The Probing In situ with Neutrons and Gamma rays (PING) instrument is a promising planetary science application of the active neutron-gamma ray technology so successfully used in oil field well logging and mineral exploration on Earth. The objective of our technology development program at NASA Goddard Space Flight Center's (NASA/GSFC) Astrochemistry Laboratory is to extend the application of neutron interrogation techniques to landed in situ planetary composition measurements by using a 14 MeV Pulsed Neutron Generator (PNG) combined with neutron and gamma ray detectors, to probe the surface and subsurface of planetary bodies without the need to drill. We are thus working to bring the PING instrument to the point where it can be flown on a variety of surface lander or rover missions to the Moon, Mars, Venus, asteroids, comets and the satellites of the outer planets

Bodnarik, J.

Burger, D.

Evans, L.

Floyd, S.

Lin, L.

McClanahan, T.

Nankung, M.

Nowicki, S.

Parsons, A.

Schweitzer, J.

Starr, R.

Trombka, J.

NASA Technical Reports Server

42nd Lunar and Planetary Science Conference (2011) 2379.pdf 
PLANETARY GEOCHEMISTRY TECHNIQUES: PROBING IN-SITU WITH NEUTRON AND GAMMA 
RAYS (PING) INSTROMENT. A. Parsons', 1. Bodnarik"', D, Burger', L Evans,,3, S. Floyd', L Lim', T. 
McClanahan], M. Namkung!, S. Nowic1d1.4, 1. Schweitzer5, R. Starrl.6, 1. Trombka l ,7 
'NASA Goddard Space Flight Center, Code 691, Greenbelt, MD 20771 (Ann.M.Parsons@nasa.gov), 'Vanderbilt 
University, 3Computer Sciences Corporation, 4University of Michigan, 5University of Connecticut, 6Catholic Uni-
versity of America, 7University of Maryland 
Introduction: The Probing In situ with Neutrons 
and Gamma rays (PING) instrument is a promising 
planetary science application of the active neutrOl1-
gamma ray technology so successfully used in oil field 
well logging and mineral exploration on Earth. The 
objective of our technology development program at 
NASA Goddard Space Flight Center's (NASA/GSFC) 
Astrochemistry Laboratory is to extend the application 
of neutron interrogation techniques to landed in situ 
planetary composition measurements by using a 14 
MeV Pulsed Neutron Generator (PNG) combined with 
neutron and gamma ray detectors, to probe the surface 
and subsurface of planetary bodies without the need to 
drill. We are thus \vorking to bring the PING instru-
ment to the point where it can be flown on a variety of 
surface lander or rover missions to the Moon, Mars, 
Venus, asteroids, comets and the satellites of the outer 
planets. 
PING represents the first time a PNG has been 
combined with both neutron and gamma ray detectors 
to create a landed instrument that can determine bulk 
surface and subsurface elemental composition and 
mineralogy without needing to alter the planetary sur-
face in any way. We have had great success demon-
strating PING's capabilities at our unique outdoor neu-
tron instrumentation test facility located at 
NASA/GSFC. We will present recent results from 
PING composition measurements made in a variety of 
experimental configurations on a known sample in a 
geometry that is identical to that which can be 
achieved on a planetalY surface. We will then compare 
the PING composition results to a trace elemental 
composition analysis performed by an independent 
laboratory. Finally, we will demonstrate the improved 
elemental sensitivity achieved by our ability to sepa~ 
rate the gamma ray spectral lines by the nuclear proc-
ess that generated them 
Principles of PING Operation: PING consists of 
three basic components: 1) a pulsed neutron generator 
(PNG) that emits intense pulses of fast (14 Me V) neu-
trons to excite materials at and below the planetaIY 
surface, 2) a gamma ray spectrometer to measure the 
characteristic gamma rays from the excited elements 
and 3) neutron detectors to measure the properties of 
the resulting lower energy epithermal and thermal neu-
trons that reach the surface. 
When a planetary surface is bombarded with 14 
MeV neutrons iI-om PING's neutron generator, the 
nuclei in the planetary materials at and below the sur-
face will be excited so that they emit gamma radiation 
characteristic of the elements present. The intensity of 
these gamma ray lines as measured by the gamma ray 
spectrometer yields the abundance of each element in 
the material. Since the scattering of neutrons in the 
material is strongly dependent 011 its hydrogen content, 
measurements of the thermal and epithermal neutron 
flux at the planet's surface provide an extremely sensi-
tive measurement of the bulk hydrogen content of the 
planetary material. Because neutron and gamma radia-
tion are so penetrating, PING will be able to determine 
the local bulk elemental abundances and mineralogy 
with a spatial resolution of I m and down to depths of 
tens of cm to I m below the surface. PING can detect a 
wide variety of elements and measure their bulk con-
centration with high precision. Accessible elements 
include, but are not limited to, C, I-l, 0, P, S, Si, Na, 
Ca, Ti, Fe, AI, CI, Mg, Mn, V and the naturally radio-
active elements K, Th, and U. 
A great advantage of using a pulsed neutron gen-
erator is the ability to identify the nuclear process (ine-
lastic scattering, thermal neutron capture or delayed 
activation) that is responsible for specific gamma ray 
lines in the spectrum. We will show how identifying 
the nuclear process by the gamma rays' arrival time 
relative to the PNG pulse is used to simplify the spec~ 
tral analysis and improve sensitivity. 
Experimental Description: Our PING prototype 
instl1lment tests are conducted at a unique neutron in-
strument test facility located at Goddard's Geophysical 
Figure l:This illustration of our b(lsic experimental con~ 
figuration shows how layers of different materials can be 
constructed to simulate different subsUfface planetary com~ 
position profiles. Here we demonstrate our ability to detect 
subsUiface water ice by placing a 2.5 cmlayer of high-
del1si~)I polyethylene bene(lth (I layer of 5 cm (hick granite 
blocks. 
https://ntrs.nasa.gov/search.jsp?R=20110008269 2019-08-30T15:06:17+00:00Z
42nd Lunar and Planetary Science Conference (2011) 
and Astronomical Observatory (GGAO) near GSFC's 
main campus [1]. At our GGAO test site, we have the 
capability to test PING using known sample materials 
in a geometry that is similar to that of future planetaty 
il1 situ applications, The test samples are thus located 
outdoors 50 III fr0111 the nearest structure. The site cur-
rently offers a single 1.8 m x 1.8 m x 0.9 m granite 
sample formation, but an identically sized Columbia 
River basalt sample will be installed in early Spring 
2011. The meter-scale size of these samples match 
typical neutron and gamma ray penetration distances 
and ensure that the 14 Me V neutrons emitted by the 
PNG interact only in this sample and in no other mate-
rial in its environment 
-11'" P-'Hl'-"'~l-'-'-'-'T" ''"'' '-"'T'T' nn" ,-'-' q,-. n, I ,-n q '"" '1"" 1'" ,-' 
10 ::\ S''''I'''' ",<-j> I"", "j 
< h .. '""""""'''-', ]. 
:, I' \\ . AJ tnr MV) 
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,..11 ' :~,~.~" ,d •• 'd,~.'-' " ,-")"-"1,.,,,-,,,, I., " •• " I "d~_ • .J ,,~,-,-,._, 
,()OO 2'>00 = 40;,0 :;000 (.:>00 7{>;:", 
~""~Qr(""V) 
Figure 2: Spectra obtained during the pulse of high~energy 
neutrons with and wifh0ll11he presence a/polyethylene. 
These sample materials were chosen because they 
have uniform composition on the appropriate size 
scale, can be easily characterized, and have low poros-
ity so that their water content is stable and independent 
of Malyland weather. The pairing of our granite with a 
basalt sample allows us to test PING on materials rep-
resentative of a variety of bodies in the solar system. 
Due to the PNG radiation safety hazard, we operate 
PING remotely from a building over 60 m away. 
Our tests involve placing our PING prototype on 
top of a large test sample (see Figure 1) to measure the 
resulting characteristic gamma rays and epithermal and 
thermal neutrons radiated by the surface. We also have 
the capability to perform layering studies using 5 em 
thick plates of the same sample materials as well as 2.5 
em thick high-density polyethylene plates to simulate 
layers of water ice, These materials and others can be 
stacked on top of the test sample to simulate a variety 
of layering and composition scenarios. 
Results: The spectra shown in Figure 2 illustrate 
the power of gated data acquisition to isolate gamma 
rays from different nuclear processes. With our PNG 
and a LaBr gamma ray spectrometer on top of our 
granite formation as shown in Figure 1, we were able 
2379.pdf 
to use a single data acquisition window fixed at a time 
during each neutron burst to isolate a gamma ray spec-
trum that is primarily due to "inelastic" high-energy 
interactions. These "inelastic" spectra shown in Figure 
2 result from two experiments, one with 2.5 cm of 
polyethylene on top of the granite and covered with 
granite plates and one without polyethylene. Since 
polyethylene is a good source of hydrogen, its presence 
more quickly moderates neutrons. The capture back-
ground shown in the inelastic spectrum with the poly~ 
ethylene is slightly lower because fewer thermal neu-
trons are present from earlier bursts. The lack of evi-
dence of the 3539 keY neutron capture line from Si, 
for example, illustrates how well this technique iso-
lates the gamma rays from inelastic processes. 
Timing Studies: In addition to time-gated gamma 
ray data acquisition spectra, we now have the ability to 
take timed tagged event-by-event data using our cus~ 
tom designed software with the Canberra Lynx Digital 
Signal Analyzer to provide a unique 
three-dimensional master data set with chan-
nel/energy, time, and intensity information. Since the 
master data set is not limited to predetermined coinci-
dence timing gates set for a specific nuclear process, 
the user is allowed the flexibility to slice the data cube 
in a multitude of ways without loss of information or 
experimental time due to the need for additional acqui-
sition windows, Time-tagged event-by-event data 
allows the user to analyze a gamma ray spectrum re-
sulting from either neutron capture, events occurring 
between the neutron pulses, or inelastic scattering 
events occurring during the neutron pulse, and extract 
the data needed to optimize timing windows to look at 
specific elements in different environments, For exam-
ple, the water content on Mars (-3%) is greater than 
that on the Moon «1%). This difference affects the 
slowing down time of neutrons on the Moon and thus 
requires a greater delay of the start of the neutron cap-
ture time window with respect to the end of the PNG 
pulse. We will present the results of our experimental 
data using the time tagged event - by-event data analy-
sis technique compared to time gated coincidence data. 
Comparison of these data will show the advantages 
and validity of this method to obtain more precise and 
sensitive elemental composition measurements. 
Conclusions: The spectra in Figure 2 demonstrate 
the capabilities of PING as well as the great flexibility 
available f01" the testing of this device in a controlled 
environment. We will compare the granite composition 
inferred from these data with the independent elemen-
tal composition analysis and the results of our com-
puter models. We will also present additional data to 
further illustrate the utility of gated data acquisition. 
References: [I] Bodnarik, et a!., LPSC 2010 #2581 


Planetary Geochemistry Techniques: Probing In-Situ with Neutron and Gamma Rays (PING) Instrument

Planetary Geochemistry Techniques: Probing In-Situ with Neutron and Gamma Rays (PING) Instrument

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