**LUNAR PROSPECTOR**

***Mission Science Background***

**Press Kit**

**September, 1998**

**National Aeronautics and **

**Space Administration**

**Media Contacts:**

**NASA Headquarters, Washington, DC**

-    Douglas Isbell, (202/358-1753, douglas.isbell@hq.nasa.gov), is the
    Public Affairs Officer for the Office of Space Science's planetary
    missions, and the Headquarters Lunar Prospector mission information
    manager

**Ames Research Center, Moffett Field, CA**

-    David Morse, (650/604-4724, dmorse@mail.arc.nasa.gov), is the
    NASA/Ames Research Center Program Support Lead and the Ames Lunar
    Prospector Public Information Officer in charge of news and press
    releases relating to the LP mission

-    Betsy Carter, (650/604-2742, ecarter@mail.arc.nasa.gov), is the
    Asst. Public Information Officer for Lunar Prospector helping to
    coordinate in all aspects of the LP media efforts

-    Erin Karle, (650/604-2287, ekarle@mail.arc.nasa.gov), is a Public
    Information Intern assisting in all aspects of the LP media and
    information dissemination efforts

**Lunar Research Institute, Gilroy, CA**

-    Rebecca Binder, (408/847-0969), Gilroy, CA., coordinates media
    relations activity on behalf of the Lunar Research Institute.

**Los Alamos National Laboratory**

-    John Gustafson (jgustaf@paopop.lanl.gov) Public Information
    Officer in charge of news and press releases relating to the LP
    mission

**Science Team Contacts**

**Lunar Research Institute, Gilroy, CA**

-    Dr. Alan Binder, (408/847-0969 abinder@mail.arc.nasa.gov), is the
    President of the Lunar Research Institute, Gilroy, CA. and the
    Principal Scientist for the mission.

**Los Alamos National Laboratory, Los Alamos, NM**

-    Dr. William Feldman,(505/667-7372 wfeldman@lanl.gov) is the lead
    scientist for the Spectrometer group.

-    Dr. David J. Lawrence, (505/667-0945) coordinates data analysis
    for the LANL spectrometer team

-    Bruce L. Barraclough, (505/667-8244, bbarraclough@lanl.gov), Los
    Alamos, NM.

-    Dr. Richard Elphic, (505/665-3693, relphic@lanl.gov), Los Alamos,
    NM.

-    Chris Heil, (505/667-9660, ceheil@lanl.gov), Los Alamos, NM.

**Jet Propulsion Laboratory, Pasadena CA**

-    Dr. Alex Konopliv (818/354-6105 Alexander.S.Konopliv@jpl.nasa.gov,
    ask@krait.jpl.nasa.gov) Jet Propulsion Laboratory, Pasadena, CA, is
    a Co-Investigator for the Lunar Prospector mission, responsible for
    the Doppler Gravity Experiment

** UC Berkeley, Space Sciences Laboratory, Berkeley, CA**

-    Dr. David Curtis (510/643-1561 curtis@ssl.berkeley.edu) University
    of California, Space Sciences Lab, Berkeley, CA

-    Dr. David Mitchell (510/643-1561 mitchell@ssl.berkeley.edu)
    University of California, Space Sciences Lab, Berkeley, CA

**Observatoire Midi-Pyrenees, Toulouse, FR**

-    Dr. Sylvestre Maurice (33/561 33 29 47) 14 Av. Edouard Belin,
    31400 Toulouse, FRANCE, coordinates data analysis for the LP
    spectrometer team

Results taken from the seven science papers published in the September
4, 1998 issue of* Science.*

TABLE OF CONTENTS

SCIENTIST'S BIOGRAPHIES 22

GLOSSARY 25

**[Introduction]{#_Toc427470311}**

Lunar Prospector, the first dedicated lunar mission in 25 years, has
already been a tremendous success. Following a near flawless launch on
Jan 6, 1998, a four-day journey to the Moon and entry into lunar orbit,
the tiny spin-stabilized spacecraft has been sending data back to Earth.
Lunar data from the circular polar-mapping orbit has been arriving since
January 15.

On March 5, 1998 Prospector scientists captured the public's imagination
by announcing the discovery of a definitive signal for water ice at both
of the lunar poles. At that time, a conservative analysis of the
available data indicated that a significant quantity of water ice,
possibly as much as 300 million metric tons, was mixed into the regolith
(lunar soil) at each pole, with a greater quantity existing at the north
pole. The first competitively selected Discovery class mission had
conclusively demonstrated that, not only could a cost-capped,
fast-development mission succeed, it could do ground-breaking science in
the process.

The first operational gravity map of the Moon was announced at the same
time. Since then, Lunar Prospector engineer's have taken advantage of
the missions own science results and the gravity data have been used to
facilitate orbit maintenance.

With nearly two thirds of Prospector\'s one-year primary mission
completed, the most recent look at Prospector\'s data reveals several
remarkable insights into lunar science and resources.

**[Mission Profile]{#_Toc427470312}**

At 9:28 p.m. (EST) on January 6, 1998, Lunar Prospector (LP) blasted off
to the Moon aboard a Lockheed Martin solid-fuel, three-stage rocket
called Athena II. It was successfully on its way to the Moon for a
one-year, polar orbit, primary mission dedicated to globally mapping
lunar resources, gravity, and magnetic fields, and even outgassing
events. About 13 minutes after launch, the Athena II placed the Lunar
Prospector payload into a "parking orbit" 115 miles above the Earth.
Following a 42-minute coast in the parking orbit, Prospector's Trans
Lunar Injection (TLI) stage successfully completed a 64-second burn,
releasing the spacecraft from Earth orbit and setting it on course to
the Moon, a 105-hour coast. The official mission timeline began when the
spacecraft switched on 56 minutes, 30 seconds after liftoff. Shortly
after turning the vehicle on, mission controllers deployed the
spacecraft's three extendible masts, or booms. Finally, the spacecraft's
five instruments \-- the gamma-ray spectrometer, alpha particle
spectrometer, neutron spectrometer, magnetometer and electron
reflectometer \-- were turned on. On Sunday, January 11, at 7:20 a.m.
(EST), Lunar Prospector was successfully captured into lunar orbit, and
a few days later began its mission to globally map the Moon.

Lunar Prospector is a small,\* spin-stabilized spacecraft in a polar
orbit with a period of 118 minutes at a nominal altitude of 100 km (63
miles). Since the Moon rotates a full turn beneath the spacecraft every
lunar cycle (\~27.3 days) as it zips around the Moon every 2 hours,
Prospector visits a polar region every hour and completely covers the
lunar surface twice a month. Prospector\'s one-year-long primary mission
with an optional extended mission of a further 6 months at an even lower
altitude enables large amounts of data to collect over time. For some
science instruments, a significant amount of time is required to obtain
high quality usable data. Thus, Prospector\'s polar orbit and
long-mission time render it ideal from the standpoint of globally
mapping the Moon.

\*(1.3m in diameter X 1.4m tall bus with three 2.5 meter science masts
carrying its five science instruments and isolating them from the
spacecraft\'s electronics)

**[Lunar Prospector Scientific Goals]{#_Toc427470313}**

As a Discovery-class mission, Prospector\'s scientific goals were
carefully chosen to address outstanding questions of lunar science both
efficiently and effectively. In the Post-Apollo era, NASA convened the
Lunar Exploration Science Working Group (LExSWG) to draft a list of the
most pressing, unanswered scientific riddles still facing the
lunar-science community. In 1992, LExSWG produced a document, entitled
"A Planetary Science Strategy for the Moon." The following lunar science
objectives were listed: How did the Earth-Moon system form? How did the
Moon evolve? What is the impact history of the Moon's crust? What
constitutes the lunar atmosphere? What can the Moon tell us about the
history of the Sun and other planets in the Solar System?

Lunar Prospector mission designers carefully selected a set of
objectives and a payload of scientific instruments which would address
as many of LExSWG's priorities as possible, while remaining within the
tight budget confines of NASA's "faster, better, cheaper" Discovery
Program.

Lunar Prospector\'s identified critical science objectives are:

-    "Prospect" the lunar crust and atmosphere for potential resources,
    including minerals, water ice and certain gases,

-    Map the Moon's gravitational and magnetic fields, and

-    Learn more about the size and content of the Moon's core.

The six experiments (five science instruments) which address these
objectives are:

-    Neutron Spectrometer (NS) \-- Map hydrogen using neutrons having
    several different energy ranges and thereby infer the presence or
    absence of water.

-    Gamma Ray Spectrometer (GRS) \-- Map 10 key elemental abundances,
    several of which offer clues to lunar formation and evolution.

 Magnetometer/Electron Reflectometer (Mag/ER) \-- These two experiments
combine to measure lunar magnetic field strength at the surface and at
the altitude of the spacecraft and thereby greatly enhance understanding
of lunar magnetic anomalies.

-    Doppler Gravity Experiment (DGE) \-- Make an operational gravity
    map of the Moon for use by future missions as well as LP by mapping
    gravity field measurements from changes in the spacecraft's orbital
    speed and position.

-    Alpha Particle Spectrometer (APS) \-- Map out-gassing events by
    detecting Radon gas (current outgassing events) and Polonium (tracer
    of recent, i.e. 50 years).

**[THE BASICS OF LUNAR SELENOLOGY (GEOLOGY)]{#_Toc427470314}**

**[Formation]{#_Toc427470315}**

The current most widely held theory of how the Moon was formed is the
impact theory. This theory suggests that a large body, possibly the size
of Mars impacted the Earth some 4 billion years ago and the material
which was thrown off, a combination of Earth material and the impactor,
coalesced into Earth\'s Moon. The body was originally molten. As it
cooled, light elements such as calcium and aluminum and silica
crystallized into feldspar and other minerals and floated upwards.
Heavier minerals such as iron and magnesium-rich olivine and pyroxene
formed and sank downward forming the lunar mantle. Incompatible elements
such as KREEP (Phosphorous-K, Rare Earth Elements, and Potassium) were
trapped between the layers. Repeated large impacts on the lunar surface
itself, around 4.1 to 3.9 billion years ago, formed craters which
gradually filled with basaltic lava. These include the large dark areas
that can be seen from Earth, the maria such as Mare Tranquilitatus-the
Sea of Tranquillity and Mare Imbrium-the Sea of Rains. Over time, the
Moon has continued to be bombarded from space by crater forming impacts.
As the Moon cooled, however, lava ceased to fill the craters, and the
impacts began to \"garden\" or break up the brittle lunar surface,
creating the powdery dust which is known as regolith or lunar \"soil."

Lunar topography can be roughly divided into two main types \-- the
maria with their distinctive dark color, and the highlands which are
significantly different in composition.

**A model diagram of the formation of the lunar crust, showing an
incompatible KREEP layer trapped between the mantle and the crust.**

**APPROACHES TO LUNAR SCIENCE AND PREVIOUS MISSIONS**

  ------------------------------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -------------------------------- --------------------------------------------------------------------------------------------------------------------- -------------------- ---------------------------------------------------------------------------- ------------------- ----------------------------------------------------------------------------------------------------------- ------------------------------- ----------------------------- -------------------------- ------------------------------------------------------------------
  **Experiment Type (\*= aboard LP)**   **Previous lunar missions**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
  Photographic Studies                  U.S. Missions: Lunar Orbiter 1-5, Surveyor 1, Surveyor 3, Surveyor 5-7, Ranger 7-9, Apollo 8, Apollo 10-17, Clementine Soviet missions: Luna 3, Luna 9, Luna 12-13, Luna 16-17, Luna19-22, Zond 3, Zond 6-8   Surface Sampling/Soil Analysis   U.S Missions: Surveyor 3, Surveyor 5-7, Apollo 11-12, Apollo 14-17 Soviet Missions: Luna 16-17, Luna 20-21, Luna 24   Magnetic Studies\*   U.S. Missions: Apollo 12, Apollo 14-17Soviet Missions: Luna 10, Luna 21-22   Gravity Studies\*   U.S. Missions: Apollo 12, Apollo 14-17, Clementine Soviet Missions: Luna 10-11, Luna 14, Luna 19, Luna 22   Alpha Particle Spectroscopy\*   U.S. Missions: Apollo 15-16   Gamma-Ray Spectroscopy\*   U.S. Missions: Apollo 15-16 Soviet Missions: Luna 10-11, Luna 22
  Neutron Spectroscopy\*                U.S. Missions: none, although Apollo 17 had a \"neutron probe\"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
  ------------------------------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -------------------------------- --------------------------------------------------------------------------------------------------------------------- -------------------- ---------------------------------------------------------------------------- ------------------- ----------------------------------------------------------------------------------------------------------- ------------------------------- ----------------------------- -------------------------- ------------------------------------------------------------------

**[Photographic Experiments]{#_Toc427470317}**

Ground-based astronomy provided early views of the Moon\'s near side,
the side that perpetually faces the Earth. In addition, thirty-eight
previous lunar missions have photographed the Moon, supplying scientists
with a plethora of still imagery and television footage of the lunar
surface. In 1959, the Soviet's Luna 3 spacecraft was the very first to
capture a full composite view of the far side of the Moon. During the
1960s and 1970s, NASA successfully flew 22 missions to the Moon,
including the historic Apollo missions. The Soviets sent another 20.
Throughout the 1960s and 1970s, these missions continued to amass images
of the Moon and, in 1965, the American public watched for the first time
live pictures transmitted from NASA's Ranger 9 spacecraft. Cameras
aboard NASA's Lunar Orbiter 1 spacecraft took the first pictures of
Earth from the Moon. All of the Apollo missions returned lunar
photographs to Earth; even the failed Apollo 13 mission yielded a
limited amount of photographic data. The U.S. Department of Defense
Clementine spacecraft, which briefly orbited the Moon in 1994 obtained a
significant set of lunar imagery. The polar orbit was an ellipse,
roughly 400 kilometers above the surface at the closest point. The
payload aboard Clementine was a camera and a topographic mapper.

**[Lunar Prospector\'s ]{#_Toc427470318}Design Philosophy**

Lunar Prospector was never intended to carry a camera, nor does it
require a true onboard computer for two key reasons. Prospector, from
its inception, was designed to be a simple, cost-efficient spacecraft.
Cameras require pointing in a given direction. The Lunar Prospector
spacecraft is spin-stabilized, an engineering strategy that is well
understood, highly successful and simple and cheap to achieve. With a
camera, Prospector would have required a whole different engineering
strategy, as well as a computer to control the camera. The result would
have been a far more complex, heavier, costlier spacecraft that may well
not have survived the Discovery selection process. Secondly, Lunar
Prospector is a science-focused mission. That is, Prospector was
designed to answer the highest-priority outstanding questions the
planetary science community still has about the Moon. The spacecraft's
five instruments were chosen according to that criterion. Previous Moon
missions have, in fact, taken thousands of pictures of the Moon. We
already have quite detailed knowledge of what the Moon looks like. What
we don\'t yet know are details about its composition, volcanic activity,
magnetic and gravitational fields and/or its resources.

**[Lunar Sampling/Soil Analysis Experiments]{#_Toc427470319}**

The first spacecraft to dig into the soil of an extraterrestrial body
(which happened to be the Moon) was NASA's Surveyor 3, which landed on a
geographic region of the Moon called the Oceanus Procellarum in April
1967. Over the next several months, each of the Surveyor landers (5-7)
probed the lunar surface with instruments called alpha-scattering
surface analyzers and soil mechanics surface samplers. Each was designed
to physically probe the lunar soil and gather measurements about the
abundances of the various elements that constitute lunar rocks and soil.
Data gathered with these two instruments was valuable, but limited in
the sense that only specific regions of the Moon were analyzed (the
landing sites). Some of the Soviet missions also excavated lunar samples
for further analyses on Earth.

All of the Apollo landers (11-17), with the exception of the failed
Apollo 13, performed experiments with lunar surface samples. With tools
such as hammers, scoops, rakes and tongs, the Apollo astronauts
collected many lunar rock samples and performed a series of tests on the
mechanics of the lunar soil. In addition, they returned over 800 ponds
of lunar rock to Earth to enable further detailed study.

**[Lunar Prospector\'s ]{#_Toc427470320}Approach**

Lunar Prospector, a polar-orbiting spacecraft, will not touch down on
the lunar surface during either its primary (first year) or extended
mission (up to an additional six months after that, until its fuel
supply runs out). While previous lunar landing missions have returned an
immense amount of physical data, the main limitation of the experiments
thus far is applicability to the Moon as a whole. Lunar soil and rocks
at the Moon's equator, where the majority of such experiments have been
conducted tell a limited story. Global elemental abundances need to be
determined. Until Prospector's confirmation of polar water ice, that
valuable resource and potential sample was not seriously considered as
the basis for a sample return mission. Before a future sample return
mission can be contemplated, it is necessary to have an understanding of
the entire global situation in order to profitably plan such a mission.
Hence, over time, scientists rely on data from both orbiters, such as LP
and landers, to completely understand a planet and develop an approach
to its study.

**[Remote Sensing Experiments]{#_Toc427470321}**

In contrast to direct geologic studies of actual lunar rocks and soil,
remote sensing experiments analyze the lunar surface and atmosphere from
a distance. Photography is, of course, a kind of remote sensing study,
one with which we are familiar. Spectroscopy, however, provides
information not discernible to the human eye. Using gamma-ray
spectroscopy, Apollo 15 and 16 were the first missions to attempt to
measure the concentrations of elements that make up the lunar crust
using spectroscopy. (A primitive version of the Apollo GRS was flown
aboard the Soviet's Luna 10 spacecraft in 1966, but this instrument
gathered only limited data). The general findings from the Apollo 15/16
GRS experiment indicated that there are two distinct geographic regions
of the Moon \-- the highlands and the mare \-- with chemical
compositions that are, in fact, markedly different (for example, iron
and magnesium being relatively enriched in the mare). Those data also
indicated that the concentrations of certain other elements, such as
thorium and titanium, are non-uniformly distributed and that the far
side of the Moon differs from the near side.

The Apollo 15/16 GRS acquired data on the abundance of four elements \--
thorium, potassium, iron, and titanium \-- near the equatorial region of
the Moon. In concert, the landing modules for those missions collected
samples from the same region, permitting comparison of chemical
composition data acquired via remote sensing techniques (GRS) and direct
sampling (mass spectrometry of soil and rock samples). Lunar Prospector
mission scientists, of course, will not be able to conduct similar
studies comparing in situ samples with remotely acquired data, however,
global coverage offers insights not achievable with single point
investigations. In addition, because we do have an existing store of
lunar rock, LP data is being compared to these samples and may reveal
important information.

**[Lunar Prospector\'s Role]{#_Toc427470322}**

Since Lunar Prospector is an orbiting spacecraft, its entire science
payload consists of remote sensing instruments, three spectrometers and
the two magnetic field instruments. As with any form of spectroscopy,
the quality of the data improves with the time of sampling (number of
counts detected). Statistically, it is very important for mission
scientists to continually gather spectral information over the same
lunar surface regions in order to subtract-out background "noise" caused
by not only the cosmic environment but also by the elements which make
up the materials on the spacecraft and the instruments themselves.
However, with LP, interference from the spacecraft and its electronics
are kept to a minimum by the fact that the instruments are separated
from the body of the vehicle by eight-foot booms.

Using spectroscopy and other remote sensing techniques, the Prospector
mission can perform global-mapping studies not possible with landing
craft, such as were typical of the Apollo series of missions. For the
scientific community, such an approach represents the logical next step
in lunar exploration. Depending upon what Prospector finds, future lunar
landers may someday return to the Moon to more thoroughly investigate
specific sites, say at the 'icy' lunar poles.

**[LUNAR PROSPECTOR]{#_Toc427470323}[']{#_Toc427470323}[S
EXPERIMENTS]{#_Toc427470323}**

**[Background]{#_Toc427470324}**

When planning the Lunar Prospector mission, designers chose six
experiments which would most closely fulfill the priorities outlined by
LExSWG, while at the same time being sufficiently economical to meet the
stringent budgeting requirements of the Discovery Program. Five
instruments aboard Prospector are conducting six experiments. Three
spectrometers (gamma-ray, alpha-particle and neutron) are globally
mapping the Moon's surface and tenuous atmosphere (consisting mainly of
gas release events) to determine which minerals and gases are present,
and in what abundancy. Two instruments, the magnetometer and electron
reflectometer, are measuring the Moon's anomalous magnetic properties,
and in doing so, beginning to characterize the nature and size of a
possible lunar core. Finally, the vehicle's own telemetry (communication
system) serves as the "instrument" for Lunar Prospector's Doppler
Gravity Experiment, which is globally mapping the Moon's non-uniform
gravitational fields.

**[Why Use Spectroscopy?]{#_Toc427470325}**

Physicists use spectroscopy for a variety a research pursuits. A rather
general term, spectroscopy is nothing more than the process of
visualizing a substance by splitting its light and other emissions into
their constituent parts. One of the simplest spectra to consider is a
rainbow: visible light is dispersed into its different energies (called
wavelengths) when it passes through droplets of rainwater in the
atmosphere. Each wavelength absorbs (and thus reflects) a different
color, which is readily apparent to the naked eye. This is so because
each wavelength has a characteristic energy level. Spectrometers are
instruments which record such dispersions of energy, called spectra.

Since it is no trivial matter to collect rocks and soil samples from
other planets, break them up into their individual elements and thereby
determine their chemical makeup, spectrometers play a major role in
planetary exploration. Knowing what planets, asteroids and moons are
made of helps scientists piece together the history and evolution of the
Solar System. One type of spectroscopy, gamma-ray spectroscopy, is a
technique in which scientists can measure (from orbit) the composition
of surface material (down to several inches) around any celestial body
possessing little or no atmosphere (such as is the case for the Moon or
for Mars, for instance).

The way all of Lunar Prospector's three spectrometers work is by
detecting (remotely, from orbit) "signature" energies emitted by various
elements in the lunar soil and atmosphere. Such energy emitted by the
Moon comes from two sources: "natural" radiation and "induced"
radiation. Just like on Earth, certain elements are naturally
radioactive and give off radiation (energy) on a constant basis. Other
elements, while not naturally radioactive, also emit energy, but in
response to constant bombardment of the Moon's surface by galactic and
solar cosmic radiation. This is induced radiation.

Unlike Earth, which has a thick, protective atmosphere, the Moon is
recipient to most, if not all, passing solar and cosmic energy causing
many interactions. The key to spectroscopy\'s value is that each element
emits a unique level of energy. By using a spectrometer, planetary
scientists can discern the chemical makeup of the surface of a planet by
looking for signature "peaks" (in energy emission) of an energy output
plot \-- an identifying barcode of sorts for the actual elements which
make up the crust and atmosphere. Because solids and gases emit vastly
different levels of energy, spectrometers are usually calibrated to
detect ranges of energies. Each of Prospector's three spectrometers
"sees" a characteristic energy range, permitting the detection of energy
particles such as fairly-low-energy neutrons (the neutron spectrometer's
range of detection is from less than 0.3 eV \[electron volts\] to
hundreds of keV \[thousand electron volts\]), high-energy gamma rays
(the gamma-ray spectrometer's range of detection is \~0.3 MeV \[million
electron volts\] to 9 MeV), higher energy neutrons (a portion of the
gamma-ray spectrometer is used to detect neutrons with energies from 0.5
MeV to 9.5 MeV) and alpha particles (the alpha particle spectrometer's
range of detection is \~4.1 MeV to 6.6 MeV).

**[Gamma-Ray Spectroscopy]{#_Toc427470326}**

Lunar Prospector's gamma-ray spectrometer (GRS) is mapping the
abundances of ten elements on the Moon\'s surface:

  --------------- --------------- ------------- -------------- ----------- ----------------
  thorium (Th)    silicon (Si)                                             
  potassium (K)   aluminum (Al)   uranium (U)   calcium (Ca)   iron (Fe)   magnesium (Mg)
  oxygen (O)      titanium (Ti)                                            
  --------------- --------------- ------------- -------------- ----------- ----------------

The GRS is especially sensitive to the heavy, radioactive element
thorium and the lighter element potassium. These elements are
particularly plentiful in the part of the crust that is last to
solidify. Thus, mission scientists are able to determine the global
distribution of KREEP (K-potassium, Rare Earth Elements, and
P-phosphorous), a chemical "tracer" of sorts which helps to tell the
story of the Moon's volcanic and impact history. The data produced by
the GRS are helping scientists to understand the origins of the lunar
landscape, and may also tell future explorers where to find useful
metals like aluminum and titanium.

**[How Lunar Prospector\'s GRS Works]{#_Toc427470327}**

A gamma ray is a very energetic photon (a tiny parcel of light) \-- more
energetic than a visible light ray or an X-ray. When gamma rays reach
the orbiting Lunar Prospector spacecraft, they pass through a crystal of
bismuth germanate (BGO crystal) in the GRS.

The various atoms inside this detector give off a flash of light when
the radiation hits them~~;~~. Gamma-ray photons with high energies
produce brighter flashes than gamma-ray photons with low energies. The
light produced by the gamma-ray is then measured by a photomultiplier
tube (PMT) which converts the light signal into an amplified electronic
signal. Finally, this electronic signal is sent back to Earth for
scientists to analyze.** **The energy of a given gamma ray tells
scientists exactly which kind of atom emitted it.

To fully appreciate the potential of LP\'s GRS, a useful comparison can
be drawn with the earlier Apollo GRS experiments. In contrast to Lunar
Prospector, which is mapping the elemental composition of the entire
lunar surface, the mapping performed by Apollo 15 and 16 only covered
about 20 percent of the lunar surface \-- specifically, the region
around the Moon's mid-portion or equator. Another difference between the
Apollo-era and recent Lunar Prospector gamma-ray spectroscopy studies is
the detecting crystal inside the GRS instrument itself. The Apollo 15/16
instrument used a sodium iodide (NaI) crystal, whereas Lunar
Prospector's crystal is composed of bismuth, germanium, and oxygen atoms
(BGO crystal).

**A comparison of simulations of an Apollo GRS spectrum and the LP GRS
spectrum.**

Since the combined atomic weight of bismuth, germanium and oxygen
exceeds that of sodium and iodine, a BGO crystal is significantly denser
than an NaI crystal. As a result, a BGO crystal is better able to stop
gamma rays in their tracks and, as such, offers greater detection
sensitivity \-- on the order of two- to eight-fold higher \-- than an
NaI crystal. What that means is that energy spectra measured with a BGO
crystal can be more cleanly separated (lines can be more easily
distinguished from one another on an energy plot) than spectra measured
with a NaI crystal (see accompanying graphic). In addition, certain
elements which were unmappable by the Apollo GRS, such as uranium,
aluminum, calcium and magnesium, can be detected with Lunar Prospector's
more sensitive instrument. This offers mission scientists more
opportunities to distinguish subtle features of the lunar landscape. The
ability to measure concentrations of aluminum and calcium, for instance,
may unearth clues as to the makeup of certain types of highland rock
formations. Similarly, the distribution of titanium serves as a useful
"probe" for mare regions. Other geochemical clues to planetary evolution
include the presence of iron stores, the ratio of iron oxide (FeO) to
magnesium oxide (MgO), the ratio of potassium to uranium (which hints at
remelting rates of primordial condensates), and the ratio of thorium
(Th) to uranium, which serves as a marker for the relative abundance of
volatile compounds.

**Sample data plot from Lunar Prospector's gamma-ray spectrometer**

While gamma-ray data are highly informative, relatively few gamma-rays
leave the Moon's surface and escape into space. Much as a camera working
in conditions of low light can compensate by increasing exposure time,
gamma ray spectroscopy generally benefits from a significantly long
detection period, allowing spectral lines to fill in over time. One
sweep \-- or even a few sweeps \-- over the Moon\'s surface would not
give mission scientists enough information to determine the
concentration of radioactive elements. In addition, the stable
(non-radioactive) elements do not emit gamma rays as readily as do
naturally radioactive ones, so it will take Lunar Prospector up to a
year or more to collect enough data to estimate the concentrations of
these elements. After a year of mapping, mission controllers expect to
drop Prospector's orbiting altitude to as low as 6 miles (10 km) above
the lunar surface, where the spacecraft will remain until it runs out of
fuel. The GRS experiment will continue to benefit from the extra time
and lower altitude.

The GRS also contributes indirectly to the search for water on the Moon.
The bismuth germanate crystal is surrounded by a shield of borated
plastic (anti-coincidence shield) that detects high-energy (fast)
neutrons. The main purpose of this shield is to allow correction for
background signal caused by solar and galactic cosmic rays. It
differentiates between gamma rays and the cosmic ray background. In
addition, because it is borated, it also measures fast (high energy) and
epithermal (medium-energy) neutron fluxes. Mission scientists are using
this information, in concert with the lower-energy (thermal and
epithermal) neutron counts detected by Lunar Prospector's neutron
spectrometer, to detect water ice at the lunar poles.

**[ALPHA-PARTICLE SPECTROSCOPY]{#_Toc427470329}**

The Apollo series of missions revealed that the Moon had not been
perpetually cold and dead, as once believed, but rather was host to a
series of dramatic volcanic eruptions in which vast seas of molten lava
flooded much of the lunar surface. While the majority of such activity
most likely occurred very early in the Moon's history over three billion
years ago, the Moon is thought to still harbor some remnant volcanic and
tectonic activity. Outgassing events, in which alpha-particle emissions
of radon leak out from the lunar interior, are scientific evidence of
such activity. Polonium, a natural-decay product of the heavier element
radon, itself a natural-decay product of the still heavier element
uranium, collects around vents and provides keys to their recent
history. This is due to the fact that the entire decay chain takes over
21 years, so that Polonium is evidence of vent activity over the last
half century. Radon gas and polonium are likely to be detected because
of their relatively long half-lives (3.8 days for \[222\] radon and 138
days for \[210\] polonium; one half-life is the amount of time it takes
for half of a given radioactive sample to decay into another substance).

Ancient volcanic vents, seismic fractures, impacts and pore openings in
the lunar soil all provide paths for radon to find its way to the lunar
surface. Actually, radon itself is present in very small quantities, but
thought to be mixed in with other gases, such as nitrogen, carbon
monoxide and carbon dioxide. Determining where and when such gas-release
events take place can tell scientists just how active the Moon actually
is, as well as help to identify the source(s) of the Moon's small and
tenuous atmosphere.

An alpha particle is the nucleus of a helium atom: two protons and two
neutrons bound together. Like gamma rays, alpha particles escape from
radioactive elements as part of their natural-decay process. The alpha
particles are emitted with a precise energy that serves as a fingerprint
for the atom from which they came. Lunar Prospector's Alpha-Particle
Spectrometer (APS) detects these events.

Housed inside the APS instrument are ten separate wafers of silicon.
Silicon is a semiconductive material. When an alpha particle hits a
silicon wafer, it creates a small track of charge. When a 25-volt bias
is applied to the silicon wafer, the alpha particle\'s charge is
funneled into an amplifier which then increases the charge.** **Since
that pulse of charge is directly proportional to the signature energy of
the alpha particle, scientists can infer the identity of the element
which emitted the alpha particle. The APS contains ten such silicon
detectors, each sandwiched between gold and aluminum disks, and arranged
on five out of six sides of a cube, enabling nearly a complete field of
detection.

The detection of gases depends very much on whether any outgassing
events occur while Lunar Prospector is in orbit and near by the event,
and how many of these there are. As with the GRS, the longer the mission
lasts, the more of these events the instrument is likely to detect.
Because the outgassing events are localized and may have limited
duration, the longer the detection time, the greater the opportunities
to detect specific events.

**[Before Lunar Prospector]{#_Toc427470330}**

Apollo 15 and 16 scientists, using an APS instrument for the first time,
found evidence for a spatially variable distribution of radon and
polonium. Those studies identified a striking correlation between
polonium and the edges of lunar maria, especially Mare Fecunditatus, but
also at nearly all maria investigated.

Earlier astronomical studies noted that the Aristarchus crater region
was the site of phenomena dubbed "transient optical events," in which
regions of the lunar surface glowed and changed color for short periods
of time. Some scientists believe that the light flashes may represent
transient venting of volatile materials.

**Factors in Analyzing APS Data**

Data acquired by the APS aboard Prospector will appear in the form of
counts \-- very similar to the way the GRS instrument works. As with the
GRS data, the number of counts accumulated (and thereby the time of
sampling), are the key determinants of the sensitivity of the data. As
such, the planned extended mission flown at low altitude will most
likely be extremely valuable. If the extended mission lasts for 6 months
as currently planned, this will provide mission scientists with 18
months' worth of mapping time, covering the entire Moon many times over.
For comparison, the Apollo 15 and 16 missions gathered only about 8
days' worth of data around the Moon's equator.

One issue mission planners have to take into account when designing
alpha-particle spectroscopic experiments (and in fact any type of
experiment in which a spectrometer measures cosmic radiation) is the
timing of the solar cycle. Repeating every 11 years, the solar cycle is
a periodic phenomenon in which the overall extent of radiation (in the
form of solar particles called protons and alpha particles) produced by
the Sun varies in a predictable manner. A new solar cycle began in 1997,
at which time sunspot activity was at a minimum and galactic cosmic rays
(GCR) were at~~ ~~their 11-year maximum. Since more GCR protons imply
more induced planetary gamma-ray emission, the present time is optimal
for performing global spectrographic mapping experiments, such as
gamma-ray and neutron spectroscopy, because the inherent signal to be
detected will be higher than usual. However, as we get closer to solar
maximum, solar activity and its associated solar energetic-particle
population will increase, leading to higher background radiation
"noise", so mission scientists must take into account such stray counts
and subtract them from the overall data.

**[NEUTRON SPECTROSCOPY]{#_Toc427470332}**

Lunar Prospector mission scientists devised the neutron spectroscopy
experiment to search for water ice at the poles of the Moon. As the
world found out on March 5, 1998, at the mission's first science data
return press conference, preliminary results from the experiment were
indeed positive: water ice does exist on the Moon, and there appears to
be more of it at the North than at the South pole. Lunar Prospector had
detected a significant amount of hydrogen which is inferred to be in the
form of water. This was the first direct evidence of the presence of
water ice at the Moon's frigid poles. Lunar Prospector is also the first
interplanetary mission ever to use the neutron spectroscopy technique to
detect water. Prospector's neutron spectrometer (NS) works by detecting
hydrogen, by way of subat[omic particles called
neutrons.]{#_Toc427470333}

**Neutron Science**

The materials we use every day are made up of molecules, which are made
up of atoms. Inside the atoms are even tinier pieces of matter called
subatomic particles. Neutrons are one type of subatomic particle \--
they are present in every atom of every molecule in our bodies as well
as in all of the synthetic and natural substances in our environment.
Besides being a basic building block of matter, neutrons serve as a
useful experimental tool for physicists. Materials scientists, for
instance, are interested in how atoms are packed within the molecules of
different materials. How the individual atoms of a given material stack
up against each other in large part determines the properties (strength,
plasticity, etc.) of that particular material. One way scientists study
molecular structure is to bombard atoms with high-energy neutrons and
then wait and see where and how fast the neutrons scatter.

The same thing happens naturally in space. When cosmic rays collide with
atoms in the lunar crust, they violently dislodge neutrons and other
subatomic particles. Some of the neutrons escape directly into space \--
essentially unchanged \-- as "fast" neutrons. Other neutrons shoot off
into the crust, where they slam into other atoms, bouncing around like
pinballs. If they only run into heavy atoms, they do not lose very much
energy in the collisions, and are still traveling at close to their
original speed when they finally bounce off into outer space. But if a
neutron encounters a hydrogen atom \-- which is the same size as a
neutron \-- it will slow greatly or even stop, much like a speeding
billiard ball running into a stationary one. If the Moon\'s crust
contains an abundance of hydrogen at a certain location \-- say, a
crater with water ice in it \-- any neutron that bounces around in the
crust before heading out to space will cool off (slow down) rapidly.
When Lunar Prospector flies over such a crater, the NS will detect a
definitive dropoff in the number of these ("epithermal" or medium
energy) neutrons.

**[How Lunar Prospector]{#_Toc427470334}[']{#_Toc427470334}[s NS
Works]{#_Toc427470334}**

The NS has two different counters \-- a cadmium-wrapped canister of
\[3\]helium and a tin-wrapped canister of \[3\]helium. When a neutron
collides with an atom of \[3\]helium, a nuclear reaction takes place,
producing a burst of energy. That burst of energy tells mission
scientists that they have detected a neutron. Except for the outside
wrapping, the two counters are nearly identical. The cadmium-wrapped
counter filters out all but the epithermal neutrons, because cadmium is
good at screening away the slow-moving thermal neutrons, whereas the
tin-wrapped counter lets all of the neutrons through. Since the two
counters are otherwise identical, counts can be subtracted, and any
difference between the two must be attributable to thermal neutrons.

Lunar Prospector measures "fast" and thermal plus epithermal neutron
flux with a separate instrument (the anti-coincidence shield of the
GRS). The respective count rates of the different types of neutron
fluxes are an indicator of hydrogen, and hence the presence of water
ice, embedded within the lunar soil.

Mission scientists receive data from the spacecraft every 32 seconds.
Since the data contain random noise, several passes over the surface and
careful statistical analysis are required to analyze the data. However,
since the spacecraft passes over the poles every orbit (whereas it
passes over any given region on the equator only a few times a month),
the NS produces the most accu[rate data in the polar
regions.]{#_Toc427470335}

**MAGNETOMETER/ELECTRON REFLECTOMETER STUDIES**

[The magnetometer and electron reflectometer aboard the Lunar Prospector
are collecting valuable data to help unravel puzzles that have intrigued
scientists for more than a quarter of a century. What kind of magnetic
field(s) exists on the Moon? What kind of natural resources are buried
in the Moon]{#_Toc427470338}[']{#_Toc427470338}[s crust and is there a
core? If so, what are its characteristics? Can we build a lunar base?
How did the Moon form and evolve \-- what is its
history?]{#_Toc427470338}

The MAG/ER experiment aboard Lunar Prospector was designed with two
primary goals in mind: scanning the lunar crust for signs of permanent
magnetization, and searching for electrical currents flowing deep within
the lunar interior \-- the sign of a conductive metallic lunar core. The
two instruments combine to calibrate the Moon's global magnetic field
strength: the magnetometer measures the field surrounding the
spacecraft, and the electron reflectometer surveys the lunar surface.

**How Much Do We Already Know about the Moon's Magnetic Field?**

Scientists have known for years that the Earth is magnetic \-- there is
a strong magnetic field surrounding our own planet, originating with
electrical currents swirling inside the Earth's iron-rich metallic core.
The boundary between the Earth's magnetosphere (a dipole field) and the
influence of the Sun's charged particle activity (from the solar wind)
for the most part balances out. At times, however, especially during a
particularly active segment of the 11-year solar cycle when solar flares
are raging, charged solar wind particles get trapped by the Earth's
magnetic field and slam into the Earth's atmosphere at extremely high
energies. As a result, the atmosphere glows, and a strange but beautiful
phenomenon called the Aurora Borealis is formed. Such events are most
prominent at the Earth's poles; hence, Alaska is an oft-cited viewing
spot for such celestial fireworks.

**Illustration showing the Earth's magnetosheath and the shock front it
creates**

The Moon is a different story. Based upon previous, albeit limited
research, scientists have suspected that the Moon has very little, if
any, magnetic field of its own. The first spacecraft to effectively
measure lunar magnetic fields was Explorer 35, several years prior to
Apollo. The Apollo 15 and 16 subsatellites orbited the Moon with
magnetometer instruments and concluded that the Moon possessed a
vanishingly small global magnetic field; however, other experiments
aboard Apollo 12, 14, 15 and 16 with either hand-held or stationary
magnetometers detected small but significant surface fields. In
particular, one unresolved issue facing the lunar scientific community
is the origin of swirl-like color markings (called "albedos") visible
from orbit on the surface of the Moon that are thought to be due to
magnetic anomalies.

**Why Are We Interested in the Magnetic Field?**

The presence of such non-uniformly distributed magnetic regions has led
planetary scientists to conjecture about the Moon's impacts (which may
have imparted some of these locally distributed magnetic properties) and
the possible presence of a small, iron-laden core (roughly estimated to
a maximum of about 500 km in radius). From the perspective of planetary
science, better understanding the size and nature of the Moon's core can
tell a lot about its evolution, history and beginnings \-- such as, did
the Moon really arise as the result of a cataclysmic collision between
the Earth and a Mars-sized body? In addition, metals discovered in the
crust may be an extremely valuable resource. Now that mission scientists
have found a potential source of water on the Moon, the presence (and
relative abundance) of other materials may become paramount to the
eventual establishment of a future possible lunar base.

**How it Works**

Lunar Prospector's magnetometer/electron reflectometer (MAG/ER)
measurements are affected by three sources: the Earth\'s magnetic field
(35,000 nano Teslas), the relatively weak field of the Moon (0 to 300
nano Teslas) and the very weak field carried from the Sun by the solar
wind (approximately 10 nano Teslas). Mission scientists are able to
compare these measurements to determine which magnetic field variations
are caused by surface features (local deposits of magnetic material) or
alternatively, by the Moon\'s core. Both instruments are copies of
detectors currently housed aboard the Mars Global Surveyor spacecraft,
launched in December 1996, with some modifications to adapt them for a
spinning spacecraft.

The triaxial fluxgate MAG is a standard device that is also used to
measure magnetic fields on Earth. "Triaxial" means that it includes
sensors to measure the strength of the field in three different
directions. This enables scientists to determine not only the maximum
strength of the field but also the direction in which it points. The
"fluxgate" is an electric coil through which the magnetic field passes.
By measuring the variation of the current passing through the coil, the
MAG determines the strength of the magnetic field. It can measure
magnetic fields as weak as one-millionth the strength of the Earth\'s
magnetic field.

Prospector's ER measures the magnetic field at the surface of the Moon.
The Moon, like every other body in the Solar System, is constantly
barraged by electrons from the solar wind. Unlike the Earth, the Moon
was not thought to have a magnetic field strong enough to repel these
tiny charged particles, and they would be expected to spiral toward the
surface in giant loops, typically several miles wide. The electrons that
descend in a tighter spiral make it to the surface of the Moon and are
absorbed there. But if there is magnetic material on the Moon, it will
reflect some of the electrons back into space. When those reflected
electrons reach the Lunar Prospector spacecraft, the ER measures their
pitch angle (the angle at which they bounce). After the pitch angles of
many electrons are tabulated, scientists will see an abrupt cutoff above
a certain angle \-- because all the electrons with a larger pitch angle
were absorbed by the Moon. That cutoff tells mission scientists just how
intense the magnetic field is at the lunar surface.

Together, the two instruments detect local variations in the Moon\'s
magnetic field that arise from selenological features on the lunar
surface. Lunar Prospector's MAG instrument not only measures lunar
magnetic fields, but also external fields present in space plasmas (a
plasma is an electrically conductive gas comprised of both neutral and
ionized particles and free electrons). As a result, only a small
fraction (about 10 percent) of the MAG's data is pertinent to lunar
scientists. What that means is that culling relevant data poses a
significant challenge for Prospector's MAG/ER team. Essentially, this
involves careful pruning of the data as well as paying attention to what
times of the month the data has been gathered, as certain times (and
thereby location relative to the Earth and its own magnetic field) are
better than others for measuring lunar fields.

The interaction between charged particles in the solar wind and the
Earth's magnetic field (about 220 miles above the surface of the Earth)
is a region scientists call the magnetosphere. Within the magnetosphere
are two separate regions: the magnetosheath (which is magnetically
"noisy") and the geomagnetic tail (which, by comparison, is "quiet"). It
is important that mission scientists take lunar magnetic measurements
while the spacecraft passes through the quieter geomagnetic tail. The
data will be expressed in units called "gammas" (which are the same as
nano Teslas, or one-billionth of a Tesla) and will be tagged with
spacecraft positional data to produce computer files which demonstrate
magnetic field components as a function of location relative to the Moon
as well as spacecraft altitude.

As is the case with all of Prospector's scientific experiments, the
spacecraft's polar orbiting pattern permits complete global analysis of
the Moon. So, for the first time, scientists can have a handle on all of
the Moon's magnetic features, not just those associated with isolated
geologic regions. Such analyses also permits scientists to correlate
magnetic properties with lunar surface features \-- the MAG data is an
essential component in analyzing the data from the ER instrument. Data
from the ER will be plotted as electron flux (number of particles per
unit area per unit time) as a function of time. The ER "probes" (from
orbit, of course) the lunar surface by recording the behavior of
space-born electrons after they bounce off of the lunar crust. But while
the ER is capable of measuring the strength of electron paths ("bent" by
tiny, locally dispersed lunar magnetic fields), this instrument is
incapable of determining where on the Moon it is measuring electrons at
any given time. Positional data from the MAG puts the ER data into
perspective, allowing mission scientists to match up electron flux
strengths with the magnetic fields along which they travel. Thus, the
two instruments (which are housed together on one of Prospector's
eight-foot booms) cooperate to provide mission scientists with a
complete picture of the Moon's magnetic and electrical properties. All
told, it will take mission scientists the full year of mapping to
acquire meaningful data about the magnetic fields of the Moon.

**GRAVITY STUDIES**

The gravity field of the Moon strongly influences the altitude of a
spacecraft in low-circular orbit. The most dramatic example is the
Apollo 16 subsatellite. After being deployed in a near-circular orbit
from the command and service module, the eccentricity increased quickly
and the spacecraft impacted the lunar surface 35 days after the release
strictly due to the force of the gravity field. Understanding the
precise nature of a planet's gravity field is vital to all exploration
and experimentation.

As presented at the March 5 science return press conference, Lunar
Prospector's Doppler Gravity Experiment (DGE) has provided the first
polar low-altitude measurement of the lunar gravity field. This provided
the spacecraft with the first truly operational gravity map of the Moon
and immediately improved orbit and fuel efficiency. Improved gravity
information will not only help scientists build better models of the
role of impact processes on the history and evolution of the Moon, but
will also help in estimating the lunar core size and metallic iron
content. A more practical benefit of the new lunar gravity data provided
by Prospector's DGE experiment is that a more precise gravity map of the
Moon will inevitably aid future mission planners in planning
fuel-efficient journeys to the Moon, and may even help identify
potential resources.

**[Lunar Prospector]{#_Toc427470340}[']{#_Toc427470340}[s
]{#_Toc427470340}Doppler Gravity Experiment**

The Moon has a large asymmetry due to the fact that the lunar crust is
thicker on the far side than on the near side and a much "bumpier"
gravitational field than the Earth, with small anomalies due to mass
concentrations on the surface. The Apollo missions helped demonstrate
such sizable positive gravity anomalies. Interestingly, they exist
within the topographically low, large circular mare basins. This
discovery was unexpected and opposite of any physical model at that time
and started the development of new models of the Moon's interior. The
features were called mascons (short for "mass concentrations"). These
bumps cause an orbiting spacecraft to speed up or slow down. The DGE is,
in effect, drawing a map of the bumps.

The DGE, unlike the other experiments aboard Lunar Prospector, requires
no extra instrumentation. All of the data is collected simply by
communicating with the spacecraft. As the spacecraft orbits the Moon,
its speed can always be determined by the Doppler effect, the same
effect that causes a police siren to sound higher when the police car is
moving toward you and lower when it is moving away from you. The
"siren," in this case, is the spacecraft\'s radio signal, whose
frequency shifts slightly as it moves toward Earth or away from it.
Relative to the near side, lunar farside gravity is poorly determined
because the spacecraft is not in view from the Earth when over the lunar
far side. However, some information is obtained by observing changes in
the LP orbit due to the accumulated acceleration of the farside gravity
as the spacecraft comes out of occultation (back into view).

By tracking the velocity of the spacecraft, mission scientists can infer
the forces acting upon it. For over 99 percent of the duration of the
mission (excepting only periods when the engines are being fired) the
only force on Lunar Prospector is gravity. Thus, by simply circling the
Moon and sending signals back to Earth, Lunar Prospector has mapped the
Moon\'s global gravitational field. Lunar Prospector completed this
gravitational map in the first two months of the mission. However, the
results of the DGE will be greatly improved with data from the extended,
low-altitude phase of the mission. At this low altitude of 6 miles (10
km), the precision of the gravity data will be improved by a factor of
over 100.

**SCIENTISTS' BIOGRAPHIES**

**Dr. Mario Acuña (Goddard Space Flight Center, Greenbelt, MD)**

Dr. Mario Acuña is a Co-Investigator for the Lunar Prospector mission,
responsible (along with Dr. Lon Hood) for the spacecraft's Magnetometer
instrument. Dr. Acuña was born in 1940, in Cordoba, Argentina, from
where he later received his undergraduate degree at the University
there. He went on to receive an MSEE degree in 1967, from the University
of Tucuman and then a doctorate in space science from the Catholic
University of America, in Washington, D.C., in 1974. From 1963 to 1967,
Dr. Acuña worked for the department of electrical engineering and the
Ionospheric Research Laboratory at the University of Tucuman, as well as
for the Argentine National Space Research Commission. These research
activities included several cooperative sounding rocket programs with
NASA's Goddard Space Flight Center involving both U.S. and South
American scientists, X-ray research with high-altitude balloons and
meteorological tracking stations. In 1967, he joined the
Fairchild-Hiller Corporation in Germantown, Maryland, to provide
engineering and scientific support services to NASA; he became head of
the Electronic Systems Division in 1968. Since 1969, Dr. Acuña has been
associated with NASA's Goddard Space Flight Center in Greenbelt,
Maryland, where his research interests have centered around experimental
investigations of the magnetic fields and plasmas in the Solar System.
He has participated in several planetary missions, including the
Explorers 47 and 50 missions, Mariner 10, Pioneer 11, Voyagers 1 and 2,
MAGSAT, Project Firewheel (Germany, Canada, United States and United
Kingdom), Viking (Sweden), the Active Magnetospheric Particle Tracer
Explorers (AMPTE: Germany, United States, United Kingdom), The
International Solar Polar Mission and the GIOTTO mission (ESA) to comet
Halley. In 1986, he was selected as the Principal Investigator for the
Mars Observer Magnetic Field Investigation (launched in 1992) and is
currently in charge of the Mars Global Surveyor spacecraft's
magnetometer. Dr. Acuña has published more than 60 research articles,
mainly in the field of planetary magnetism.

**Dr. Alan Binder (Lunar Research Institute, Gilroy, CA)**

Dr. Alan Binder is Principal Investigator and flight director for the
Lunar Prospector mission. Dr. Binder earned a bachelor's degree in
physics in 1961 from Northern Illinois University, and in 1967, earned a
doctorate in geology and lunar and planetary science from the University
of Arizona's Lunar and Planetary Laboratory. His main research interests
center around the origin, petrological and structural evolution of the
Moon, as well as its possible economic utilization. Dr. Binder has 35
years of experience in the fields of planetary astronomy and planetary
geosciences. He was a Principal Investigator on the 1976 Viking Mars
Lander Camera Team. For 10 years, he both taught and conducted lunar
research in Germany and served as an advisor to the European Space
Agency in its studies of a lunar polar orbiter mission. While in
Germany, Dr. Binder also developed the proposed German and American
lunar exploration program, "Selene," which was to be a series of lunar
landers used to set up a geophysical station network and return samples
to Earth. Selene was the forerunner to NASA's proposed Common Lunar
Lander (Artemis), a project on which Dr. Binder also worked. He has
authored or coauthored some 60 scientific papers, mainly in the areas of
lunar and Mars geology, geochemistry, petrology and geophysics.

**Mr. David Curtis (Space Sciences Laboratory, Berkeley, CA)**

David Curtis has an M.S. in Electrical Engineering and an M.A. in
Physics and has worked as an Electrical Engineer at the University of
California, Berkeley, Space Sciences Laboratory for over 15 years. His
experience includes Instrument Project Manager for the Wind 3DP
instrument and the Mars Observer, Mars Global Surveyor, and Lunar
Prospector Electron Reflectometer instruments; Lead Engineer for the
digital/processor electronics for the AMPTE IRM plasma instrument, the
Cluster CIS instrument, the Giotto RPA PAD system, and the FAST
Instrument Data Processing Unit (IDPU) digital system. He designed and
implemented the FAST Mission Operations Center/Science Operations Center
and also designed the FAST IDPU.

**Dr. William Feldman (Los Alamos National Laboratory, Los Alamos, NM)**

Dr. William Feldman is a Co-Investigator for the Lunar Prospector
mission and serves as the Spectrometer Group Leader, overseeing the
operation of three of the spacecraft's instruments: the neutron
spectrometer, gamma ray spectrometer and alpha particle spectrometer.
Dr. Feldman was born in 1940. He received a bachelor's degree in physics
from the Massachusetts Institute of Technology in 1961 and later earned
a doctorate in nuclear structure from Stanford University, in 1968. He
has 17 years of experience in analyzing and interpreting solar wind and
magnetospheric data. He has participated in the design of seven plasma
experiments and an energetic electron dosimeter. Dr. Feldman was the
Principal Investigator on a total-absorption neutron spectrometer rocket
experiment and a fast neutron spectrometer launched aboard the Naval
Research Laboratory LAEC spacecraft. He was also a Co-Investigator on a
variety of missions, including Pioneer 10 and 11, IMP 6, 7 and 8, ISEE
1,2 and 3, Mariner 10, Giotto JPA and the Ulysses Space Plasma Physics
Experiments. Dr. Feldman was also a member of the Mars Observer Gamma
Ray Spectrometer Team, with responsibility for the neutron
sensor/charged particle anti-coincidence shield and is chairman of the
Solar Probe Science Study Team. He has authored or co-authored more than
180 scientific papers.

**Dr. Lon Hood (University of Arizona, Tucson, AZ)**

Dr. Lon Hood is a Co-Investigator for the Lunar Prospector mission,
responsible (along with Dr. Mario Acuña) for the spacecraft's
Magnetometer instrument. Dr. Hood was born in Marshall, Texas in 1949,
and received a bachelor's degree in physics in 1971 from Northeast
Louisiana University. He later earned a doctorate in geophysics and
space physics from the University of California, Los Angeles, where he
studied mapping and interpretation of lunar crustal magnetic anomalies
using the Apollo 15 and 16 subsatellite magnetometers. Dr. Hood is
presently a staff member of the Lunar and Planetary Laboratory at the
University of Arizona, where his research for the past several years has
focused on theoretical and observational studies of lunar magnetism,
outer planet magnetospheres and the terrestrial middle atmosphere. He
has served on a number of NASA committees on the Moon and asteroids and
has authored or co-authored some 60 scientific papers and two book
chapters.

**Mr. G. Scott Hubbard (NASA Ames Research Center, Moffett Field, CA)**

Mr. Scott Hubbard is NASA mission manager for Lunar Prospector and also
a Co-Investigator, responsible for the spacecraft's Gamma Ray
Spectrometer instrument. Mr. Hubbard received a bachelor's degree in
physics from Vanderbilt University in 1970 and has done graduate work at
the University of California, Berkeley. He is the originator of the Mars
Pathfinder (formerly MESUR) mission. He is currently Deputy Director of
Space at NASA Ames Research Center, where he supervises studies,
hardware development and mission operations on such missions as Pioneer
and the Galileo Probe. Mr. Hubbard has also contributed experimental
hardware to numerous ionizing radiation investigations, including
balloon experiments, Apollo-Soyuz and HEAO-Cand ISEE-3. While at
Lawrence Berkeley Laboratory, he developed the first thin-window
germanium charged-particle telescope, as well as basic technology for
ultra-pure germanium gamma ray devices and for far infrared
photoconductors. Before coming to Ames, Mr. Hubbard was General Manager
for Canberra Semiconductor, and a Senior Research Physicist at SRI
International. He has received numerous honors, including NASA's
Exceptional Achievement Medal and is the author of more than 30 papers
on radiation detection and space missions.

**Dr. Alexander Konopliv (Jet Propulsion Laboratory, Pasadena, CA)**

Dr. Alexander Konopliv is a Co-Investigator for the Lunar Prospector
mission, responsible for the Doppler Gravity Experiment, which will use
the spacecraft's telemetry data to measure the Moon's gravitational
fields. Dr. Konopliv was born in Minneapolis, Minnesota in 1960 and
received a bachelor's degree in aerospace engineering and mechanics from
the University of Minnesota in 1982. In that same year, he received a
master's degree in aerospace engineering from the Massachusetts
Institute of Technology, and in 1986, he earned a doctorate in aerospace
engineering from the University of Texas at Austin. Dr. Konopliv has
been involved in planetary gravity analysis since 1991 as a member of
the Planetary Gravity Analysis Group in the Navigation Systems Section
of the Jet Propulsion Laboratory. Currently, he is processing the
Magellan Doppler tracking data and combining it with the Pioneer Venus
Orbiter tracking data to produce a 75th degree and order spherical
harmonic gravity field model. This high resolution gravity field model
will be made available to the Magellan science team for geophysical
investigation. Dr. Konopliv's work on the lunar gravity field from the
reduction of Apollo and Lunar Orbiter data provides the basis for
determining the lunar orbit maintenance requirements for Lunar
Prospector. This gravity field model was also used by the Clementine
mission during operations for real-time orbit determination of the
spacecraft. Dr. Konopliv has authored or co-authored a dozen papers on
planetary gravity fields and celestial mechanics.

**Dr. David J. Lawrence (Los Alamos National Laboratory, Los Alamos,
NM)**

Dr. David Lawrence is a Post-Doctoral Research Associate on the Space
Physics Team in Space and Atmospheric Sciences at Los Alamos National
Laboratory. As a member of the Lunar Prospector Spectrometer Team, he
has carried out much of the initial analysis for the LP
gamma-ray spectrometers and neutron spectrometers. He received his B.Sc.
in physics and mathematics from Texas Christian University in 1990,
followed by his M.A. in physics from Washington University, St. Louis in
1992 and his Ph.D. in physics from Washington University, St. Louis in
1996. Since arriving at Los Alamos, Dr. Lawrence has contributed to a
variety of space physics and planetary science projects. These include
preparing data analysis code and carrying out data analysis for the
Lunar Prospector mission. He has also assisted in the construction,
testing, and calibration of the Plasma Experiment for Planetary
Exploration (PEPE) instrument for the NASA New Millennium program. He
has also conducted magnetospheric studies using data from the LANL
Magnetospheric Plasma Analyzer instruments. Prior to his work at Los
Alamos, he designed, tested, flew, and analyzed data for a high-altitude
balloon experiment designed to measure the elemental abundances of the
galactic cosmic rays heavier than iron. He is a member of the American
Geophysical Union, the American Physical Society, and a full member of
Sigma Xi. Dr. Lawrence has authored or co-authored over a dozen papers
on balloon and spacecraft instrumentation along with topics of space and
planetary science.

**Dr. Robert Lin (University of California, Berkeley, CA)**

Dr. Robert Lin is a Co-Investigator for the Lunar Prospector mission,
responsible for the spacecraft's Electron Reflectometer instrument. Dr.
Lin was born in Kwangsi, China in 1942 and later became a U.S. citizen.
He received a bachelor's degree in physics from Cal Tech in 1962 and
earned a doctorate in physics from the University of California,
Berkeley, in 1967. He is currently Professor of Physics and Associate
Director of the Space Sciences Laboratory at U.C. Berkeley. Dr. Lin has
developed experiments for numerous missions, including lunar orbiting
Explorer 35 and the Apollo 15 and 16 subsatellites. Dr. Lin and his
colleagues developed the electron reflectometer technique for remotely
measuring surface magnetic fields on planetary bodies. He is the
Principal Investigator for the plasma and energetic particle experiment
on the Wind spacecraft, lead Co-Investigator for the Electron
Reflectometer experiments on the Mars Observer and Mars Global Surveyor
spacecraft, and Principal Investigator for hard X-ray and gamma ray
spectrometer experiments for astrophysics and solar physics from
balloons. He is also a Co-Investigator on Ulysses, ISTP Cluster and
Equator spacecraft experiments. Dr. Lin has authored or co-authored 236
papers on solar, interplanetary, planetary, magnetospheric physics and
astrophysics.

**Dr. Sylvestre Maurice (Observatoire Midi-Pyrenees, Toulouse, France)**

Dr. Maurice is an astronomer on the planetology team of the Laboratory
of Astrophysics in Toulouse. As a member of the Lunar  Prospector
Spectrometer Team, he has carried out much of the initial analysis for
the LP neutron spectrometer. He received his B.Sc. in aeronautics and
space engineeing from \`\`Sup-Aero\'\', Toulouse, in 1990, followed by
his M.S. in astrophysics from Toulouse University, the same year, and
his Ph.D. in astrophysics from Toulouse University  in 1994. He was then
a post-doc for 2 years at the European Space Agency in the Netherlands,
and a post-doc for 16 months at the Los Alamos National Laboratory in
New Mexico. In 1998, Dr. Maurice was awarded a permanent position at the
Observatoire Midi-Pyrenees in  Toulouse, France. Since his graduation,
Dr. Maurice has contributed to  a variety of space physics and planetary
science projects. These include modeling the magnetosphere of Saturn in
preparation to the  CASSINI mission and understanding the complex
interaction of the  Shoemaker-Levy 9 comet with Jupiter\'s
magnetosphere. He has also  conducted magnetospheric studies around the
Earth using data from  geosynchronous satellites. For these topics, Dr.
Maurice has authored or co-authored over 15 refereed papers.

**GLOSSARY**

**gamma ray **a type of high-energy radiation

**highlands** heavily cratered light-colored regions of the lunar
surface (the Moon's oldest rocks)

**KREEP **an elemental composite material (used by scientists as a
chemical tracer) consisting of [K]{.underline}-potassium,
[R]{.underline}are [E]{.underline}arth [E]{.underline}lements, and
[P]{.underline}-Phosphorous

**Lunar eclipse **period in which the Earth is positioned so as to
obscure the Moon from sunlight

**maria **smooth, dark regions of the lunar surface (the Moon's youngest
rocks)

**mascon **concentrations of mass on the lunar surface

**outgassing **venting of gases from the lunar interior

**regolith **a mixture of fine dust and rocky debris (produced by meteor
impacts) covering the lunar surface

**selenology** scientific study of the history of the Moon, as recorded
in rocks