Showing papers by "Jet Propulsion Laboratory published in 2003"

The systems biology markup language (SBML): a medium for representation and exchange of biochemical network models.

Abstract: Motivation: Molecular biotechnology now makes it possible to build elaborate systems models, but the systems biology community needs information standards if models are to be shared, evaluated and developed cooperatively. Results: We summarize the Systems Biology Markup Language (SBML) Level 1, a free, open, XML-based format for representing biochemical reaction networks. SBML is a software-independent language for describing models common to research in many areas of computational biology, including cell signaling pathways, metabolic pathways, gene regulation, and others. ∗ To whom correspondence should be addressed. Availability: The specification of SBML Level 1 is freely available from http://www.sbml.org/.

A broadband superconducting detector suitable for use in large arrays

Abstract: Cryogenic detectors are extremely sensitive and have a wide variety of applications (particularly in astronomy), but are difficult to integrate into large arrays like a modern CCD (charge-coupled device) camera. As current detectors of the cosmic microwave background (CMB) already have sensitivities comparable to the noise arising from the random arrival of CMB photons, the further gains in sensitivity needed to probe the very early Universe will have to arise from large arrays. A similar situation is encountered at other wavelengths. Single-pixel X-ray detectors now have a resolving power of ΔE < 5 eV for single 6-keV photons, and future X-ray astronomy missions anticipate the need for 1,000-pixel arrays. Here we report the demonstration of a superconducting detector that is easily fabricated and can readily be incorporated into such an array. Its sensitivity is already within an order of magnitude of that needed for CMB observations, and its energy resolution is similarly close to the targets required for future X-ray astronomy missions.

New exponential bounds and approximations for the computation of error probability in fading channels

Abstract: We present new exponential bounds for the Gaussian Q function (one- and two-dimensional) and its inverse, and for M-ary phase-shift-keying (MPSK), M-ary differential phase-shift-keying (MDPSK) error probabilities over additive white Gaussian noise channels. More precisely, the new bounds are in the form of the sum of exponential functions that, in the limit, approach the exact value. Then, a quite accurate and simple approximate expression given by the sum of two exponential functions is reported. The results are applied to the general problem of evaluating the average error probability in fading channels. Some examples of applications are also presented for the computation of the pairwise error probability of space-time codes and the average error probability of MPSK and MDPSK in fading channels.

Quantum technology: the second quantum revolution

Abstract: We are currently in the midst of a second quantum revolution. The first quantum revolution gave us new rules that govern physical reality. The second quantum revolution will take these rules and use them to develop new technologies. In this review we discuss the principles upon which quantum technology is based and the tools required to develop it. We discuss a number of examples of research programs that could deliver quantum technologies in coming decades including: quantum information technology, quantum electromechanical systems, coherent quantum electronics, quantum optics and coherent matter technology.

Science objectives and early results of the DEEP2 Redshift Survey

Abstract: The DEIMOS spectrograph has now been installed on the Keck-II telescope and commissioning is nearly complete. The DEEP2 Redshift Survey, which will take approximately 120 nights at the Keck Observatory over a three year period and has been designed to utilize the power of DEIMOS, began in the summer of 2002. The multiplexing power and high efficiency of DEIMOS enables us to target 1000 faint galaxies per clear night. Our goal is to gather high-quality spectra of ≈ 60,000 galaxies with z>0.75 in order to study the properties and large scale clustering of galaxies at z ≈ 1. The survey will be executed at high spectral resolution, R=λ/Δλ ≈ 5000, allowing us to work between the bright OH sky emission lines and to infer linewidths for many of the target galaxies (for several thousand objects, we will obtain rotation curves as well). The linewidth data will facilitate the execution of the classical redshift-volume cosmological test, which can provide a precision measurement of the equation of state of the Universe. This talk reviews the project, summarizes our science goals and presents some early DEIMOS data.

Summer upwelling in the South China Sea and its role in regional climate variations

Abstract: Seasonal and interannual variations of summer upwelling off the South Vietnam coast and the offshore spread of cold water are investigated using a suite of new satellite measurements. In summer, as the southwesterly winds impinge on Annam Cordillera (a north-south running mountain range on the east coast of Indochina) a strong wind jet occurs at its southern tip offshore east of Saigon, resulting in strong wind curls that are important for ocean upwelling off the coast. In July and August an anticyclonic ocean eddy develops to the southeast, advecting the cold coastal water offshore into the open South China Sea (SCS). The center of this cold filament is located consistently north of the wind speed maximum, indicating that open-ocean upwelling helps to cool the ocean surface. Corroborating evidence for the cold filament is found in ocean color observations that reveal a collocated tongue of high chlorophyll concentration. The development of this cold filament disrupts the summer warming of the SCS and causes a pronounced semiannual cycle in SST. Moreover, the cold filament is an important player in interannual variability in the summer SCS. In 1998, the cold filament and mid-summer cooling never took place, giving rise to a strong basin-wide surface warming. Interannual SST variance has a local maximum over the climatological cold filament, and is much greater than the variance over the adjacent Indian and western Pacific Oceans. A cold filament index is constructed, which displays significant lagged correlation with SST in the eastern equatorial Pacific and Indian Oceans, indicative of a teleconnection from El Nino.

Mars-like soils in the Atacama Desert, Chile, and the dry limit of microbial life

Abstract: The Viking missions showed the martian soil to be lifeless and depleted in organic material and indicated the presence of one or more reactive oxidants. Here we report the presence of Mars-like soils in the extreme arid region of the Atacama Desert. Samples from this region had organic species only at trace levels and extremely low levels of culturable bacteria. Two samples from the extreme arid region were tested for DNA and none was recovered. Incubation experiments, patterned after the Viking labeled-release experiment but with separate biological and nonbiological isomers, show active decomposition of organic species in these soils by nonbiological processes.

Constraints on the equation of state of dark energy and the Hubble constant from stellar ages and the CMB

Abstract: We place tight constraints on the redshift-averaged, effective value of the equation of state of dark energy, w, using only the absolute ages of Galactic stars and the observed position of the first peak in the angular power spectrum of the CMB. We find w -1, this finding suggests that within our uncertainties, dark energy is indistinguishable from a classical vacuum energy term. We detect a correlation between the ages of the oldest galaxies and their redshift. This opens up the possibility of measuring w(z) by computing the relative ages of the oldest galaxies in the universe as a function of redshift, dz/dt. We show that this is a realistic possibility by computing dz/dt at z~0 from SDSS galaxies and obtain an independent estimate for the Hubble constant, H_0 = 69 \pm 12 km s-1 Mpc-1. The small number of galaxies considered at z>0.2 does not yield, currently, a precise determination of w(z), but shows that the age--redshift relation is consistent with a Standard LCDM universe with $w=-1$.

The Magnetorotational Instability in Core-Collapse Supernova Explosions

Abstract: We investigate the action of the magnetorotational instability (MRI) in the context of iron-core collapse. Exponential growth of the field on the timescale Ω-1 by the MRI will dominate the linear growth process of field-line "wrapping" with the same characteristic time. We examine a variety of initial rotation states, with solid-body rotation or a gradient in rotational velocity, that correspond to models in the literature. A relatively modest value of the initial rotation, a period of ~10 s, will give a very rapidly rotating proto-neutron star and hence strong differential rotation with respect to the infalling matter. We assume conservation of angular momentum on spherical shells. Rotational distortion and the dynamic feedback of the magnetic field are neglected in the subsequent calculation of rotational velocities. In our rotating and collapsing conditions, a seed field is expected to be amplified by the MRI and to grow exponentially to a saturation field. Results are discussed for two examples of saturation fields, a fiducial field that corresponds to vA = rΩ and a field that corresponds to the maximum growing mode of the MRI. We find, as expected, that the shear is strong at the boundary of the newly formed proto-neutron star and, unexpectedly, that the region within the stalled shock can be subject to strong MHD activity. Modest initial rotation velocities of the iron core result in sub-Keplerian rotation and a sub-equipartition magnetic field that nevertheless produce substantial MHD luminosity and hoop stresses: saturation fields of order 1015-1016 G can develop ~300 ms after bounce with an associated MHD luminosity of ~1052 ergs s-1. Bipolar flows driven by this MHD power can affect or even cause the explosions associated with core-collapse supernovae.

New evidence for enhanced ocean primary production triggered by tropical cyclone

Abstract: [1] New evidence based on recent satellite data is presented to provide a rare opportunity in quantifying the long-speculated contribution of tropical cyclones to enhance ocean primary production. In July 2000, moderate cyclone Kai-Tak passed over the South China Sea (SCS). During its short 3-day stay, Kai-Tak triggered an average 30-fold increase in surface chlorophyll-a concentration. The estimated carbon fixation resulting from this event alone is 0.8 Mt, or 2–4% of SCS's annual new production. Given an average of 14 cyclones passing over the SCS annually, we suggest the long-neglected contribution of tropical cyclones to SCS's annual new production may be as much as 20–30%.

The three-dimensional solar wind around solar maximum

Abstract: [1] Ulysses is now completing its second solar polar orbit, dropping back down in latitude as the Sun passes through its post-maximum phase of the solar cycle. A mid-sized circumpolar coronal hole that formed around solar maximum in the northern hemisphere has persisted and produced a highly inclined CIR, which was observed from ∼70°N down to ∼30°N. We find that the speed maxima in the high-speed streams follow the same slow drop in speed with decreasing latitude observed in the large polar coronal holes around solar minimum. These results suggest a solar wind acceleration effect that is related to heliolatitude or solar rotation. We also find that the solar wind dynamic pressure is significantly lower in the post-maximum phase of this solar cycle than during the previous one, indicating that while the heliosphere is larger than near solar minimum, it should be smaller than during or after the previous maximum.

Angular Momentum Transport by MHD Turbulence in Accretion Disks: Gas Pressure Dependence of the Saturation Level of the Magnetorotational Instability

Abstract: The saturation level of the magnetorotational instability (MRI) is investigated using three-dimensional MHD simulations. The shearing box approximation is adopted and the vertical component of gravity is ignored, so that the evolution of the MRI is followed in a small local part of the disk. We focus on the dependence of the saturation level of the stress on the gas pressure, which is a key assumption in the standard alpha disk model. From our numerical experiments it is found that there is a weak power-law relation between the saturation level of the Maxwell stress and the gas pressure in the nonlinear regime; the higher the gas pressure, the larger the stress. Although the power-law index depends slightly on the initial field geometry, the relationship between stress and gas pressure is independent of the initial field strength, and is unaffected by Ohmic dissipation if the magnetic Reynolds number is at least 10. The relationship is the same in adiabatic calculations, where pressure increases over time, and nearly-isothermal calculations, where pressure varies little with time. Our numerical results are qualitatively consistent with an idea that the saturation level of the MRI is determined by a balance between the growth of the MRI and the dissipation of the field through reconnection. The quantitative interpretation of the pressure-stress relation, however, may require advances in the theoretical understanding of non-steady magnetic reconnection.

Athena Mars rover science investigation

Abstract: [1] Each Mars Exploration Rover carries an integrated suite of scientific instruments and tools called the Athena science payload. The primary objective of the Athena science investigation is to explore two sites on the Martian surface where water may once have been present, and to assess past environmental conditions at those sites and their suitability for life. The remote sensing portion of the payload uses a mast called the Pancam Mast Assembly (PMA) that provides pointing for two instruments: the Panoramic Camera (Pancam), and the Miniature Thermal Emission Spectrometer (Mini-TES). Pancam provides high-resolution, color, stereo imaging, while Mini-TES provides spectral cubes at mid-infrared wavelengths. For in-situ study, a five degree-of-freedom arm called the Instrument Deployment Device (IDD) carries four more tools: a Microscopic Imager (MI) for close-up imaging, an Alpha Particle X-Ray Spectrometer (APXS) for elemental chemistry, a Mossbauer Spectrometer (MB) for the mineralogy of Fe-bearing materials, and a Rock Abrasion Tool (RAT) for removing dusty and weathered surfaces and exposing fresh rock underneath. The payload also includes magnets that allow the instruments to study the composition of magnetic Martian materials. All of the Athena instruments have undergone extensive calibration, both individually and using a set of geologic reference materials that are being measured with all the instruments. Using a MER-like rover and payload in a number of field settings, we have devised operations processes that will enable us to use the MER rovers to formulate and test scientific hypotheses concerning past environmental conditions and habitability at the landing sites.

On the orbital forcing of Martian water and CO2 cycles: A general circulation model study with simplified volatile schemes

Abstract: [1] Variations in the Martian water and CO2 cycles with changes in orbital and rotational parameters are examined using the Geophysical Fluid Dynamics Laboratory Mars General Circulation Model. The model allows for arbitrary specification of obliquity, eccentricity, and argument of perihelion as well as the position and thickness of surface ice. Exchange of CO2 between the surface and atmosphere is modeled, generating seasonal cycles of surface ice and surface pressure. Water is allowed to exchange between the surface and atmosphere, cloud formation is treated, and both cloud and vapor are transported by modeled winds and diffusion. Exchange of water and CO2 with the subsurface is not allowed, and radiative effects of water vapor and clouds are not treated. The seasonal cycle of CO2 is found to become more extreme at high obliquity, as suggested by simple heat balance models. Maximum pressures remain largely the same, but the minima decrease substantially as more CO2 condenses in the more extensive polar night. Vapor and cloud abundances increase dramatically with obliquity. The stable location for surface ice moves equatorward with increasing obliquity, such that by 45° obliquity, water ice is stable in the tropics only. Ice is not spatially uniform, but rather found preferentially in regions of high thermal inertia or high topography. Eccentricity and argument of perihelion can provide a second-order modification to the distribution of surface ice by altering the temporal distribution of insolation at the poles. Further model simulations reveal the robustness of these distributions for a variety of initial conditions. Our findings shed light on the nature of near-surface, ice-rich deposits at midlatitudes and low-latitudes on Mars.

Mapping Hydrothermally Altered Rocks at Cuprite, Nevada, Using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), a New Satellite-Imaging System

Abstract: The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a 14-band multispectral instrument on board the Earth Observing System (EOS), TERRA. The three bands between 0.52 and 0.86 μ m and the six bands from 1.60 and 2.43 μ m, which have 15- and 30-m spatial resolution, respectively, were selected primarily for making remote mineralogical determinations. The Cuprite, Nevada, mining district comprises two hydrothermal alteration centers where Tertiary volcanic rocks have been hydrothermally altered mainly to bleached silicified rocks and opalized rocks, with a marginal zone of limonitic argillized rocks. Country rocks are mainly Cambrian phyllitic siltstone and limestone. Evaluation of an ASTER image of the Cuprite district shows that spectral reflectance differences in the nine bands in the 0.52 to 2.43 μ m region provide a basis for identifying and mapping mineralogical components which characterize the main hydrothermal alteration zones: opal is the spectrally dominant mineral in the silicified zone; whereas, alunite and kaolinite are dominant in the opalized zone. In addition, the distribution of unaltered country rocks was mapped because of the presence of spectrally dominant muscovite in the siltstone and calcite in limestone, and the tuffaceous rocks and playa deposits were distinguishable due to their relatively flat spectra and weak absorption features at 2.33 and 2.20 μ m, respectively. An Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) image of the study area was processed using a similar methodology used with the ASTER data. Comparison of the ASTER and AVIRIS results shows that the results are generally similar, but the higher spectral resolution of AVIRIS (224 bands) permits identification of more individual minerals, including certain polymorphs. However, ASTER has recorded images of more than 90 percent of the Earth’s land surface with less than 20 percent cloud cover, and these data are available at nominal or no cost. Landsat TM images have a similar spatial resolution to ASTER images, but TM has fewer bands, which limits its usefulness for making mineral determinations.

Biologically Inspired Intelligent Robots

Abstract: From the Publisher: Advances in biologically inspired technologies, such as artificial intelligence and artificial muscles, are making the possibility of engineering robots that look and behave like humans a closer reality. The multidisciplinary issues involved in the development of these robots include materials, actuators, sensors, structures, functionality, control, intelligence, and autonomy. This book reviews various aspects ranging from the biological model to the vision for the future.

Cosmological constraints from archeops

Abstract: We analyze the cosmological constraints that Archeops places on adiabatic cold dark matter models with passive power-law initial fluctuations. Because its angular power spectrum has small bins in l and large l coverage down to COBE scales, Archeops provides a precise determination of the first acoustic peak in terms of position at multipole l_peak=220 +- 6, height and width. An analysis of Archeops data in combination with other CMB datasets constrains the baryon content of the Universe, Omega(b)h^2 = 0.022 (+0.003,-0.004), compatible with Big-Bang nucleosynthesis and with a similar accuracy. Using cosmological priors obtainedfrom recent non-CMB data leads to yet tighter constraints on the total density, e.g. Omega(tot)=1.00 (+0.03,-0.02) using the HST determination of the Hubble constant. An excellent absolute calibration consistency is found between Archeops and other CMB experiments, as well as with the previously quoted best fit model.The spectral index n is measured to be 1.04 (+0.10,-0.12) when the optical depth to reionization, tau, is allowed to vary as a free parameter, and 0.96 (+0.03,-0.04) when tau is fixed to zero, both in good agreement with inflation.

Reproduction and metabolism at − 10°C of bacteria isolated from Siberian permafrost

Abstract: We report the isolation and properties of several species of bacteria from Siberian permafrost. Half of the isolates were spore-forming bacteria unable to grow or metabolize at subzero temperatures. Other Gram-positive isolates metabolized, but never exhibited any growth at - 10 degrees C. One Gram-negative isolate metabolized and grew at - 10 degrees C, with a measured doubling time of 39 days. Metabolic studies of several isolates suggested that as temperature decreased below + 4 degrees C, the partitioning of energy changes with much more energy being used for cell maintenance as the temperature decreases. In addition, cells grown at - 10 degrees C exhibited major morphological changes at the ultrastructural level.

Miniature Thermal Emission Spectrometer for the Mars Exploration Rovers

Abstract: [1] The Miniature Thermal Emission Spectrometer (Mini-TES) will provide remote measurements of mineralogy and thermophysical properties of the scene surrounding the Mars Exploration Rovers and guide the rovers to key targets for detailed in situ measurements by other rover experiments. The specific scientific objectives of the Mini-TES investigation are to (1) determine the mineralogy of rocks and soils, (2) determine the thermophysical properties of selected soil patches, and (3) determine the temperature profile, dust and water-ice opacity, and water vapor abundance in the lower atmospheric boundary layer. The Mini-TES is a Fourier Transform Spectrometer covering the spectral range 5–29 μm (339.50 to 1997.06 cm−1) with a spectral sample interval of 9.99 cm−1. The Mini-TES telescope is a 6.35-cm-diameter Cassegrain telescope that feeds a flat-plate Michelson moving mirror mounted on a voice-coil motor assembly. A single deuterated triglycine sulfate (DTGS) uncooled pyroelectric detector with proven space heritage gives a spatial resolution of 20 mrad; an actuated field stop can reduce the field of view to 8 mrad. Mini-TES is mounted within the rover's Warm Electronics Box and views the terrain using its internal telescope looking up the hollow shaft of the Pancam Mast Assembly (PMA) to the fixed fold mirror and rotating elevation scan mirror in the PMA head located ∼1.5 m above the ground. The PMA provides a full 360°of azimuth travel and views from 30° above the nominal horizon to 50° below. An interferogram is collected every two seconds and transmitted to the Rover computer, where the Fast Fourier Transform, spectral summing, lossless compression, and data formatting are performed prior to transmission to Earth. Radiometric calibration is provided by two calibration V-groove blackbody targets instrumented with platinum thermistor temperature sensors with absolute temperature calibration of ±0.1°C. One calibration target is located inside the PMA head; the second is on the Rover deck. The Mini-TES temperature is expected to vary diurnally from −10 to +30°C, with most surface composition data collected at scene temperatures >270 K. For these conditions the radiometric precision for two-spectra summing is ±1.8 × 10−8 W cm−2 sr−1/cm−1 between 450 and 1500 cm−1, increasing to ∼4.2 × 10−8 W cm−2 sr−1/cm−1 at shorter (300 cm−1) and longer (1800 cm−1) wave numbers. The absolute radiance error will be <5 × 10−8 W cm−2 sr−1/cm−1, decreasing to ∼1 × 10−8 W cm−2 sr−1/cm−1 over the wave number range where the scene temperature will be determined (1200–1600 cm−1). The worst-case sum of these random and systematic radiance errors corresponds to an absolute temperature error of ∼0.4 K for a true surface temperature of 270 K and ∼1.5 K for a surface at 180 K. The Mini-TES will be operated in a 20-mrad panorama mode and an 8-mrad targeted mode, producing two-dimensional rasters and three-dimensional hyperspectral image cubes of varying sizes. The overall Mini-TES envelope size is 23.5 × 16.3 × 15.5 cm, and the mass is 2.40 kg. The power consumption is 5.6 W average. The Mini-TES was developed by Arizona State University and Raytheon Santa Barbara Remote Sensing.

Color-selected galaxies at z~6 in the Great Observatories Origins Deep Survey

Abstract: We report early results on galaxies at z~6, selected from Hubble Space Telescope imaging for the Great Observatories Origins Deep Survey. Spectroscopy of one object with the Advanced Camera for Surveys grism and from the Keck and VLT observatories a shows a strong continuum break and asymmetric line emission, identified as Lya at z=5.83. We detect only five spatially extended, z~6 candidates with signal-to-noise ratios > 10, two of which have spectroscopic confirmation. This is many fewer than would be expected if galaxies at z=6 had the same luminosity function as those at z=3. There are many fainter candidates, but we expect substantial contamination from foreground interlopers and spurious detections. Our best estimates favor a z=6 galaxy population with fainter luminosities, higher space density, and similar co-moving ultraviolet emissivity to that at z=3, but this depends critically on counts at fluxes fainter than those reliably probed by the current data.

The Odin satellite - I. Radiometer design and test

Abstract: The Sub-millimetre and Millimetre Radiometer (SMR) is the main instrument on the Swedish, Canadian, Finnish and French spacecraft Odin. It consists of a 1.1 metre diameter telescope with four tuneable heterodyne receivers covering the ranges 486-504 GHz and 541-581 GHz, and one fixed at 118.75 GHz together with backends that provide spectral resolution from 150 kHz to 1 MHz. This Letter describes the Odin radiometer, its operation and performance with the data processing and calibration described in Paper II.

The ars Detoxification System Is Advantageous but Not Required for As(V) Respiration by the Genetically Tractable Shewanella Species Strain ANA-3

Abstract: Arsenate [As(V); HAsO42−] respiration by bacteria is poorly understood at the molecular level largely due to a paucity of genetically tractable organisms with this metabolic capability. We report here the isolation of a new As(V)-respiring strain (ANA-3) that is phylogenetically related to members of the genus Shewanella and that also provides a useful model system with which to explore the molecular basis of As(V) respiration. This gram-negative strain stoichiometrically couples the oxidation of lactate to acetate with the reduction of As(V) to arsenite [As(III); HAsO2]. The generation time and lactate molar growth yield (Ylactate) are 2.8 h and 10.0 g of cells mol of lactate−1, respectively, when it is grown anaerobically on lactate and As(V). ANA-3 uses a wide variety of terminal electron acceptors, including oxygen, soluble ferric iron, oxides of iron and manganese, nitrate, fumarate, the humic acid functional analog 2,6-anthraquinone disulfonate, and thiosulfate. ANA-3 also reduces As(V) to As(III) in the presence of oxygen and resists high concentrations of As(III) (up to 10 mM) when grown under either aerobic or anaerobic conditions. ANA-3 possesses an ars operon (arsDABC) that allows it to resist high levels of As(III); this operon also confers resistance to the As-sensitive strains Shewanella oneidensis MR-1 and Escherichia coli AW3110. When the gene encoding the As(III) efflux pump, arsB, is inactivated in ANA-3 by a polar mutation that also eliminates the expression of arsC, which encodes an As(V) reductase, the resulting As(III)-sensitive strain still respires As(V); however, the generation time and the Ylactate value are two- and threefold lower, respectively, than those of the wild type. These results suggest that ArsB and ArsC may be useful for As(V)-respiring bacteria in environments where As concentrations are high, but that neither is required for respiration.

CAMPOUT: a control architecture for tightly coupled coordination of multirobot systems for planetary surface exploration

Abstract: Exploration of high risk terrain areas such as cliff faces and site construction operations by autonomous robotic systems on Mars requires a control architecture that is able to autonomously adapt to uncertainties in knowledge of the environment. We report on the development of a software/hardware framework for cooperating multiple robots performing such tightly coordinated tasks. This work builds on our earlier research into autonomous planetary rovers and robot arms. Here, we seek to closely coordinate the mobility and manipulation of multiple robots to perform examples of a cliff traverse for science data acquisition, and site construction operations including grasping, hoisting, and transport of extended objects such as large array sensors over natural, unpredictable terrain. In support of this work we have developed an enabling distributed control architecture called control architecture for multirobot planetary outposts (CAMPOUT) wherein integrated multirobot mobility and control mechanisms are derived as group compositions and coordination of more basic behaviors under a task-level multiagent planner. CAMPOUT includes the necessary group behaviors and communication mechanisms for coordinated/cooperative control of heterogeneous robotic platforms. In this paper, we describe CAMPOUT, and its application to ongoing physical experiments with multirobot systems at the Jet Propulsion Laboratory in Pasadena, CA, for exploration of cliff faces and deployment of extended payloads.

Planetary Rover Developments Supporting Mars Exploration, Sample Return and Future Human-Robotic Colonization

Abstract: We overview our recent research on planetary mobility. Products of this effort include the Field Integrated Design & Operations rover (FIDO), Sample Return Rover (SRR), reconfigurable rover units that function as an All Terrain Explorer (ATE), and a multi-Robot Work Crew of closely cooperating rovers (RWC). FIDO rover is an advanced technology prototypes its design and field testing support NASA's development of long range, in situ Mars surface science missions. Complementing this, SRR implements autonomous visual recognition, navigation, rendezvous, and manipulation functions enabling small object pick-up, handling, and precision terminal docking to a Mars ascent vehicle for future Mars Sample Return. ATE implements on-board reconfiguration of rover geometry and control for adaptive response to adverse and changing terrain, e.g., traversal of steep, sandy slopes. RWC implements coordinated control of two rovers under closed loop kinematics and force constraints, e.g., transport of large payloads, as would occur in robotic colonies at future Mars outposts. RWC is based in a new extensible architecture for decentralized control of, and collective state estimation by multiple heterogeneous robotic platforms—CAMPOUTs we overview the key architectural features. We have conducted experiments with all these new rover system concepts over variable natural terrain. For each of the above developments, we summarize our approach, some of our key experimental results to date, and our future directions of planned development.

Resonant returns to close approaches: Analytical theory ?

Abstract: We extend ¨ Opik's theory of close encounters of a small body (either an asteroid or a comet) by explicitly introducing the nodal distance and a time coordinate. Assuming that the heliocentric motion between consecutive close encounters is Keplerian, or given by an explicit propagator, we can compute the initial conditions for an encounter as functions of the outcomes of a previous one; in this way it is possible to obtain a completely analytical theory of resonant returns. It is found that the initial conditions of a close encounter that lead to a resonant return must lie close to easily computable circles on the b- plane of the first encounter. By further assuming that the nodal distance varies uniformly with time, due to secular perturbations, and considering the derivatives of the coordinates on the b-plane of the second encounter with respect to those on the b-plane of the first encounter, we compute in the latter the location, shape and size of collision keyholes.