Construction and Resource Utilization Explorer - ESA Science

Construction and Resource Utilization Explorer: Regolith Characterization using a Modular Instrument Suite and Analysis Tools Jerome B. Johnson1, William V. Boynton2, Keil Davis3, Richard Elphic4, Brian Glass5, Albert F. C. Haldemann6, Frederick W. Adams7 1

USA ERDC-CRREL, PO Box 35170, Ft. Wainwright, AK 99703 University of Arizona, Lunar & Planetary Lab., 1629 E Univ. Blvd., Tucson, AZ 85721 3 Honeybee Robotics, 460 West 34th Street, New York, NY 10001 4 Los Alamos National Laboratory, ISR-1, MS-D466 Los Alamos, NM 87545 5 NASA AMES Research Center, Moffett Field, CA 94035 6 JPL, California Institute of Technology, MS 238-420, 4800 Oak Grove Dr., Pasadena, CA 91109 7 NASA John F. Kennedy Space Center, YA-D4, Kennedy Space Center, FL 32899 907-353-5179, [email protected] 2

Abstract. The Construction Resource Utilization eXplorer (CRUX) is a technology maturation project for the U.S. National Aeronautics and Space Administration to provide enabling technology for lunar and planetary surface operations (LPSO). The CRUX will have 10 instruments, a data handling function (Mapper - with features of data subscription, fusion, interpretation, and publication through geographical information system [GIS] displays), and a decision support system (DSS) to provide information needed to plan and conduct LPSO. Six CRUX instruments are associated with an instrumented drill to directly measure regolith properties (thermal, electrical, mechanical, and textural) and to determine the presence of water and other hydrogen sources to a depth of about 2 m (Prospector). CRUX surface and geophysical instruments (Surveyor) are designed to determine the presence of hydrogen, delineate near subsurface properties, stratigraphy, and buried objects over a broad area through the use of neutron and seismic probes, and ground penetrating radar. Techniques to receive data from existing space qualified stereo pair cameras to determine surface topography will also be part of the CRUX. The Mapper will ingest information from CRUX instruments and other lunar and planetary data sources, and provide data handling and display features for DSS output. CRUX operation will be semiautonomous and near real-time to allow its use for either planning or operations purposes.

INTRODUCTION The success of future lunar and planetary missions will depend critically on the ability to identify optimal sites to conduct lunar and planetary surface operations (LPSO) related to in situ resource utilization (ISRU), construction, environmental management, and surface mobility. Successful LPSO will require a good knowledge of local surface relief and roughniss, geotechnical properties (e.g., grain size, mineralogy, bulk density, thermal and mechanical properties) and, the concentration and distribution of resources (with a particular interest in the presence of water). We are developing a Construction Resource Utilization eXplorer (CRUX) that consists of an integrated modular suite of instruments (Prospector-Surveyor) combined with display (Mapper) and decision support system (DSS) analysis tools to characterize regolith resources, surface conditions, and geotechnical properties (Figure 1). The CRUX is a NASA technology maturation project for the Exploration Systems Research and Technology Program, Exploration Systems Mission Directorate designed to provide critical technology for a return to the Moon and later planetary exploration. The current project focus is to operate under lunar conditions in keeping with current NASA priorities, but with the recognition that our development path should also take into account the possibility of surface operations on Mars at some future date. International Lunar Conference 2005

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FIGURE 1. CRUX architecture. The central Mapper-DSS subscribes to lunar and planetary data from CRUX Prospector/Surveyor instruments, and other historical or near real-time data sources. The Mapper stores, fuses, interprets and displays data layers while the DSS creates and displays data products derived from model analysis, analytical data interpretation, and intelligent data mining to facilitate the planning and conduct of LPSO. CRUX instrument operations will be semiautonomous and interactions will be in near real-time to facilitate LPSO support.

Integrated modularity allows instruments to be added or removed from the instrument suite and operate seamlessly with existing installed instruments and associated control and analysis software. The instrument suite and associated software will be designed to allow additions, deletions, or modifications to the instrument suite as needed to accommodate future mission architectures that may include robotic or human controlled landers or mobile platforms. The selection and deployment of the CRUX instrument suite will be determined based on existing lunar and planetary satellite data, and exploration priorities. Once deployed, the Surveyor will have geophysical instruments to survey the upper portion of the local regolith to help locate optimal drilling sites. The Prospector will use an instrumented drill to measure down-hole, site-specific, geotechnical properties of the regolith, and detect water, to a depth of 2 m. Surveyor data, when linked to Prospector borehole data, will provide an accurate, reliable way to regionally map regolith geotechnical properties and ISRU potential. Surface relief and roughness will be derived from a Surveyor mounted stereo camera system. Ten instruments have been selected for the Prospector/Surveyor package to provide a rich dataset of regolith geotechnical, surface, resource, and water information. Prospector components include a drill subsurface access system (SAS) that can acquire samples, a borehole neutron probe (BNeuP) to detect hydrogen, a thermal conductivity and diffusivity probe (TCDP) to determine thermal properties, a mechanical properties probe (MPT) to determine shear and compaction, an electrical properties probe (EPP) for dielectric constant and density measurements, and a down-hole camera (DCAM) to observe particle size and mineral composition. Sample analysis to determine mineral and elemental concentration is done using a Thermal Evolved Gas Analyzer (TEGA). The Surveyor geophysical instruments include a seismic profiler (SEIP), ground-penetrating radar (GPR), and surface neutron probe (SNeuP), for hydrogen detection, to profile the upper 1—2 m of regolith. A stereo-pair regolith camera (RCAM) is used for terrain reconnaissance and determining surface topography. This suite of instruments delivers data for analysis to the Mapper/DSS. While the CRUX instruments are useful individually, their true value is reached when they are integrated to provide interrelated information that can be fused to derive regolith property information that cannot be determined from a single data source. To fully optimize the use of these data for decision-making, we will focus strongly on instrument integration, data fusion and display, and DSS tools. The Mapper/DSS will use data fusion of CRUX instruments, International Lunar Conference 2005

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other available data, and models to provide information about regolith properties needed for Lunar and Planetary Surface Operations (LPSO) that cannot be determined otherwise. The combination of regolith property data measurement, data fusion methods, DSS tools, and display functions provide a robust decision support system in which location-referenced raw and interpreted data from the CRUX instrument suite, along with other (e.g., lunar satellite) data, can be rapidly visualized, updated, and communicated to guide further site investigations or LPSO activities, or to plan future LPSO activities. This will be an enabling technology for LPSO with benefit to future solar system exploration.

LUNAR SURFACE OPERATIONS REQUIREMENTS Lunar Regolith Resources ISRU of oxygen, hydrogen, and water enables substantial mission architecture efficiency and cost reductions (Beyond Earth’s Boundaries report, Lofgren, 1993; Hoffmana and Kaplan, 1997). While Lunar soils contain abundant oxygen in the form of oxide minerals, no significant source of hydrogen had been identified until the recent data from the Lunar Prospector mission. The data from Prospector’s neutron spectrometer have been interpreted as showing significant quantities of hydrogen (in an uncertain chemical form) in the permanently shadowed craters of the lunar poles (Feldman et al, 1998, 2000). Even though the resolution of these data is only 10s of kilometers, the mapping shows significant deposits in large (> 40 km in diameter) craters in the lunar polar regions (longitude >75°), where temperatures can range from 40 to 100K, depending on the amount of radiation received from nearby crater walls and other features (Vasavada et al., 1999). These temperatures are sufficient to preserve water layers for billions of years if they are covered by a thin layer of regolith (Vasavada et al., 1999; Salvail and Fanale, 1994). Radiation from extra-solar sources (such as cosmic rays and UV radiation) can drive reactions involving hydrogen, water and the regolith. The analysis of the Lunar Prospector data places the hydrogen concentration at 1700 ± 900 ppm, which would translate to 1.5 ± 0.8% as water in the crater floor bottom regolith near the south pole. Given the coarse resolution of the data, local concentration of up to 10% water may be present near the north pole, a clearly significant deposit for ISRU production. If these deposits resulted from comet impacts, the layers may be even more concentrated and contain a variety of other valuable compounds, such as CO, methanol, carbon dioxide, ammonia and methane (Allamandola et al., 1999). Modeling of such cometary impacts suggest that a 10 cm thick layer would survive for a billion years (Crider and Vondrak, 2000, 2002). Since random drilling and excavation to locate such deposits would be both costly and ineffective, our approach is to use the Prospecter-Surveyeor/Mapper-DSS to optimize the surveying and prospecting efforts that support LPSO – making it an enabling technology for ISRU. Oxygen can be produced from the oxide minerals on the Moon by several processes, most of which require high temperatures and lots of energy for electrolysis. However, these processes would produce oxygen at any location. All have their problems or are limited in some way. Hydrogen reduction of iron oxide bearing minerals is the lowest temperature option and easiest to implement, but requires more regolith to be heated to ~900ºC. Water is produced, but yields follow the FeO concentration of the feedstock. Locating higher concentrations of FeO (not free elemental iron) would be of interest. Hydrogen supplies must be found or brought from Earth to implement this process. If solar hydrogen is found, but no water, then this process would be a leading candidate for implementation to produce oxygen. Efficient ISRU requires identification of the richest “ore bodies” (primarily water), which cannot be accomplished using orbital instruments, which lack resolution. The methods used to map deposits in support of ISRU must have a resolution that is significantly better than the size of deposits (minimally, about one to five meters in the surface horizontal plane), be able to resolve to 0.2 meters in depth, and provide an indication of the chemical form of hydrogen. These limits are in the range of the proposed Prospecter-Surveyor/Mapper-DSS capabilities. Lunar Regolith Construction For the CRUX project, construction is defined as any activity affected by regolith and surface properties including: spacecraft operations, mobility systems, structures, and excavation for ISRU or infrastructure development. Regolith International Lunar Conference 2005

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properties and mineralization are not uniformly distributed spatially or with depth, making it necessary to survey them before initiating construction or ISRU activities to ensure safe, reliable, and cost-effective operations. Terrestrial experience supports this requirement, especially as regolith complexity increases due to non-uniform distributions of regolith properties, possible water (in polar regions) and rocks, which can produce variable and changing conditions (e.g., ice melting from rocket blast or structural heating). Safe, cost-effective lunar infrastructure designs and excavation operations may require knowledge of regolith bearing capacity, short-term shear strength, and frictional characteristics. Moreover, proper operational situational awareness (e.g., knowledge of buried rocks, regolith ripability, and thermal and electrical properties to facilitate excavation, resource recovery, and the placement, protection and operation of lunar infrastructure) demand reliable information on regolith subsurface conditions and mechanical, electrical, and thermal properties. Of particular interest, is to determine the mechanical properties of lunar polar regolith for which no data exists. Significant geotechnical information for non-polar lunar regolith is available from Apollo lunar investigations that can be used to facilitate designs of infrastructure in non-polar regions (Heiken et al, 1991). The mechanical properties of interest fall into two broad categories – short-term strength and deformation characteristics. Problems in the first category include bearing capacity of foundations and slope stability (these relate to the design of blast-resistant berms, launch pads, battery storage systems, habitable structures, and vehicle pathways) and the design variables are in situ friction angle, cohesion, unconfined compressive strength, shear strength and tensile strength for intact regolith. The second category deals with settlements caused by the weight of structures and vehicles, and must be considered to avoid unnecessary stresses in the structure or mobility problems – both of which can be caused by excessive deformation of the regolith. These settlements will depend on the imposed loads and on the density, void ratio, particle size distribution, Young's modulus and Poisson's ratio of the regolith.

CRUX INSTRUMENT SUITE The NASA Exploration Systems Research and Technology Program, Exploration Systems Mission Directorate’s technology maturation program is designed to increase the readiness level technology that is important to space exploration so that it will be available when specific mission requirements arise. Technology readiness levels (TRLs) are a systematic metric/measurement system that has been used within NASA to assess the maturity of a particular technology and to compare the development maturity between different types of technology. TRLs 1—4 include basic and feasibility research efforts, TRLs of 4—5 involves technology development of components and breadboard validation in laboratory and relevant operating environments. The goal of our technology maturation project is to mature the CRUX instrument technology from their starting TRLs to TRL 6, which involves a system or subsystem model or prototype demonstration in a relevant environment (ground or space). Our system is the suite of instruments operating with the Mapper/DSS as an integrated whole and our relevant environment for instrument demonstration will be in a ground based test chamber under near-lunar conditions. The CRUX achieves flexibility and cost effectiveness while focusing on measurements and functions that will provide important regolith properties information to conduct LPSO by combining instruments with mature terrestrial and/or space heritage in a modular and integrated fashion (Table 1). Instruments with a development heritage for space application have starting TRLs that range from 4—5 while those instruments with terrestrial heritage have starting TRLs of from 2—3. The TEGA and stereo camera have space mission heritage and do not require additional technology maturity per se. For these, the CRUX is developing interface technology to allow CRUX to make use of the existing technologically mature instruments. First, a sample acquisition and transfer technology to allow the SAS drill to acquire a regolith sample and transfer it to the TA while preserving volatiles. Second, data handling and fusion for integration of stereo camera output data without a hardware imaging system, hence, the CRUX RCAM is a virtual RCAM (VRCAM). The starting TRLs for of the CRUX components, and their functions, are shown in Table 1. During the brief tenure of the CRUX project, Phase I started in May, 2005, we initiated trade studies to facilitate design needs, developed prototype designs for less mature technologies and the Mapper/DSS, redesigned some of more mature technologies to fit the roles of shallow subsurface exploration, and conducted preliminary testing of some of our more mature technologies.

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TABLE 1. CRUX components, starting NASA technology readiness levels (TRL), heritage, and function. The project completion target is to mature instruments to TRL-6 (technology demonstration in a relevant environment). Crux components Starting TRL Heritage Function Subsurface Access 4/5 NASA funded; Drilling; sample acquisition System (SAS) Honeybee Robotics and sample handling for Prospector surface instruments Prospector Borehole 5 NASA funded; Los Detect subsurface hydrogen Neutron Probe Alamos National and profile its distribution with (BNeuP) Laboratory (LANL) depth Prospector Electrical 3/4 NASA funded project Borehole regolith dielectric Properties Probe constant (infer water/ice (EPP) content), electrical conductivity, and density Prospector Thermal 3 NASA funded: Receives the sample from the Analyzer (TA) University of Arizona SAS for controlled heating and is the front end to the thermal evolved gas analyzer (TEGA) Prospector Downhole 2/3 JPL internal project Borehole stratigraphy, texture, Microscopic Camera and grain properties (DCAM) Prospector 2/3 Geotech. Engineering Borehole regolith shear Mechanical industry, Engineer strength index & compaction Properties Tester Research and properties (MPT) Development Center (EDRC) Prospector Thermal 2/3 Geophysical heat flow Regolith thermal properties Conductivity and community, ERDC Diffusivity Probe (TCDP) Surveyor Seismic 4 NASA & Department Complement and extend Profiler (SEIP) of Defense funded: JPL borehole data; density; wave & ERDC projects speed; stratigraphy 4 NASA funded; JPL Complement and extend Surveyor Ground borehole data; high resolution Penetrating Radar (GPR) subsurface profiles Surface Neutron 5 NASA funded; LANL Detect near-surface hydrogen Probe (SNeuP) Determine surface features and Surveyor Virtual N/A NASA funded; Mars topography Surface Stereo rovers - JPL Camera VRCAM CRUX Executive N/A NASA funded; Ames Provide executive level control Control Software Research Center for of instrument integration, (CEC) rover applications operation, and data delivery to the Mapper/DSS Mapper-DSS N/A US Army Corps of Near real-time data collection, Engineers operations, storage, handling, fusion, & ERDC interpretation; DSS tools & displays.

Surveyor Instruments Surveyor instruments include geophysical instruments (SNeuP, SEIP, and GPR) and the stereo camera that are best deployed using a mobile platform to provide high-resolution measurements of regolith properties over relatively large area. The geophysical measurements provide information about near subsurface of the regolith that can be used to determine high-value locations to deploy the Prospector drill and instrument package to make direct measurements of regolith properties. Prospector measurements can then be used to interpret the geophysical data to provide a more accurate understanding of regolith properties, and their variation, in the regions around the drill-hole.


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Further improvements in mapping regolith properties can be made through additional Prospector instrumented drill measurements in conjunction with data fusion interpretation. The SNeuP neutron spectrometer is a remote sensing tool for locating hydrogenous materials by detecting a large decrease (up to nearly two orders of magnitude) of the epithermal neutron leakage flux. This flux develops as highenergy neutrons, created from galactic comic ray impingement on lunar or planet surfaces with a thin or nonexistent atmosphere, lose energy either by elastically or inelastically scattering in the planetary material or are absorbed by neutron capture reactions. It is sensitive to hydrogenous material abundances of less than 1 wt% within about 70 cm of the surface over a target surface footprint size of ~1 m diameter, if cosmic rays are the primary neutrongenerating source. The instrument is currently under development through a NASA Mars Instrument Development Program (MIDP) grant as the HYDRA Neutron Spectrometer, with one system fabricated and tested, and a second in development. SNeuP’s heritage includes the Lunar Prospector neutron spectrometer, programmatic neutron detectors for treaty monitoring, and the Mars Odyssey neutron spectrometer. For terrestrial field testing, a neutron source is used to provide a signal for the HYDRA detectors because galactic cosmic rays do not reach the Earth’s surface. Figure 2 shows data from a mini-rover traverse over three buried polyethylene sheets (a proxy for water ice) using an RTG-like neutron source; enhancements in thermal counting rate (blue) are very pronounced over the buried polyethylene “ice” slabs (light green). Other count rate variations are due to variable soil water content and variable soil cover thickness. We have performed a number of field tests that demonstrated HYDRA’s functionality and sensitivity to buried hydrogenous materials. HYDRA has also been temperature tested from -40º to +40º C with no degradation of performance.

FIGURE 2. HYDRA field test data taken during a traverse over three buried polyethylene slabs (green bars) The mini-rover carrying HYDRA modules is shown to the right of the data graph.

The SEIP includes a source of the seismic waves, seismometers to detect the wave arrivals, communication (by a cable or radio link), digitizers, and computational hardware to measure the P and S -wave speeds of the shallow regolith by detecting the wave arrivals as a function of horizontal distance from the source. The type, number, and spacing of the receivers to give suitable performance are being determined through trade studies that will be used to develop a Phase I design. Specialized seismometers with very low weight and power requirements as shown in Figure 3 will be incorporated into the design (Pike et al., 2005). The SEIP will be used to complement the Prospector and GPR measurements by extending lunar regolith strength measurements tens to hundreds of meters away from Prospector borehole measurments, detecting shallow ice inclusions or areas of ice-bonded soil, and determine the depth of the regolith. Because the seismic wave velocity is a direct measure of the elasticity and density of the material it passes through, it can be used to infer the strength as well as aspects of the composition (e.g., loose soil vs. soil with ice vs. rock) as a function of depth. Seismic measurements sample roughly one-fourth the horizontal offset, measuring wave arrivals over 20 meters will provide information down to about 5 meters in depth. Because ice inclusions or ice-bonded soils are expected to have much higher velocities than the normal regolith (at least 1000 m/s [Barnes, 1965]), the system will also be able to detect and map these inclusions. SEIP measurements will complement the higher resolution GPR measurements by providing deeper information about the regolith. International Lunar Conference 2005

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FIGURE 3. A low power miniature seismometer with an embedded 24 bit digitizer is being developed for the seismic profiler (Pike et al, 2005).

The CRUX GPR is designed to detect layering, subsurface objects, and to infer regolith physical property to high resolution using data fusion interpretations and measurement from Prospector instruments, the SNeuP, and the SEIP. The CRUX GPR is a modification of an 80 MHz frequency GPR that was developed for the Mars under the MIDP. The Mars GPR was intended for deeper penetration of up to 100 m, at a moderate resolution of 0.5 m. The CRUX GPR operates at 800 MHz, penetrating up to 5 m, but with finer depth resolution (about 10 cm). The first proptotype of the CRUX GPR has been designed, fabricated and successfully field tested at the Quester gas pipeline site in Indio, CA. This test site was used since two buried steel pipes are well known targets (1 m depth, 76 cm diameter, separated by 11.5 m). Two sets of antennas were tested with the GPR electronics: a resistively loaded dipole antenna pair and a pair of RC-loaded bowtie antennas. Both sets gave comparable GPR traces, with the resistively loaded antenna set providing slightly better performance. Traces of the two buried metal pipes at the Indio site appear as the two “eyebrows” in the GPR traces are shown in Figure 4.

FIGURE 4. Examples of CRUX GPR field-test data from the Quester gas pipeline site in Indio, CA.

The CRUX stereo camera will be used to characterize the regolith surface to detect surface objects, generate regional topography, and provide a general visual image of the surroundings needed to maintain a situational awareness and provide navigational aids. Since topographic information derived from stereo camera systems is a space-proven technology, we will simulate the stereo camera (VRCAM) using existing stereo pair pictures to


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generate regional topography or include a-priori orbital topographic data to facilitate development of the MapperDSS.

Prospector Instruments At sites selected on the basis of information from the Surveyor, the Prospector will use an instrumented drill to measure down-hole, site-specific, geotechnical properties of the regolith, and detect water, to a depth of 2 m. The final drill design and mode of deployment of instruments in the resulting borehole will be determined through trade studies that are currently underway. Some instruments may descend into the borehole with the drill in order to detect volatiles that have the potential of being disturbed by the drilling process. Other instruments may be lowered into the borehole after the drill has been removed using an Inspector into which instruments have been installed. The main component of the Prospector is the SAS, which includes a drilling capability, the ability to acquire a regolith sample and transfer it to the TA, and functions to deploy instruments downhole using the either the drill or the Inspector. A preliminary design for a drilling assembly that can be used for rotary or rotary-percussive

drill is shown in Figure 5. The percussive and rotary motions of the drill string are actuated independently by separate sets of DC motors inside the drive head. An additional motor provides movement of the drill in the vertical direction and is responsible for maintaining an axial force on the bit, commonly known as “weight-on-bit.” The drill is designed to create a hole 2 m deep and 38mm in diameter. Current design plans are for a drill system that uses drill and Inspector segments that couple together to achieve the desired depth and flexibility of changing out instruments while maintaining a reasonable drill tower height. A set of slip rings integrated into the drive head can be used to relay data from any sensors or instruments placed inside the rotating drill to the stationary data acquisition system mounted on or near the drill platform.

FIGURE 5. Preliminary design of the Rotary and Rotary-Percussive drill system.

The main benefit of a rotary-percussive drilling system is that it minimizes the required axial load, or weight-on-bit, which is highly advantageous on the moon since it has only 1/6th of the Earth’s gravity. An additional benefit of rotary-percussive drilling is higher efficiency, because it produces coarser cuttings than a rotary drill. A higher efficiency of cuttings removal is also expected due to the continuous shaking of soil particles on the surface of the auger flutes. However, a drawback to rotary-impact drilling is the excessive vibration that might preclude the integration of downhole instruments inside the drill string, which is one of the driving considerations for using the drill system to deploy an instrumented Inspector. Experience from the Apollo missions, and with lunar regolith samples returned to Earth suggest that a 2 m borehole does not collapse, so use of the inspector is warranted (Heiken et al, 1991, p.521).


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The BNeuP is currently the only Prospector instrument integrated into the drill system Figure 6. The BNeuP is a mature drill-integrated neutron spectrometer borehole/well-logging tool for locating hydrogenous materials. It is sensitive to such materials within about 10 m of the surface, if cosmic rays are the primary neutron-generating source. The BNeuP (also referred to as D-HYDRA), is currently under development in partnership with Honeybee Robotics under a NASA MIDP with one system fabricated and under test. Its heritage includes the heritage of the SNeuP/ HYDRA. Polyethylene

FIGURE 6. BNeuP/D-HYDRA drill-integrated neutron spectrometer (on left) and test data for traverse of a two-meter borehole in limestone (right). A drawing of the test configuration is shown above the test data – dry limestone blocks separated by polyethylene ‘water ice’ proxy.

The TA sample acquisition system will be integrated into the drill system, but integration of the remaining Prospector instruments in the drill or the Inspector will be decided based on the outcome of the trade studies that are currently underway. Current trends are, however, to move more of the instruments to the inspector, to allow for larger instrument volume, and to use the drill system actuation capability to aid the conduct of borehole measurements independent of drilling activity. These instruments include the MPT (shear strength and indenter), EPP, DCAM, and TCDP. Use of the Inspector will require methods to allow reentry into an open or collapsed borehole. The MPT is designed to provide information on the geotechnical characteristics of lunar and planetary regoliths that will be required for a wide range of surface operations and resource recovery activities. Such measurements are necessary because the current state of knowledge of granular media behavior does not allow the reliable assessment of the mechanical properties in lunar or planetary environments based on physical properties measurements alone. It is critical that the MPT obtain at least rudimentary mechanical properties information. To measure short-term strength, a shear strength device will employ three retractable vanes that will engage the sidewall of the borehole as it travels down a borehole in a spiral motion; a load cell will monitor the net torque produced as the vanes cut into the borehole wall several mm. To monitor the time-dependent deformation response of regolith under compressive loading conditions, an indenter, that will apply a known load over a specified area to the surface of the regolith will be deployed on the bottom of a drill or Inspector segment. Both devices will use the robotic drill for actuation and contain a transducer whose output will be recorded as a function of time. While the robotic deployment of these devices may be unique, the basic methods are commonly used in terrestrial applications. The EPP consists of four electrical probes that “see” into the regolith a distance that is about four times the probe spacing to measure soil impedance as a function of frequency which is then converted to soil dielectric constant and resistivity. Dielectric constant measurements from the borehole EPP can be used to help interpret surface GPR measurements to better define layer depths and constituents. Apollo measurements of the low-frequency dielectric constant of lunar regolith samples devoid of moisture is proportional to density (Figure 7). The EPP may also be able to detect ice directly due to the high static dielectric constant for ice of between 90 and 100 at 0°C and increases with decreasing temperatures increasing to a range of between 100 and 130 at –40°C (Hobbs, 1974). Also shown in Figure 7 are additional data from minerals typically found on the lunar surface. Notice that a single line fits both soil and mineral data. Also shown in the figure are outlier minerals, Titanates and water/ice. The titanites, such as Ilmenite, were part of the lunar soils but were found for the most part at concentrations less than 10% and so do not


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appreciably change the distribution. Thus, a dielectric constant measurement that exceeds 5 indicates the presence of a significant amount of an outlier mineral. The identification of ice follows from the relaxation in the dielectric constant with frequency. Below the relaxation frequency the value for ice is between 80 and 130 and above that frequency it is 3. (Hobbs, 1974, M. Bittelli, M. Flury, and K. Roth, “Use of dielectric spectroscopy to estimate ice content in frozen media” Water Resources Research, Vol. 40 W04212 2004). The initial development are concerned with developing a suitable probe configuration and miniaturizing the impedance spectrometer.

FIGURE 7. Dielectric constant for water ice and titanium oxides and the dielectric constant for lunar soils and solid minerals as a function of density, excluding titanium oxides (Heiken et al, 1991, p. 538 ; Handbook of Chemistry and Physics, 74th Edition).

The DCAM is a small framing camera designed to fit within the inspector for deployment into a borehole to image the side-walls of the hole, to a depth of about 2 meters. Its function is to obtain information on regolith layering and texture, grain properties, borehole morphology, structural heterogeneity, and the presence of ice in lenses or on grains. The DCAM design parameters are still in the very early stages of development, but with desired capabilities that include a spatial resolution of about 30 µm per pixel, with a frame size of 512 x 512 or 1024 x 1024 and a “Skeleton” coverage, which includes the borehole backbone plus circular ‘ribs’ every third field of view equivalent. Desired spectral options include pseudo-color (3 bands) at some or all coverage with the possibility to add an ice band imaging capability at >900 nm (2-color differential method) at some or all coverage. Trade studies for the DCAM are at an early stage with investigations into camera optics, data transport methods, and imaging technology (CCD vs. CMOS), and operation characteristics at very low temperatures. Characterization of light source operation requirements at cold temperatures and spectral emission shift characteristics with temperature have begun and show that some LED’s can perform at the required low temperatures.. Regolith thermal properties are related to grain size, degree of grain bonding, the presence of volatiles like water, and in situ gases and, with proper interpretation, TCDP measurements can be used to infer regolith properties, especially when used with other CRUX instruments like the DCAM and EPP. Understanding regolith thermal properties is important for any engineering infrastructure in contact with or buried in regolith that are affected by heat flow processes. The TCDP uses a method of measuring thermal properties (diffusivity and conductivity) that is now more than 50years old (von Herzen and Maxwell, 1959). It is called a transient or dynamic method because it can be done in minutes, rather than waiting long (days) for thermal stability to be achieved. A needle, much like a hypodermic needle, is inserted into the reogolith. Inside this thin needle is a heater and a thermocouple. As the needle is heated, the rise in temperature of the needle is monitored and the rate of change of needle temperature is inversely related to the thermal conductivity. The linear rise of the needle, extrapolated back to zero time, provides the thermal diffusivity. The needle will be mounted vertically on the base of an Inspector segment that will be sent down a bore hole at intervals. Depending on regolith hardness, the needle will either be pushed or drilled into the material and then the test will be conducted. Trade studies to determine the conditions that require needle insertion by pushing or drilling are nearly complete and development of a hybrid needle with a drill tip that will allow either method of installation has been started. International Lunar Conference 2005

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The primary direct measure of regolith volatile properties is the combination of the SAS sample acquisition and delivery system and the TA, which receives the sample from the SAS and applies a controlled sample heating volatilize minerals and elements for analysis by the evolved gas analyzer (EGA). The combined TA and EGA is referred to as the TEGA. The TEGA instrument is a thermal and evolved-gas analyzer. It was originally flown on the 1998 Mars Polar Lander Mission, which failed to land successfully. It is being rebuilt, with substantial changes, for the Phoenix lander mission, which is scheduled to launch in August, 2005 and to land near the north pole of Mars in 2008. The TA for the TEGA was designed to receive crushed samples from a scoop, but for CRUX it will be redesigned to receive samples from a drill. Depending on the nature of the drill, the interface might be very different from the Phoenix lander design. The TEGA ovens are very small with inside dimensions of about 2.4 mm diameter and 8 mm long (Figure 8). The male half, which contains the sample, is inserted into the female half, which contains the heater and temperature sensor. This design will be changed as ongoing design discussions and trade studies dictate.

FIGURE 8. TEGA TA oven, which is delivered to the planetary surface in two halves. The small tapered male half receives the sample and is then inserted into the female half making a seal with the tapered joint. The female half contains the heater and temperature sensor.

As the sample is heated, various gases are evolved depending on the nature of the sample. These gases are passed on to an evolved-gas analyzer (EGA), which determines the nature of the gases that are evolved. The evolved gas is carried to the EGA with a stream of high-purity nitrogen. In the case of the Mars TEGA, the EGA is a magneticsector mass spectrometer, which can determine both the quantity of the evolved gas and its isotopic composition. The previously constructed Mars Polar Lander TEGA used tunable diode lasers to identify the quantity and composition of evolved gases (Boynton et al., 2001). Evolved gas analysis can be conducted using either mass spectrometry or tunable diode laser technology. Mass spectrometry has the advantage of being able to detect lower concentrations and requiring fewer gas molecules to conduct analyses. For an application to measuring the lunar regolith, especially in the cold permanently shaded polar regions, TEGA is useful for its ability to determine the amount of ice, volatile hydrocarbons, and other minerals that may be present. It can detect ice, either calorimetrically as shown in Figure 9, or by seeing a release of H2O detected in the EGA at a temperature near 0 deg C. It can detect the presence of organic compounds based on the mass spectrum of the evolved gases in the EGA. Specific design for the SAS sample acquisition system and the TA sample receiving system will be formulated through trade studies to determine the influence of drilling and regolith handling on retained volatiles in the regolith. If too much energy is imparted into the regolith, water ice or adsorbed solar wind hydrogen may be volatilized reducing the accuracy of the measurement and/or producing explosive release of the volatilized substance. Theoretical and experimental studies are being conducted to determine and predict the fate of retained volatiles in the regolith to allow development of designs for sample acquisition and to set drilling protocols. Preliminary results indicate that keeping volatile temperatures below 150K should prevent significant loss of volatiles during drilling and sample transfer.


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Differential Power (mW)

50 40

Water evaporation Water ice melting

30 20 10 0 -10

0

10

20

30

40

Temperature (°C)

FIGURE 9. Calorimeter output for ice upon heating. The first peak represents the melting of the ice and the second represents the vaporization of the resulting water. The area of the peak is equal to the heat of the phase change. For ice this heat is well known, and can be used to determine the amount of ice present.

Instrument Integration and Control Instrument integration and control are linked and consist of three parts: (1) physical integration of instrument components into drill or Inspector segments and with drill system functions to the highest degree possible, (2) integration of instrument control to coordinate operation of CRUX instruments, communication between instruments and the Mapper/DSS, and transfer of measured data to appropriate storage location for use by Mapper/DSS, and (3) physical integration of both Surveyor and Prospector instruments with a close proximity modular interface connection scheme to ensure no interference in performance between instruments or the drill occurs. Physical integration of drill instruments will progress in a spiral approach with each instrument developer developing their Propector instrument in a stand alone mode to test function and operability during spiral 1. In subsequent spirals the individual Prospector instruments will be collocated in drill or Inspector segments as appropriate to increase operational efficiency (Figure 10). 2.5 Š 3.7 cm

DRILL STRING (Honeybee)

100 cm

SHEAR VANE (CRREL)

NEUTRON SPECTROMETER INTERFACE: MECHANICAL/ ELECTRIC (Honeybee) ELECTRICAL PROBE (JPL))

FLUTES and CAVITY (Honeybee)

ELECTRONICS (JPL)

DRIVE MOTOR

DRIVE MOTOR

10 cm

LOAD CELL

DOWN-HOLE CAMERA (JPL)

CUTTING HEAD (DETACHABLE?) (Honeybee) THERMAL PROBE (CRREL)

INDENTER (CRREL)

FIGURE 10. Concept for fully integrated drill or Inspector segment.

Integration and control of heterogeneous instruments and subsystems relies on the CRUX Executive Controller (CEC). This capability is built upon the MARTE Instrument Interface (MInI), which is a simple and flexible communications package that was originally developed to ease the software development and integration process for the Mars Astrobiology Research and Technology Experiment (MARTE). MARTE is a complex, multi-national project that is developing and demonstrating an integrated drilling, sample handling, and science payload in order to simulate a Mars drilling mission. It has supported the development of many instruments and control systems across a number of widely separated institutions in Spain, Texas, California, Oklahoma, and New York. All of these pieces needed to be developed independently at separate home institutions, but yet come together during a short integration period and communicate across a number of different platforms. MInI was developed in order to facilitate this process. International Lunar Conference 2005

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The CEC software approach is built upon the Common Object Request Brokering Architecture (CORBA), thus enabling it to communicate seamlessly across a wide range of platforms and operating systems as shown in Figure 11. MInI is a client/server architecture, and allows any number of clients to connect to any number of servers. At the center of this architecture is a module called the Instrument Dispatcher. When a client wants to send a command to a server, it specifies the server name in the command message and then sends it on to the instrument dispatcher. The instrument dispatcher forwards the command to the appropriate server if that server has been registered.

Figure 11. Strawman CEC client-server architecture, built on CORBA.

All data messages utilize strings, and a built in string library is used to pack the data into these messages, as well as extract the data from them. What is required from the standpoint of client and server are previously agreed to labels for commands, data requests, and any accompanying parameters. MInI provides the CEC with several utilities that helps with the server development process. First, it provides a configuration utility. To create a MInI server, a CEC configuration file can be made that contains the labels of the commands, data requests, and parameter names. The configuration utility will then create a standard, working MInI server that supports these command requests. The control software that is used to control the device or instrument is then added to this standard template in order to finish the server. A MInI graphical user interface client can be used to send commands to any server to test its operation.

Technology Readiness Level 6 Qualification The end goal of the CRUX project is to demonstrate the CRUX instrument suite to a TRL 6 via functional tests in a near-lunar environment. This testing will also verify the integrated modular approach for the instruments along with software control, display, and analysis capabilities provided by the CEC and Mapper/DSS. The TRL 6 CRUX demonstration environment will be provided by modifying an existing vacuum test chamber located at KSC. Design modifications to ensure vacuum, temperature, and instrument suite accommodation capabilities are currently underway at KSC. Nominal vacuums of 10-6 torr and lunar sky temperatures of 77 °K will be used to simulate the near-lunar environment. Actual lunar vacuums of 10-10 to 10-12 are cost prohibitive and technically difficult to achieve in a laboratory setting. However, the nominal testing vacuum of 10-6 torr is achievable in a laboratory setting and eliminates convective heat transfer. Lunar sky temperatures of 77 ºK will be accomplished by using liquid nitrogencooled cold shrouds around the interior of the chamber. A 40 ºK temperature of the regolith will be accomplished by using liquid helium cooling plates. Prior to actual testing, several issues will require careful study to ensure proper TRL 6 functional tests. The process of pumping down the chamber must be carefully orchestrated to prevent or minimize the cryogenic shields and cooling plates from acting as cryogenic vacuum pumps. Once liquid cryogenics flow through the cryogenic shields


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and cooling plates, gaseous particles in the vacuum chamber will become solids upon contact with the shields/plates. Once these solid particles reach a critical point the shields and cooling plates will no longer be effective. In addition, the pumping down process and the preparation of the regolith must be strictly controlled to minimize an explosive gas release from regolith. This occurs as the pressure differential between gasses in the regolith and vacuum test chamber increase during the pump down. Primary demonstration of the instrument modularity and overall integration, the CEC, and Mapper/DSS will be conducted at the JPL Mars Yard, the CRREL regolith chamber, and other facilities as needed.

MAPPER/DSS ARCHITECTURE The Mapper/DSS is the tool that will allow engineers and astronauts to utilize CRUX measurements inconjunciton with existing lunar and planetary data to plan and conduct LPSO. It is a service-oriented approach to the acquisition, management, analysis and dissemination of real-time geospatial data collected during CRUX missions (Figure 12). Using the Mapper/DSS, CRUX data and mission telemetry will be acquired and managed as eXtensible Markup Language (XML) documents over a scalable web service bus. Web Services will be used not only to acquire but to process and disseminate data at all levels of processing from raw telemetry to reduced data streams to model output. Principal technical components of the Mapper/DSS include the Oracle database with spatial and temporal data elements for data persistence, management, and replication; Interactive Data Language (IDL) for server side data reduction and analysis; and the Eclipse (an open source development platform for software alignment and integration) with the ongoing development of NASA’s Science Activity Planer (SAP/Maestro), commercial and open source geospatial components including GIS from Earth Sciences Research Institute (ESRI), geotools (an open source Web applications development application) and mapserver (an open source Web map delivery application). The use of open source and standard software platforms ensures compatibility and interoperability with existing NASA software development efforts.

Java Desktop

P R E S E N T

P E R S I S T

A N A L Y Z E P R O C E S S

A C Q U I R E

Web Browser

CRUX DSS

Web Service Client

CRUX Mapper

GeoTools MapServer

Eclipse IDL

SQL

LabView

CRUX Web Services (XML RPC Via SOAP)

Application Server Java

CRUX for ArcGIS

ESRI SDE Security, Role-Based Access and Data Versioning

SOAP/XML

Lunar & Planetary Data Archive: Apollo, etc

Any Client

ArcGIS Server

CRUX Data Warehouse

MInI Dispatcher

CRUX Instrument Suite

ArcGIS Desktop

OGC

Future Lunar & Planetary Mission Data

FIGURE 12. Architecture of the Mapper/DSS.

Principal data flow into the Mapper/DSS comes from the CRUX instrument suite measurements, along with archival lunar and planetary data, and future mission data. CRUX instrument data passes through the CEC Mini Dispatcher and is made available via object request broker (ORB) publish and subscribe mechanism. Archival data is converted from legacy formats and loaded directly to a Mapper/DSS database when necessary or may be accessed from cooperating programs via web service interface. Future mission data are anticipated to be accessed by a combination of standards based web services including XML/RPC via SOAP, and Open Geospatial Consortium (OGC) web


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services. The CRUX data warehouse is responsible for persistence and dissemination of all relevant program data. The data warehouse will be responsible for data archive, replication to distributed sites, data security and role-based review, validation and release. Multi-versioned data will also be supported in the data warehouse. It is anticipated that any data reduction or analysis that can be done at the data warehouse/persistence tier will be done at this tier. This could include server side IDL, Java applications and stored database procedures. Above the data warehouse tier of our architecture a series of application development and deployment frameworks will allow a diverse suite of users to use any standards-based application to display and analyze CRUX program data. Anticipated clients include a Java desktop application built upon the Eclipse framework. This application and its modules should allow for integration of unique CRUX analysis capabilities with the NASA Maestro/Science Activity Planner. A webbased Mapper/DSS interface will provide the broadest possible audience access to data visualization and analysis tools. The web-based system which is currently under development supports geographic display and analysis of program data, and the display and query of models processed through the decision support system. Commercial off the shelf software such as ESRI ArcGIS, ENVI IDL, and MATLAB along with a suite of open source and proprietary data reduction and analysis tools will be used to analyze and reduce CRUX data. These tools will interact with the warehouse via common protocols such as ODBC, ESRI SDE, and through a series of data discovery and delivery web services provided at this tier. The delivered products from Mapper/DSS will be a series of science-based engineering guidelines and data interpretation protocols implemented in software. These guidelines will be driven by engineering scenarios developed as needed by astronauts and engineers. As an example consider the need to determine the concentration and distribution of water and hydrogen in the polar lunar regolith (or only hydrogen elsewhere). The primary CRUX instrument measurements might be existing satellite neutron spectrometer data to guide surveyor instruments, which in turn guide deployment of Prospector instruments to conduct site specific measurements. To accurately evaluate if hydrogen detected by neutron spectrometers is solar wind hydrogen or water ice requires direct measurement by a TEGA like device, which can then be used through dada fusion processes to more accurately interpret the spectrometer data.

Data Integration, Fusion, and Decision Support The Mapper/DSS achieves its full power when data are integrated to provide interrelated information that can be fused to derive regolith property information that cannot be determined from a single data source. The fused data and model results can then be delivered to aid LPSO decision-making. Data fusion methods, which use complementary data sets to determine information about the regolith that cannot be determined from individual instrument measurement data, are an integral part of our data analysis approach. To demonstrate the data fusion and decision support system approach we again use the example characterizing the distribution and form of hydrogen. Hydrogen, depending whether it is in the form of water or solar wind deposits, is a potential source of fuel, water, and oxygen for space operations. Lunar Prospector orbital neutron probe data imply that regions of enhanced hydrogen exist in the lunar polar regions, possibly associated with permanently shadowed craters, but the form of that hydrogen is unknown. Data fusion methods can resolve both the interpretation uncertainties of the neutron data and produce 3D characterization of regolith hydrogen. Primary data fusion is between the TEGA, SNeuP, and BNeuP. The BNeuP provides information about hydrogen as a function of depth and time and the TEGA can detect water, solar wind hydrogen, and other elements or molecules as a function of depth. Data fusion consists of using the hydrogen concentration as a function of depth information from BNeuP and TEGA to help interpret SNeuP data to generate 3D information. Secondary information from the GPR, the DCAM, and the EPP, along with models of known and expected physical properties of granular materials to correlate different data sets, can improve our characterization of the hydrogen distribution. By combining individual data displays with the results derived from data fusion and models, products for operational decision-making can be produced (Figure 13). Some of these products may be maps of hydrogen distribution, regolith layering, individual borehole plots, and other important information for LPSO.


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FIGURE 13. Example display showing DSS support using data fusion between SNeuP, BNeuP, and TEGA measurements to derive water/solar wind hydrogen ratios and using that information to interpret SNeuP data to estimate regional water and solar wind hydrogen distribution.

CONCLUSIONS We have described the CRUX project which is advancing the technological readiness of an integrated and modular suite of instruments for robotic and crewed geotechnical operations in lunar and planetary environments. A significant part of the project is the Mapper/Decision-Support-System software tool that can be deployed in the operations center on the ground, or even with the user in space to optimize operational geotechnical decisions.

ACKNOWLEDGMENTS We thank D. Albert, M. Buehler, D. Carrier, D. Cole, S., Kim, D. Lueck, T. McCann, M. Sturm, and R. Sullivan for their contributions. Some of the work described in this paper was performed by the Engineer Research and Development Center (CRREL and GSL), Honeybee Robotics, Los Alamos National Laboratory, the University of Arizona, and Applied Research Associates, funded under the NASA BAA NO. 04-02, “Research and Development Opportunities in Human and Robotic Technology” by NASA Project Number NNA05AC60I. Some of the work was performed by the Jet Propulsion Laboratory (California Institute of Technology), Ames Research Center, and Kennedy Space Center under contracts with the National Aeronautics and Space Administration.

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