**IAC-04-Q5.07**

**PAM: Biologically inspired Engineering and Exploration Mission
Concept, Components, and Requirements for asteroid population survey**

**P.E. Clark**

**Location: Code 695, NASA/GSFC, Greenbelt, MD 20771 USA**

**Affiliation: L3 Communications, GSI., 3750 Centerview Drive,
Chantilly, VA 20151 USA**

**Pamela.Clark@gsfc.nasa.gov**

**M.L. Rilee**

**L3 Communications, GSI, 3750 Centerview Drive, Chantilly, VA 20151
USA**

**Michael.L.Rilee.1@gsfc.nasa.gov**

**S.A. Curtis**^1^**, C.Y. Cheung**^1^**, W. Truszkowski^2^, G.
Marr^3^**

^1^**Code 695,** ^2^**Code 588,** ^3^**Code 595, NASA/GSFC, Greenbelt,
MD 20771 USA**

**u5sac@lepvax.gsfc.nasa.gov**

**M. Rudisill**

**MS 328, NASA/LARC, Hampton, VA 23681 USA**

**m.rudisill@pop.larc.nasa.gov**

**[ABSTRACT]{.underline}**

PAM, the Prospecting Asteroid Mission, is an application of the
Autonomous NanoTechnology Swarm (ANTS) mission architecture. Here, we
analyze the nature and use of spacecraft structures required for PAM, an
ANTS mission application for a low gravity, low density multi-body
target population survey. PAM consists of 1000 picocraft organized into
10 specialist classes with highly maneuverable/configurable solar sails,
a no-expendables propulsion system suitable for this application. The
basic design elements are self-similar low-power, low-weight,
addressable components and individual systems capable of operating as
fully autonomous, yet addressable, adaptable units as called for by
swarm demands and environmental needs. With 10 to 20 subswarms operating
simultaneously, hundreds of asteroids could be explored during a mission
traverse of an asteroid belt. We discuss conceptual and physical models
of spacecraft and components, now achieving realization due to the
construction of the first ANTS prototype with fully addressable nodes
capable of reversible deployment of struts with required rigidity. The
PAM concept will be enabled through incremental advances in technology
leading to the availability of NEMS systems and allowing construction of
space-adapted gossamer structures, including tethers, struts to provide
structural frameworks, and multi-layer surfaces for the sail or
instruments.

**[Context of the ANTS Approach]{.underline}**

The ANTS approach to exploration \[1,2,3,4,5\] discussed here is
directly relevant to the NASA's Exploration Initiative goals of robotic
exploration of the solar system emphasizing origins, evolution, and fate
(future) of the physical universe on scales ranging from planetary to
cosmic \[6,7\]. The mission application, Prospecting Asteroid Mission,
is directly in line with the new Initiative science agenda, where the
focus is on exploring small bodies to search for evidence of life
\[6,7\]. Study of the main asteroid belt, a dynamic small body
population which includes the oldest remnants of the early solar system,
will provide insight on origin and evolution of the solar system, the
dynamic processes and components, physical, chemical, and biological,
which shaped it.

The PAM concept would result in direct use of enabled technologies and
further development of enabling technologies identified in the
Initiative \[6,7\] as well: a) self-repairing autonomous systems and
robotics, b) formation flying capability, including capability for
responsive attitude control in close range, c) low-cost close-range
communication and tracking capability, d) advanced power and propulsion,
e) strong, durable, low aerial density structures, and f) low power and
mass sensors.

In this paper, we will describe the conceptual framework, design, and
models, for PAM hardware and its operation, based on ongoing work. We
will identify requirements and essential features, and assess
capabilities the ANTS architecture to provide a comprehensive asteroid
survey (**Tables 1 and 2**).

What is the nature of the contribution to solar system exploration that
multi-spacecraft missions can provide, as compared to the currently
utilized single spacecraft missions or near Earth observation programs
\[8a, 8b\]? Ground based or even Earth orbiting observatories, even with
projected improvements in sensitivity, will be not be able to provide
measurements for more remote, smaller, or darker asteroids, which must
be observed by spacecraft. We must have observations from these
more-difficult-to-observe objects in order to understand the formation
and evolution of the asteroid belt. Single spacecraft missions are
useful in providing extensive documentation for one to a handful of
previously observed asteroids, but are not designed for surveying a wide
range of unexplored asteroids, an application for which multi-spacecraft
missions are ideally suited. Multi-sensor spacecraft have flown before
(NEAR) or are about to fly (DAWN) to solar system bodies such as
asteroids. For optimal operations, essential sensors, such as imagers,
spectrometers, and altimeters, have very different requirements for a)
illumination conditions, b) pointing geometry, c) distance to target,
and d) orbital configuration. This translates into constant compromise
to meet sensor requirements and results in less efficient collection of
high quality data, a problem that is magnified when a small, irregularly
shaped, low gravity object, such as an asteroid, is being explored.

The ANTS/PAM \[1,2,3,4,5\] calls for clusters of single sensor
spacecraft, working individually or as teams, to meet these challenges
(**Table 3**). In this way, individual instrument operational and
overall science requirements can be met, and optimized, simultaneously,
reducing the time required to obtain comprehensive observations as well
as increasing the quality of those observations, for each target.

**[The ANTS Concept]{.underline}**

ANTS SMART (Super Miniaturized Addressable Reconfigurable Technology)
architecture was initiated at Goddard Space Flight Center (GSFC) to
develop a new kind of structural material capable of changing its form
to optimize its function, adapt to a new environmental demand, or repair
itself (4,5). The basic unit of the structure is a tetrahedron
consisting of nodes interconnected with struts that can be reversibly
deployed or stowed. 3D networks are formed from interconnecting
reconfigurable tetrahedra, making structures which are scalable,
massively parallel system that can be fabricated presently using
macroscopic electromechanical systems (EMS)-***ART***, and in the future
Micro-EMS (MEMS)-***MART*** or nano-EMS (NEMS)-***SMART*** (with aerial
densities of 100, 5, and 1 g/cm^2^, respectively) as enabled by
technology advancement. This highly integrated 3-dimensional mesh of
actuators and structural elements is composed of nodes that are
addressable as are pixels in an LCD screen. The full functionality of
such a system requires fully autonomous operation, and will ultimately
be realized through a neural basis function (NBF) which possesses
bilevel intelligence at every level, from subsystem to swarm. Such
capability allows both autonomic operation at the actuator level in
response to an environment demand and heuristic operation for decision
making among various options or in response to an external request. The
ANTS architecture for PAM will be discussed here. The development and
basis of SMART material and the NBF is discussed elsewhere (9a,9b,9c).

**[PAM: Application of ANTS to an Asteroid Survey Mission]{.underline}**

The PAM application, summarized in **Table 4**, requires MART to SMART
level application of the ANTS architecture, which should be available in
about two decades, in keeping with long-term Exploration Initiative plan
for robotic exploration of the next target, mainbelt asteroids, beyond
Mars.

Major milestones in the exploration of small bodies, the Near Earth
Asteroid Rendezvous (NEAR) mission to asteroid 433 Eros and DS1 mission
to comet Borelly, have already occurred in this decade. NEAR (10), the
first mission to demonstrate the capability to remain in long-term
stable orbit around an asteroid to perform a mapping mission, has
provided a rich context for understanding the characteristic complexity
of an asteroid and demanding requirements for mission maneuvering and
data-taking operations. DS1 (11) demonstrated the feasibility of a low
thrust propulsion system for small body encounter as well as the
capability for automated optical navigation based avoidance of debris
dynamically generated around an active comet. DAWN (12) is about to
harness the gains made by both of those mission, by using ion propulsion
to map two large asteroids representing extremes in asteroid evolution,
Vesta and Ceres, from orbit.

Whereas the traditional missions excel at exploring larger asteroids
sequentially, the PAM concept is designed for the systematic studying of
an entire population of objects \[1,2,3,4,5\]. The ANTS approach
involves the use not of a smart spacecraft with 'drones', but of a
totally autonomous truly distributed intelligent network of sensors, or
sciencecraft, with solar sails for propulsion, and thus minimal
requirement for expendables (**Figure 1**) (See also ANTS: The Movie at
the official ANTS website \[1\]). Sciencecraft each have specialized
instrument capability (e.g., advanced computing, imaging, spectrometry,
etc.) and heuristic systems that are both adaptable and evolvable.
Subswarms of sciencecraft can operate autonomously, allowing the optimal
gathering of complimentary measurements for selected targets. Many
subswarms would operate simultaneously within a broadly defined
framework of goals to select targets from among available candidate
asteroids.

![](media/image1.jpeg){width="3.055511811023622in"
height="2.513779527559055in"} We first considered the Autonomous
Nano-Technology Swarm (ANTS) architecture for a future application, the
PAM concept: a 1000-member swarm of picoclass (1 kg) autonomous
sciencecraft based on carbon-based NEMS technology and utilizing Super
Miniaturized Addressable Reconfigurable Technology (SMART) (3) \[13\].
The basic design elements are self-similar low-power, low-weight,
addressable, reconfigurable components and systems capable of operating
as fully autonomous, yet adaptable units as called for by swarm demands
and environmental needs. Craft use highly configurable solar sails
capable of autonomous attitude control, a highly maneuverable, no
expendables propulsion system well suited to this application. The swarm
would be composed of 10 science specialist classes (approximately 100
members of each class), identical except for one specialty 'instrument'.
Classes include Leader/Messengers (CPU/Communication enhanced), imagers,
various spectrometers, altimeters, radio science, and magnetometers. The
swarm would be divided into 10 to 20 subswarms with approximately equal
numbers of each class in each subswarm. Within each subswarm, each class
would operate autonomously at an asteroid target, because orbital
configuration and viewing strategy for the classes are highly variable
and depend on the requirements of the class 'instrument'. 10 to 20
subswarms would operate concurrently. Target observation times would be
on the order of one month. Typical distances of hundreds of thousands of
kilometers between kilometer-size asteroids would allow detection (by
imagers) and selection of the next target even before departure from a
given target, and travel to that target on the order of weeks. Thus,
tens or even hundreds of asteroids could be explored during a the
anticipated 5 year traverse of the asteroid belt.

**[SCIENCE RATIONALe FOR PAM]{.underline}**

Using this approach to survey the main asteroid belt, a population
consisting of millions of small, remote bodies, is most cost/effective
in terms of science and resource exploration. Although a large fraction
of solar system objects are asteroids, relatively little data is
available for them because the vast majority of them are too small to be
observed except as single point measurements except in close proximity
(**Table 5**) \[8a,8b\]. Within the asteroid population are remnant
planetesimals dating back to formation of solar system, the most
primitive, unmodified material known. These small bodies originated in
the transitional region between inner (rocky) and outer (solidified
gases) solar system, the asteroid belt. Determination of the systematic
distribution of physical, compositional, and dynamic properties within
the asteroid population is crucial in the understanding of the solar
system formation. In addition, there has been interest in asteroids as
sources of exploitable resources. Far more reconnaissance is required
before a true assessment is achieved. Such an assessment could focus on
systematic survey questions:

**1) What is the true distribution of elements, minerals, rock types,
parent bodies from early solar system, and potential resources? Where
are the olivine-dominated samples of parent body 'mantle' and chondrites
which, according to models and the meteorite collection, should
dominate?**

**2) What is the nature of regolith formation and modification in space
(Space Weathering) and its potential use for construction?**

**3) What is the nature of the relationship between dynamical and
compositional properties in the small body population, and, by
implication, in the early solar system?**

**[ANTS/PAM Design Features]{.underline}**

PAM **spacecraft** **(Figure 2)** components are nanotechnology-based
SMART structures forming tetrahedral networks of nano-struts, tethers,
or sheets which are reversibly deployable/stowable from MEMS or NEMS
nodes and equipped for wireless operation \[13\]. The design is
optimized for both pre-and post-launch operation.

**MEMS nodes** are used in several ways. The greatest number are
structural nodes which spool/unspool nanotubule struts using a MEMS
opposing 'tape measure' kind of device which links or unlinks the
oppositely wound tubules **(Figure 3).** Tubules with opposite
orientations develop great tensile strength when combined, or vice
versa, as in fact, to a somewhat lesser extent, two such EMS tape
measures would. Similar nodes are also used to deploy/stow tethers or as
attachment points for nanocomponent subsystems, such as instruments.
Nodes can also be used to deploy nanotubules, or even carbon fiber
composite with 'memory' and relatively low aerial density (5 g/cm^2^)
currently available, in layers, to form sheets, using a stack of tape
'roll' devices and nanotubes, or carbon fiber composites, with highly
compressible structural properties. Such nodes would be used in the
solar sail.

![](media/image2.jpeg){width="3.1389763779527557in"
height="2.486220472440945in"}![](media/image3.jpeg){width="3.013779527559055in"
height="1.1807086614173228in"}![](media/image4.jpeg){width="3.083464566929134in"
height="0.8334645669291338in"} A **100 sq meter solar sail** consisting
of 10,000 100 sq cm triangular facets is supported by a **space frame**
consisting of two layers of interconnected nodes, forming a lightweight
3D truss structure. A portion of this sail is illustrated in **Figure
4**. The sail would be made of specially designed carbon-based material
with 100 times aerial stretch capability. Layers of interlocking
nanotubes, specially designed dendritic springs \[14,15,16,17\], would
reversibly deploy in arcs from tape 'roll' nodes. Tailored,
multi-feature nanotube design is certainly a major technology driver.
So, another option would be to use 'memory' carbon film on carbon
microfiber composite \[18\], currently available at 5 g/cm^2^ aerial
density, deployed on Polymer/Carbon Nanotube Composite (PNC) springs and
structural elements \[19\].

Very effective solar sail navigation and attitude control **(Figure 5)**
could potentially be achieved by a 10,000 reversibly deployable
component sail on a highly reshapable frame seen in **Figure 4** (See
Sail Animations at official ANTS website \[1\]). Each sail facet's
effective area can be controlled, as the number of layers and the extent
to which each layer is deployed, is changed. By controlling the extent
and placement of deployed facets, the amount and center of pressure can
be controlled, and the speed and direction of the sail, and spacecraft,
changed. Theoretically, depending on the geometry of the sail, it would
be possible to deploy as few as 3 or 4 facets properly distributed, and
lower sail area by more than a factor of 1000 (the nominal requirement)
while controlling the attitude. The shape and size of the space frame
itself can also be dramatically modified, reorient the sail, quickly
change the direction of momentum vectors, accelerate, decelerate, or
make the spacecraft effectively 'disappear'. The implementation of the
solar sail is discussed elsewhere in detail \[20\].

Attached to the space frame by a network of long tethers is a small
**space platform** consisting of three layers of interconnected nodes,
making a more robust framework to which all subsystems are tethered,
including SMART instruments **(Figure 2)**. The extent and direction of
all tether deployment can be controlled. This design allows the
propulsion system to operate completely independently of all other
subsystems. When instruments need to 'see' through the sail, the extent
and direction of tether deployment can be changed and a 'viewing hole'
easily accommodated in the sail and its frame.

![](media/image5.jpeg){width="3.1389763779527557in"
height="6.833464566929134in"} The entire spacecraft is initially stowed
(predeployment) in a 100 cm^3^ **SMART box** **(Figure 2 inset**),
allowing for a much smaller pre-deployment size and minimizing 'cargo'
requirements during travel from the assembly to deployment sites. The
box is equipped with nano communication and propulsion devices, so it
can travel and communicate with the swarm for short distances in space.
Once the box delivers and releases the spacecraft, it can form a flat
sheet and return itself for reuse.

1000 such boxed craft are initially packaged in a 1 cubic meter **SMART
cube** at the assembly site, for delivery to the deployment site in deep
space. In fact, the spacecraft assembly process employs ANTS
architecture and is part of the PAM mission concept. **(Figure 6**) (See
also Manufacturing Movie at the official ANTS website \[1\]). The
facility, which could be located on the Earth or in a low G environment,
is equipped to generate tetrahedral networks of any size or shape, using
ANTS strut-deploying, layer-deploying, and instrument subsystem
deploying nodes. In the case of PAM, the large Space Frame would be
constructed from two layers of structural nodes. A layer of
sail-deploying nodes would be attached to the top layer. Tether
deploying nodes would be attached to the bottom layer. Meanwhile the
space platform would be constructed from a small space frame with an
additional layer of nodes, plus nodes for each subsystem. The space
platform would then be attached to the space frame via its tethers. The
entire spacecraft would then by stowed to its smallest possible size, a
cluster of interconnected nodes, attached to and enclosed in the SMART
box, which would then be attached to its neighboring boxes to form the
SMART cube. If already in deep space, the SMART cube could travel to the
deployment site directly. Alternatively, the SMART cube could be placed
in a cargo hold for transportation to a location in deep space.

**[PAM SCIENCE OPERATIONS]{.underline}**

Each class **(Table 6**) would employ different strategies in the use of
components and subsystems during the active part of PAM \[4,8\].
Leader/Communicators would be enhanced for high level communication and
processing functions which would occur at some distance from a target to
keep the subswarm in view, and wouldn't require the fine adjustment in
attitude control needed by sciencecraft requiring measurements closer to
the target. Science operations could vary substantially from instrument
to instrument. Instruments are listed in rough sequence, in terms of
stringency of operational requirements, by distance (furthest to
closest) and time (least to most) requirements. Most likely, the visible
imaging spectrometer would be used extensively during cruise to detect
potential targets, and then refine knowledge of the location and nature
of the target on the way to the selected target. The required viewing
conditions for each instrument vary considerably, and might well affect
the choice of targets. Optimal operation is easily accommodated in
either near terminator orbits or darkside stationkeeping for the
majority of instruments. However, the Near Infrared and X-ray
spectrometers, crucial for determining composition, are the most
difficult instruments to accommodate, requiring as much close proximity,
illumination and direct (subsolar point, nadir pointing) geometry as
possible. Real 'stationkeeping' would be virtually impossible to achieve
on the sunlit side of an asteroid due to combined photonic and
gravitational forces. On the other hand, an equatorial orbit of a string
of instruments in a given spectrometer class would be possible, provided
the effective sail area can be decreased by a factor of a thousand,
something which should be very achievable to a 10,000 partially
deployable facets.

PAM spacecraft would certainly study a selected target by providing the
highest quality and coverage of measurements from a particular class,
forming 'Virtual Teams' \[4,8a,8b\]. 'Virtual Instrument Teams' would be
formed from those within each class, to optimize data acquisition.
Another strategy would involve providing a comprehensive set of
measurements to solve a particular scientific problem, by forming
'Virtual Experiment Teams' of multiple sensors (**Table 6**). First, a
3D model would be generated for adequate navigation and maneuvering
around a target. Thus, the **Asteroid Detector/StereoMapper** team would
be necessity go in first. It would consist of two wide field imaging
spectrometers with enhanced navigational (location and pointing
awareness) capability separated by distances varying from hundreds of
kilometers to kilometers would be used to detect and determine the orbit
of potential targets at a distance, or move to within kilometers of a
target to obtain astronomical classification and figure properties and
identify candidates for detailed studies. The **Dynamic Modeler**
consisting of an enhanced radio science instrument, altimeter, and wide
field imager separated by tens of kilometers to kilometers would be used
to acquire detailed figure parameters (including shape model) and
dynamic properties (spin, density, mass distribution).

Various combinations of instruments could be used to study composition
and history. A **Petrologist** consisting of X-ray, Near Infrared,
Gamma-ray, Thermal IR, and wide field imager separated by tens of
kilometers to kilometers would be used to determine the abundances and
distribution of elements, minerals, and rocks present, from which the
nature of geochemical differentiation, origin, and history of the
object, and its relationship to a 'parent body' could be inferred. A
**Photogeologist** consisting of Narrow Field and Wide Field Imagers and
Altimeter separated by tens of kilometers to kilometers would be used to
determine the nature and distribution of geological units based on
texture, albedo, color, and apparent stratigraphy as expressed on the
surface, from which the nature of the dynamic history and origin of the
object could be inferred. A **Prospector** consisting of altimeter,
magnetometer, Near Infrared, Infrared, and X-ray spectrometers separated
by tens of kilometers to kilometers could be used to determine the
distribution of 'resources', including Fe/Ni and volatiles on
preselected candidates for 'mining'.

**[Realizing the ANTS Concept: Requirements and Enabling
Technologies]{.underline}**

As part of the ANTS/PAM study, we have determined the major requirements
for such mission **(Table 7**) \[13\]. We should be able to meet all of
these requirements with anticipated, incremental technology developments
over the next two decades.

We require incremental improvements in subsystems in a couple of key
areas. To meet our power requirements more than 2 AU from the sun, we
require batteries weighing well under a kilogram and producing tens or
hundreds of milliwatts. Such nuclear batteries are already under
development. Small, low power communication, navigation, and tracking
devices are also under development.

Key technology drivers for ANTS/PAM are the use of **carbon-based
materials and structures** (MART or MEMS systems) and, ideally, NEMS for
all mechanical components, in order to minimize mass and power
requirements. Ultimately, to minimize the mass and power requirements,
ANTS structures will be built entirely on carbon-based materials.
Currently available carbon fiber composites \[19\] are the most
lightweight, durable, and rigid materials that are currently available,
and now approach are minimal aerial density requirement (5 g/cm^2^).
Specially manufactured thin sheets of this carbon film on fiber material
with shape memory have already been manufactured as potential solar sail
material \[18\]. A particular area of concern for our application would
be the ability to 'retain' memory over potentially millions of
deployments, and the power expenditure requirement to hold the material
at partial deployment. Carbon nanotubules themselves \[14,15,16,17\] are
even stronger and lighter weight, have lower aerial densities (1
g/cm^2^) and, if the ability to create very long (many centimeters to
many meters) CNTs while retaining the properties of individual CNTs is
realized, these would be an ideal basis for structural elements \[21\].
We would then use CNTs with the attributes already observed in
individual CNTs and required for a particular ANTS functions, long and
straight, or shorter, spring-like, and branching.

The development of **autonomous navigation without appendages** is
another critical area. We have already developed simulations of the
movement of single, 4, 12, and continuous tetrahedral structures (See
still and movies at the official ANTS website \[1\]). The first
demonstration model of an EMS-level (ART) single ANTS tetrahedron,
designed to be a walker (TET), will be completed in October 2004 (TRL
3). Plans are underway to test the TET in January 2005 in Antarctica
with remote operation via the Internet using a 3-D graphical user
interface. We have completed a preliminary conceptual design of a
4-tetrahedron system (4-TET) capable of carrying a scientific payload in
a central node, and have proposed to build and test that system on a
field campaign in Iceland ('Mars on Earth') (TRL 6). The next milestone
will be to build the 12TET model. At this level, the ability for
'continuous' movement clearly emerges.

PAM utilizes a totally new type of space architecture based on an
autonomous, addressable, reconfigurable components. The potential
flexibility and adaptability of such a system demands a level of
artificial intelligence we are in the process of developing through our
role in ST-8 COTS High Performance Computing and Multi-agent Simulations
using Beowulf clusters here at GSFC \[1,9c\].

**[Acknowledgements]{.underline}**

We would like to acknowledge the important contributions to this work
made by our students Jason Leggett, Richard Watson, Noah Desch, Tom
Comberiate, and Jeff Lee, as well as by our colleagues Clark Chapman,
Lucy McFadden, and Jack Trombka. We thank NASA/GSFC IR&D, GSFC Codes 695
and 588, and the RASC program for their support.

**[References]{.underline}**

\[1\] The Official ANTS website: http://ants.gsfc.nasa.gov

\[2\] Curtis, S.A. et al., 2000.: Autonomous Nano-Technology Swarm.
Proceedings of the 51^st^ International Aeronautical Congress,
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\[3\] Clark, P.E., Iyengar, J., Rilee, M.L., Truszkowski, W., Curtis,
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\[4\] Rilee, M.L., Clark, P.E., and Curtis, S.A., 2002. IAU Proceedings,
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\[5\] Curtis, S.A., Truszkowski,W.F., Rilee, M.L., and Clark, P.E.,
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\[6\] The President's Vision for Space Exploration, February 2004.

\[7\] Report of the President's Commission on Implementation of United
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\[8a\] Clark, P.E., Curtis, S.A., Rilee, M.L., Truszkowski, W., Marr,
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\[8b\] Clark, P.E., Curtis, S.A., Rilee. M.L., Cheung, C.Y., 2003, From
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\[9a\] Rilee, M.L., Curtis, S.A., Clark, P.E., Cheung, C.Y.,
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\[9b\] Rilee, M.L., Curtis, S.A., Clark, P.E., Cheung, C.Y.,
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systems applications (this meeting).

\[9c\] Cheung, C.Y., Curtis, S.A., Rilee, M.L., Clark, P.E., Shaya, E.,
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\[10\] NEAR official website: http://near.jhuapl.edu

\[11\] DS1 official website: http://nmp.jpl.nasa.gov/ds1/

\[12\] Dawn official website: http://dawn.jpl.nasa.gov/

\[13\] Curtis, S., Clark, P.E., Cheung, C.Y., Rilee, M.L., Truszkowski,
W., Marr, G., 2004, The ANTS Mission Architecture and its application to
the PAM Mission, DRM (Final Report) for the RASC program.

\[14\] http://pubs.acs.org/cen/

coverstory/7924/ 7924nanotubules.html

\[15\] www.foresight.org/Conferences/

MNt05/Sinott

\[16\] http://www.ipt.arc.nasa.gov/

\[17\] http://www.nature.com/cgi-taf/
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n6883/full/393346a0_r.html

\[18\] http://www.esli.com

\[19\]http://www.meetingsmanagement.com/pdf/PF_2004.pdf

\[20\] Curtis, S.A., Cheung, C.Y., Clark, P.E., Marr, G., Rilee, M.L.,
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\[21\] http://news.bbc.co.uk/1/hi/sci/

tech/3872931.stm