Richard Alena

Automating CapCom Using Mobile Agents and Robotic Assistants

Mobile Agents (MA) is an advanced Extra-Vehicular Activity (EVA) communications and computing system to increase astronaut self-reliance and safety, reducing dependence on continuous monitoring and advising from mission control on Earth. MA is voice controlled and provides information verbally to the astronauts through programs called “personal agents.” The system partly automates the role of CapCom in Apollo-including monitoring and managing navigation, scheduling, equipment deployment, telemetry, health tracking, and scientific data collection. Data are stored automatically in a shared database in the habitat/vehicle and mirrored to a site accessible by a remote science team. The program has been developed iteratively in authentic work contexts, including six years of ethnographic observation of field geology. Analog field experiments in Utah enabled empirically discovering requirements and testing alternative technologies and protocols. We report on the 2004 system configuration, experiments, and results, in which an EVA robotic assistant (ERA) followed geologists approximately 150 m through a winding, narrow canyon. On voice command, the ERA took photographs and panoramas and was directed to serve as a relay on the wireless network.

Fault tolerance in ZigBee wireless sensor networks

Wireless sensor networks (WSN) based on the IEEE 802.15.4 Personal Area Network standard are finding increasing use in the home automation and emerging smart energy markets. The network and application layers, based on the ZigBee 2007 PRO Standard, provide a convenient framework for component-based software that supports customer solutions from multiple vendors. This technology is supported by System-on-a-Chip solutions, resulting in extremely small and low-power nodes. The Wireless Connections in Space Project addresses the aerospace flight domain for both flight-critical and non-critical avionics. WSNs provide the inherent fault tolerance required for aerospace applications utilizing such technology. The team from Ames Research Center has developed techniques for assessing the fault tolerance of ZigBee WSNs challenged by radio frequency (RF) interference or WSN node failure.12

Communication system architecture for planetary exploration

Future human missions to Mars will require effective communications supporting exploration activities and scientific field data collection. Constraints on cost, size, weight and power consumption for all communications equipment make optimization of these systems very important. These information and communication systems connect people and systems together into coherent teams performing the difficult and hazardous tasks inherent in planetary exploration. The communication network supporting vehicle telemetry data, mission operations, and scientific collaboration must have excellent reliability and flexibility. We propose hybrid communication architectures consisting of space-based links, a surface-based deployable mid-range communications network and a cluster of short-range links to solve the problems of connectivity and bandwidth, while meeting the other constraints of weight and power. A network of orbiting satellites could cover much of the planet surface, but this space-based capability may not be optimal for cost or performance. Specifically, a minimal space-based capability can be augmented using mobile cellular repeaters deployable by robots and human EVA. This method results in an increase in the number of radio nodes, but the distances separating them is decreased. This results in a significant increase in bandwidth and decrease in radio power and therefore node size, complexity and power consumption. The paper discusses the results of field-testing such hybrid radio systems for the support of scientific surveys. System analysis of design tradeoffs will yield insight into optimal solutions that will be compared to other approaches providing a method of effectively evaluating new candidate architectures.

Heterogeneous Spacecraft Networks: Performance analysis for low-cost Earth Observation missions

Heterogeneous Spacecraft Networks (HSNs) are network environments in which spacecraft from different missions and institutions can communicate with each other at low cost and with low impact on overall system resources. The Mission Design Center (MDC) at NASA Ames Research Center has been studying solutions for low cost multi-spacecraft systems for a number of years. One may now build on the idea to interconnect clusters of spacecraft with each other to have them act as mobile nodes belonging to the same collaborative mission. Recent progress in small satellite technology is significant, and one of the advantages of small satellites lies precisely in the large quantity of spacecraft that can be produced at accessible costs. It follows naturally that small satellites are an interesting candidate platform for development and demonstration of the HSN concept. This paper is the second in a series of three companion papers. The general concept of operations for HSNs in LEO and a number of future applications are proposed in the first paper [6], while enabling technology such as devices and lower layer protocols are discussed in paper three [7]. In this paper, we pick up the scenario of a low-cost and multi-institutional network of Earth Observation (EO) missions in LEO and conduct network performance analysis using the AGI System Tool Kit (STK) and the open-source Network Simulator (NS-3). A multi-spacecraft network consolidates the individual capabilities of each spacecraft from different institutions by combining benefits of both frequent revisit and concentrated observation. Complementary and correlated data could be collected simultaneously from a large set of distributed spacecraft utilizing HSN capability. In this specific configuration, communication distance between spacecraft, related delays and error rate are the major factors in network performance. Also, average duration of communication opportunities between spacecraft is usually very limited. Thus, it is important to simulate orbital dynamics, link margins, and protocols simultaneously to analyze network performances. In this paper, we compare some existing protocols to obtain a measure for the practical performance of the candidate network. We focus on best-effort data delivery, an approach necessitated by the severe constraints on communications resulting from low-cost and low system resource small spacecraft. In the application layer, we show that packet size and data rate of a source node also affect overall performance of the network. We present the resulting figures of merit from our simulations. The paper concludes with a summary of the simulation results.

A viable COTS based wireless architecture for spacecraft avionics

Wireless communications has more to offer for spacecraft avionics than just reduced mass and space. A team at NASA Ames Research Center (ARC) is actively involved in designing and implementing wireless systems, and is part of a multi-center NASA effort to investigate wireless sensor networks (WSN) for spacecraft sponsored by the NASA Engineering and Safety Center. In this paper, we describe an implementation of ZigBee run over an IEEE 802.16.2 network architecture, and explain how this topology can be adapted to meet the rigorous challenges presented by the space environment. We present current ZigBee applications and deployments and compare ZigBee with some competing network architectures. We also present some of the wireless sensor network research and development that has been accomplished at ARC and discuss future plans. Our results show that ZigBee can meet requirements and provide the opportunity to develop a smart spacecraft infrastructure modeled on the “smart home” vision, and outline some steps that might be taken to bring this model to reality.

Wireless Space Plug-and-Play Architecture (SPA-Z)

Space Plug-and-Play Architecture (SPA), defined by the Air Force Research Laboratory, is a new standard for spacecraft component interconnections (AIAA-S-133-x-2013) providing new capability for managing intelligent components. Wireless Sensor Networks (WSN) based on the IEEE 802.15.4 Personal Area Network standard are finding increasing use in the home automation and emerging smart energy markets. The network protocol and application layers can be based on the ZigBee standard as defined by the ZigBee Alliance, providing a framework for component-based software that supports solutions from multiple vendors. SPA and ZigBee create selfconfiguring ad-hoc networks, but differ in their approach. SPA focuses on self-configuring components using wired interconnects while ZigBee forms self-configuring wireless networks. The optimal combination of SPA with ZigBee technology can bring the advantages of both methods to next-generation spacecraft by using self-configuring wireless networks for data and intelligent components with universal SPA-compliant interfaces. Mesh-enabled WSNs provide inherent fault tolerance and SPA provides dynamic fault management leading to low-power, low-cost ancillary sensing solutions for spacecraft. Self-configuring architectures are the key for supporting a large number of sensors in dynamic configurations, allowing intelligent response for fault tolerant networks. Plug-and-Play for sensor networks could be defined as the capability for application software to query any sensor module connected to the ad-hoc dynamic network using module resident information defining the sensors characteristics. The embedding of sensor information into each Wireless Sensor Module (WSM) allows identifying each sensor unambiguously and accurately in terms of function and status, without the use of any configuration database. The IEEE 1451 Smart Transducer Interface Standard defines Transducer Electronic Datasheets (TEDS) containing key information regarding sensor characteristics such as name, description, serial number and calibration information. SPA defines an extensible format called xTEDS using XML embedded meta-information for sensor management enabling software to identify the sensor and interpret the sensor data stream without reference to any external information. The application software is able to read the status of each sensor module, responding in real-time to changes of WSN configuration and provide the appropriate response for maintaining overall sensor system function, even when sensor modules fail or the network is reconfigured. Temporal integrity of sensor data delivery is ensured by the use of a global network clock and embedding timestamps into each measurement result accurate to one millisecond. SPA provides high-level mechanisms for self-configuration and integration with other spacecraft components and can significantly improve interoperability. The architecture and technical feasibility for creating wireless fault-tolerant sensor networks is presented through integration of SPA, IEEE 1451 and ZigBee into the proposed SPA-Z architecture. SPA provides the broad framework, the IEEE 1451 standards provide templates for TEDS and sensor management and ZigBee provides effective wireless network management. The approach is to tailor these multiple standards into a viable architecture. The result conforms to multiple standards, enables deterministic response and provides a capable publish/subscribe interface to application software. Our proposed software architecture for intelligent sensor management using the SPA standard will be discussed in the context of the specific tradeoffs required for effective use. Two examples are presented, the first highlights SPA-Z advantages for reconfigurable payloads and the second describes the development of a SPA compliant WSN.

An executable choreography framework for dynamic service-oriented architectures

Interoperability and loose coupling requirements are pushing the next generation of distributed applications towards more decentralized and more dynamic interaction schemes, which the classic request/response communication paradigm can hardly accommodate. Hence, sound foundations and mechanisms for the establishment of unanticipated peer-to-peer interactions across organizational boundaries are of significant importance to upcoming middleware platforms. The executable choreography framework (ECF) is a middleware-level framework that targets dynamic and decentralized service compositions. The ECF combines transparent context propagation with aspect-oriented software composition techniques to dynamically refine the default control and data flow of service invocations. The framework provides a ground for experimentation with dynamic and distributed workflows, and a base to assess their safety and applicability when deployed across organizational boundaries

Migrating Fault Trees To Decision Trees For Real Time Fault Detection On International Space Station

Fault Tree Analysis shows the possible causes of a system malfunction by enumerating the suspect components and their respective failure modes that may have induced the problem. Complex systems often use fault trees to analyze the faults. Fault diagnosis, when error occurs, is performed by engineers and analysts performing extensive examination of all data gathered during the mission. International Space Station (ISS) control center operates on the data feedback from the system and decisions are made based on threshold values by using fault trees. Since those decision-making tasks are safety critical and must be done promptly, the engineers who manually analyze the data are facing time challenge. To automate this process, this paper present an approach that uses decision trees to capture the contents of fault trees and detect faults by running the telemetry data through the decision trees in real time. Decision trees (also called classification trees) are the binary trees built from data samples and can classify the objects into different classes. In our case, the decision trees can classify different fault events or normal events. Given a set of data samples, decision trees can be built and trained, and then by running the new data through the trees, classification and prediction can be made. In this way, diagnostic knowledge for fault detection and isolation can be represented as diagnostic rules; we call this tree the diagnostic decision tree (DDT). By showing the fault path in decision trees, we also can point out the root cause when a fault occurs. Since all the procedures and algorithms are available to build decision trees, the trees built are cost effective and time effective. Because the diagnostic decision trees are based on available data and previous knowledge of subsystem logic, the DDT can also be trained to predict faults and detect unknown faults. Based on this, the needs for on-board real time diagnostics can readily be met. Diagnostic Decision Trees are built based on the fault trees as static trees that serve as the fundamental diagnostic trees, and the dynamic DDTs are built over time from vehicle telemetry data. The dynamic DDT will add the functionalities of prediction, and will be able to detect unknown faults. Crew or maintenance engineers can use the decision tree system without having previous knowledge or experience about the diagnosed system. To our knowledge, this is the first paper to propose a solution to build diagnostics decision trees from fault trees, which convert the reliability analysis models to diagnostic models. We show through mapping and ISS examples that the approach is feasible and effective. We also present future work and development

Space networking and protocols for planetary exploration and analog planetary sites

System flexibility and simplicity must be maximized for future human and robotic missions to Mars and other planets. A network deployed on the surface of another planet must interoperate with a space-based communication link and/or network, as well as the Earth-side networking segment. The operation of the space-based segment should be simple, but should be able to respond to environmental and system variations causing varying degradation of the link quality. An ongoing study into space and regional communication issues is taking place in the Canadian Arctic, at a prime Mars analog research field site. Preliminary results are demonstrating the needs for simplified operation of the space-based component, and a need to respond to ionospheric and tropospheric propagation variations. Such variations require fine control of the space-based segment, but also require network protocols and operational protocols that can maximize the science and other data uplink and downlink capacity of the complete integrated network system at any given moment of time.

Heterogeneous Spacecraft Networks: Wireless network technology assessment

Constellations of small satellites are useful for a number of earth observation and space exploration missions. The Heterogeneous Spacecraft Network project is defining operations concepts and promising technology that can provide greater capability at lower cost. Typically, such spacecraft can communicate with each other in orbit and with ground stations for spacecraft operation and downlink of science data. However, small spacecraft often cannot utilize the capability delivered by networks such as the Universal Space Network, even if the mission could afford the cost. Small spacecraft have significant constraints in terms of power availability, attitude stability and overall mass and volume, requiring innovative technology for implementing highly functional satellites. A major challenge for such missions is selecting communications technology able to function in the space environment, able to meet the requirements for both inter-satellite and space-to-ground data links and fit within the resources available on small satellites. Moreover, the cost of the technology needs to be as low as possible to facilitate participation by a broad range of organizations. Finally, the communications networks should conform to standards allowing broad adoption and the use of common infrastructure for multiple missions. Communications technology based on the IEEE 802 family of local area and metropolitan area network standards can be adapted to meet the needs of such missions. This paper will identify possible development paths for improved communication between small satellites and to the ground by reviewing and evaluating standards-based technology for use by small satellite missions. Methods for greatly extending both range and data rate will be proposed and analyzed. It will review and evaluate the IEEE 802.11 wireless network standards, the ITU WCDMA 3G cell phone standard and the IEEE 802.15.4 Personal Area Network standard. A simple set of communication requirements will define the trade offs between standards and identify the technical capability needed for such missions. Specifically, the improvements needed to the Physical Layer to extend range to 1200 Km and the ability to comply with spectrum management constraints will be investigated. Authentication and encryption will be addressed along 1with adjustments to the Media Access Control layer that can optimize data transfer rates over a broad range of distances and conditions. The paper concludes with recommendations for standards-based communication technology development for small satellites supported by the results of this trade study. The primary objective is to greatly reduce the cost of data communication for small satellites by establishing a common infrastructure able to meet the needs of most missions.