measurements that match user needs or desires 

based on their individual backgrounds or training.

2.3 Analysis Two

Analysis of the above, known engineering needs and existing knowledge of the lunar 

regolith provides the following points:

• Unless they were measured during Apollo, many of the measurements of interest cannot be 

known with precision for lunar materials, as they would have to be measured in situ. This is obviously true for phenomena that are sensitive to precise interactions between aggregates of particles in situ, such as bearing strength. While some data for bearing strength exists from Apollo, 

to state that the bearing strength of any given regolith is known sufficiently to verify and validate 

a simulant’s performance is unreasonable.

• Any single parameter can be measured in many ways and the method of measurement strongly 

affects the values determined. Often the correspondence between two methods of measurement 

is poor.

• Selecting which method of measurement is used is often contentious because each user will 

make many specific measurements in a specialized way. Simulants will be needed for more 

than a decade and will be measured by numerous groups with updated equipment. 

• Estimates of the volumes of simulant that will be needed are at best speculative, 

and production of additional simulant will require repeated precise measurements. 

• Critical measurements should not be limited to a single person or piece of equipment.

• There is a cost, often very substantial, to making a measurement. A conservative estimate 

of the number of measurements will have to be made.

• The average particle size of the lunar regolith is approximately 50 μm (50 microns).

• The average grain size is substantially smaller than the average particle size.

• The regolith has substantial and functionally significant variations on almost any spatial scale 

of relevance to engineering.

• There is no standard method for comparison of two mixtures of particulates when the 

composition, sizes, and shapes of the particles can all vary simultaneously.

• The materials of interest, regolith and simulants, are geological products. They are not 

engineered products.

• The body of knowledge that describes the materials of interest is geology.
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2.4 Assumptions

A statement of two explicit assumptions made is necessary in addition to the given 

objectives, derived requirement, stated design considerations, and compiled salient facts.

2.4.1 First Assumption

The behavior of the regolith is not uniquely a function of being on the Moon. We are 

assuming that there is nothing about being on the Moon that changes the physics of materials 

in manners unknown on Earth. In simple terms, physics is physics.

2.4.2 Second Assumption

Conceptually, one can find two divergent approaches to measurement standards. One is 

based on a systematic language and requires a framework of integrated concepts, and the other 

approach is ad hoc.

Familiar examples of the first approach are standards related to the load-bearing capacity 

of structural components. These standards use a common terminology taught in basic physics and 

depend on the formal concepts of science. It should be further noted that using such measurements 

frequently requires use of the formal concepts (e.g., bending resistance of a steel beam).

In the ad hoc approach, a test is created that relates to a property of interest, but the measurement protocols and results cannot be immediately tied to anything else. An example of this 

approach used in soil engineering is the Atterberg limit codified in American Society for Testing 

Materials (ASTM) D4943-08 “Standard Test Method for Shrinkage Factors of Soils by the Wax 

Method.” While very useful in practical applications, it is highly problematic to relate numbers 

obtained under ASTM D4943-08 to other parameters except by making organized suites of measurements and seeking correlations. First principles are not needed to express or use these 

measurements.

Both systematic and ad hoc methods are commonly used in measurement standards. There 

are benefits and problems with each approach. The systematic approach has the advantage of 

explicit ties to basic concepts; such measurements can say something fundamental. It has a disadvantage in that some knowledge of the basic concepts is needed to use or understand the measurements. The ad hoc approach has the advantage of directly addressing a specific need. The major 

disadvantage to the ad hoc method is that it is almost useless where broad application in different 

fields is needed. 

There is no common framework of basic concepts to guide and inform different uses. An ad 

hoc approach is commonly used within highly specialized and tightly restricted applications; understanding their limitations and their utility frequently depends on considerable technical knowledge. 

Further, it is common that specialized applications in a field will develop multiple versions of the 

same ad hoc “standard” measurement to suit specific types of problems. It is impractical to rigorously relate the results of one “standard” measurement to another “standard” measurement.
7

Simulants will be needed by a broad range of users with diverse technical backgrounds 

who will be using the simulants in unrelated ways. Questions about load-bearing capacity are quite 

different from questions of air filtration, water filtration, high-temperature melting, or movement induced by rocket plume exhaust; yet, all are dealing with the same regolith. It was therefore 

assumed that, in this case, an organized approach to measurement standards was overwhelmingly 

superior and probably the only tractable approach. The number of desired ad hoc measurements is 

almost certainly beyond any reasonable budget.

Therefore, a set of measurements was sought that would be based on a systematic language 

and a framework of integrated concepts. Because the lunar regolith is a geologic material made 

from broken and melted rock, it was concluded that the source of the most rigorous vocabulary 

and conceptual framework for this purpose was from the field of geology.
8
9

3. DETERMINATION OF MEASUREMENTS

Most people will agree that what the regolith or simulants are made of has bearing on many 

of the properties of engineering interest. Geologically, the lunar regolith is broken and melted 

(glass) rock. The individual particles of the regolith are a variable mixture of pieces of rock, pieces 

of minerals, and pieces of glass (see table 3 for representative particle compositions of lunar highlands regolith). Rocks, of the type relevant to the Moon, are various combinations of minerals and 

glasses. Glass is a brittle solid that does not show atomic ordering on a scale sufficient to diffract 

x rays. In theory, its composition can be almost anything, but the lunar glasses are dominantly 

silicate based because the dominant source materials for the glasses are silicate minerals. To a 

geologist, lunar rocks are defined in a context of mineralogy.

Table 3. Average proportion of particles in lunar highlands 

regolilth from Apollo 16 core 64001/64002.

Sample 64001/64002 

Particle Type %

Monomineralic particles

 Plagioclase

 Pyroxene

 Olivine

 Opaque (oxides and sulfides)

Crystalline lithics

Breccia fragments

Agglutinates

Glass

Total

23.5

21.5

1.7

0.2

0.1

0.7

27.9

40.0

7.8

100.0

Note: Data are summarized and averaged from references 3 and 4.

Mineralogy, of course, is the study of minerals. According to the Glossary of Geology,1 a 

mineral is a naturally occurring chemical element or compound having a definite chemical composition and usually a characteristic crystal form. One of the subsidiary statements in the definition 

of mineral is “A naturally occurring, usually inorganic, crystalline substance with characteristic 

physical and chemical properties that are due to its atomic arrangement.”1 What does this definition mean to an engineer?

First, the natural world does not assemble atoms in geologic solids at random. There is 

almost always order on very large scales involving >>109 atoms per discrete entity (grain, particle, 

crystal, etc.). Only certain orders or patterns occur naturally. On Earth, <5,000 such patterns (i.e., 

minerals) are known, and most of those are extremely rare. Known patterns from the Moon are 

less than a few hundred.2 When one examines a pattern (i.e., mineral), one finds the atoms are 

assembled into an extremely consistent spatial pattern termed a unit cell. The unit cell is repeated 
10

in three dimensions to form a lattice (fig. 1). Within a given lattice, an element can only occupy 

specific positions. This in turn limits the ratios of the elements within a mineral. For example, the 

mineral forsterite (Mg2SiO4) must have one silicon atom for every two magnesium atoms and four 

oxygen atoms. Thus, it is the presence of specific minerals in the lunar regolith that restricts its composition. In addition, the elements are going to be locked together in a restricted number of ways.

Figure 1. Model of the mineral gypsum (CaSO4⋅2H2O).

Noted in the subsidiary statement to the definition of a mineral is the fact that a mineral 

will have characteristic properties (i.e., specific, physical and chemical properties). Thus, a forsterite 

crystal from the Moon must have the same hardness, magnetic susceptibility, dielectric constant, 

chemistry, strength, melting point, or any additional property of a forsterite crystal from Earth. 

This is a very tight constraint on the engineering performance of both regolith and simulants.

To the extent lunar regolith is made of minerals and the minerals control the performance of the 

regolith, simulant with the same mineralogy will replicate the behavior of the regolith.

This constraint raised the following two questions: 

(1) To what extent is the regolith made of minerals?

(2) To what extent do minerals solely control the performance of the regolith? 

The first question has been answered by numerous studies of regolith samples obtained by 

Apollo astronauts (table 3).3,4 The regolith is effectively a mixture of glasses and minerals. Therefore, mineralogy strongly constrains the performance of regolith and simulants. It was also realized 

during these studies that the number of minerals on the Moon compared to Earth is actually small, 

and that fewer than 20 minerals could describe >99% of the regolith. Further, most of the 20 minerals are common terrestrial minerals.
11

Due to the fact that the word mineral does not adequately describe the constituents of the 

lunar regolith, the word particle is used. A particle is hereby defined as a solid entity that, in concept, could be separated from other particles without breaking chemical bonds, either surface to 

surface or lattice. A grain is a physically distinct subset of a particle, typically crystalline.

The second question was initially very difficult. Any answer would require knowledge of all 

the ways the simulant might be used and all the interactions of the simulant with the equipment; 

this was functionally impossible. One approach to addressing this problem was to ask experts to 

recommend what properties might be common to many needs and sufficient to permit adequate 

testing of components and systems bound for the Moon. This was done in a workshop held in 

Huntsville in January, 2005.5 At the workshop, an effort was made to tabulate properties needed 

to understand engineering interactions with the regolith. The result was a list of 31 properties, too 

long to be economically practical. Further, many of the implied measurements violated one or 

more items in table 2.

3.1 Important Factors

An observation was made upon examination of the list from the 2005 workshop. If one 

understands what controls many of the properties of interest in addition to mineralogy, only a few 

factors are important. Nine factors were informally titled as follows:

(1) Minerals.

(2) Glass.

(3) Rocks.

(4) Aggregations of disparate materials in single particles.

(5) Mechanical structures within a grain or particle.

(6) Relationships between grains.

(7) The size of the particles.

(8) The shapes of the particles.

(9) How the particles are packed together.

A critical realization was made at this stage. Due to complexity, when dealing with mixtures 

of particles, practical treatments of behavior may be forced to deal with measurements of the collection, but their theoretical understanding is very commonly, if not always, founded in the behaviors of individual particles. There is commonly an implicit assumption that if the particles could 

be understood, the property of interest would be deterministic. By corollary, if the particles were 

reproduced exactly, the observed behavior would be reproduced exactly.

It was also noted that factors one through four concern particle composition. Factors five 

through eight are geometric attributes of individual grains or particles. Factor nine addresses an 

emergent property that arises from collections of particles.
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3.1.1 Background Factors

Mineralogy has already been discussed; however, there are subtleties that have not been 

discussed such as the mineralogy of solid solutions, the distribution of trace elements, and lattice 

strains due to mechanical and chemical phenomena. The logic used to select a subset of the lunar 

minerals has not been discussed, but these are clearly secondary or tertiary to a statement that mineralogy is a powerful tool in reproducing lunar regolith.

Background knowledge of each of the other factors is also necessary in order to understand 

the applicability and limitations of the above corollary.

Glass is of major importance; it can be more than 50% of the total mass of the regolith. In 

theory it could be made from anything found on the Moon, but it typically has a restricted compositional range. It is produced by only two methods, meteor impacts and volcanism. Therefore, 

most of the glass will typically have a relatively narrow range of mechanical and chemical properties, especially compared to the minerals. The conclusion was reached that it would be sufficient to 

measure the abundance of glass to characterize the simulant. As long as the glass composition was 

roughly similar to that of the rest of the simulant, detailed glass chemistry was not needed.

Rocks are simple collections of grains. The grains can be all one mineral or combinations 

of minerals. Rocks can also incorporate glasses. Many of the particles in the regolith are fragments 

of rocks. Rocks do not behave the same way as particles made up of single minerals or glass. The 

differences are reasonably well understood and are often due to the type of rock. It was therefore 

reasonable to incorporate a measure of the abundance of rocks by specific type. This was a simplifying assumption and, to a limited extent, helped deal with the next two points.

Aggregations of materials in a single particle, such as those found in the lunar regolith, are 

very difficult to replicate. For this work, rock could be considered a special case of such particles; 

however, it is very simple geologically to treat rocks as discrete constituents of the regolith. Therefore, it was decided to restrict consideration of aggregations to the subset of particles in the 

regolith for which there is no natural, terrestrial analog.

The most well known aggregations on the lunar surface are agglutinates. These are aggregate particles composed of particles welded together by spatter glass. The glass of agglutinates contains spheres or globules of metallic iron that are frequently ≈30 nm in diameter. Agglutinates can 

comprise up to 60% of selected regolith. Many regolith particles also have rims composed of glass 

layers a few nanometers thick; these contain small globules of metallic iron. It is presumed that the 

rims are directly deposited from the vapor phase. The abundance of these rims in lunar regolith 

is currently unknown.

Agglutinates and the vapor deposited rims would certainly have impacts on engineering 

performance. Unfortunately, there was no language to quantitatively describe them or any standard 

methods to measure them. This makes it very difficult to have quantitative measures, which are 

necessary if one is to satisfy requirement 1. There was also no mechanical or chemical data 

on the behavior of lunar agglutinates. 
13

Finally, no one was attempting to reproduce the vapor deposited rims, which were very 

poorly characterized and difficult to study. The decision was made that agglutinates had to be 

accounted for in some way and the rims could, at least initially, be ignored. How to define, 

characterize, and count agglutinates was a problem delayed for further consideration. 

The first four of the nine factors (i.e., mineralogy, glass, rocks, and aggregations) define what 

the particles are made of; in other words, the particle’s composition. In a geologic sense, the only 

things known in the regolith that fall outside these four are the vapor deposited rims.

3.1.1.1 Mechanical Structures. The mechanical structures within a grain or particle include 

things like lamellae (alternating crystals of two related compositions that often appear as stripes) 

and disruptions of the original grain (such as broken grains). There is no standardized way to 

express these features, no accepted way to measure these features, and no data on how common 

these features are. No data exist to describe how these features affect anything. Reason suggests 

these features will have some bearing on the strength of individual particles; however, if the particles mechanically fail, they can then be treated as discrete particles. It was therefore decided that 

this feature would have to be ignored for measurements, but a caveat would be associated with 

them. At present, it was assumed that this could be a substantial problem or limitation only when 

considering particles bigger than ≈1 cm.

A similar situation exists for relationships between grains within a particle. There are 

attempts in various literatures to deal with this consideration; however, there is no standardization, 

and the affects of grain-to-grain relationships can be very complex. As with features within a grain, 

it was therefore decided that this feature would have to be ignored for measurements, but a caveat 

would be associated with them. It was anticipated that this would be a substantial problem or limitation when considering techniques to beneficiate the regolith, where grain-to-grain relationships 

are extremely important. There are other possible situations where grain-to-grain relationships 

are important, but the judgment was made that the engineering sophistication necessary for such 

things was well in the future for lunar applications.

If something cannot be measured in a standardized way, there is no standard language to 

describe it, and its impact is likely to be relatively minor compared to other things, prudent management of resources and time suggests ignoring the effect, at least initially. Thus, the effects of 

mechanical structures within grains and particles and the relationships between particles would 

not be considered in the first generation of standard measurements.

3.1.1.2 Particle Size. Particle size is intellectually an easy concept; however, definition is 

quite difficult. It becomes a question of how size is measured. A cursory examination of literature 

about the regolith showed the following: 

• The size range of particles does not show discrete limits, which is not analogous to terrestrial 

geologic materials.

• The particle size range in samples easily goes from multicentimeter to submicron, which is five 

orders of magnitude.
14

• There are at least 10 discrete minerals, rocks, and agglutinates that are substantial constituents 

of the regolith.

• Except by hand, there are no practical technologies to measure an individual particle’s size along 

with any other property. 

Consideration of the number of measurements needed to characterize a size distribution 

given the number of constituents led to the conclusion that at least 105 discrete values would be 

needed for each sample of regolith or simulant evaluated. It was therefore decided that knowledge 

of each individual particle’s size, along with its composition, was not practical; however, the distribution of sizes could be obtained for the regolith or simulant as a whole. It would be necessary, 

at least initially, to assume the size distribution for the whole would be representative of the size 

distribution of each constituent.

It should be noted that the assumption of identical size distributions was not necessary for 

the FoM software. It is relatively straightforward to write the code such that when component specific size data becomes available it will transparently override the assumption of a common 

size distribution.

A question was asked about the significance and likely impact of the assumption of identical size distribution of each constituent. There is no clear way to quantitatively evaluate this. There 

is data that suggested some variation in composition with size; however, the differences are not 

major and informed judgment suggests they are not large enough, compared to other factors, to 

merit concern at the beginning.

The assumption of uniformity in shape is also used because shape is an easy concept that 

is hard to measure. Useful values require thousands of measurements, and measurements of an 

individual particle cannot be linked to the particle’s composition. 

3.1.1.3 Interaction of Multiple Particles. Each point discussed above deals with individual 

particles. However, there are many phenomena of interest to engineers that involve how multiple 

particles interact (e.g., shear strength). Is it necessary to know the size, shape, composition, and 

spatial orientation of each particle to understand the behavior of the bulk?

In almost all, if not all cases, it is not necessary if two assumptions can be made: (1) Random and (2) uniform distributions. In other words, are there biases in size, shape, composition, 

or orientation that are functions of spatial location? There is little data on the regolith showing 

preferential orientation of particles,6 and there is no data showing broad scale sorting of size or 

shape. Visual inspection of the regolith shows no apparent preferences. Compared to Earth, this is 

extremely unusual. There is spatial variation in composition. The mare are clearly different compared to the highlands. The surface commonly has more agglutinates. In contrast, within a single 

Apollo sample, there appears relatively little ordering of composition, at least compared to terrestrial materials. Therefore, it is likely that an assumption of uniform, internal randomness to each 

sample is not unreasonable.
15

Having established that randomness and uniform distributions are reasonable assumptions, 

what measure or measures are needed to characterize the relationships between particles? Packing density is the only measure needed to characterize the relationships between particles. If the 

specific gravities of the constituents are known, the size and shape distributions are known and the 

particles are randomly and uniformly distributed. The only variable left is the tightness of packing 

of the particles.

3.1.1.4 Considerations Not Covered by This Approach. At this point, the objectives and consequent requirement have directed attention to basically four parameters: composition, size distribution, shape distribution, and density. The numerous assumptions made are known to be robust 

and are based on available data, common practice, and fundamental understandings.

There are things clearly not explicitly covered by this approach. For example, magnetism is 

not well handled and is very problematic to reproduce. Nonetheless, magnetism is important and 

how well it is described depends on what causes the magnetism. If it is derived from specific minerals, it is likely to be well described. If it is due to the agglutinates, it is likely to be well described. If 

it is due to something else, it is not likely to be well described. 

Another thing, not recognized as important at the time, is spectral properties: reflectance, 

transmittance, and emission. For this, there is substantial data on the lunar materials. As with 

magnetism, how well it is handled depends on what causes it. If it is dominated by agglutinates and 

other elements of composition, it is likely to be handled well. Otherwise, it will not be handled well.

3.2 Additional Considerations

Some final notes are in order as follows:

• There are things in terrestrial materials that are not present in studied lunar regolith (e.g., 

hydrous alteration phases). Simulant producers and users must be aware of this fact and must 

consider it during analysis. The impacts of these differences are as varied as the differences 

themselves.

• Even though the numbers of parameters to be measured are very few and quite simple, there are 

serious technical hurdles to getting the measurements. Commonly, these problems derive from 

the extremely fine average particle size of the regolith. It is daunting to consider how hard it 

would be to make even more specialized measurements when common, ordinary measurements 

are so difficult.

• The reduction to just four basic parameters must be recognized as just a way station, sufficient to 

start. The parameters selected are clearly able to robustly constrain the performance of simulant 

with respect to regolith, though they do not permit prediction of behavior.
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4. SPECTROSCOPY

4.1 Addendum of May 30, 2010

In the spring of 2010, the impact of the lunar regolith’s reflectance, absorption, transmittance, and emission of electromagnetic (EM) radiation was identified as a significant consideration 

for thermal system design. 

As stated in table 2, there are several considerations any measurement proposed for an FoM 

should meet. Definitions of the relevant measures are well understood in the remote sensing communities. Appropriate and necessary measurements can be obtained for both the Moon and the 

simulants. Existing process controls clearly are sufficient to obtain reproducible spectral behavior. 

The existing simulants vary substantially in their albedos. This variation is stated to be highly significant for design purposes. 

Spectral measurements, while subtly difficult, are commonly done in a highly reproducible 

manner with good comparability between labs. The number of measurements required could be as 

low as one and is not likely to exceed three. One or more of the other parameters do not obviously 

and definitively control the variation in albedo. 

Spectroscopy is one of the most powerful tools in modern science. It is used in virtually 

every field because the data are extremely informative. Spectroscopy, in the general sense, clearly 

satisfies the considerations for inclusion. With future development, an FoM will probably need to 

be defined for spectroscopy. 
17

REFERENCES

1. Gary, M.; McAfee, R., Jr.; and Wolf, C.L.; (eds.): Glossary of Geology, American Geological Institute, Falls Church, VA, 805 p, 1974.

2. Frondel, J.W.: Lunar Mineralogy, Harvard University Press, Cambridge, MA, 323 p, 1975.

3. Basu, A; and McKay, D.S.: “Petrologic Profile of Apollo 16 Regolith at Station 4,” Proceedings 

of the 15th Lunar and Planetary Science Conference, Part 1, J. of Geophys. Res., Vol. 89, Sup., 

pp. C133–C142, 1984.

4. Houck, K.J.: “Modal Petrology of Six Soils From Apollo 16 Double Drive Tube 64002,” Proceedings of the 13th Lunar and Planetary Science Conference, Part 1, J. of Geophys. Res., Vol. 87, 

Sup., pp. A210–A220, 1982.

5. Sibille, L.; Carpenter, P.; Schlagheck, R.; and French, R.A.: “Lunar Regolith Simulant Materials: Recommendations for Standardization, Production, and Usage,” NASA/TP—2006–214605, 

p. 118, 2006.

6. Mahmood, A.; Mitchell, J.K.; and Carrier, W.D., III: “Grain Orientation in Lunar Soil,” 

Proceedings of the 5th Lunar Science Conference, Geochimica et Cosmochimica Acta, Vol. 3, Sup. 5, 

pp. 2347–2354, 1974.
18

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Generation of Requirements for Simulant Measurements

C.M. Schrader,* J.E. Edmunson,* and D.L. Rickman

George C. Marshall Space Flight Center

Marshall Space Flight Center, AL 35812

National Aeronautics and Space Administration

Washington, DC 20546–0001

Unclassified-Unlimited

Subject Category 91

Availability: NASA CASI (443–757–5802)

Prepared by the Earth Sciences Office

* BAE Systems, Huntsville, Alabama 

M–1234

Technical Memorandum

NASA/TM—2010–216445

lunar simulant, figure of merit, requirements

01–09–2010

UU 24

NASA

U U U

This TM presents a formal, logical explanation of the parameters selected for the figure of merit (FoM) algorithm. The FoM algorithm 

is used to evaluate lunar regolith simulant. The objectives, requirements, assumptions, and analysis behind the parameters are provided. 

A requirement is derived to verify and validate simulant performance versus lunar regolith from NASA’s objectives for lunar simulants. 

This requirement leads to a specification that comparative measurements be taken the same way on the regolith and the simulant. In turn, 

this leads to a set of nine criteria with which to evaluate comparative measurements. Many of the potential measurements of interest are 

not defensible under these criteria. For example, many geotechnical properties of interest were not explicitly measured during Apollo 

and they can only be measured in situ on the Moon. A 2005 workshop identified 32 properties of major interest to users. Virtually all 

of the properties are tightly constrained, though not predictable, if just four parameters are controlled. Three parameters (composition, 

size, and shape) are recognized as being definable at the particle level. The fourth parameter (density) is a bulk property. In recent work, 

a fifth parameter (spectroscopy) has been identified, which will need to be added to future releases of the FoM.

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