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We integrate systems of measurement and modeling to improve estimation of uncertainties in above-ground biomass AGB derived from remote sensing. The outcome provides a unified starting point for the climate-change carbon community to assess uncertainty and sensitivity data and methodologies, and ultimately supports decision-making about which missions and instruments to develop for a desired cost/benefit ratio. Initial results include fusion of remote-sensing techniques e.g., radar and lidar, uncertainties associated with measurement and modeling, and the impact of potential uncertainty correlations across aggregated unit areas. Biomass uncertainty estimates are presented at the single-hectare level for the forestlands of California. Using a forest biomass map of California, we calculate changes in variance e.g., 2 orders of magnitude as a function of uncertainty correlation assumptions, with correlations extending to spatial scales up to 100 km. Using a variogram formalism to derive the correlation shape and magnitude, we show that the estimated variance for California above-ground biomass is between 1% and 2% 1 standard deviation for our current best estimate of the correlation range at 5-10 km-i.e., we bound the standard deviation by a factor of 2. This contrasts with 0.025% 1 standard deviation if one does not include the correlation term.

Five potential methods of preventing an asteroid from colliding with Earth—Kinetic Impactor (KI), Ion Beam Deflection (IBD), Gravity Tractor (GT), Enhanced Gravity Tractor (EGT), and Laser Ablation (LA)—are compared, with the objective of helping to inform a NASA decision regarding which technology or technologies could be demonstrated in space on the proposed 2019 Asteroid Robotic Redirect Mission (ARRM). Three design blocks are considered, which differ in the power available to the deflection technology and the mass at low-Earth orbit. We plot the required warning time (up to 30 years between discovery of the hazard and potential collision with Earth) vs. asteroid diameter for each of four technologies (gravity tractor without enhancement is considered only as a trim/verification candidate) under each design block, and illustrate sensitivities of results to important parameters.

There is an important need for a consistent analytical foundation supporting the selection and monitoring of R&D tasks that support new system concepts that enable future NASA missions. This capability should be applicable at various degrees of abstraction, depending upon whether one is interested in formulation, development, or operations. It should also be applicable to a single project, a program comprised of a group of projects, an enterprise typically including multiple programs, and the overall agency itself. Emphasis here is on technology selection and new initiatives, but the same approach can be generalized to other applications, dealing, for example, with new system architectures, risk reduction, and task allocation among humans and machines. The purpose of this paper is to describe one such approach, which is in its early stages of implementation within NASA programs, and to discuss several illustrative examples. © 2004 Wiley Periodicals, Inc. Syst Eng 7: 285–302, 2004

One of the key issues in space exploration is that of deciding what space tasks are best done with humans, with robots, or a suitable combination of each. In general, human and robot skills are complementary. Humans provide as yet unmatched capabilities to perceive, think, and act when faced with anomalies and unforeseen events, but there can be huge potential risks to human safety in getting these benefits. Robots provide complementary skills in being able to work in extremely risky environments, but their ability to perceive, think, and act by themselves is currently not error-free, although these capabilities are continually improving with the emergence of new technologies. Substantial past experience validates these generally qualitative notions. However, there is a need for more rigorously systematic evaluation of human and robot roles, in order to optimize the design and performance of human-robot system architectures using well-defined performance evaluation metrics. This article summarizes a new analytical method to conduct such quantitative evaluations. While the article focuses on evaluating human-robot systems, the method is generally applicable to a much broader class of systems whose performance needs to be evaluated.

The Telerobotics Program of the National Aeronautics and Space Administration (NASA) Office of Space Science is developing innovative telerobotics technologies to enable or support a wide range of space missions over the next decade and beyond. These technologies fall into four core application areas: landers, surface vehicles (rovers), and aerovehicles for solar system exploration and science; rovers for commercially supported lunar activities; free-flying and platform-attached robots for in-orbit servicing and assembly; and robots supporting in-orbit biotechnology and microgravity experiments. Such advanced robots will enable missions to explore Mars, Venus, and Saturn‘s moon Titan, as well as probes to sample comets and asteroids. They may also play an important role in commercially funded exploration of large regions on Earth‘s Moon, as well as the eventual development of a human-supporting Lunar Outpost. In addition, in-orbit servicing of satellites and maintenance of large platforms like the International Space Station will require extensive robotics capabilities.

A Mars sample-return mission has been proposed within NASA's Mars Exploration Program. Studying Martian samples in laboratories on Earth could address many important issues in planetary science, but arguably none is as scientifically compelling as the question of whether biosignatures indicative of past or present life exist on that planet. It is reasonable to ask before embarking on a sample-return mission whether equivalent investigation of Martian biosignatures could be conducted in situ. This study presents an approach to (1)identifying an optimal instrument suite for in situ detection of biosignatures on Mars,and (2)comparing the projected confidence level of in situ detection in a 2026 timeframe to that of Earth-based analysis. We identify a set of candidate instruments, the development of which is projected to be achievable by 2026 well within a $200 million cost cap. Assuming that any biosignatures near the surface of Mars are similar to those of terrestrial life, we find that this instrument suite, if successfully developed and deployed, would enable in situ biosignature detection at essentially the same level of confidence as that of Earth-based analysis of the same samples. At a cost cap of half that amount,the confidence level of in situbiosignature detection analysis could reach about 90% that of Earth-based investigations.

This paper summarizes salient activities within the NASA Telerobotics Program, emphasizing complete telerobotic system prototypes which have been built and tested in realistic scenarios relevant to prospective users. The paper also describes complementary developments in longer-term component technologies. >

NASA's recent attention and interest in sending a human mission to land on a Near-Earth asteroid raises the question of need for a robotic surveyor. This paper describes a Bayesian approach for comparing the productivity and cost-risk tradeoffs of sending (versus not sending) one or more robotic surveyor missions prior to a human mission to land on an asteroid. The probability of finding an asteroid suitable for landing was derived from an analysis of more than 1200 asteroids in order to define a quantitative estimate of suitability. The low cost of the surveyors relative to the human mission underlined the multi-surveyor strategy as relatively inexpensive insurance against the risks of encountering an unsuitable asteroid for landing on arrival by a human mission.

This paper reviews the evolution of NASA's planning for planetary rovers (i.e. robotic vehicles which may be deployed on planetary bodies for exploration, science analysis, and construction) and some of the technology that has been developed to achieve the desired capabilities. The program is comprised of a variety of vehicle sizes and types in order to accommodate a range of potential user needs. This includes vehicles whose weight spans a few kilograms to several thousand kilograms; whose locomotion is implemented using wheels, tracks, and legs; and whose payloads vary from microinstruments to large scale assemblies for construction. We first describe robotic vehicles, and their associated control systems, developed by NASA in the late 1980's as part of a proposed Mars Rover Sample Return (MRSR) mission. Suggested goals at that time for such an MRSR mission included navigating for one to two years across hundreds of kilometers of Martian surface; traversing a diversity of rugged, unknown terrain; collecting and analyzing a variety of samples; and bringing back selected samples to the lander for return to Earth. Subsequently, we present the current plans (considerably more modest) which have evolved both from technological 'lessons learned' in the previous period, and modified aspirations of NASA missions. This paper describes some of the demonstrated capabilities of the developed machines and the technologies which made these capabilities possible.

The productivity of scientific exploration of the Moon and Mars has been significantly improved through the mobility of roving vehicles (rovers) since these vehicles allow scientists to conduct operations well beyond the immediate vicinity of the landing area. This paper reports on a quantitative approach developed to evaluate the productivity of alternative human and robot work-system alternatives for a lunar science mission. A graph-search approach for task planning was used for assigning human and robotic work systems to scientific tasks in order to evaluate the productivity of different mobility options. The results were used to identify the benefits and costs of alternative rover combinations in order to establish guidelines for the roles of the different vehicle types. Pressurized rovers displayed advantages over unpressurized rovers due to enhanced range and duration yielding more science productivity. Multiple pressurized rovers were found to be more productive than multiple unpressurized rovers.

In a restricted science budget environment and increasingly numerous required technology developments, the technology investment decisions within NASA are objectively more and more difficult to make such that the end results are satisfying the technical objectives and all the organizational constraints. Under these conditions it is rationally desirable to build an investment portfolio, which has the highest possible technology infusion rate into flight missions. Arguably the path to infusion is subject to many influencing factors, but here only the challenges associated with the very initial stages are addressed: defining the needs and the subsequent investment decision-support process. It is conceivable that decision consistency and possibly its quality suffer when the decision-making process has limited or no traceability. This paper presents a structured decision-support framework aiming to provide traceable, auditable, infusion-driven recommendations towards a selection process in which these recommendations are used as reference points in further discussions among stakeholders. In this framework addressing well-defined requirements, different measures of success can be defined based on traceability to specific selection criteria. As a direct result, even by using simplified decision models the likelihood of infusion can be probed and consequently improved.

A series of studies is conducted to develop a systematic approach to optimizing, both in terms of the distribution and scheduling of tasks, scenarios in which astronauts and robots accomplish a group of activities on the Moon, given an objective function (OF) and specific resources and constraints. An automated planning tool is developed as a key element of this optimization system.

A study is conducted to determine the relative productivity of employing two pressurized or two unpressurized robotic rovers with two teams of astronauts to accomplish a group of activities on the Moon. An automated planning tool is used to calculate the optimal sequence of events, given an objective function and sets of assumptions and constraints. For the mission scenario studied, a pair of pressurized rovers is shown to be about 7 times as productive as a pair of unpressurized rovers when calculating benefits divided by marginal operational costs. This is primarily due to a constraint that limits astronauts to a maximum of 8 hours per day in space suits. The unpressurized rovers require the astronauts to wear space suits at all times, severely limiting the distance they can travel from the lander-habitat; the pressurized rovers permit the astronauts to remove their suits while driving, monitoring robotic activities, and resting between work periods.

The Jet Propulsion Laboratory (JPL) formulates and conducts deep space missions for NASA (the National Aeronautics and Space Administration). The chief technologist of JPL has the responsibility for strategic planning of the laboratory's advanced technology program to assure that the required technological capabilities to enable future JPL deep space missions are ready as needed; as such he is responsible for the development of a Strategic Plan. As part of the planning effort, he has supported the development of a structured approach to technology prioritization based upon the work of the START (Strategic Assessment of Risk and Technology) team. A major innovation reported here is the addition of a temporal model that supports scheduling of technology development as a function of time. The JPL Strategic Technology Plan divides the required capabilities into 13 strategic themes. The results reported here represent the analysis of an initial seven.

As part of a multi-agency effort to improve America's air transportation system, NASA has undertaken a study to develop and demonstrate a systematic method for selecting capability investments based on their projected return on investment.

The portfolio allocation problem is pervasive to all RD technology probabilities and costs at each link have been deduced and documented using information from Office of Space Science databases. These numbers are assumed to be the best estimates at present, which need to be reviewed and updated by NASA domain experts. The decision tree approach described, developed for an example long term (e.g. 2025) mission, is amenable to the introduction of time dependence if one is to consider investment strategies for nearer term endeavors, or programs comprised of time sequences of several projects.

One of the key issues in space exploration is that of deciding what space tasks are best done with humans, with robots, or a suitable combination of each. In general, human and robot skills are complementary. Humans provide as yet unmatched capabilities to perceive, think, and act when faced with anomalies and unforeseen events, but there can be huge potential risks to human safety in getting these benefits. Robots provide complementary skills in being able to work in extremely risky environments, but their ability to perceive, think, and act by themselves is currently not error-free, although these capabilities are continually improving with the emergence of new technologies. Substantial past experience validates these generally qualitative notions. However, there is a need for more rigorously systematic evaluation of human and robot roles, in order to optimize the design and performance of human-robot system architectures using well-defined performance evaluation metrics. This article summarizes a new analytical method to conduct such quantitative evaluations. While the article focuses on evaluating human-robot systems, the method is generally applicable to a much broader class of systems whose performance needs to be evaluated.

In 1985, NASA instituted a research program in Telerobotics to develop and provide the technology for applications of telerobotics to the United States Space program. The purpose of this paper is to describe the goals, organizing framework and content of that endeavor. The body of the paper reviews the actual tasks which comprise the content of the program which is now seven years old and has evolved significantly in terms of its content, goals and approach. The lessons learned in that time comprise the organizing framework of the current program. This organizing framework is also described.

Miniature robots enable low-cost planetary surface exploration missions as well as new military missions in urban terrain where small robots provide critical assistance to human operations. These space and military missions have many similar technological challenges. This article describes the technologies under development, the applications where these technologies are relevant to both space and military missions, and the status of the most recent technology demonstrations in terrestrial scenarios.

This paper presents the first results of a comprehensive application of the sensitivity theory developed for the FORSS code system to the analysis of fast reactor integral experiments. A variety of...

Calculated results have been obtained of the uncertainties in the neutron scalar flux, the energy deposition per unit volume, and the displacements per atom in the toroidal field coil of a tokamak experimental power reactor due to neutron cross-section errors in iron and carbon, which are major constituents of the blanket-shield-coil configuration considered. The calculations were carried out using perturbation theory to obtain sensitivity profiles for the various cross sections of interest, and these profiles were then combined with cross-section error estimates, including correlations, to obtain the uncertainties. Each of the three responses--the neutron scalar flux, the energy deposition per unit volume, and the displacements per atom--is found to be very sensitive to the cross sections in the energy group that contains the source (approx. 2.2 pJ) since a deuterium-tritium source is assumed, and each of the responses is found to have a relative standard deviation of approx. 100% due to neutron cross-section errors in iron.

The total 235U content of low enrichment power reactor fuel assemblies has been determined by interrogation with Li(p,n) neutrons (200 to 500 keV) produced by a Van de Graaff proton accelerator and by measurement of fission-induced delayed neutrons. To extend the application of this assay technique and to optimize its implementation, numerical calculations have been performed using a modified Monte Carlo approach. Experimental measurements from a BWR-type fuel assembly have verified the mathematical model employed. By incorporating results from both calculation and measurement, a system is being designed to assay the total 235U content of power reactor fuel elements with an overall uncertainty within 2%. Using commercially available fuel handling equipment, the analysis time for the entire element is estimated to be ∼30 min.

The reliable prediction of performance, safety and economic parameters requires a knowledge of the neutron distribution in space, energy and time from the level of a single fuel pin to that of the entire reactor. The behavior of the neutrons is formally governed by the Boltzmann equation (1,2). This equation is so complicated that there is no possibility of obtaining exact solutions, but for the most highly idealized situations. As a result, much effort has gone into developing methods and computational algorithms to approximate its solution. New and more efficient approaches are continually being developed to attack problems for which the conventional methods are not adequate or needlessly time consuming. This process is closely tied to the computer capability. If it were possible to analyze the core physics at little cost, further research in code development and design methodology would scarcely be warranted. However, this is not the present state of the art for reactor design. It is interesting to speculate about the future, and although the “1984 date” is highly optimistic, we quote Lathrop (3): “Hence, it is possible that by 1984, say, the ingenuity of methods developers combined with increased computer power may provide the final solution to multidimensional core analysis problems.”

This paper presents a methodology for a concise representation of the 3-D world model for a mobile robot, using range data. The process starts with the segmentation of the scene into "objects" that are given a unique label, based on principles of range continuity. Then the external surface of each object is partitioned into homogeneous surface patches. Contours of surface patches in 3-D space are identified by estimating the normal and curvature associated with each pixel. The resulting surface patches are then classified as planar, convex or concave. Since the world model uses a volumetric representation for the 3-D environment, planar surfaces are represented by thin volumetric polyhedra. Spherical and cylindrical surfaces are extracted and represented by appropriate volumetric primitives. All other surfaces are represented using the boolean union of spherical volumes (as described in a separate paper by the same authors). The result is a general, concise representation of the external 3-D world, which allows for efficient and robust 3-D object recognition.

A description is given of the computer code CAVALIER, which provides a simple means for estimating the uncertainties in calculated neutronics parameters that result from uncertainties in nuclear data. This code uses predetermined detailed multigroup sensitivity coefficients in SENPRO format for specific reactor and/or shielding assemblies and multigroup cross-section covariance uncertainties in COVERX format. Also described is the computer code COVERT, which converts unformatted (binary) covariance files to card image form and vice versa. This is useful for transferring covariance files from one installation to another. These two codes, along with extended compilations of sensitivity coefficients and covariance matrix libraries are currently available through the Radiation Shielding Information Center (RSIC) at Oak Ridge National Laboratory.

Calculated results are presented of the uncertainties in the neutron scalar flux, the energy deposition per unit volume, and the displacements per atom in the toroidal field coil of a tokamak experimental power reactor due to neutron cross-section errors in iron and carbon which are major constituents of the blanket-shield-coil configuration considered. The calculations were carried out using perturbation theory to obtain sensitivity profiles for the various cross sections of interest, and these profiles were then combined with cross- section error estimates, including correlations, to obtain the uncertainties. Each of the three responses--the neutron scalar flux, the energy deposition per unit volume, and the displacements per atom--is found to be very sensitive to the cross sections in the energy group which contains the source (approximately 14 MeV since a D-T source is assumed), and each of the responses is found to have a relative standard deviation of approximately 100 percent due to neutron cross- section errors in iron.