Scientific investigations at a lunar base

Vol. 17, No. 7, pp. 675-690, 1988 Printed in Great Britain

0094-5765/88 $3.00 + 0.00 Pergamon Press plc

Acta Astronautica

SCIENTIFIC

Michael National

B.

INVESTIGATIONS

Duke

and

Aeronautics

Lyndon

B.

Wendell

and

Johnson

Houston,

AT A

Texas,

W.

LUNAR

BASE

Mendell

Space

Administration

Space

Center

U.S.A.

Abstract Scientific investigations to be carried out at a lunar base can have significant impact on the location, extent, and complexity of lunar surface facilities. Among the potential research activities to be carried out are: (1) Lunar Science: Studies of the origin and history of the Moon and early solar system, based on lunar field investigations, operation of networks of seismic and other instruments, and collection and analysis of materials; (2) Space Plasma Physics: Studies of the time variation of the charged particles of the solar wind, solar flares and cosmic rays that impact the Moon as it moves in and out of the magnetotail of the Earth; (3) Astronomy: Utilizing the lunar environment and stability of the surface to emplace arrays of astronomical instruments across the electromagnetic spectrum to improve spectral and spatial resolution by several orders of magnitude beyond the Hubble Space Telescope and other space observatories; (4) Fundamental physics and chemistry: Research that takes advantage of the lunar environment, such as high vacuum, low magnetic field, and thermal properties to carry out new investigations in chemistry and physics. This includes material sciences and applications; (5) Life Sciences: Experiments, such as those that require extreme isolation, highly sterile conditions, or very low natural background of organic materials may be possible; and (6) Lunar environmental science: Because many of the experiments proposed for the lunar surface depend on the special environment of the Moon, it will be necessary to understand the mechanisms that are active and which determine the major aspects of that environment, particular3y the maintenance of high-vacuum conditions. From a large range of experiments, investigations and facilities that have been suggested, three specific classes of investigations are described in greater detail to show how site selection and base complexity may be affected: (1) Extended geological investigation of a complex region up to 250 kilometers from the base requires long range mobility, with transportable life support systems and laboratory facilities for the analysis of rocks and soil. Selection of an optimum base site would depend heavily on an evaluation of the degree to which science objectives could be met. These objectives could include lunar cratering, volcanism, resource surveys or other investigations; (2) An astronomical observatory initially instrumented with a VLF radio telescope, but later expanding to include other instruments, requires site preparation capability, "line shack" life support systems, instrument maintenance and storage facilities, and sortie mode transportation. A site perpetually shielded from Earth is optimum for the advanced stages of a lunar observatory; (3) an experimental physics laboratory conducting studies requiring high vacuum facilities and heavily instrumented experiments, is not highly dependent on lunar location, but will require much more flexibility in experiment operation and EVA capability, and more scphisticated instrument maintenance and fabrication facilities.

srPaper I ~ A - 8 6 - 5 0 9 p r e s e n t e d a t t h e 3 7 t h C o n g r e s s of the I n t e r n a t i o n a l Astronautical *.A.n/7--C

Federation,

Innsbruck,

Austrla, 675

4-11 October

1986.

676

Michael B. Duke and Wendell W. Mendell

Introduction

During the past several years, a series of workshops and symposia have been held which have begun to identify the rationale for and characteristics of a permanent base on the Moon and Duke, 1986).

1984; Mendell,

1986; Burns,

1986; Keaton and Duke,

In space exploration plans, new emphasis

to the role of lunar bases National Commission

on

(Duke et al, 1985;

Space,

1986).

has

development, suspect

for

scientific

These

research,

in

resource

the initial

space

terms

of

race.

We

impetus for e s t a b l i s h m e n t of a lunar

c o m p e t i t i o n or space cooperation. w h i c h economic

1986;

(commercial)

and expansion of horizons for the human

that

given

reports have

base will come from p o l i t i c a l l y motivated decisions,

major

been

Koelle,

g e n e r a l l y described the uses of a base on the Moon its u s e f u l n e s s

(Keaton

scenario,

in

reasons related to the use of lunar resources

for

projects

either of these cases,

An alternative

either space

is the driver,

is also a possibility.

significant scientific

research could

In be

a c c o m p l i s h e d and science would probably form a part of the public rationale

for the undertaking.

c o n s i d e r e d the scientific

With this in mind, we have

research that might be u n d e r t a k e n

relatively early in a lunar base program,

in an effort to initiate

d i s c u s s i o n at a more detailed level than has previously been e x p l o r e d and to begin to specify the manner in which science facilities and requirements would affect decisions of a r c h i t e c t u r e or location of a lunar base.

Origin and History of the Moon

The Moon is a small planetary body, related to the Earth in its origin, simple

in its evolutionary history.

probably intimately

and apparently

relatively

A l t h o u g h it has been studied

locally in more detail than any other planet except Earth, major questions

about its origin and history remain

Workshop,

1986).

(LGO Science

The most promising current hypothesis

involves

the Moon's origin through collision of a Mars-sized planet with the young Earth, (Hartmann,

following separation of the Earth's core

1986; Hartmann and Davis,

1975).

If this e x p l a n a t i o n

Scientific investigations at a lunar base

is correct,

677

the origin of the Earth and Moon are intimately tied,

and the later history of the Earth can only be understood light of this early,

intense event.

However,

in the

because the early

history of the Earth is no longer directly accessible

through

rocks, which have been recycled by geological activity, understanding

the Moon offers the only possibility to test the

hypothesis.

The Moon itself is a somewhat evolved planet. first 200-400 million years of its became largely molten and segregated in feldspathic

rocks and now

history,

During the

the outer regions

into a less dense crust,

represented by the lunar highlands.

Major impacts bombarded this crust, creating huge basins, about 3900 million years ago.

At this point,

up to

the large basins

began to be filled with dark volcanic basaltic maria.

rich

rocks of the lunar

This episode continued to perhaps 2000 million years ago,

after which the lunar surface has been struck occasionally by large meteoroids,

such as the

ones that

produced the rayed

craters Copernicus and Tycho, and by a myriad of smaller meteoroids

that have ground the surface layer to form the lunar

regolith.

Current efforts are concentrating on understanding

earliest history, the major

the

through the study of rock fragments excavated by

basin impacts which have survived the later events.

These are typically small fragments in the lunar regolith "soil" and in breccias,

fragmental

rocks created in impact events, which

are still large enough for modern techniques to determine composition and age.

The Lunar Environment

Taylor attributes

(1986) has reviewed the beneficial

and detrimental

of the lunar environment as it applies to activities

the lunar surface.

The melting of the exterior

regions of the

Moon apparently thoroughly outgassed the planet, have been lost due to the Moon's 1/6 gravity.

at

and these gases

The results are

rocks that contain virtually no residual gases or combined volatiles

(water of crystallization)

and virtually no atmosphere.

678

Michael B. Duke and Wendell W. Mendell

The nighttime atmosphere approximately

2x105

is a collisionless gas with a density of

atoms per cubic centimeter,

most of which

atoms are from solar wind gases weakly implanted in the lunar soil.

The surface diurnal

the lunar equator, centimeters depth.

temperature

ranges from 100 - 385 K at

but is constant at about 253 K below a few The slow rotation of the Moon yields days and

nights that are 14 Earth days long at the lunar equator, points near the lunar poles may be in permanent light shadow

but some

(hot) or

(cold) as the rotational axis is nearly p e r p e n d i c u l a r

the plane of the ecliptic.

The lunar magnetic

10 -4 smaller than that of the Earth at its

to

field is 10 -2 to

equator,

and the

release of seismic energy is 109 smaller than that of Earth;

the

m a x i m u m moonquake magnitude would be in the background noise on Earth.

External

fluxes of m i c r o m e t e o r o i d s

and charged particle

radiation are inevitably present.

Lunar Science

Many questions

remain about the origin and history of the

Moon.

These have been summarized in the LGO Science

Workshop

Report

(1986), which has documented the contributions

expected

from a satellite Observer).

in polar orbit around the Moon

They include:

(i) What is the origin of the Moon?;

(2) How did the lunar crust and mantle evolve?; m a g m a t i c history of the Moon?; of

impact

processes

(3) What

is

the

(4) What is the history and nature

on the Moon?;

(5) Is there an iron-rich

core?;

(6) What is the Moon's thermal history?;

origin

of lunar paleomagnetism?;

the lunar regolith?

(Lunar G e o s c i e n c e

and

(7) What is

the

(8) what is the nature of

Most of these questions can be finally

resolved only with intensive study of the Moon at several sites and by the probing of its interior utilizing geophysical techniques operated over long periods of time.

The first lunar

base,

to all of the

if p r o p e r l y sited,

can make contributions

questions.

Cintala,

et al (1986) have described the geological

i n v e s t i g a t i o n possible with a lunar surface traverse of some 4000 km and 29 sites across Mare constrained

Imbrium.

set of observations,

We describe here a more

consistent with a lunar base

Scientific investigations at a lunar base

679

w h i c h serves as a base camp for extended surface explorations, requiring less intensive site chosen

is the Apollo

alternatives emphases.

long-range

traverse capability.

15 landing site; however,

could be illustrated,

but

The base

many e x c e l l e n t

with somewhat d i f f e r e n t

The advantage of choosing one of the Apollo

science

sites for

an initial base is that the general geological aspects of the landing site are known from the Apollo studies

(Spudis and Ryder,

1985).

Examples of investigations include:

samples and previous

to be u n d e r t a k e n from this base

(i) Studies of a major b a s i n - f o r m i n g event

Imbrium event);

(2) C h a r a c t e r i z a t i o n of the latest

lunar v o l c a n i c activity; c o m e t a r y and asteroidal

i.

and

(e.g.,

the

(youngest)

(3) Deciphering the history of

impact on the Moon's

surface.

D e t a i l e d Exploration of the Imbrium Basin

The Imbrium Basin was a major

impact event that o c c u r r e d

about 4000 million years ago, excavating a crater 700 km in d i a m e t e r and perhaps

20 km deep.

Subsequently,

the floor p r o b a b l y

rebounded and then later was filled with basaltic lavas. distance

Within a

of 250 km of the Apollo 15 site it will be possible

to

i n v e s t i g a t e a sequence of basin ejecta deposits that were excavated

from the lunar mantle and crust by the Imbrium event.

It may be possible of the pre-mare the deeper resulting

to derive

information on the vertical

crust as the farther

from the original

the e x c a v a t i o n depth of samples.

Topographic and structural

of melt features

from the impact can be sampled and studied using

geophysical

techniques.

Using deep drilling techniques,

the later mare volcanic

p r e - m a r e volcanic investigated. potassium,

rim,

from the impact can be reached from which accurate ages

f o r m a t i o n to be studied.

underlying

crater

Melt sheets and pools

for the impact event can be determined and mechanisms

resulting

structure

fill can be sampled.

rocks, exposed in the Apennine Bench,

These

the rocks Possibly can be

rocks are believed to be rich in elements

rare-earth elements and phosphorous

contain i n t e r e s t i n g mineral deposits.

(KREEP)

and may

680

Michael B. Duke and Wendell W. Mendell

The base elements are shown in Table i. from reconnaissance,

required to support detailed investigation It is anticipated that studies will proceed

in which instruments are emplaced and samples

collected at various locations,

Tab. ICharacteristics

then more detailed study, as

for Lunar Base 'to Support Geological Investigations

Base Camp (includes habitats,

life support,

etc.)

Laboratory Facilities Sample preparation Sample analysis microscope,

(thin section)

(scanning electron microscope,

x-ray fluorescence)

Sample storage

(soils,

rocks, cores)

Sample documentation/data Map preparation Geophysical

facility

facility (computer system)

Instrumentation

Main station

Seismic station

Neutral

ion mass spectrometer Remote station / Traverse vehicle

Seismic stations

(remote emplacement)

Traverse gravimeter

Active

seismic

Magnetometer Traverse Vehicle 250 km range Capability to carry drop tanks to remote sites I0 kw power Remote Shelters Unpressurized

solar flare "huts"

Scientific investigations at a lunar base

samples are analyzed and questions refined.

681

This will require

that remote stations be reoccupied from time to time.

Also,

shelters are required for quick occupancy in the event of solar flares.

2.

Volcanic History

Three distinctive epochs of volcanism can be studied at the Hadley Base Site.

These include pre-mare volcanism, the

mare-filling volcanics and late-mare or post-mare volcanism.

The

mare-filling period produced the feature known as Hadley Rille, apparently a collapsed lava tube which could have base development implications if open sections remain.

The Apollo 15 samples

included evidence of volcanic fire fountains that produced deposits of volcanic glass in the form of tiny spheres, which commonly contain thin volatile-rich surface coatings.

Location of

the source of these glasses is of considerable interest for volcanic mechanism and resource-related studies.

The later

volcanism is of interest because it can yield information of the thermal history of the Moon, and may contain fragments of crustal materials as inclusions, mantle can be gained.

from which information on the underlying

Dark deposits which may mark volcanic

vents, and features which may represent volcanic cones are present in the vicinity of Hadley Base.

Field locations to study each of

these features can be reached with modest surface traverse capability.

Here also,

it will be desirable to set up

local shelters for field crews, for protection from solar flares, to provide support while detailed local investigation is underway.

3.

Impact History

A unique record which possibly can only be read on the Moon is the historical abundance of comets and Earth-crossing asteroids, which can be sampled through the intensive study of impact craters.

The experiment would involve sampling all impact

craters in a given area (say 20 km square).

By studying the

features of the craters, the compositional glass formed by the impact, and the distribution of fragments of the impacting object, it should be possible to distinguish primary from secondary

682

Michael B. Duke and Wendell W. Mendell

craters, object,

the compositional

characteristics of the impacting

and the age of each crater.

The capability of trenching

the regolith to up to 10 meters depth would allow older craters to studied in a similar manner,

allowing the impactor

flux to be

d o c u m e n t e d as a function of time.

Lunar A s t r o n o m i c a l Observatories

Several unique aspects of the lunar environment

characterize

it

and d i s t i n g u i s h it from other locations on Earth or in space(Smith,

1986).

diffraction-limited

The high vacuum of the lunar surface offers imagery utilizing sensors and arrays that are

p a r t i c u l a r l y sensitive and will not suffer from significant decay due to molecular contamination.

The vacuum,

absence of magnetic

field and low ion density in the lunar ionosphere should lead to a lunar sky that is even darker than that seen from Earth orbit, to the very high terrestrial airglow. base for instruments,

The Moon's

stability as a

including an absence of seismic noise, will

allow instruments to remain in fixed position and o r i e n t a t i o n extended periods of time, and the slow rotational will allow long exposures objects.

due

for

rate of the Moon

for very faint sources or variable

The lower gravity and lack of winds will e v e n t u a l l y allow

the construction of very large instruments with very precise positions.

Some of these instruments may be adapted to natural

lunar landforms,

such as craters, which may allow A r e c i b o - l i k e

antennas to be utilized. materials

If ways are found to utilize

in construction,

lunar

many of the t r a n s p o r t a t i o n costs for

such large antennas may be offset by using local materials. Finally,

the far side of the Moon is permanently shielded from the

natural and artificial noise of the Earth.

The advantages of the Moon as an observatory site must be compared to that of other potential UV-optical

observatories,

sites for space observatories. Stockman(1986)

For

has made the comparison

shown in Table i.

The types of astronomical

facilities that have been proposed and

their c h a r a c t e r i s t i c s are presented in Table 2.

Scientific investigations at a lunar base

The

requirements

683

for a lunar astronomical o b s e r v a t o r y are varied,

d e p e n d i n g on the instruments to be established. characteristic

One important

of modern astronomy is the strategy of c o n s t r u c t i n g

t e l e s c o p e s which provide the s i g n a l - g a t h e r i n g capability, c h a n g i n g out the d e t e c t o r s / i n s t r u m e n t s new analytical

at the focus to introduce

c a p a b i l i t y as technology advances.

to be the case for lunar telescopes as well, observatory's

but

This is e x p e c t e d

making an

a s s o c i a t i o n with a manned base a valuable asset.

l o c a t i n g the o b s e r v a t o r y within easy t r a n s p o r t a t i o n distance a base

(5-50km),

servicing and instrument

environment

can provide

flexibility to o b s e r v a t o r y operations.

not c u r r e n t l y

from

replacement capability,

s u p p o r t e d by shops and laboratories at the base, considerable

By

Instruments

in use can be stored in a controlled high v a c u u m

at the main base.

Isolation of sensor systems from the inhabited base also must be considered. outgassed

Potential

sources of c o n t a m i n a t i o n include v o l a t i l e s

from habitats and suited astronauts;

surface activities, vibrations

dust raised by

traveling along ballistic trajectories;

and d i s p l a c e m e n t s

e q u i p m e n t at the base.

related to m o v e m e n t of people and

Location of communications antennas on the

surface or in space may interfere with some sensors. it appears

In general,

that separation of the o b s e r v a t o r y from the base

a c t i v i t y by distance of a few kilometers

should be satisfactory.

Placing the o b s e r v a t o r i e s at higher elevation than the base f a c i l i t y should be effective, behind

ridges or mountains

as could siting the instruments

from the base. A t t e n t i o n should be paid

to p r e p a r a t i o n of the observatory site to minimize c o n t a m i n a t i o n problems

that might arise during o b s e r v a t o r y servicing.

Instrumentation

for astronomical o b s e r v a t o r i e s will be f a b r i c a t e d

on Earth and transported to the Moon in the early stages of a lunar base.

P r e p a r a t i o n of the site will be an important step in

o b s e r v a t o r y emplacement, Transportation

depending on the type of installation.

routes from the base to the o b s e r v a t o r y site must

be e s t a b l i s h e d and stabilized, by v e h i c l e s

in order to support routine visits

carrying people and replacement instruments.

p r o b a b l y be desirable

to establish

"lineshack"

It will

shelter c a p a b i l i t y

MichaelB. Dukeand Wendell W. Mendell

684

Tab,2:

LAUNCH

ADVANTAGES

FOR A S T R O N O M I C A L

COSTS

MAINTENANCE

PLATFORM

MOON

LOW

HIGH

HIGH

SS/LB

VERY GOOD

POOR

SIMPLE

OPS.

COMPLEX

SCIENCE

EFF.

35%

OPTICAL

BACKGROUND

LB

VERY

GOOD

SIMPLE

90%

EARTH/ZODIACAL

STAB.

ORBITS

GEO

SCIENCE

MAX.

IN V A R I O U S

LEO

STS/SS*

MAINTAINABILITY

THERM.

FACILITIES

45%

ZODIACAL

ZODIACAL

POOR

VERY GOOD

EXP.

45 M I N

17 H

LARGE APERTURES

LIMITED

LIMITED

VERY

GOOD

14 D A Y S

GOOD POTENTIAL

UPGRADING

GOOD

CONFIGURATION

RIGID

*STS

at

= SPACE

SHUTTLE;

the o b s e r v a t o r y

flares.

As

the

m a y be p o s s i b l e particularly shields,

site,

costs

more

components

lunar

RIGID

FLEXIBLE

of the

(supports,

with

thereby

BASE

protection

establishment and m o r e

materials,

associated

EXCELLENT

LB = L U N A R

to p r o v i d e

of a l u n a r

to m a n u f a c t u r e

from

STATION;

in o r d e r

capability

structural

etc.)

transportation

SS = S P A C E

POOR

from

increases,

it

components,

insulation, decreasing

expansion

solar

of l u n a r

light

the astronomy.

Scientificinvestigationsatalunarba~

685

TYPICAL LUNAR A S T R O N O M I C A L O B S E R V A T O R Y INSTRUMENTS

INSTRUMENT

OPTICAL

CHARACTERISTIC

INTERFEROMETER

REFERENCE

M I C R O A R C S E C O N D RESO-

BURKE(1985)

LUTION AT OPTICAL WAVELENGTHS

M O O N - E A R T H RADIO

<30 M I C R O A R C S E C O N D

INTERFEROMETER

R E S O L U T I O N AT <6CM

BURNS(1985)

WAVELENGTH

V E R Y LOW F R E Q U E N C Y

OPENS 10-100M WAVE-

DOUGLAS &

RADIOASTRONOMY

LENGTH REGION TO STUDY

SMITH(1985)

LARGE R A D I O T E L E S C O P E

FAR-SIDE E M P L A C E M E N T

OLIVER(1985)

(SETI)

Some

instruments may benefit from emplacement out of line of sight

from Earth. At an early stage in lunar development,

however,

much

can be done w i t h i n a few tens of kilometers of any base site chosen.

S e l e c t i o n of a lunar base site near the lunar limb may

provide

an optimum way to provide an initial

with

ready access to a more extensive

frontside

facility

future far-side observatory,

perhaps a few hundred kilometers distant.

Physics / C h e m i s t r y Laboratory

The lunar e n v i r o n m e n t

is characterized by high v a c u u m with

a r b i t r a r i l y high pumping capacity,

excellent access to insolation,

and the virtual absence of an internal magnetic lunar surface there is a constant a few meters below the surface,

field.

flux of energetic

At the

radiation,

but

all radiation is absent except

for

n e u t r i n o s and radioactive decay products from n a t u r a l l y o c c u r r i n g potassium,

uranium,

and thorium.

The latter could,

be made a r b i t r a r i l y low by selecting natural are d e p l e t e d

in radioactive

species.

in principle,

lunar m a t e r i a l s

By suitable

thermal

that

686

Michael B. Duke and Wendell W. Mendell

management,

it should be possible to develop sustained very high

(several thousand degrees Centigrade)

or very low (<5 K)

temperatures.

Fundamental physics investigations

could be u n d e r t a k e n when

very low radiation backgrounds are necessary, neutrinos

(Shapiro,

1985; Petschek,

e.g.,

for d e t e c t i n g

1985; Cherry and Lande,

or studying the electric dipole moment of the neutron Duke,

1986).

1985)

(Keaton and

The stability of the lunar surface may make possible

the d e t e c t i o n of gravity waves predicted by the theory of relativity.

Experiments at low temperatures might include

research on properties of matter near absolute

zero.

Techniques

for the isotopic separation of 3He from 4He or hydrogen d e u t e r i u m might be developed. accelerators material

H y p e r v e l o c i t y e l e c t r o m a g n e t i c mass

could be used to investigate

impact phenomena and

properties under very high shock pressures.

The nature of the facilities physics

from

required for a fundamental

facility are are not now known in specific detail.

However,

based on the speculation above,

such a facility would

seem to be c h a r a c t e r i z e d by the following attributes:

i.

Large volumes which are m a i n t a i n e d at high v a c u u m should

be provided with structures to allow for experiment emplacement, sensor p o s i t i o n i n g and remote observation, or unshielded, temperature

depending on requirements

control.

Access

these may be shielded

for radiation and

to the facility would be through

telerobotics or space-suited technicians. 2.

Adequate

power

(tens of kilowatts)

are n e c e s s a r y in order

to provide thermal control and stable high voltage power supplies for experiments. 3.

Underground,

heavily radiation-shielded tunnels may be

required. 4.

Provision must be made for adequate support of

experimentation.

This includes data processing as well as shops

for fabrication of experiment and equipment maintenance.

The location of these facilities

is probably not d e p e n d e n t on

intrinsic properties of the Moon and can be established at any

Scientific investigations at a lunar base

base site.

687

There will be a need to isolate the facilities

certain types of interaction with other activities,

particularly

those which would affect the high vacuum conditions. facility will also be distinguished

The physics

from other facilities by a

relatively large staff of scientists, crew,

from

technicians,

and supporting

in order to maintain a suitable pace of experimentation.

Conclusion

Scientific uses of the Moon will require three distinct classes of support capability.

Geological

require emphasis on long range mobility, coring and trenching apparatus, to provide

for rapid progress

exploration will

emplaced instruments,

and analytical apparatus

in field geological

in order

characterization

and selection of samples to return to Earth for detailed investigation.

Field crews will have to supported for extended

stays away from the base camp in order to take advantage of mobility.

Astronomical

facilities will generally require significant

emplacement of facilities,

probably by human crews, but may not

require permanent crews on-site.

Maintenance

can be provided by

crews form the base, which will probably be separated from the observatory 25 - 500 km.

Rapid,

reliable long-range

transportation will be required. maintenance facility.

The base camp will require

facilities and will provide a data processing However,

much analysis may still be accomplished by

astronomers on Earth.

A physics laboratory will be characterized by extensive surface and subsurface

structures,

complex sensor/data systems

requirements,

and real time operations by scientists and

technicians.

Shop facilities

for experiment modification and

fabrication will be desirable and provision made for substantial on-site

staff

(20 persons).

688

Michael B. Duke and Wendell W. Mendell

Site selection for a base that will support geological e x p l o r a t i o n will be determined primarily by the science requirements.

Capabilities

for extended exploration may be

d e v e l o p e d either by emplacing additional bases or e x p a n d i n g traverse

capability.

Site selection for astronomical

o b s e r v a t o r i e s may be dominated by ability to access the lunar farside and by the local characteristics of the site considerations). consideration

craters)

Site selection is probably not a major

for a lunar physics facility,

characteristics

(engineering

of the site

although special

(engineering properties,

access to

may be important.

The e s t a b l i s h m e n t of lunar base characteristics and optimal sites should be investigated further,

as requirements are

d e v e l o p e d more completely.

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