A non-technical look back at the first two years of ALSEP

Bendix Aerospace Systems Division

USRA Houston Repository

Apollo Lunar 
Surface Experiments 
Package (ALSEP) 
TWO YEARS OF LUNAR SCIENCE 
ALSEP SYSTEM 
The Apollo Lunar Surface Experiments 
Package (ALSEP) is a system of scientific 
instruments carried to the Moon on the 
Apollo spacecraft and set up on the lunar 
surface by the Apollo crew. Using a self-
contained power supply and communications 
equipment, each ALSEP collects and transmits 
to Earth scientific and engineering data for 
extended periods following astronaut depar-
ture. 
APOLLO 12 ALSEP ON THE MOON 
Tranquillity to Hadley and Beyond 
APOLLO MISSION 11 
LUNAR LOCATION TRANQUI LLiTY 
DEPLOYMENT DATE JUL20,1969 
DESIGN LIFE (DAYS) 14 
OPERATING TIME (DAYS)* 71 
* As of 19 November 1971 
Each ALSEP provides 9 million measurements per day. 
12 14 
OCEAN OF STORMS FRA MAURO 
NOV 19,1969 FEB 5,1971 
365 365 
730 287 
Aerospace 
Systems Division 
15 
HADLEY 
JU L 31, 1971 
365 
111 
LUNAR SCIENCE NETWORK ESTABLISHED 
ALSEP SENDS SIGNIFICANT LUNAR SCIENCE DATA 
The Apollo 12 Lunar Surface Experi ments 
Package (ALSEP) continues to transmit to 
Earth scientific and engineering data after 
more than two years of operation on the lunar 
surface. Deployment of the Apo ll o 12 ALSEP 
on the lunar surface on November 19, 1969 
provided man with the first long-term on-site 
scient ific station on another planet. Deploy-
ment of the Apollo 14 ALSEP on February 5, 1971 
and the Apollo 15 ALSEP on July 31 , 1971 estab-
!ished an ALSEP network providing the capa -
bility of collecting and transmitting simul-
taneous scientific data from three remote 
points on the lunar surface . The ALSEP net-
work has transmitted and continues to transmit 
a wealth of scientific data for the continuing 
investigation of the Moon and its relationship 
to Earth. 
The three stations have accepted and executed 
more than 19,000 commands from Earth and re-
turned ten bi lli on data measurements . The 
ALSEP experiments investigate the evolution 
of the Moon and the solar system through in -
struments such as seismometers, magnetometers, 
temperature probes, and ion detectors. Estab-
li shment of a network of instruments with 
successive lunar landings enables the def ini -
tion of the location , velocity, and intensity 
of lunar events. 
MISSION ASSIG NMENTS 
"" 
APOLLO 11 12 1"3 14 15 16 
A LSE P ~ LOCA T ION 23.4°E 23. 5"W 17.5"W 3. r E 15 .5 E 
EX PERIMENT OY N 3.0
0 S 3. 7"S 26 .1°N 8 .9 'S 
PASSI VE SEISM IC EXPER IMENT • • • • • • 
A CTIVE SE ISM IC EXPERIMENT • • Because of power and weight limitations, 
no single flight can carryall the experi-
ments. A different combination has been 
assigned to each of the Apollo flights. 
SUPRATHERM A L ION DETECT OR • • • 
COLD-CATHODE ION GAGE • • • • 
SO LA R WIND SPECTROMETE R • • 
CH A RGED PA RT! CLE EXPER IMEN T • • 
LUNAR SURFACE MAGNETOMETER • • • 
HEAT F LOW EXPER IMENT • • • 
LAS ER RANGING RETRO REF L ECTOR • • • 
- TENTAT I VE 
MOONQUAKES DEEPER THAN EARTHQUAKES 
PASSIVE SEISMIC EXPERIMENT 
The three ALSEP Passive Seismic Experiments 
(PSE) provide information on the internal 
composition of the Moon by monitoring natural 
and man-made seismic events. The three stations, 
separated by as much as 1100 kilometers , make 
it possible to determine the location of seis-
mic events, such as the moon quakes that occur 
with regularity when the Moon is at apogee and 
perigee of the orbit. It has been determined 
that the epicenter of the majority of these 
moonquakes is approximately 600 kilometers 
sout-southwest of the Apollo 12 ALSEP and the 
depth of focus appears to be nearly 800 kilo-
meters which is deeper than any known earth-
quake. 
In addition to the periodic moonquakes, epi-
sodes of frequent small moon quakes have been 
observed. The source of these moonquake 
"swarms" has yet to be determined but they 
may well result from continuing minor adjust-
ments to stresses in the Moon's outer crust. 
Seismic evidence of a I unar crust and mantle 
has been discovered. The crust in the region 
of the Apollo 12 and 14 stations appears to 
be between 25 and 70 kilometers thick and 
may consist of two layers. 
ACTIVE SEISMIC EXPERIMENT 
I n addition to the PSE an Active Seismic Experi-
ment (ASE) was deployed at the Apollo 14 
ALSEP site. The ASE measures seismic sources 
such as the astronauts' movements or the de-
tonation of small explosive devices. The data 
obtained thus far indicate that the ASE mea-
surements are in agreement with predictions 
obtained from PSE data. A major phase of the 
ASE investigations, using ground-activated 
grenades, will be performed after data collec-
tion from other Apollo 14 ALSEP experiments 
is virtually complete . 
Time In Minutes 
o 10 20 30 40 50 60 
I I 
CHANGE OF GA IN 
150 ~IM 
nil I 
" 
....... : 
';::::::'" ~·ri.IIt.II'''IU.''''''''''''''''-----j 
L~\ I ~\ PAC T 
NOV 20 
t · · ' 11 
NATU RAL 
[VENT 
DEC iO 
NA1URAL 
EVENT 
rEB IS 
1970 
1909 
• III 
lIILtt 
-.-~ 
10 MIN 
HI. I't I II J d. • Q II I 1 
TYPICAL SEISMIC DATA 
I 6 N~\ 
. .,.,. 
I 0 N~~ ~ ; 
"I:: 
Hr. 
I 0 N~\ 
17 
- 4 . l'W 
139°S 
s 
E 
C 
0 
N 
0 
G 
E 
N 
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R 
A 
T 
I 
0 
N 
MAGNETISM ON THE MOON 
LUNAR SURFACE MAGNETOMET ER 
The ALSEP Lunar Surface Magnetometer (LSM) 
and the Lunar Portable Magnetometer (LPM) 
have been deployed on the lunar surface to 
study intrinsic remanent lunar magnetic 
fields and the global magnetic response of 
the Moon to large-scale solar and terrestrial 
magnetic fields. 
A study of the interaction between the mag-
netic field of a planet and the hot ionized 
gas emanating from the sun permits one to 
determine the accretion of an atmosphere, 
radiation belts, and absorbed gases during 
the evolutionary phase of that planet. 
Using the magnetometer experiments on 
Apollo 12, 14, and 15, local steady fields 
have been calculated at a total of four lunar 
sites. The steady fields were 38±3 gammas at 
the Apollo 12 LSM site, 103t5 and 43t6 gammas 
at the two Apollo 14 LPM sites, and 6t4 gammas 
at the Apollo 15 LSM site . 
By comparison, the field at the Earth's 
equator is approximately 35,000 gammas. These 
fields are all atrributed to remanent magnet-
2043 2045 
ization in the nearby subsurface material. 
The remanent fields could be due to a variety 
of types of sources, including possible nearby 
platelike regions that were originally uni-
formly magnetized but have subsequently been 
changed by some mechanism such as meteoroid 
shock impact. The fact the remanent magnetic 
fields could be extended over two orders of 
magnitude indicates that the lunar surface 
steady field varies widely with location on 
the Moon; magnetic concentrations (magcons) 
evidently exist at widely separated regions 
of the Moon. The large differences in magnetic 
remanence properties of the Apollo 15 and 
Apollo 12-14 regions suggest the possibility 
that they were formed at different times under 
different ambient field conditions or that the 
magnetic properties of the materials in the 
two regions differ su bstantially. 
The electrical conductivity of the lunar in-
terior has been determined from magnetic field 
step-transient measurements. The data fit a 
spherically symmetric three-layer lunar model 
having a thin outer crust of very low electr i-
cal conductivity. For the case of an olivine 
Moon, the temperatures of the three layers are 
approximately as follows: crust 4400 K, inter-
mediate layer 8100 K, and core 12400 K. 
2047 2049 
Time . G.m. t. 
MAGNETOMETER DATA CROSSING BOW SHOCK 
PRECISE DISTANCE: EARTH- TO-MOON 
LASER RANGING RETRO-REFLECTOR 
The Laser Rang in g Retro -Ref lectors (L R R R) 
dep loy ed on the lunar surface on the Apollo 11, 
14, and 15 missions serve as reference points 
in measuri ng prec ise ranges between the array 
and points on Earth using the technique of short 
pulse laser ranging. 
The Apollo 11 and 14 retro-reflectors are both 
near the equator , but are well separated; and 
the retro-ref lector deployed by the Apollo 15 
crew completes a triangular network for pre -
cision ranging by Earth-based lasers. The 
Apollo 15 LRRR has 300 retro-reflectors, com-
pared to 100 reflectors on the Apollo 11 and 
14 arrays. These reflectors have made poss ible 
the measurement of the Earth -Moon separation 
(240,000 miles) with an uncertainty of 6 inches. 
The better s ignal-to-noise ratio avai lable 
with the larger retro-reflector permits more 
frequent ranging measurements and the use of 
telescopes of smaller aperture than used with 
the smaller arrays. The third array prov ides 
the im portant long north-south baseline sep-
arat ion with the Apollo 11 and the Apollo 14 
retro-reflectors. Accumulation of data neces-
sary to the planned astronomical, geophysical, 
and general relat ivi ty experiments will req uire 
ranging measurements over a period of years. 
.. 
--
APOLLO 14 ON TH E MOON 
HEAT FLOW FROM MOON HALF THAT OF EARTH 
LUNAR HEAT FLOW EXPERIMENT 
The temperature of the moon is being monitored 
by the Lunar Heat Flow Experi ment which was 
deployed on the lunar surface by the crew of 
Apollo 15. The heat flow experiment is designed 
to make temperature and thermal property mea-
surements within the lunar subsurface to deter-
mine the rate at which heat is flowing out of 
the Moon. This loss of heat is directly related 
to the rate of internal heat production and to 
the internal temperature profile. 
Initial measurements with this instrument show 
a subsurface temperature one meter below the 
surface of 252.40 K at one probe site and 250.70 K 
at the other, temperatures which are about 350 K 
above the mean surface temperature. From a 
depth of 1 meter down to 1.5 meters, the temp-
erature increases at the rate of 1.750 K/meter 
±2%. Conductivity measurements of values be-
tween 1.4 x 10-4 and 2.5 x 10-4 W/cmoK were 
determi ned at depth and are a factor of 7 to 
10 above the conductivity of the surface layer, 
thus indicating that conductivity increases 
with depth. 
Preliminary analysis indicates that the heat 
flow from beneath the Apollo 15 site is 
3.3 x 10-6 W/cm2 ± 15%. This value is approxi-
mately half the average of heat flow from the 
Earth. With the assumption that this figure 
is an accurate representation of the heat flow 
at the Apollo 15 site (data accumulation from 
a number of lunations will be required for 
accuracy), and with the further assumption 
that this figure represents the Moon-wide 
value, then consideration of the Moon as a 
sphere with uniform internal heat generati on 
yields a picture of the Moon with far more 
radioactivity than has been previously ex-
pected, and far more radioactive than sug-
gested by the ordinary chrondites and the 
carbonaceous chrondites which have formed 
the bases of standard · models of the Earth 
and Moon to date. 
TH E RMOCOUP LES ""'~ I ~ 
PROBE 2 
TEMPERATURE 
( CM INCHES RANGE 
- --SI,JRFA~~ _ 0 - 0 - _320°F TO i-l8So F -- SOSoF 
---- ~ - 50 - 20 - - -------
~ 
"1 - 100 -- 40 -
~J 
:0 
----I~j - 150 
PRO B E ----z--. l · 
STOP '. 
PROBE 1 
60 
CONSTANT TEMP. (_4° F I 
APOLLO 15 ALSEP HEAT FLOW EXPERIMENT 
LUNAR ATMOSPHERE 
Gas Clouds - Water Vapor 
The ALSEP Suprathermal Ion Detector Experi ment 
(SIDE), the associated Cold Cathode Gage Experi-
ment (CCG E), and the Charged-Particle Lunar 
Environment Experiment (CPLEE) are measuring 
the dynamics of the lunar ion atmosphere. 
SUPRAT HERMA L ION DE TECTOR 
The network of ALSEP Su prather mal Ion Detectors 
are continuing to provide information on the 
energy and mass spectra of positive ions close 
to the lunar surface. These ions can be grouped 
into two classifications; those resulting from 
ionization of gases generated at the Moon by 
natural and man-made sources and those which 
arrive from sources beyond the near-Moon envi-
ronment. 
Evidence of the operation of a prompt ioniza-
tion and acceleration mechanism operating in 
the lunar exosphere has been discovered based 
on the data from the Apollo 12 and 14 instru-
ments. Electric and magnetic fields near the 
lunar surface can be studied by observing 
their effects on the motions and energies of 
the ions after they are generated. The net-
work of three SIDE instruments (Apollo 12, 14, 
and 15) now operating on the Moon allows a 
more precise determination of dimensions and 
motions of ion clouds moving across the lunar 
surface. 
An example of the significant results of the 
SI DE experiments is the detection of water 
vapor in the lunar exosphere by the Apollo 14 
SI DE . Water from some unknown depth below the 
surface is believed to be liberated by seismic 
activity, and vaporized instantly upon ex-
posure to the lunar atmosphere. The vapor is 
then dispersed over a wide area; some fraction 
of it becomes ionized and is subsequently de-
dected by the SIDE. 
COL D CATHODE GAGE EXPER IM EN T 
The A LSEP Cold Cathode Gage Experiment (CCGE) 
measures the density of the tenuous lunar 
atmosphere at the lunar surface. This thin 
concentration of gases is supplied by the 
solar wind, by the possible continued release 
of molecu les from the Moon's interior through 
the lunar crust, and venting and outgassing 
from the lunar module and other space gear. 
The data from the Apollo 12, 14, and 15 CCGE 
instruments have shown that the gas concentra-
tions observed during the lunar days appear 
to be due overwhelmingly to contaminants re-
leased by the lunar module and its associated 
equi pment. However, the concentrations observed 
during the lunar nights, typically less than 
2 x 105 particles/cm 3 , are lower even than 
those expected from just the neon component 
of the solar wind alone. This suggests that 
the contaminant gases from spacecraft equip-
ment remain adsorbed at the low night-time 
temperatures, and that the lunar surface it-
self is not saturated with neon, but that the 
rate of neon release from the surface is much 
slower than the rate of neon implantation. 
APOLLO 15 ALSEP ON THE MOON 
LUNAR ATMOSPHERE 
Gas Clouds - W ater Vapor 
CHARG ED-PAR T ICLE LUNA R ENVI RONMENT EX PE RI M ENT 
The ALSEP Charged -Particle Lunar Envi ronment 
Experiment (CPLEE) which was deployed by the 
crew of Apollo 14 measures the ambient fluxes 
of charged particles, both electrons and 
ions, with energies in the range of 50 to 
50,000 eV. One of the most stable features 
observed is the presence of low-energy elec-
trons whenever the landing site is illuminated 
by the Sun. The variation in the low-energy-
electron flux during the lunar eclipse of 
February 10, 1971 provided strong evidence 
that the electrons are photoelectrons liberated 
frrom the lunar surface. The solar-wind flux 
observed by the CPLEE has exhibited rapid time 
variations (periods of approxi mately 10 sec), 
both when the Moon is in interplanetary space 
and when it is immersed in the magnetospheric 
tail of the Earth. Passage of the Moon through 
the magnetopause and magnetospheric tai I has 
produced some particularly interesting data, 
including rapidly fluctuating low energy (50-
to 200-eV) electrons, fluxes of medium-energy 
electrons lasting from a few minutes to tens 
of minutes, and electrons that have energy 
spectra remarkably si mi lar to those observed 
above terrestrial auroras. Thus, auroral par-
ticles appear to penetrate far into the magnet-
ospheric tai I, an observation that, if con-
firmed, contains important implications concern-
ing the general topology of the magnetosphere. 
After the Apollo 14 LM ascent-stage impact, two 
plasma clouds, which were separated in time by 
a few seconds, passed the CPLEE. The clouds 
were traveling at approximately 1 km/sec and 
had diameters of 14 and 7 km. 
MAGNETOPAUSE 
~ CARTH ~~-~~-N-----+~ ~~------{~~~~ GEOMAGNETIC TAIL 
/ 
TRANSITION 
REGION 
EARTH 'S WAK E IN THE SOLAR WIND 
ALSEP LUNAR LABORAT ORY SU RVEYS EARTH 'S ENVI RONMENT 
SOLAR WIND SPECTROMETER 
The two Solar Wind Spectrometer Experiments 
(SWS) deployed on Apollo 12 and 15 missions 
are designed to determine the interaction of 
the Moon and the solar wind. The solar wind, 
or plasma, is the top layer of the atmosphere 
of the Sun (often called the corona), which 
is completely ionized and is expanding into 
space at hypersonic velocity in all directions. 
The Solar Wind Spectrometer Experiments are 
operating 1100 km apart at the Apollo 12 and 
the Apollo 15 sites. Solar wind plasma, mag-
netosphere plasma, and magneto pause crossings 
have been observed by both instruments which 
show good agreement between these observations; 
for example, simultaneous (within 15 seconds) 
changes in proton densities and velocities 
are detected at both sites. As first measured 
with the Apollo 12 instrument the solar plasma 
right at the lunar surface is indistinguishable 
from the solar plasma some distance out from 
the surface (monitored by orbiting instru-
ments), both when the Moon is ahead of and 
when the Moon is behind the magnetic bow 
shock of the Earth. 
SCIENTIFIC EXPLORATION GOES FORWARD 
r ) 
t ..-: • 
. 
APOLLO 16 ALSEP PREPARED FOR 1972 FLIGHT TO THE MOON 
Future Lunar Exploration 
The two remaining Apollo miSSions, Apollo 16 
and Apollo 17, will also carry ALSEP systems 
to further the scientific investigation of the 
Moon . The subsequent ALSEP's will consist of 
varying experi ment arrays to supplement and 
complement those scientific experiments already 
operating on the lunar surface. For example, an 
additional seismometer will be deployed to 
complement the seismic sensing network. Fur-
ther particle and field measurements will be 
made with magnetometers, gravimeters, and ion 
detectors. Thermal characteristics of the lunar 
surface will be explored with a second heat 
flow experiment. 
The ALSEP to be carried on Apollo 17, presently 
the last planned Apollo mission, is designed 
for a two-year operational life. Each of the 
earlier ALSEP's will be operational for a 
minimum of one year. The continuing long-term 
scientific measurement and data collection of 
lunar exosphere, surface mantle, and whole body 
properties are essential to the understanding 
of the Earth-Moon relationsh i p and the solar 
system. The two-year anniversary of the first 
ALSEP marks a major milestone in systematic 
scientific lunar exploration. 
Apollo Lunar Surface Experiments Packages are developed by the Aerospace Systems Division of The Bendix Corporation 
under the direction of the National Aeronautics and Space Administration Manned Spacecraft Center. 
For additional information please contact: The Bendix Corporation 
Aerospace Systems Division 
ALSEP Program Director 
3300 Plymouth Road 
Ann Arbor, Michigan 48107 


Apollo Lunar Surface Experiments Package (ALSEP) two years of lunar science

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Apollo Lunar Surface Experiments Package (ALSEP) two years of lunar science

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