The scientific objectives of the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission are: (1) determine the composition of the lunar atmosphere, investigate processes controlling distribution and variability - sources, sinks, and surface interactions; and (2) characterize the lunar exospheric dust environment, measure spatial and temporal variability, and influences on the lunar atmosphere. Impacts on the lunar surface from meteoroid streams encountered by the Earth-Moon system are anticipated to result in enhancements in the both the lunar atmosphere and dust environment. Here we describe the annual meteoroid streams expected to be incident at the Moon during the LADEE mission, and their anticipated effects on the lunar environment

Colaprete, A.

Elphic, R. C.

Glenar, D. A.

Hermalyn, B.

Sarantos, M.

Stubbs, T. J.

Wang, Y.

NASA Technical Reports Server

THE IMPACT OF METEOROID STREAMS ON THE LUNAR ATMOSPHERE AND DUST 
ENVIRONMENT DURING THE LADEE MISSION.  T. J. Stubbs1, D. A. Glenar2,1, Y. Wang2,1, B. Hermalyn3, 
M. Sarantos2,1, A. Colaprete3, R. C. Elphic3, and the LADEE Science Team, 1NASA Goddard Space Flight Center, 
Greenbelt, MD 20771, 2University of Maryland, Baltimore County, Baltimore, MD 21250, 3NASA Ames Research 
Center, Moffett Field, CA 94035, (Timothy.J.Stubbs@NASA.gov).  
 
 
Introduction:  The scientific objectives of the Lu-
nar Atmosphere and Dust Environment Explorer 
(LADEE) mission are: (1) determine the composition 
of the lunar atmosphere, investigate processes control-
ling distribution and variability – sources, sinks, and 
surface interactions; and (2) characterize the lunar ex-
ospheric dust environment, measure spatial and tem-
poral variability, and influences on the lunar atmos-
phere [1]. Impacts on the lunar surface from meteoroid 
streams encountered by the Earth-Moon system are 
anticipated to result in enhancements in the both the 
lunar atmosphere and dust environment [2,3]. Here we 
describe the annual meteoroid streams expected to be 
incident at the Moon during the LADEE mission,  and 
their anticipated effects on the lunar environment. 
The LADEE science payload consists of three in-
struments: the Ultraviolet/Visible Spectrometer (UVS) 
for measuring emission lines from exospheric species 
and scattered light from exospheric dust; the Lunar 
Dust Experiment (LDEX) for in situ measurement of 
exospheric dust; and the Neutral Mass Spectrometer 
(NMS) for in situ measurement of exospheric species. 
All three instruments are potentially capable of detect-
ing the effects of an encounter with a meteoroid 
stream. LADEE nominally has a 100-day science mis-
sion in which its retrograde equatorial orbit (inclina-
tion ≈ 157°) will take it below 50 km altitude at peri-
apsis near lunar sunrise. Lunar Orbit Insertion (LOI) 
occurred on 6 October 2013 and the current End-of-
Mission (EOM) is planned for 25 March 2014 before 
the lunar eclipse on 15 April 2014 (although this could 
conceivably be extended). 
Meteoroid Streams: The Earth-Moon system fre-
quently encounters debris trails from short- and long-
period comets, as well as asteroids, which are referred 
to as meteoroid streams [4]. The meteoroids in these 
streams have similar velocities and are on near-parallel 
trajectories, such that when they enter the Earth’s at-
mosphere the resulting shower of meteors (or shooting 
stars) appears to be emanating from a virtual point on 
the sky called the radiant. Meteor (and meteoroid) 
rates vary as a function of the Earth’s position in its 
orbit, with an activity curve that increases to a peak 
and then decreases. Annual streams are those that 
regularly encounter the Earth each year. In Table 1 we 
list the 18 IAU established annual streams that will 
encounter the Moon during the LADEE mission [5]. 
These streams are relatively well characterized and are 
broad enough that it is reasonable to assume that both 
the Earth and Moon will pass through them. 
Unlike at the Earth, all of the stream meteoroids in-
cident at the Moon will impact its surface and create 
ejecta clouds and release species into the exosphere 
[2,3]. Since they move on near-parallel trajectories we 
expect to observe asymmetries in their effects on the 
lunar environment. Therefore, it is necessary to know 
the locations where the streams are normally incident 
on the lunar surface (i.e., the locations of the stream 
radiants in the Moon frame).  
In Fig. 1, the location of the radiants for the 18 an-
nual streams at the time of peak activity are plotted as 
Selenographic Solar Ecliptic (SSE) latitude and local 
time. The points are color-coded to show the Zenith 
Hourly Rate (ZHR) at the peak in meteor shower activ-
ity. (ZHR is the hourly rate of meteors seen by stand-
ard a observer on the Earth under optimum viewing 
conditions.) For our purposes, ZHR serves as rough 
guide to the meteoroid flux rates incident at the Moon. 
For comparison, the Hourly Rate (HR) for sporadic 
background meteors that are no longer associated with 
any streams is ≈9.5. Only six of the 18 streams have 
peak ZHRs that exceed this background HR, so its 
reasonable to assume that these streams will likely 
have the most noticelable effects on the lunar envi-
ronment compared with typical conditions. The gray 
shading in Fig. 1 indicates the latitudinal range of the 
LADEE orbit. 
Meteoroid Stream Radiants at the Moon
La
tit
ud
e 
(S
SE
)  [
 de
g ]
Local Time (SSE)  [ hr ]
 
 
0 3 6 9 12 15 18 21 24
−90
−60
−30
0
30
60
90
0 15 30 45 60 75 90 105 120
Figure 1
https://ntrs.nasa.gov/search.jsp?R=20150011019 2019-08-31T08:00:52+00:00Z
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The Impact of Meteoroid Streams on the Lunar Atmosphere and Dust Environment During the LADEE Mission

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