Several recently suggested concepts for conducting astronomy from a lunar base are cited. Then, the process and sequence of events that will be required to design an observatory to be emplaced on the Moon are examined

Johnson, Stewart W.

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DESIGN OF LUNAR BASE OBSERVATORIES 
Stewart W. Johnson 
Principal Engineer 
The BDM Corporation 
1801 Randolph Road, S.E. 
Albuquerque, New Mexico 87106 
Introduction 
In this paper, several recently suggested concepts for conducting astronomy from a .lunar base 
are  cited. Then, the process and sequence of events that will be required to design an  observatory to 
be emplaced on the Moon are  examined. 
Background 
In the 21st century, a lunar base will be established which will eventually support 
astronomical observations from the lunar surface. Several nations and groups of nations will have 
the capability to advance space colonization beyond Earth orbit. Mankind will return to the Moon, 
and, when we do, eyes will turn skyward. Man will seek the means to make the best possible use of 
the characteristics and the environment of the Moon that provide such a n  excellent platform for 
astronomical observations. 
Observatory Options 
Many astronomical observatory concepts and instrument configurations have been suggested 
for use on the lunar surface. At recent workshops and conferences, the concepts have been discussed 
in increasing detail (refs. 1 to 4). Additional concepts were suggested and discussed a t  the NASA- 
sponsored workshop on Astronomical Observations From a Lunar Base, held in Houston, Texas, in 
January 1986. 
Each observatory concept has its own set of advantages, constraints, and cost drivers. Each 
requires a different mass of material and effort to be expended on the lunar surface. For each concept, 
there is an  anticipated return in knowledge. 
A Moon-Earth radio interferometer (MERI) has been suggested (ref. 2) which could begin with 
a 10- to 15-m-diameter antenna on the Moon. This antenna, functioning with antennas on Earth and 
possibly in Earth orbit, would achieve resolution (at the 6-cm wavelength) 30 times better than the 
proposed Very Long Baseline Array and 10 000 times better than the existing very large array (VLA). 
Progression would then be to larger or multiple antennas on the Moon. 
Another suggested instrument for installation on the lunar surface is a very low frequency 
(VLF) radio telescope (ref. 3) to investigate the now largely inaccessible radio sky in the 10-m and 
longer wavelengths. Terrestrial ionospheric absorption prevents terrestrial observations in these 
wavelengths. This VLF radio telescope would consist of a central computer facility and many short 
wires, each equipped with a n  amplifier and a digitizer, laid on the lunar surface over an  area of 
approximately 15 by 30 km. 
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Optical interferometers capable of resolution approaching 1 parcsec may be feasible on the 
Moon. Burke (ref. 4) suggests a Y-shaped array of twenty-seven 1-m optical telescopes linked to a 
central correlation station through a set of variable time delays. Each arm of the Y would be 6 km 
long. 
Other concepts proposed include a very large Arecibo-type telescope, sets of instruments for 
x-ray and gamma-ray astronomy, infrared astronomy, search for extraterrestrial intelligence (SETI), 
and observations from possible permanently shadowed zones in craters near the lunar poles. Some 
design considerations for four observatory options follow. For each option, there are common design 
considerations, such as making use of lunar materials (e.g., for shielding in the near term and for 
manufacturing composite structural materials in the far term), minimizing mass to be transported 
from Earth,  packaging for transport, and reducing erection complexity. 
1. MER1 -parabolic dish radio antennas 
a. Site selection and characterization 
b. Thermal strain rates a t  sunrise and sunset 
c. Sunshield 
d. Foundation excavation and placement 
e. Foundation dynamics 
f. Breakdown into transportable packages with semiautomated erectability 
g. Shielding for electronics and other vital operations 
2. VLF radio telescope - wires on surface over a large area 
a. Site selection and characterization 
b. Capability to traverse large area and place wires 
c. Erection and shielding o f a  control facility 
3. Optical interferometer 
a. Site selection and characterization 
b. Control capability (stringent requirements limiting differential settlements, tide 
compensation) 
c. Location of a suitable site for 6-km-long rails laid out on lunar surface 
d. Dynamic response of lunar rubble to movement of telescopes 
128 
4. Arecibo-type radio telescope 
a. Selection of existing crater 
b. Rim-to-floor transportation 
c. Tension and shear-resisting anchors for cables 
d. Foundation elements and support structure 
e. Design for thermal strain compensation 
Advantages of the Environment 
The features of the lunar environment that are inviting to astronomers are  the large, stable 
platform (with a relatively benign seismic environment), the extremely tenuous atmosphere, the 
possibility of uninterrupted observations for 14 days, and (on the far side) the avoidance of earthshine 
and radiofrequency interference of terrestrial origin. Also of significance is the lower acceleration 
due to gravity (one-sixth terrestrial). There is ample material for shielding and, during the night 
(and at the lunar poles), an environment advantageous to keeping detectors at their required low 
temperatures. 
The Design Process 
Some issues (not in order of importance) to be resolved in the process of designing a n  
astronomical observatory for the lunar surface are type of observatory, operational function of lunar 
observatory, collectorslsensorslcontrols, sites and site characterization, observatorylregolith 
interface, materials for fabrication, positioninglconstruction, development process, data management 
system, life-cycle servicing, observatorylinfrastructure interface, and shielding. The type of 
observatory can be selected after enough is known about each proposed concept to be able to quantify 
the mass required on the Moon, the effort to emplace, and the scientific return. Because the 
suggested concepts need more development and some effort toward optimizing, quantification is not 
feasible currently. 
When each viable observatory alternative has been brought to sufficient design maturity, it 
will be evaluated fairly for priority placement on the Moon. The approach to be initiated for each 
alternative consists of determining expected increase in knowledge, investment cost, and assembly 
effort; comparing alternatives on the basis of the determinations; and arriving a t  possible time- 
phasing for development of each alternative. Questions then to be asked include 
1. What is the “right” development sequence for each observatory concept? 
2. Given an agreed-to development sequence, 
a. What are the technical requirements? 
b. What are  the issues to be resolved? 
c. What are  the development steps? 
129 
To obtain a fair, unbiased comparative ranking of design solutions for a Moon-based 
observatory and to identify all alternative solutions, the approach should include the following steps. 
1. Perform tradeoff and optimization studies to place each concept in its most competitive 
position. 
2. Be alert to alternative component combinations that yield better design solutions. 
3. Identify areas requiring experimental results or technological development. 
4. Identify costs and risks associated with each alternative. 
The goal is to provide a traceable path to the best design solution for a lunar astronomical 
observatory and to get a n  estimate of life-cycle cost. Testing will be done to provide design data, to 
verify mathematical models for observatory performance, and to investigate critical behavior 
characteristics. Extensive facilities and resources are  required for test and evaluation of space 
systems (ref. 5 ) .  Results of tests will enable verifying designs and identifying problem areas to be 
corrected. Essential test and evaluation resources must be planned and developed. 
The design process for a lunar observatory is shown in figure 1. We are  now in “the ‘thinking’ 
and gathering of ideas phase” for an astronomical observatory on the Moon. 
Twenty years ago, Herbig and others (refs. 6 and 7 )  suggested the telescope shown in figures 2 
and 3 with the portrayed erection sequence. Today, we think in terms of adaptive optics and 
interferometric arrays. By early in the 21st century, the observatory system design process should 
arrive a t  one or more promising concepts from which a “best” solution can be established. A prototype 
can then be built and tested. Satisfactory design solutions should be ready for emplacement on the 
Moon by about 2010. Telescopes take a long time to develop. Development of the Hubble Space 
Telescope has required more than 20 years. Studies should be initiated now to define a lunar-based 
set of astronomical instruments and experiments for the year 2010. Our knowledge of the Moon from 
previous expeditions will be very useful in the design process (refs. 8 and 9). 
References 
Duke, M. B.; Mendell, W. W.; and Keaton, P. W., compilers: Report of the Lunar Base Working 
Group, LALP-84-43. Los Alamos National Laboratory (Los Alamos, N.M.), 1984. 
Burns, J. 0.: A Moon-Earth Radio Interferometer. In Lunar Bases and Space Activities in the 
21st Century, W. W. Mendell, ed., Lunar and Planetary Institute (Houston, Tex.), 1985, pp. 
293-300. 
Douglas, J .  N.; and Smith, H. J.: A Very Low Frequency Radio Astronomy Observatory on the 
Moon. In Lunar Bases and Space Activities in the 21st Century, W. W. Mendell, ed., Lunar and 
Planetary Institute (Houston, Tex.), 1985. 
Burke, B. F.: Astronomical Interferometry on the Moon. In Lunar Bases and Space Activities 
in the 21st Century, W. W. Mendell, ed., Lunar and Planetary Institute (Houston, Tex.), 1985, 
pp. 281-291. 
Tidd, W. J . ;  Freyer, E. M.; and Johnson, S. W.: Space and Its impact on Test Resources and 
Requirements. In Test Ranges and Facilities for the Next Ten Years, International Test and 
Evaluation Association (Burke, Va.), 1985, pp. 293-306. 
130 
6. A Study of Scientific Mission Support of a Lunar Exploration System for Apollo. In Final 
Report, Vol. 111, Scientific Studies, Par t  2, SID 65-289-3 (X65-164941, North American 
Aviation, 1965, pp. 235-243. 
7. Scientific Mission Support for Extended Lunar Exploration. In Final Report, Vol. 3, Detailed 
Technical Report, SID 66-957-3 (N67-34106), North American Aviation, 1966, pp. 273-288. : 
8. Johnson, S. W.: Siting and Constructing Telescopes and Interferometers on the Moon. 
Preprint IAF-85-406 of the 36th Congress of the International Astronautical Federation 
(Stockholm, Sweden), 1985. 
~ 
I 
I 9. Johnson, S. W.; and Leonard, R. S.: Design of Lunar-Based Facilities: The Challenge of a 
Lunar Observatory. In Lunar Bases and Space Activities in the 21st Centry, W. W. Mendell, I 
ed., Lunar and Planetary Institute (Houston, Tex.), 1985. 
131 
THE "THINKING" AND 
GATHERING OF IDEAS PHASE 
A 
OBJECTIVES, PERFORMANCE ADMISSIBLE 
REQUIREMENTS, FACTORS AND COMPONENTS 
CONSTRAINTS CRITERIA 
PERCEIVED 
- 
THE REAL NEEDS 
DETERMINE IF 
WORTHWHILE 
SATISFACTORY kl S:EiI%N IMPROVEMENTS 
CAN BE 
REALIZED 
HOW SUCCESS 
WILL BE 
MEASURED AND 
RANKED 
WHAT ARE THE 
BUILDING 
BLOCKS 
CONCEPTUALIZING SOLUTIONS AND PROPERLY 
EVALUATING THEM 
'1 4TH PROBLEM 5TH PROBLEM EVOLVE A SET ESTABLISH THE SOLUTIONS SOLUTION 
THE PROMISING 
CONCEPTS 
SELECT THE BEST 
CONCEPT AND 
0 PTI M IZE 
TESTING AND KNOWING 
VERIFICATION WHEN TO STOP 
6TH PROBLEM 
BUILD AND TEST 
A PROTOTYPE 
EVALUATE 
ANALYSIS AND 
EXPERIMENTAL 
RESULTS TO 
THE DESIGN IS 
SATISFACTORY 
AND READY 
TO FINALIZE 
Figure 1.-  The system design process (the seven problems of design). 
132 
UNLOAD FROM LUNAR 
LANDING VEHICLE 
TRANSPORT TO OBSERVATORY 
SITE 
-5 
c- 
DEPLOY PRIMARY MIRROR SYSTEM 
AND INSTRUMENT ROOM 
UNLOAD COMPONENTS 
WITH DAVIT 
Figure 2.- Deployment of 100-in. horizontal telescope, part I. 
1.33 
UNLOAD 200-IN. SIDEROSTAT INSTALL DOME SEGMENTS 
DEPLOY INFLATABLE TUNNEL ALIGN OPTICS; 
ACTIVATE AND CHECK OUT 
Figure 3.- Deployment of 100-in. horizontal telescope, part 11. 
134 


Design of lunar base observatories

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