EXPLORATION OF THE MOON’S THERMAL EMISSION FROM THE DATA OF THE
CLEMENTINE SPACECRAFT AND OF THE GOMS ARTIFICIAL EARTH SATELLITE. S.G.
Pugacheva, V.V. Shevchenko. Sternberg State Astronomical Institute, Moscow University, 13 Universitetsky
pr., 119992 Moscow, Russia, pugach@sai.msu.ru.
Introduction. New satellite measurements of
the lunar surface radiation temperature were used to
study of thermal radiation of the Moon in the
infrared (10.5-12.5 micron) spectral range. The
basic material for investigations are the scanned
cosmic spectrozonal images of the lunar surface
transmitted by the first Russian geostationary
artificial meteorological satellite “GOMS” and
digital images of the Moon acquired by the
Clementine spacecraft. In this paper we describe an
analytic model for the thermal field, which is
realized as an angular function of the thermal
infrared radiation emitted by the lunar surface and
analyse thermal anomalies of the lunar surface.
The
Russian
Geostationary
Artifical
Meteorological Satellite “GOMS”. This satellite
was placed in a circular orbit on October 31, 1996,
in accordance with the program “Meteorological
Service for the Population”. The orbit’s altitude is
35800 km, and the standing point is a longitude of
76oE. The artificial satellite had the onboard
television complex (BTVC), whose optical system
transmitted the real-time digital images of terrestrial
clouds, snow cover, and ice cover. The IR channel
of the BTVC recorded the radiation temperature of
the oceanic surface and of the upper boundaries of
clouds. The optical system of the spacecraft has a
mirror objective 400 mm in diameter. The
instantaneous fields of vision are 6.3 and 22.5
arcsec in the visible (0.4-0.7 micron) and in the IR
range (10.5-12.5 micron) respectively. The infrared
channel records thermal fluxes from objects with
radiation temperature between 213 and 313 K. With
certain geometry of the observation and
illumination, the lunar disk was seen in the frame of
the BVTC objective simultaneously with the
Earth’s Image (fig. 1).
Figure 1. An infrared image of the Earth,
obtained aboard the GOMS geostationary
spacecraft. Upper left: an image of the Moon.
This circumstance predetermined the choice of
the Moon as a natural object with steady-state
characteristics of the reflected and own radiation
for calibrating the instruments onboard the satellite.
To calibrate the electrical signal of the on-board
television complex, the computer simulates on its
monitor a digital image of the Moon’s brightness in
the visible ad IR range [1, 2]. The computer images
are simulated from the photometric database of the
ground-based observations [3]. Digital images of
the temperature of the lunar surface are shown in
fig. 2.
Figure 2. Cosmic image of the lunar surface in
the IR range (10.5-12.5 m), obtained on July 15,
1996, at the Moon’s phase angle of +35.4o.
Photograph no. 07151400.r45. Contours represent
surface-temperature
variations
within
the
isothermal-latitude range 250.0-394.9 K.
The Spatial Angular Function of Thermal
Emission of the Moon. When constructing the
angular function, we used as the input parameters
the Moon’s obtained by GOMS, as well as the
results of ground-based measurements of the
thermal lunar-surface radiation [4]. At a fixed
incidence angle, the angular thermal-radiation
function is depicted in the rectangular coordinates
(x, y, z) as the surface described by the radiation
temperature vector in the range of positive values of
the angular parameters: the incidence angle i, the
reflection angle , and the azimuthal angle A
between the plane of the incident and reflected rays.
The analytic expression for the lunar-surface
thermal radiation is a trigonometric function whose
EXPLORATION OF THE MOON’S THERMAL EMISSION: S.G. Pugacheva, V.V. Shevchenko.
arguments are the values of the angular parameters
i, , and A:
30
Th mg/g
TA = 0 = [110.233 – 95.070 cos(i)] 
cos( - i) + 186.364 cos(i) +199.283,
TA>0 = T(A = 0)  {1 - 3798.767 
[1 - cos(i)]    A}.
Value of the Parameters
25
FeO weight%
U*10 ppm
K/100 ppm
20
Iron
15
Uranium
Potassium
10
5
The root-mean-square error in the determination
of the radiation temperature is 0.94% for mare
regions and 2.24% for highland regions.
Thermal infrared imaging of the Moon from
Clementine. The main instrumentation on
Clementine consists of four cameras, one of which
was a long-wave infrared (LWIR) camera. The
LWIR camera used a catadioptic lens with a 128 
128 HgCdTe FPA. The FPA was operated at 65 K.
Wavelength range was controlled by the cold filter
to 8.0 to 9.5 m. Brightness temperatures were
calculated with the Planck function for emission
from a blackbody assuming unit emissivity;
brightness temperatures range from a high of about
380 K on the equator-facing interior southern rim to
a low of about 270 K on the southward-facing
interior northern rim.
A comparison between theoretical values of
thermal radiation and numerical data of the
measurements from Clementine. A comparison
the common thermal models and results
measurements of thermal emission show a
systematic departure of the measured values from
the average values. These deviations, depending on
the surface albedo, characterize the photometric
inhomogeneity of the lunar surface layer. The
differences of temperature of the lunar surface layer
indicate the extremely low heat conduction and
high porosity of the material. Major factors of the
photometric inhomogeneity are strong irregularities
of the relief and the varied heat conduction of the
lunar ground. We have compared the Lunar
Prospector data of thorium and iron contents [5]
and values IR radiation of the surface for landing
sites. Figure 3 represents the diagram of
relationship between fluctuation of thermal
emission and local thorium and iron content in
different lunar regions. The lines show a mean
polynomial trend.
The correlation coefficients are 0.85 (Th) and
0.88 (FeO). The content of the elements Potassium
(K) and Uranium (U) at lunar surface is showed on
the figure 3.
The separate points represent areas of number of
landing sites: Surveyor I, III, V, VI, VII, Lunokhod
1 and 2, Apollo 11 and 12, and an area in sinus
Media (Lunar Orbiter II).
Thorium
0
0
1
2
3
4
5
6
7
Fluctuation of the Temperature (T K)
Figure 3. The polynomial trends of the Iron,
Thorium, Potassium, and Uranium are showed.
Landing
Sites
The Table of the Statistical Data
Th
FeO
U*10
T K
mg/g
wei.%
ppm
K/100
ppm
Surveyor I
5,07
4,96
22,50
15,9
17,57
Surveyor III
5,54
7,30
22,80
21,7
27,81
Surveyor V
5,95
4,40
18,80
10,0
15,80
Surveyor VII
0,00
1,05
5,24
1,5
5,08
Apollo 11
5,95
4,60
15,20
13,1
9,60
Apollo 12
5,21
6,95
20,30
21,7
27,16
Lunokhod 1
3,91
4,92
14,90
16,1
14,15
Lunokhod 2
1,72
2,63
11,59
7,8
5,66
Surveyor VII
6,28
5,76
21,40
20,8
18,58
Apollo 15
Lunar
Orbiter II
0,31
0,62
3,61
2,7
4,74
9,1
11,60
Correlation
4,66
6,90
11,80
0,8478
0,8800
0,7975 0,7136
Conclusions. The distribution of the radioactive
elements (U, K, Th) at the lunar surface is an
important scientific task for investigations of lunar
evolution. The radioactive elements have provided
continuous heat over the lifetime of the Moon. The
concentration of the radioactive elements provides a
suitable condition for radioactive heating and
basaltic flow to the basin. Probably Th and FeO
enter into composition of ejecta lunar materials.
KREEP-rich materials concern to mare basalt with
a high content FeO. The local assimilation KREEPrich materials ascribed to volcanic extrusions
released or localized by impact and essentially
influence on thermal balance of the Moon.
References: [1] S.G. Pugacheva, V.V.
Shevchenko, V.V. Novikov (1993) Astron. Vestn.,
vol.27, no.4, pp.47-64 [2] S.G. Pugacheva, V.V.
Shevchenko, V.V. Novikov et al. (1997) Astron.
Vestn., vol.31, no.1, pp.64-69. [3] S.G. Pugacheva,
V.V. Shevchenko et al. (1999) Astron. Vestn.,
vol.33, no.1, pp.29-35 [4] S.G. Pugacheva, V.V.
Shevchenko (2001) Astron. Vestnik., vol.35, no.3,
pp.199-207. [5] Lawrence D.J. et al. (2000) JGR,
105, No. E8, 20,307-20,331.