**Electrostatic Dust Removal and Collection Devices for Planetary
Surfaces**

PI P.E. Clark

CoI's: J. Keller, T. Stubbs, W. Farrell, M.L. Rilee

Collaborators S.L. Curtis, J.A. Nuth

Consultants O.E. Berg, W.D. Carrier

Cover Page place holder

**Scientific/Technical/Management Section**

**I. Challenges, Objectives, and Their Significance**

Missions to sample the surfaces of atmosphereless bodies, including the
Moon, asteroids, and Mercury, have been identified as crucial components
of solar system exploration over the next decades (Solar System
Exploration Committee, 2002; President's Commission, 2004). Detailed
study of the physical and chemical nature of the fine particulate
portion of the regoliths of these bodies is a key to understanding
micrometeorite bombardment and the nature of regolith formation (e.g.,
Noble et al, 2001). Even for the Moon, such details are relatively
sparse (McKay et al, 1991; Carrier et al, 1991) because of the
difficulty in effective control, collection, and measurement of regolith
fines (\<10 **μ**) (Carrier, personal communication, 2005), an issue
which must be resolved for future missions (Gaier, 2005; Gaier and
Creel, 2005; Taylor et al, 2005). Our inter-disciplinary team, a blend
of capabilities including theoretical and observational study of
dynamics field and particle interactions on planetary surfaces,
laboratory instrument design and development, field study, and mission
operations, is well suited to investigate the feasibility of a
transferable technology for control and collection of dust with a wide
spectrum of properties by the range of atmosphereless body lander/rover
instrument suites currently envisioned.

**1. Challenge:** Fields, charged particles, and dust particle
interactions on the Moon and presumably other atmosphereless bodies are
complex (Criswell, 1973; McCoy et al, 1974; Berg et al, 1976; Sickafoose
et al, 2001; Stubbs et al, 2005). Their interactions are dependent on
environmental conditions and on the highly variable particle properties
including size, shape, and composition as well as magnetic or electrical
properties. In addition, although foundational work on dust behavior in
fields has been done (Colver, 1976; Horanyi et al, 1998; Brach et al,
2000; Cheng et al, 2002) there is relatively little empirical simulation
of dust behavior at payload surfaces within the context of surrounding
non-conducting, dusty plasma/regolith environment. **Objective**: We
will test our concept of regolith particle interactions with payloads on
atmosphereless surface environments by performing empirical simulations
of the interaction between solar wind, energetic plasma, regolith
particles, regolith surface, and foreign (spacecraft) surface in a
temperature-controlled vacuum chamber fitted with a UV source and
electron/ion beams acting as solar wind and plasma. Regolith particles
will be represented by fines (\<10 **μ**) with the morphology and
mechanical properties of lunar dust. **Significance**: Both the proposed
dust transfer and theoretical predictions will be tested in our
simulator, allowing proof of concept of dust behavior as an essential
preliminary step in the development of a dust collecting device.

2\. **Challenge:** The strategies initially implemented to deal with
lunar regolith failed to remove or contain smaller particles (Gaier,
2005; Gaier and Creel, 2005). A currently proposed strategy based
increased magnetic susceptibility in lunar fines (Taylor et al, 2005)
may not work uniformly well for fines of non-mare, or non-lunar,
composition. **Objective**: We will develop a conceptual design and
laboratory breadboard for electrostatic fine particulate collection
based on dust interactions already observed in the laboratory (e.g.,
Colver, 1976; Olansen et al, 1989; Brach et al, 2000; Cheng et al,
2002a,b). We will validate the effectiveness of this method for dust
collection and compare our results to those of other dust control
strategies. Our approach will involve using a particle beam to increase
the charging of dust and an oppositely charged surface collector to
attract particulates of the desired size range, an approach similar to
one used to control spacecraft potential in a highly charged environment
(Comfort et al, 1998). **Significance**: Landers and rovers will be able
to sample particulates at will, and before dust clogs surfaces and
causes overheating or scratching, turning potential limitation into
opportunity.

**II. Context of Proposed Work**

**A. The significance of Dust in the Solar System**

Bombardment has affected every surface in the solar system, modifying
and forming regolith on exposed surfaces. On atmosphereless bodies,
including the Moon as well as Mercury and the asteroids, the regolith
maintains a record of this process, as well as a record of solar wind
and cosmic ray interactions. As a result, a major emphasis for future
solar system exploration has been on sample return to solar system
bodies, including South Pole Aitken Sample Return to the Moon (Solar
System Exploration Committee, 2002).

The study of fine particulates in the solar system has been identified
as an important area of study capable of providing insight on the
operation and interaction of processes that shape contemporary character
of planetary bodies (Solar System Exploration Committee, 2002). Remains
of the impactors generally remain in the fine particulate portion of the
regolith. The composition of these micrometeorite remnants will give
insight on the nature of interplanetary dust (Lindsay and Srnka, 1975).
The development of technologies for gathering, handling, and analyzing
samples, particularly 'harder to obtain' samples such as the fine
particulates, will play a crucial role in the study of dust. Without the
fines, accurate assessments of bulk composition, impactor flux and
impact record, and space weathering mechanisms cannot be obtained (e.g.,
Noble et al, 2001).

**B. The Nature of Fine Particulates on Atmosphereless bodies**

Fine particulates on the Moon arise from both natural and induced
sources (Carrier et al, 1991; McKay et al, 1991). Typically,
above-ground dust has been observed to be generated naturally from
secondary ejecta from meteorite bombardment or from electrostatic
levitation (Berg et al, 1976; Rhee et al, 1977). When spacecraft are
introduced into this environment, natural sources are thought to become
a minor component. Upon impact, particularly landing, the local induced
stirring of the regolith caused dust to be suspended long enough to come
into contact with conducting surfaces. Dust adhered to everything and
couldn't be removed as anticipated. Attempts were made to collect lunar
regolith samples which contained dust. The fine particulate portion
couldn't be contained as anticipated. Dust behaved like Velcro and
couldn't be simply brushed off. Three mechanical strategies were
considered for removing dust (Gaier, 2005), including brushing off, jet
and shield, and vibrating. Brushing was chosen as the low mass, low cost
option. In fact, there was little time to study the impact of dust on
moving parts in a lunarlike environment. Brushing in fact caused surface
abrasion and did not remove the 10% of the dust represented by the fines
(\<10 micron) (Gaier and Creel, 2005). On the other hand, lunar fines,
because of their electrostatic charging, were relatively difficult to
collect in sample bags along with other size range particles. Within
hours, seals were broken, samples contaminated, and portions of the
samples, especially fines, lost.

Study of Apollo soil samples revealed much about the nature of the
regolith and the causes of mechanical problems experienced during the
Apollo landings (Mitchell et al, 1972; Carrier et al, 1991; McKay et al,
1991). The lunar regolith is a soil-like layer above bedrock generated
by impact of meteorites in a range of sizes and dominated by particles
ranging in size from centimeter to submicron scales, with rocks, some as
large as boulders, interspersed (Carrier et al, 1991; McKay et al,
1991). Repeated small meteorite impacts have caused extensive remelting
and generate glassy particles, known as agglutinates. As a result, soil
fragments are thus highly irregular angular, and sharp, elongated (1:3
axis length ratio), and with high specific surface area. They have 8
times as much surface area as a population of spheres with equivalent
particle size distribution. Reentrant shapes act as Velcro-like hooks.
Such particles are thus shard-like and highly abrasive. They are highly
anisotropic, porous, and compressible, aligning along long axes.

Ten to twenty percent of the collected soil particles, called the lunar
fines, or dust, are below 10 microns in size. Agglutinates are thought
to form from this fine component (McKay et al, 1991). Limited studies
done on lunar fines indicates that they are systematically less mafic in
composition, higher in silicic and felsic components (Walker and Papike,
1981; Devine et al, 1982; McKay et al, 1991), in keeping with systematic
trends observed for the range of larger size fractions of lunar soils.
Mechanical and morphological properties of fines have not been directly
studied, but, based on observations, are thought to share 'reentrant'
morphology and abrasiveness, but to be weaker mechanically, due to their
extensively glassy nature (Carrier et al, 1991; McKay et al, 1991;
Carrier, 2003, personal communication).

On the average, the fine portion of collected lunar soils have higher
magnetic susceptibilities than larger particles (Carrier et al, 1991).
At first, this effect was thought to result from the increased abundance
of separate metallic iron components (McKay et al, 1991). Now, the
prevailing view is that nanophase metallic iron coatings induced by
space weathering account for a relatively larger portion of grains by
volume and surface area and produce this effect (Taylor et al, 2001;
Taylor et al, 2005). The increase in metallic iron abundance and in
magnetic susceptibility with decreasing grain size, as well as the
capability for efficiently collecting particles magnetically in the
10-20 micron size range, has been demonstrated for mare soils (Taylor et
al, 2000). As a result, magnetic capture has been proposed as a dust
collection mechanism (Taylor et al, 2005). A question remains as to how
much variation in magnetic susceptibility is present among all lunar
fines, including highland and mixed highland/mare soils, as well as
non-lunar fines, and whether this approach would work equally
effectively for the smallest and least mafic particles (\<10 microns).

Lunar fines shows low electrical conductivity and dielectric loss
(Carrier et al, 1991), and, because they do not easily conduct charge,
and tend to remain electrostatically charged (Sickafoose et al, 2001).
Charging is temperature, particle size, and irradiation dependent
(Stubbs et al, 2005). Greater illumination and temperature increase
surface potential. Smaller particles may become more negatively charged
due to greater surface area/volume. Less mafic particles tend to have
lower loss tangents and greater conductivity and are thus more apt to
become electrostatically charged more quickly (Sickafoose et al, 2001).
This electrostatic behavior resulted in particles ultimately covering,
clogging, and contaminating oppositely charged conducting or
non-conducting surfaces and mechanisms to varying degrees (Carrier et
al, 1991; Gaier and Creel, 2005; Katzen and Edwards, 1991).

Electrostatic charging of the Moon occurs via interaction of solar UV
light with the surface causing photoemission of electrons and
interaction of the local plasma environment (Stubbs et al, 2005).
Charged dust grains are repelled from like-charged surface or attracted
to oppositely charged surface. Dust repulsion results in dust grains
being lifted above the surface (Manka, 1973; Criswell, 1973; McCoy et
al, 1974; Berg et al, 1976; Murphy and Vondrak, 1993) to distances which
depend inversely on the size of the grain. Surface charging on the
dayside is driven by photoelectron currents, resulting in electron
depletion and positive charging of the surface; on the nightside, plasma
electron currents result in electron accumulation and negative charging
of the surface (Manka, 1973). The net potential falls to zero in the
so-called 'Dead Zone' about ten degrees from the terminator on the
sunlit side (Stubbs et al, 2005). Perhaps permanently shadowed craters
regions have smaller versions of the 'dead zones' near their perimeters.
Great differences in charging on either side of the terminator result
from the net flow of particles, particularly smaller ones, from the
illuminated to unilluminated areas (Berg et al, 1976; Berg, 1978). This
results in net positive charge in illuminated areas and negative charge
in dark areas. The lowest electrical conductivity, highest
chargeability, and highest risk of spark discharge occurs in the dark
when two mobile objects meet (Stubbs et al, 2005).

**III. Technical Approach to Developing an Electrostatic Dust Sweeping
Tool**

This work combines our inter-disciplinary team's expertise in (1)
laboratory dust experiments, (2) ion beam injection and measurement with
its related SEC space physics heritage, (3) terrestrial, lunar, and
interstellar dust and electrification processes, (4) lunar dust
distribution and geological settings, (5) plasma processes, and (6)
operational impacts of lunar dust, in order to explore how an
electrostatically-based device can be used to modulate the electrical
potential of conducting surfaces and hence to self clean surfaces
exposed to a dusty environment and collect dust samples.

Understanding, simulating, and, ultimately, being able to control dust
interactions with surfaces and charged particles on planetary regoliths
is now an issue of considerable interest. Theoretical modeling of
surfaces/plasma/dust interactions is an important contribution to the
effort, and has been going on here at Goddard Space Flight Center (e.g.,
Ogilvie et al, 1996; Farrell et al, 1998; Murphy et al, 1993; Stubbs et
al, 2005). Present models depend on parameters which are not fully
constrained, and must depend on simplifying assumptions due to the
complexity of interactions (Stubbs et al, 2005). Ultimately, models can
and should be verified and tested by empirical laboratory simulations.

The properties and behaviors of individual particles in the presence of
plasmas or photoemissive surfaces have been studied in the laboratory
for many years. Colver (1976) demonstrated that both highly conducting
and dielectric particles tens of microns in size and larger can be
charged and transported between two oppositely charged plates. Olansen
et al (1989) levitated particles against gravity, demonstrating a
dependence on current independent of the nature of the particle. A
number of workers have observed the charging and levitation of lunar
dust grains, Horanyi et al (1998) in the presence of an electron beam
representing plasma and Sickafoose et al (2001) in the presence of
photoemissive surfaces. Brach et al (2000 developed analytical models of
the impact process that can be used to predict particle capture. Cheng
et al (2002a,b) have demonstrated that both increased surface roughness
and particle irregularity (elongation) decrease adhesion efficiency.

Starting with this theoretical and observational work as well as dust
behavior already observed on the lunar surface (Criswell, 1973; McCoy et
al, 1974; Berg et al, 1976; Rhee et al, 1977) as input for an empirical
simulation, we will begin to demonstrate how such interactions,
particularly those involving not only plasma and regolith dust, but a
third component, a conducting surface from a space structure or vehicle.

Based on the nature of interactions seen during the Moon landings,
empirical work should be done with material of analogous particle size
distributions and, as much as possible, morphological (abrasive,
adhesive), and compositional (thermal, tribological, electrical,
magnetic) properties (Gaier and Creel, 2005). A material made from
crushed volcanic ash, such as lunar soil simulant JSC-1, or the proposed
replacement JSC-1a (Lofgren, personal communication, 2005), would be
appropriate. The simulant is designed to represent compositional, as
well as mechanical and morphological, characteristics of lunar glass
(McKay et al, 1994). The characteristic persistent adhesion and abrasion
of these particles when interacting with a charged surface is a result
of the combined electrical and physical properties, which cause the
particles to be easily charged, electrostatically attracted, and then
almost impossible to dislodge by physical means alone.

We will create a laboratory simulation of the changing of potential
induced by solar illumination and plasma interactions, and the resulting
electrostatic interactions, to learn how to control the potential of
surfaces to repel or attract dust. We hope to demonstrate that we can
change the potential of vehicle surfaces in a way that causes dust to be
repelled for cleaning or attracted for sampling. The laboratory
simulation will act as a feasibility study for a laboratory 'breadboard'
self-cleaning device based on the use of combined electron or ion beams
(Comfort et al, 1998), acting as plasma dust sweeper that would scan a
surface constantly to control its potential, and a plate of the opposite
potential. Our results will be compared to those available for the
proposed 'magnetic sweeper' (Taylor et al, 2005) operating under
comparable conditions.

**IV Methodology and Tasks**

**Task 1: Problem Definition**

Lunar dust, and presumably analogous fine particulates in other
atmosphereless regoliths, possesses properties that distinguish it from
the water-weathered dust typically found on Earth, because lunar dust is
almost exclusively the result of micrometeorite impacts impinging on the
surface of the Moon (McKay et al, 1991). The energy of these impacts is
such that glassy (agglutinatic) melts can be formed leading to extremely
sharp edges and interlocking configurations. The characteristic
'reentrant' shape and resulting high surface area of lunar dust greatly
enhance its ability to accommodate static charges (Carrier et al, 1991;
McKay et al, 1991). This in turn results in greater potential for dust
transport in Lunar electric fields or in response to local charging that
takes place at the lunar surface. Solar wind and electric field
exposures vary greatly as illumination conditions change on the surface,
causing regional variations in charge distribution and potentially
resulting in dust flow. Impacts, natural or induced, locally stir up
charged dust which is then attracted to oppositely charged objects
(Carrier et al, 1991; McKay et al, 1991; Stubbs et al, 2005).

The question is, how do we simulate these conditions in the laboratory?
Our entire inter-disciplinary team will consider this problem. We will
attempt to recreate the atmosphereless regolith environment, with
non-conducting regolith and a range of materials, from conducting to
insulating representing the foreign object surface, represented by two
plates. Upper or lower plate, or both, must be easily transformable from
conducting to non-conducting surface or vice versa. In a vacuum chamber,
we will represent photo-emissive behavior on illuminated dusty surfaces,
resulting in positive charging, via UV sources, and negative charging on
shaded surfaces, via cold plasma generation from electron or ion sources
to produce a low power electric field. Resulting Electric Field
intensity and levitated \<10 micron particle density will be measured by
electric field and tunable laser. Ion and electron beams will be used to
change the charging of the conducting plate, representing a robotic
explorer, and cause dust to be discharged from it or attracted to it,
acting as electrostatic 'dust sweeper'. Plasma beams could also be used
to represent external plasma interaction with the surface. We must also
be able to change the positions of the plates representing a mobile
robotic component impacting the lunar regolith, continually stirring up
dust which must then be mitigated.

**Task 2: Laboratory Feasibility Studies: Set-Up**

We will attempt to recreate the environments inducing the observed
behavior of dust on the Moon, including electrostatic dust transport and
sticking on the moon observed by the Apollo astronauts and documented by
the LEAM experiment on Apollo 17 (Berg et al, 1976; Berg, 1978; Rhee et
al, 1977; Zook and McCoy, 1991). A team of experimentalists and
instrumentalists, led by J.W. Keller and W.M. Farrell, with Otto Berg
who designed the LEAM experiment as a consultant, will consider this
problem. Our set up will allow us to quantify the level of charging and
electric field intensity required to levitate or remove particles.

The experiment is aimed at understanding the science behind the
transport of dust, with results of this work applicable to the
technology necessary to gather samples and protect equipment from lunar
dust. The capability of charging and transporting both dielectric and
conducting dust grains with lunarlike size distributions between highly
charged surfaces has already been demonstrated (Colver, 1976; Olansen et
al, 1989; Horanyi, 1998; Brach et al, 2000; Cheng et al, 2002a,b;
Sickafoose et al, 2001) and we will apply these results in our overall
environmental simulation.

Dust Sample: We will use an appropriate lunar soil split if available,
or simulant with morphologies and size range which approximate lunar
soil. JSC-1 (McKay et al, 1994) or its new equivalent, JSC-1a, designed
for research on dust control and equipment durability, is a likely
choice if available by then. A suitable simulant could also be made from
crushed and sieved volcanic glass which will generate particles in the
appropriate size range. As a final step, to test the behavior of dust
itself, we would use the finest portion of lunar soil or simulant. A
range of materials could be used to represent the foreign object
surface, including a range of metals, coatings, and fabrics used on
spacecraft.

Environmental Simulation: Temperature-controlled vacuum chambers with
many fittings in a range of sizes are available through Co-investigators
Nuth and Keller here at Goddard. UV sources, electric field sources, IR
tunable lasers, and electric field detectors are also readily available
in their laboratories. Ion and plasma beam instruments to control
electrostatic charging of dust will be purchased as part of this
proposal.

**Task 3: Laboratory Feasibility Studies: Simulation**

The team of experimentalists and instrumentalists, with principal roles
played by J.W. Keller and J.A. Nuth, will perform the laboratory
simulations as illustrated in Figure 1. In one likely configuration,
dust particles will be placed on metallic plate covered with thin
non-conductive material such as diamond film to isolate the dust
electrically but to allow it to be subjected to controlled electric
fields. Although average grain size of lunar dust is \~70 microns, the
most-difficult-to-obtain fines are of particular interest. So, we will
begin our experiments be testing a range of sizes, but complete the
process by using the \<10 micron fraction where electrostatic forces for
highly charged dust particles compete with mechanical adhesion and are
comparable or greater than gravitational forces under lunar conditions
(Sickafoose et al, 2001; Stubbs et al, 2005). Sufficient quantities of
dust will be used to cover the test area so that the surface will not be
exposed and the top layer of dust is not in contact. The dust will be
placed ![](media/image1.wmf){width="5.083858267716535in"
height="3.6251968503937007in"}under ultra high vacuum and allowed to
outgas sufficiently so that residual gasses will not affect the
electrical properties of the dust. The dust will be subjected to low
potential (1 -- 1000 eV) via tungsten filament, representing a cold
plasma, and/or UV light sources (L~α~), representing sunlight, while we
observe the response of the dust to the electrostatic forces that ensue.
In cases where the dust levitates from the surface, the relative density
of the dust can be measured using scattered laser light. The levitated
dust will be neutralized using low energy charged particle beams of the
opposite charge and the temporal response will be observed. We will also
determine how well this strategy works as a function of particle sizes
and environmental conditions.

**Task 4: Conceptual Design for Dust Cleaner/Collector**

The analysis of simulation results will be led by plasma physicists
experienced in observational work and modeling (Farrell et al, 1998;
Stubbs et al, 2005). Analysis will begin with an understanding of
surface potential and dust loading as a function of UV intensity and low
energy plasma intensity. When the UV intensity is high, we anticipate a
strongly positive dielectric surfaces, as has been measured in sunlight
on the Moon. As UV intensity drops, the surface potential should show a
correlative drop toward zero. The low energy plasma dominates. As the UV
diminishes, the cold plasma will dominate and the surface should develop
a more negative potential. Dust loading of the conducting plate should
increase when the electric field increases negatively or positively.
Then the ability of ion or electron beams to drive the surface potential
of the conducting plate to zero and discharge dust or increase the
surface potential and attract dust will be studied as a function of UV
intensity. We will also determine what happens when both surfaces act as
non-conducting ones because of the ubiquitous presence of dust. The
results will lead to a conceptual design for dust control device, which
will include a charging beam to increase charging and surface potential
of a dust covered surface and an oppositely charged plate/container to
remove and collect the dust. Such components will be introduced in the
laboratory simulation to test their effectiveness.

**Task 5: Breadboard Dust Tool**

The interdisciplinary team of plasma physicists, experimentalists, and
soil specialists, led by P.E. Clark and S.A. Curtis, will evaluate the
effectiveness of plasma beams and oppositely charged plates for dust
control, in the context of other proposed or developing strategies
(e.g., vibration, magnetic capture, AC wave across the surface).
Interactions between components in the lunar environment and dust
collector based on theoretical modeling must be confirmed by
observations.

We will design and test the dust cleaner/collector scheme (Figure 2) in
the laboratory simulator. The collection device components will consist
of an electron gun to increase the charging and an oppositely charged
capture device to charge up, attract, remove and collect the dust.

Our electron gun component will be designed to place a defocused beam of
100 nA on a 3 cm diameter area. At this current flux, a 1 micron
diameter dust particle will initially charge up at the rate of \~600
electrons per second and will rapidly saturate the capacity of the
particle to carry additional charge. Relatively modest electric fields
of 10^4^ V/m is sufficient to overcome the lunar gravitational field and
accelerate a 1 micron particle to the plate. We will adapt a Comstock
(Comstock Inc., 1005 Alvin Weinberg Drive, Oak Ridge, Tennessee 37830)
electron source that we have in-hand to act as the electron gun for our
dust sweeper. The source uses a hot filament to boil off electrons and
is capable of delivering several milliamps of current. However we will
run the filament at low temperatures for the smaller currents that we
anticipate will be required. The optics are designed to give a small
spot size at a distance of several centimeters, but we will modify the
optics to move the focus very close to the source at the aperture of the
dust collecting plate. This and an additional optic at the aperture will
provide a divergent beam for broad coverage over the target.

In order to prevent dust particles from immediately losing their charge
upon hitting the front capture plate (Olanson et al, 1989), we will
attach a thin semiconductor material such as a silicon wafer to the
front of the plate. The resistivity of the silicon can be controlled by
appropriate doping and will be designed to optimize the time constant
associated with bleeding off the charge on the dust particles while
maintaining sufficient charge neutrality of the plate so that the
electric fields imposed by the conductor plate behind the silicon is not
cancelled.

How will the nature of the spacecraft surface covered with insulating
dust affect electrostatic discharge? If the spacecraft surface is
conducting the discharge would be relatively rapid. As long as the
discharge rate occurs as the RC time constant, as anticipated, an
electron gun will be able to charge the surface up fast enough to
overcome bleeding of charge. If the spacecraft surface is
non-conducting, will the electron gun be able to provide sufficient
potential to be attracted to oppositely charged plate? We anticipate
that the gun will have a high enough current to offset charging due to
the solar wind and the photoemissive effect which is 10-100 times higher
than solar wind.

What happens when the conductivity of the surface or the average
particle size varies? How can we deal with dual polarity surface
generated by variation in light and shadow on a structure causing
differential charging and dust movement (Criswell, 1973)?

![](media/image2.jpeg){width="5.833464566929134in"
height="4.41259842519685in"} 'Wiping' with electrons (electron beam)
under influence of positively charged plate (through which beam emerges)
seems a good approach to control and collect dust and prevent charging
of the electron gun, provided the gun is always pointed at a target on
the spacecraft. In case this doesn't work, because the gun is
inadvertently fired at a target off the spacecraft, we will need to test
the effectiveness of a strategy, such as a plate off to the side to
counter electrons leaving the gun.

How will our approach for dust collection compare with a
magnetically-based approach? We anticipate that we will demonstrate
greater ease and efficiency in dust removal and retrieval and less
interference with instrument and spacecraft systems.

The answering of these questions will lead to the construction of a
laboratory breadboard for the dust cleaner/collector device.

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