Showing papers presented at "IEEE Aerospace Conference in 2008"

Human Body Detection and Geolocalization for UAV Search and Rescue Missions Using Color and Thermal Imagery

Abstract: Recent advances in the field of Unmanned Aerial Vehicles (UAVs) make flying robots suitable platforms for carrying sensors and computer systems capable of performing advanced tasks. This paper presents a technique which allows detecting humans at a high frame rate on standard hardware onboard an autonomous UAV in a real-world outdoor environment using thermal and color imagery. Detected human positions are geolocated and a map of points of interest is built. Such a saliency map can, for example, be used to plan medical supply delivery during a disaster relief effort. The technique has been implemented and tested on-board the UAVTech1 autonomous unmanned helicopter platform as a part of a complete autonomous mission. The results of flight- tests are presented and performance and limitations of the technique are discussed.

An Integrated UAV Navigation System Based on Aerial Image Matching

Abstract: The aim of this paper is to explore the possibility of using geo-referenced satellite or aerial images to augment an Unmanned Aerial Vehicle (UAV) navigation system in case of GPS failure. A vision based navigation system which combines inertial sensors, visual odometer and registration of a UAV on-board video to a given geo-referenced aerial image has been developed and tested on real flight-test data. The experimental results show that it is possible to extract useful position information from aerial imagery even when the UAV is flying at low altitude. It is shown that such information can be used in an automated way to compensate the drift of the UAV state estimation which occurs when only inertial sensors and visual odometer are used.

Mars Science Laboratory Entry, Descent, and Landing System Overview

Abstract: In 2010, the Mars science laboratory (MSL) mission will pioneer the next generation of robotic entry, descent, and landing (EDL) systems by delivering the largest and most capable rover to date to the surface of Mars. In addition to landing more mass than prior missions to Mars, MSL will offer access to regions of Mars that have been previously unreachable. The MSL EDL sequence is a result of a more stringent requirement set than any of its predecessors. Notable among these requirements is landing a 900 kg rover in a landing ellipse much smaller than that of any previous Mars lander. In meeting these requirements, MSL is extending the limits of the EDL technologies qualified by the Mars viking, Mars pathfinder, and Mars exploration rover missions. Thus, there are many design challenges that must be solved for the mission to be successful. Several pieces of the EDL design are technological firsts, such as guided entry and precision landing on another planet, as well as the entire sky crane maneuver. This paper discusses the MSL EDL architecture and discusses some of the challenges faced in delivering an unprecedented rover payload to the surface of Mars.

Uncertainty Management for Diagnostics and Prognostics of Batteries using Bayesian Techniques

Abstract: Uncertainty management has always been the key hurdle faced by diagnostics and prognostics algorithms. A Bayesian treatment of this problem provides an elegant and theoretically sound approach to the modern Condition-Based Maintenance (CBM)/Prognostic Health Management (PHM) paradigm. The application of the Bayesian techniques to regression and classification in the form of Relevance Vector Machine (RVM), and to state estimation as in Particle Filters (PF), provides a powerful tool to integrate the diagnosis and prognosis of battery health. The RVM, which is a Bayesian treatment of the Support Vector Machine (SVM), is used for model identification, while the PF framework uses the learnt model, statistical estimates of noise and anticipated operational conditions to provide estimates of remaining useful life (RUL) in the form of a probability density function (PDF). This type of prognostics generates a significant value addition to the management of any operation involving electrical systems.

Overview of Terrain Relative Navigation Approaches for Precise Lunar Landing

Abstract: The driving precision landing requirement for the Autonomous Landing and Hazard Avoidance Technology project is to autonomously land within 100 m of a predetermined location on the lunar surface. Traditional lunar landing approaches based on inertial sensing do not have the navigational precision to meet this requirement. The purpose of Terrain Relative Navigation (TRN) is to augment inertial navigation by providing position or bearing measurements relative to known surface landmarks. From these measurements, the navigational precision can be reduced to a level that meets the 100 m requirement. There are three different TRN functions: global position estimation, local position estimation and velocity estimation. These functions can be achieved with active range sensing or passive imaging. This paper gives a survey of many TRN approaches and then presents some high fidelity simulation results for contour matching and area correlation approaches to TRN using active sensors. Since TRN requires an a-priori reference map, the paper concludes by describing past and future lunar imaging and digital elevation map data sets available for this purpose.

Persistent Surveillance Using Multiple Unmanned Air Vehicles

Abstract: Search and exploration using multiple autonomous sensing platforms has been extensively studied in the fields of controls and artificial intelligence. The task of persistent surveillance is different from a coverage or exploration problem, in that the target area needs to be continuously searched, minimizing the time between visitations to the same region. This difference does not allow a straightforward application of most exploration techniques to the problem, although ideas from these methods can still be used. In this research we investigate techniques that are scalable, reliable, efficient, and robust to problem dynamics. These are tested in a multiple unmanned air vehicle (UAV) simulation environment, developed for this program. A semi-heuristic control policy for a single UAV is extended to the case of multiple UAVs using two methods. One is an extension of a reactive policy for a single UAV and the other involves allocation of sub-regions to individual UAVs for parallel exploration. An optimal assignment procedure (based on auction algorithms) has also been developed for this purpose. A comparison is made between the two approaches and a simplified optimal result. The reactive policy is found to exhibit an interesting emergent behavior as the number of UAVs becomes large. The control policy derived for a single UAV is modified to account for actual aircraft dynamics (a 3 degree-of-freedom nonlinear dynamics simulation is used for this purpose) and improvements in performance are observed. Finally, we draw conclusions about the utility and efficiency of these techniques.

The CubeSat Approach to Space Access

Abstract: As advances in technology make payloads and instruments for space missions smaller, lighter, and more power efficient, a niche market is emerging from the university community to perform rapidly developed, low-cost missions on very small spacecraft - micro, nano, and picosatellites. Among this class of spacecraft, are CubeSats, with a basic form of 10 times 10 times 10 cm, weighing a maximum of 1kg. In order to serve as viable alternative to larger spacecraft, small satellite platforms must provide the end user with access to space and similar functionality to mainstream missions. However, despite recent advances, small satellites have not been able to reach their full potential. Without launch vehicles dedicated to launching small satellites as primary payloads, launch opportunities only exist in the form of co-manifest or secondary payload missions, with launches often subsidized by the government. In addition, power, size, and mass constraints create additional hurdles for small satellites. To date, the primary method of increasing a small satellite's capability has been focused on miniaturization of technology. The CubeSat Program embraces this approach, but has also focused on developing an infrastructure to offset unavoidable limitations caused by the constraints of small satellite missions. The main components of this infrastructure are: an extensive developer community, standards for spacecraft and launch vehicle interfaces, and a network of ground stations. This paper will focus on the CubeSat Program, its history, and the philosophy behind the various elements that make it a practical an enabling alternative for access to space.

The CloudSat Mission and the A-Train: A Revolutionary Approach to Observing Earth's Atmosphere

Abstract: On April 28, 2006 a millimeter radar system, designed expressly for the vertical profiling of hydrometeors, was launched from Vandenburg Air Force Base. Both Cloudsat, carrying the cloud profiling radar (CPR), and the lidar satellite CALIPSO, were inserted into nearly identical orbits each approximately one minute behind the NASA Earth Observing System (EOS) Aqua satellite and in formation with the French PARASOL satellite and the EOS Aura satellite. This creates the A- Train satellite constellation. The early results of the CloudSat mission underscore the value of synergy of the A- Train observations for studying clouds and precipitation.

Autonomous Landing and Hazard Avoidance Technology (ALHAT)

Abstract: The ALHAT project is funded by NASA to develop an integrated AGNC (autonomous guidance, navigation and control) hardware and software system capable of detecting and avoiding surface hazards and guiding humans and cargo safely, precisely and repeatedly to designated lunar landing sites. There are important interdependencies driving the design of a lunar landing system including such things as lander hazard robustness, landing site conditions (terrain and natural lighting), trajectories, sensors, crew involvement, and others. The ALHAT system must be capable of operating in a wide range of lunar environments and supporting global lunar access for both crewed and robotic missions. This paper discusses the major factors driving the design of a lunar landing system as well as the current state of the technology development. The supporting analysis and testing results will be presented that show the system interdependencies and their relative importance, as well as the trades needed to optimize the landing system. The emphasis is on the final phase of the landing where hazard detection and avoidance (HDA) and hazard relative navigation (HRN) are the primary considerations in achieving a safe landing. The current sensor options being considered and the status of the development of those sensors are discussed.

Fault Tolerant ICAP Controller for High-Reliable Internal Scrubbing

Abstract: High reliable reconfigurable applications today require system platforms that can easily and quickly detect and correct single event upsets. This capability, however, can be costly for FPGAs. This paper demonstrates a technique for detecting and repairing SEUs within the configuration memory of a Xilinx Virtex-4 FPGA using the ICAP interface. The internal configuration access port (ICAP) provides a port internal to the FPGA for configuring the FPGA device. An application note demonstrates how this port can be used for both error injection and scrubbing (L. Jones, 2007). We have extended this work to create a fault tolerant ICAP scrubber by triplicating the internal ICAP circuit using TMR and block memory scrubbing. This paper will describe the costs, benefits, and reliability of this fault-tolerant ICAP controller.

Overview of the MEDLI Project

Abstract: The Mars Science Laboratory Entry, Descent, and Landing Instrumentation (MEDLI) Project's objectives are to measure aerothermal environments, sub-surface heatshield material response, vehicle orientation, and atmospheric density for the atmospheric entry and descent phases of the Mars Science Laboratory (MSL) entry vehicle. The flight science objectives of MEDLI directly address the largest uncertainties in the ability to design and validate a robust Mars entry system, including aerothermal, aerodynamic and atmosphere models, and thermal protection system (TPS) design. The instrumentation suite will be installed in the heatshield of the MSL entry vehicle. The acquired data will support future Mars entry and aerocapture missions by providing measured atmospheric data to validate Mars atmosphere models and clarify the design margins for future Mars missions. MEDLI thermocouple and recession sensor data will significantly improve the understanding of aeroheating and TPS performance uncertainties for future missions. MEDLI pressure data will permit more accurate trajectory reconstruction, as well as separation of aerodynamic and atmospheric uncertainties in the hypersonic and supersonic regimes. This paper provides an overview of the project including the instrumentation design, system architecture, and expected measurement response.

Runtime FPGA Partial Reconfiguration

Abstract: Field-programmable gate arrays (FPGAs) are now being integrated into many space-based applications. FPGAs are being used as replacements for application-specific integrated circuits (ASICs) without considering new options offered by their reprogrammable nature. Runtime partial reconfiguration can potentially reduce the number of devices or the device size, thereby reducing both size and power consumption. A system that requires either transmit or receive capabilities at any given time, but not both, can switch between the two modes in a fraction of a second using partial reconfiguration. The current approach requires that both modes be implemented simultaneously, thereby wasting power and requiring more resources. The idea of adaptively allocating limited FPGA resources is also applicable to hardware-accelerated software-defined radios. The hardware accelerators are loaded into FPGA(s) as they are needed. Partial reconfiguration allows swapping of accelerators much faster than is possible with current methods, and with less disruption to other processes running in parallel. This technology significantly reduces power consumption critical for space and portable ground-based applications of FPGA technology. A software-defined radio was designed with a reprogrammable forward error correction (FEC) block supporting multiple FEC codes to demonstrate one practical use of this technology. This paper provides an overview of the design flow necessary for partial reconfiguration and comments on the additional overhead necessary for creating such a design. In addition, limitations to this emerging technology are outlined.

Analysis of On-Board Hazard Detection and Avoidance for Safe Lunar Landing

Abstract: Landing hazard detection and avoidance technology is being pursued within NASA to improve landing safety and increase access to sites of interest on the lunar surface. The performance of a hazard detection and avoidance system depends on properties of the terrain, sensor performance, algorithm design, vehicle characteristics and the overall all guidance navigation and control architecture. This paper analyzes the size of the region that must be imaged, sensor performance parameters and the impact of trajectory angle on hazard detection performance. The analysis shows that vehicle hazard tolerance is the driving parameter for hazard detection system design.

Cognitive Radio: From Spectrum Sharing to Adaptive Learning and Reconfiguration

Abstract: This paper introduces important cognitive radio developments like spectrum sharing, learning and adaptation algorithms, and the software and hardware architecture to support these functions. A cognitive radio is defined here as a transceiver that is aware of its environment and can combine this awareness with knowledge of its user's priorities, needs, operational procedures, and governing regulatory rules. It adapts to its environment and configures itself in an appropriate fashion. The radio learns through experience and is capable of generating solutions for communications problems unforeseen by its designers. Our spectrum sharing cognitive radio is built upon GNU radio and uses the universal software radio peripheral (USRP) device as our radio front end platform. We use cyclostationary feature analysis to detect low SNR modulated signals because of its ability to distinguish between modulated signals, interference, and noise in low signal to noise ratios. A parallel algorithm running on a cell broadband engine (Cell BE) is used to attack the associated high computational complexity. A new spectrum sensing scheme, incorporating spectrum monitoring, data transmission, and dynamic channel switching, is designed to fully utilize the idle time of the primary user. Our work is based on the concept of a cognitive engine: an intelligent software package that "reads the meters" and "turns the knobs" of any attached software defined radio (SDR) platform. Using an eclectic combination of artificial intelligence techniques including case-based decision theory, multi-objective genetic algorithms, and neural networks, it implements a system of nested cognition loops. Applied to public safety communications, this technology is the basis of a working prototype Public Safety Cognitive Radio that can scan the public safety spectrum (multiple bands and multiple waveforms, all incompatible) and configure itself to interoperate with any public safety waveform that it finds within 0.1 seconds of determining that a signal is present.

A Game Theoretic Data Fusion Aided Path Planning Approach for Cooperative UAV ISR

Abstract: Cooperative and intelligent path planning is important for UAVs to carry out coordinated intelligence, surveillance and reconnaissance (ISR) in adversarial environments. In this paper, we propose a game theoretic data fusion aided platform routing algorithm for cooperative ISR. Our approach consists of three closely coupled components: 1) closed-loop data fusion. The Level 1 (Object), Level 2 (Situation) and Level 3 (threat) data fusion form a closed-loop structure, in which Markov game theoretic intent inferences will execute from the results of Level 1 and Level 2 results. The estimated threat intents will be fed back to the Level 2 fusion to improve the performance of the entity aggregation. 2) Cooperative platform routing based on Pareto-optimization, social foraging, and cooperative jamming. Given the threat information including the threat intents from the data fusion module, a Pareto-optimal problem is formed and graph-cut based fast solution serves as a reference trajectory for a foraging algorithm, which further dynamically refines the reference path to avoid pop-up obstacles detected along the planned path. 3) display/monitor module, in which relevant threats and constraints information are indicated, the terrain data are shown, and current real route and planned route are highlighted, compared, and evaluated. The commander's suggestions can be inputted in this mode.

Survival Analysis Approach to Reliability, Survivability and Prognostics and Health Management (PHM)

Abstract: Survival analysis, also known as failure time analysis or time-to-event analysis, is one of the most significant advancements of mathematical statistics in the last quarter of the 20th century. It has become the de facto standard in biomedical data analysis. Although reliability was conceived as a major application field by the mathematicians who pioneered survival analysis, survival analysis failed to establish itself as a major tool for reliability analysis. In this paper, we attempt to demonstrate, by reviewing and comparing the major mathematical models of both fields, that survival analysis and reliability theory essentially address the same mathematical problems. Therefore, survival analysis should become a major mathematical tool for reliability analysis and related fields such as Prognostics and Health Management (PHM). This paper is the first in a four part series in which we review state-of-the-art studies in survival (univariate) analysis, competing risks analysis, and multivariate survival analysis, with focusing on their applications to reliability and computer science. The present article discusses the univariate survival analysis (survival analysis hereafter).

Orbital Express Advanced Video Guidance Sensor

Abstract: In May 2007 the first US-sponsored fully autonomous rendezvous and capture was successfully performed by DARPA's Orbital Express (OE) mission. For the following three months, the Boeing ASTRO spacecraft and the Ball Aerospace NEXTSat performed multiple rendezvous and docking maneuvers to demonstrate some of the technologies needed for satellite servicing. MSFC's advanced video guidance sensor (AVGS) was a near-field proximity operations sensor integrated into ASTRO's Autonomous Rendezvous and Capture Sensor System (ARCSS), which provided relative state knowledge to the ASTRO GN&C system. AVGS was one of the primary docking sensors included in ARCSS. This paper provides an overview of the AVGS sensor that flew on orbital express, a summary of the AVGS ground testing, and a discussion of AVGS performance on-orbit for OE. The AVGS is a laser-based system that is capable of providing bearing at midrange distances and full six degree- of-freedom (6-DOF) knowledge at near ranges. The sensor fires lasers of two different wavelengths to illuminate retro- reflectors on the long range target (LRT) and the Short Range Target (SRT) mounted on NEXTSat. The retro- reflector filters allow one laser wavelength to pass through and be reflected, while blocking the other wavelength. Subtraction of one return image from the other image removes extraneous light sources and reflections from anything other than the corner cubes on the LRT and SRT. The very bright spots that remain in the subtracted image are processed to provide bearing or 6-DOF relative state information. AVGS was operational during the Orbital Express unmated scenarios and the sensor checkout operations. The OE unmated scenarios ranged from 10 meters to 7 kilometers ending in either a docking or a free-flyer capture. When the target was pointed toward the AVGS and in the AVGS operating range and field-of-view (i.e. along the approach corridor of the NEXTSat), the AVGS provided full 6-DOF measurements. The AVGS performed very well during the sensor check-out operations, effectively tracking beyond its 10-degree Pitch and Yaw limit-specifications. AVGS also provided excellent performance during the unmated operations, effectively tracking its targets, and showing good agreement between the SRT and LRT data. The AVGS consistently exceeded the tracking range expectations for both the SRT and LRT. During the approach to re-mate in scenario 3-1 recovery the AVGS began tracking the LRT at 150 m, well beyond the OE specified operational range of 120 meters, and functioned as the primary sensor for the autonomous rendezvous and docking. For all scenarios, the AVGS was used while ASTRO was in the approach corridor to NEXTSat, and during close proximity operations and docking.

Using Duplication with Compare for On-line Error Detection in FPGA-based Designs

Abstract: It is well known that SRAM-based FPGAs are susceptible to single-event upsets (SEUs) in radiation environments. A variety of mitigation strategies have been demonstrated to provide appropriate mitigation and correction of SEUs in these environments. While full mitigation of SEUs is appropriate for some situations, some systems may tolerate SEUs as long as these upsets are detected quickly and correctly. These systems require effective error detection techniques rather than costly error correction methods. This work leverages a well-known error detection technique for FPGAs called duplication with compare (DWC). This technique has been shown to be very effective at quickly and accurately detecting SEUs using fault injection and radiation testing.

Ultra Low Voltage Level Shifters to Interface Sub and Super Threshold Reconfigurable Logic Cells

Abstract: Ultra-low power consumption often comes at the price of reduced performance for energy conscious electronics - particularly reconfigurable circuits. Operating devices at ultra-low voltage levels provides the lowest energy per operation, but can penalize the frequency of operation by several orders of magnitude. A more optimized approach is to segregate the logic based on performance requirements and use multiple voltage levels to supply separate voltage islands in an integrated circuit. The concept can be extended such that the low performance circuits can be supplied with a voltage below the threshold voltage of the transistor (i.e. subthreshold logic), however no analysis has been completed to date with regards to the performance and operation of the level shifters required for communication between voltage islands of such disparate levels. This paper compares a variety of existing level shifters as well as several proposed level shifters in the context of up-converting subthreshold signals to superthreshold levels.

Micro Unmanned Aerial Vehicle Visual Servoing for Cooperative Indoor Exploration

Abstract: Recent advances in the field of micro unmanned aerial vehicles (MAVs) make flying robots of small dimensions suitable platforms for performing advanced indoor missions. In order to achieve autonomous indoor flight a pose estimation technique is necessary. This paper presents a complete system which incorporates a vision-based pose estimation method to allow a MAV to navigate in indoor environments in cooperation with a ground robot. The pose estimation technique uses a lightweight light emitting diode (LED) cube structure as a pattern attached to a MAV. The pattern is observed by a ground robot's camera which provides the flying robot with the estimate of its pose. The system is not confined to a single location and allows for cooperative exploration of unknown environments. It is suitable for performing missions of a search and rescue nature where a MAV extends the range of sensors of the ground robot. The performance of the pose estimation technique and the complete system is presented and experimental flights of a vertical take-off and landing (VTOL) MAV are described.

Bayesian Extreme Value Statistics for Novelty Detection in Gas-Turbine Engines

Abstract: We present a novel method for the identification of abnormal episodes in gas-turbine vibration data, in which we show 1) how a model of normal engine behaviour is constructed using signatures of "normal" engine vibration response; 2) how extreme value theory (EVT), a branch of statistics used to determine the expected value of extreme values drawn from a distribution, can be used to set novelty thresholds in the model, which, if exceeded, indicate an "abnormal" episode; 3) application to large data sets of modern gas-turbine flight data, which shows successful novelty detection results with low false-positive alarm rates. The advantages of this approach over previous work are 1) a very low false-positive alarm rate, while maintaining sufficient sensitivity to detect known abnormal events; 2) the use of a Bayesian framework such that uncertainty in the distribution of "normal" data is modelled, giving a principled, probabilistic interpretation of results; 3) an implementation that is sufficiently "lightweight" in processing and memory resources that real-time, on-line novelty detection is possible in an "on-wing" engine health-monitoring system.

Models and Algorithms for Detection and Tracking of Coordinated Groups

Abstract: In this paper, we describe models and algorithms for detection and tracking of group and individual targets We develop two novel group dynamical models, within a continuous time setting, that aim to mimic behavioural properties of groups We also describe two possible ways of modeling interactions between closely spaced targets using Markov Random Field (MRF) and repulsive forces These can be combined together with a group structure transition model to create realistic evolving group models We use a Markov Chain Monte Carlo (MCMC)-Particles Algorithm to perform sequential inference Computer simulations demonstrate the ability of the algorithm to detect and track targets within groups, as well as infer the correct group structure over time

Robot Mobility Concepts for Extraterrestrial Surface Exploration

Abstract: Future space missions are directed to robotic precursor missions to nearby celestial objects. Various science experiments are meant to be performed by autonomous robotic vehicles including detection of widely speculated polar-ice in lunar craters and detect signs of past life on Mars. The locomotion subsystem plays a key role in moving a robot on a surface with high performance capabilities, irrespective of the nature of the terrain. Locomotion on extraterrestrial surfaces can be achieved by a wheeled rover, tracked rover, legged walker or a hybrid vehicle. The first three modes can be classified based on the number of wheels, tracks, or legs the robot possesses. Hybrids can be either a wheeled-leg or a legged-track combination. A survey of different locomotion concepts available for lunar, planetary, and other space exploration missions has been performed and discussed. Choosing the right locomotion mode is a difficult task for a particular mission with each having its own pros and cons. Therefore, a comparative assessment of the various modes which could be used as a quick reference tool is also provided.

Development of a Satellite Sensor Network for Future Space Missions

Abstract: Future spacecraft are envisioned as autonomous, miniature, intelligent and massively distributed systems. At the Surrey Space Centre, a research project is currently under investigation, which aims to develop a picosatellite sensor network using the CubeSat platform. The proposed satellite sensor network will be used to demonstrate technology advances in space, including modified IEEE 802.11 wireless standard for inter-satellite links (ISL), distributed computing for computationally intensive onboard signal processing, and reconfigurable system-on-a-chip (SoC) design.

A Software Safety Certification Tool for Automatically Generated Guidance, Navigation and Control Code

Abstract: Model-based' design and automated code generation are being used increasingly at NASA. Many NASA projects now use MathWorks Simulink and Real- Time Workshop for at least some of their modeling and code development. The trend is to move beyond simulation and prototyping to actual flight code, particularly in the Guidance, Navigation, and Control domain. However, there are substantial obstacles to more widespread adoption of code generators in such safety-critical domains. Since code generators are typically not qualified, there is no guarantee that their output is correct, and consequently the generated code still needs to be fully tested and certified. Moreover, the regeneration of code can require complete recertification, which offsets many of the advantages of using a generator. Indeed, manual review of autocode can be more challenging than for hand-written code. Since the direct V&V of code generators is too laborious and complicated due to their complex (and often proprietary) nature, we have developed a generator plug-in to support the subsequent certification of the code that is generated. Specifically, the AutoCert tool supports certification by formally verifying that the generated code is free of different safety violations, by constructing an independently verifiable certificate, and by explaining its analysis in a textual form suitable for code reviews. This enables missions to obtain assurance about the safety and reliability of the code without excessive manual V&V effort and, as a consequence, increases the acceptance of code generators in safety-critical contexts. The generation of explicit certificates and textual reports is particularly well-suited to supporting independent V&V. The key technical idea of our approach is to exploit the idiomatic nature of auto-generated code in order to automatically infer logical annotations. These allow the automatic formal verification of the safety properties without requiring access to the internals of the code generator. The approach is independent of the particular generator used but is currently being adapted to code generated using MathWorks Real-Time Workshop, an automatic code generator that translates from Simulink/Stateflow models into embedded C code.

System Health Monitoring for Space Mission Operations

Abstract: Many spacecraft provide an abundance of system status telemetry that is monitored in real time by ground personnel and archived to allow for further analysis. In the flight control room, controllers typically monitor these values using text or graphical displays that incorporate individual parameter limit checking or simple trend analysis. Recent developments in data mining techniques for anomaly detection make it possible to use the wealth of archived system data to produce more sophisticated system health monitoring applications. These "data driven" applications are capable of characterizing and monitoring interactions between multiple parameters and can complement existing practice to provide valuable decision support for mission controllers. Data driven software tools have been successfully applied to mission operations for both the Space Shuttle and the International Space Station. These tools have been applied to engineering analysis of spacecraft data to detect unusual events in the data, and to real-time system health monitoring in the flight control room. Augmenting traditional mission control software with advanced monitoring tools can provide controllers with greater insight into the health and performance of the space systems under their watch. Adding heuristic rule based methods that encode system knowledge obtained from seasoned mission controllers can also be helpful to less experienced personnel. We will describe how such techniques have been applied to NASA mission control operations and discuss plans for future mission control system health monitoring software systems.

Next Generation Rover for Lunar Exploration

Abstract: As NASA refines its plans for the return of humans to the lunar surface, it becomes very clear that surface mobility will be critical to outpost buildup and exploration activities. NASA's Exploration Technology Development Program is investing in a broad range of surface mobility projects. Within this range of projects falls a rover vehicle, capable of moving suited crew members and cargo. A prototype, known as Chariot has been developed. This prototype vehicle is a multipurpose, reconfigurable, modular lunar surface vehicle. And, with the right attachments and/or crew accommodations, Chariot will be capable of serving a large number of functions.

Application of a Safety-Driven Design Methodology to an Outer Planet Exploration Mission

Abstract: Traditional requirements specification and hazard analysis techniques have not kept pace with the increasing complexity and constraints of modern space systems development. These techniques are incomplete and often consider safety late in the development cycle when the most significant design decisions have already been made. The lack of an integrated approach to perform safety-driven system development from the beginning of the system lifecycle hinders the ability to create safe space systems on time and within budget. To address this need, the authors have created an integrated methodology for safety-driven system development that combines four state-of-the-art techniques: 1) intent specification, a framework for organizing system development and operational information in a hierarchical structure; 2) the STAMP model of accident causation, a system-theoretic framework upon which to base more powerful safety engineering techniques; 3) STAMP-based hazard analysis (STPA); and 4) state analysis, a model-based systems engineering approach. The iterative approach specified in the methodology employs state analysis in the modeling of system behavior. STPA is used to identify system hazards and the constraints that must be enforced to mitigate these hazards. Finally, intent specification is used to document traceability of behavioral requirements and subject them to formal analysis using the SpecTRM-RL software package. In this paper, the application of this methodology is demonstrated through the specification of a spacecraft high gain antenna pointing mechanism for a hypothetical outer planet exploration mission.

Cost-Benefit Analysis Methodology for PHM Applied to Legacy Commercial Aircraft

Abstract: This paper presents a methodology to perform cost-benefit analysis on the application of prognostics and health management (PHM) for existing (legacy) commercial aircraft. The methodology takes into account the characteristics of the commercial aircraft operation business to yield estimates of the economic feasibility of the application of the technology to these platforms. Included among such characteristics, are the strong focus on the improvement of aircraft dispatch reliability and reduction of maintenance costs, the lack of provisions for PHM systems on legacy aircraft and the availability of maintenance and operational field data. The PHM benefits range from improved troubleshooting, passing through condition-based maintenance scheduling, to the optimization of the logistic supply chain. The formulation accounts for costs, from development to implementation, and risks intrinsic to such technologies. Means to quantify each benefit and each cost are outlined. In most cases, this quantification depends on specific details of the aircraft or internal processes of the aircraft operator. The paper presents guidelines to develop such calculations and the tools that may be used to analyze the results. The final product of the methodology is a cost- benefit model which provides insight to the aircraft original equipment manufacturer (OEM) and to the aircraft operator on how PHM technologies should be applied in order to maximize their bottom lines.

MIMO Phased-Array for SMTI Radar

Abstract: Waveform diversity techniques for radar have gained considerable interest over the past several years. Novel radar waveforms have been proposed to improve detection performance and metric accuracy (i.e., angle estimation performance). This paper explores the potential for using a waveform diversity technique known as multiple input, multiple output (MIMO) radar to improve the detection performance of slow moving surface targets from a moving radar platform. The MIMO radar system achieves superior performance by transmitting unique uncorrelated waveforms from each antenna subaperture as opposed to the traditional approach of transmitting a single coherent waveform across the entire aperture. The results show that the radar system minimum detectable velocity (MDV) can be reduced by exploiting the ability of a MIMO system to effectively increase the radar antenna aperture.