Complete Bibliography
Architectural Concepts for Human-Rated Automation
ABSTRACT - Since the beginning of human spaceflight, spacecraft designers have emphasized simplicity of design to minimize failures and have relied on a large ground staff to assist flight crews. As spacecraft and missions have grown in complexity, human workload has grown, keeping operational costs high and limiting productivity. A more progressive approach to automation can address these problems if risk can be reduced. We believe that a major contributor to risk of automation is weak architecture, leading to designs that are difficult to understand, analyze, verify, and operate. This paper explores architectural considerations of human-rated automation for space systems, where safety is paramount. Improved architectural concepts for automation are analyzed. We focus on goal-oriented control, and how goal- oriented analysis and design address the concerns associated with increased automation.
AIAA Infotech@Aerospace 2010.
Atlanta, GA.
April
Model-Based Software Quality Assurance with the Architecture Analysis and Design Language
ABSTRACT - Model-based software quality assurance (MB-SQA) provides a rigorous framework for the verification and validation of software systems through the systematic modeling and analysis of formal architecture representations. This paper describes the results of applying an MB-SQA practice framework that utilizes the Architecture Analysis and Design Language (AADL) to JPL's Mission Data System (MDS) reference architecture. The MDS is a unified reference architecture for space mission flight, ground, and test systems. In the case study, the AADL assurance practice framework and several AADL-based analyses were applied to the evaluation of critical quality attributes of the MDS reference architecture as well as an MDS adaptation for the control of a heated camera. The results of the case study demonstrate the utility of the practice framework and the AADL-based analyses in addressing (1) the modeling of key MDS architectural themes and (2) quality assurance with respect to performance, particularly flow latency.
AIAA Infotech@Aerospace 2009.
Seattle, WA.
April
A Control Architecture for Safe Human-Robotic Interactions During Lunar Surface Operations
ABSTRACT - Long duration human-robotic missions to the Moon and beyond will require increased use of automation beyond current Space Shuttle and International Space Station practice. This paper explores the application of a model- and state-based goal-oriented control architecture to solving the problem of coordinating activities between humans and robots to improve the reliability and safety of these interactions. A goal-oriented control system continuously enforces constraints on states of the system to achieve not only control goals, but also to enforce passive constraints, such as safety constraints, on those activities.
AIAA Infotech@Aerospace 2009.
Seattle, WA.
April
An Architectural Pattern for Goal-Based Control
ABSTRACT -
Time-based command sequencing is the time-honored paradigm for control of spacecraft and rovers in NASA's robotic missions, but the paradigm has been increasingly strained to accommodate today's missions. Goal-based control is a new paradigm that supports time-driven and event-driven operation in a more natural way and permits a melding of sequencing and fault protection into a single control paradigm. This paper describes goal-based control as an architectural pattern in terms of intent, motivation, applicability, structure, and consequences. This paper is intended to help flight and ground software engineers understand the new paradigm and how it compares to time-based sequencing.
IEEE Aerospace Conference.
Big Sky, MT.
March
Goal-Based Operations of an Antenna Array for Deep Space Communication
ABSTRACT -
NASA is currently evaluating the benefits of transitioning to a highly reconfigurable network of arrayed disk antennas to support an increasing number of deep space missions. The next-generation Deep Space Network (NG-DSN), as currently conceptualized, would require extensive automation to reduce operations cost and handle the increased complexity associated with monitoring and controlling the larger number of antennas. This paper presents a prototype operations architecture for the proposed NG-DSN that is fundamentally based on three concepts: physical state variables of the system to be controlled. expressions of operational intent for those state variables ("goals"), and models describing the benavior of these state variables and their interactions. These concepts shape the software design of an automated control system, the model-based systems engineering analysis that feeds the design, and the human operator interface to the control system. This control system provides for automation of capabilities such as resource allocation and fault recovery (both localized and system-wide). This paper describes the development and demonstration of the control system on prototype antenna array hardware at the Jet Propulsion Laboratory.
iSAIRAS.
Los Angeles, CA.
Feb
Comparison of Goal-Based Operations and Command Sequencing
ABSTRACT -
In robotic space missions the purpose of any operations paradigm is to achieve specific objectives while protecting the health of the space vehicle(s). Unfortunately, in the dominant paradigm of command sequencing, the representation of such objectives, health constraints and other dependencies is left behind in the ground-based activity planning process and never carried into uplinked products where it can support context-specific status monitoring, resource allocation, fault protection, and general automation on the spacecraft. In contrast, in the paradigm of goal-based operations, operational objectives are ever-present, from the beginning of activity planning all the way to execution on a space vehicle. This paper examines the change in operations perspective from command sequencing to goal-based operations, with particular emphasis on the uplinked product—termed a goal network—and the design of goal elaborators needed to generate it.
SpaceOps.
Heidelberg, Germany.
May
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 developmen 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 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.
IEEE Aerospace Conference.
Big Sky, MT.
March
GN&C Fault Protection Fundamentals
ABSTRACT -
Addressing fault tolerance for spacecraft Guidance, Navigation, and Control has never been easy. Even under normal conditions, these systems confront a remarkable blend of complex issues across many disciplines, with primary implications for most essential system functions. Moreover, GN&C must deal with the peculiarities of spacecraft configurations, disturbances, environment, and other physical mission-unique constraints that are seldom under its full control, all while promising consistently high performance.
Adding faults in all their insidious variety to this already intricate mix creates a truly daunting challenge. Appropriate tactical recovery must be ensured without compromise to mission or spacecraft integrity, even during energetic activities or under imminent critical deadlines. If that were not enough, the consequences of a seemingly prudent move can have profoundly negative long-term consequences, if chosen unwisely, so there is often a major strategic component to GN&C fault tolerance, as well. Therefore, it is not surprising that fault protection for GN&C has an enduring reputation as one of the more complex and troublesome aspects of spacecraft design is one that will only be compounded by the escalating ambitions of impending space missions.
Despite these difficulties, experience has suggested methods of attack that promise good results when followed consistently and implemented rigorously. Upon close scrutiny, it is strikingly clear that these methods have roots in the same fundamental concepts and prin
ciples that have successfully guided normal GN&C development. Yet it is disappointing to note that the actual manifestation of these ideas in deployed systems is rarely transparent. The cost of this obfuscation has been unwarranted growth in complexity, poorly understood behavior, incomplete coverage, brittle design, and loss of confidence.
The objective of this paper is to shed some light on the fundamentals of fault tolerant design for GN&C. The common heritage of ideas behind both faulted and normal operation is explored, as is the increasingly indistinct line between these realms in complex missions. Techniques in common practice are then evaluated in this light to suggest a better direction for future efforts.
American Astronautical Society 31st Annual AAS Guidance and Control Conference.
Breckenridge, CO.
Feb
Verification Procedure for Generalized Goal-Based Programs
ABSTRACT -
Safety verification of fault-tolerant control systems is essential for the success of autonomous robotic systems. A control architecture called Mission Data System, developed at the Jet Propulsion Laboratory, takes a goal-based control approach. In this paper the development of a method for converting a goal network control program into a hybrid system is given and a process for converting logic associated with the goal network into transition conditions for the hybrid automata is developed. The resulting hybrid system can then be verified for safety in the presence of failures using existing symbolic model checkers. An example task and goal network is designed, converted to hybrid automata, and verified using symbolic model checking software for hybrid systems.
AIAA Infotech@Aerospace Conference.
Rohnert Park, CA.
May
Safety Verification of a Fault Tolerant Reconfigurable Autonomous Goal-Based Robotic Control System
ABSTRACT -
Fault tolerance and safety verification of control systems are essential for the success of autonomous robotic systems. A control architecture called Mission Data System (MDS), developed at the Jet Propulsion Laboratory, takes a goal-based control approach. In this paper a method for converting goal network control programs into linear hybrid systems is developed. The linear hybrid system can then be verified for safety in the presence of failures using existing symbolic model checkers. An example task is simulated in MDS and successfully verified using HyTech, a symbolic model checking software for linear hybrid systems.
IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS).
San Diego, CA.
Oct/Nov
Goal-Based Operations: An Overview
ABSTRACT - Operating robotic space missions via time-based command sequences has become a limiting factor in the exploration, defense,
and commercial sectors. Command sequencing was originally designed for comparatively simple and predictable missions, with safe-
mode reponses for most faults. This approach has been increasingly strained to accommodate today's more complex missions, which
require advanced capabilities like automomous fault diagnosis and response, vehicle mobility with hazard avoidance, opportunistic
science observations, etc. Goal-based operation changes the fundamental basis of operations from imperative command sequences
to declarative specifications of operational intent, termed goals. Execution based on explicit intent simplifies operator
workload by focusing on what to do rather than how to do it. The move toward goal-based operations, which has already begun in
some space missions, involves changes and opportunities in several places: operational processes and tools, human interface
design, planning and scheduling, control architecture, fault protection, and verification and validation. Further, the need
for future interoperation among multiple goal-based systems suggests that attention be given to areas for
standardization. This overview paper defines the concept of goal-based operations, reviews a history of steps in this
direction, and discusses the areas of change and opportunity through comparison with the prevalent operational paradigm
of command sequencing.
AIAA Infotech@Aerospace Conference.
Rohnert Park, CA.
May
Model-Based Engineering Design Pilots at JPL
ABSTRACT - This paper discusses two recent formulation phase Model-Based Engineering Design pilot projects at the Jet Propulsion Laboratory. It describes how model-based functional and state analyses were synthesized and integrated with system performance simulation and mission planning then piloted in the formulation phase of two deep space missions.
IEEE Aerospace Conference.
Big Sky, MT.
March
Practical Application of Model-based Programming and State-based Architecture to Space Missions
ABSTRACT - Innovative systems and software engineering solutions are required to meet the increasingly challenging demands of deep-space robotic missions. While recent advances in the development of integrated systems and software engineering approaches have begun to address some of these issues, these methods are still at the core highly manual and, therefore, error-prone. This paper describes a task aimed at infusing MIT's model-based executive, Titan, into JPL's Mission Data System (MDS), a unified state-based architecture, systems engineering process, and supporting software framework. Results of the task are presented, including a discussion of the benefits and challenges associated with integrating mature model-based programming techniques and technologies into a rigorously-defined domain specific architecture.
IEEE International Conference on Space Mission Challenges for Information Technology.
Pasadena, CA.
July
Application of State Analysis and Goal-Based Operations to a MER Mission Scenario
ABSTRACT - State analysis is a model-based systems engineering metholodogy employing a rigorous discovery process which articulates
operations concepts and operability needs as an integrated part of system design. The process produces requirements on system and
software design in the form of explicit models which describe the system behavior in terms of state variables and the relationships
among them. By applying state analysis to an actual MER flight mission scenario, this study addresses the specific real world
challenges of complex space operations and explores technologies that can be brought to bear on future missions. The paper first
describes the tools currently used on a daily basis for MER operations planning and provides an in-depth description of the planning
process in the context of a Martian day's worth of rover engineering activities, resource modeling, flight rules, science
observations, and more. It then describes how state analysis allows for the specificatino of a corresponding goal-based sequence
that accomplishes the same objectives, with several important additional benefits.
SpaceOps Conference.
Rome, IT.
June
A Model-Based Requirements Database Tool for Complex Embedded Systems
ABSTRACT - It has become clear that spacecraft system complexity is reaching a threshold where customary methods of control are no
longer affordable or sufficiently reliable. At the heart of this problem are the conventional approaches to systems and software
engineering based on subsystem-level functional decomposition, which fail to scale in the tangled web of interactions typically
encountered in complex spacecraft designs. Furthermore, there is a fundamental gap between the requirements on software specified
by systems engineers and the implementation of these requirements by software engineers. Software engineers must perform the
translation of requirements into software code, hoping to accurately capture the systems engineer's understanding of the system
behavior, which is not always explicitly specified. This gap opens up the possibility for misinterpretation of the systems
engineer's intent, potentially leading to software errors. This problem is addressed by a systems engineering methodology
called State Analysis which provides a process for capturing system and software requirements in the form of explicit models.
This paper describes (1) how requirements for complex aerospace systems can be developed using State Analysis, (2) how these
requirements inform the design of the system software, and (3) how this process has been aided through a State Analysis Database
(SDB) and supporting multi-platform client. The SDB provides a productive, collaborative development environment for State Analysis
that is shared by both systems and software engineers.
International Council on Systems Engineering (INCOSE) International Symposium.
Washington DC.
May
State-Based Models for Planning and Execution
ABSTRACT - Many traditional planners are build on top of existing execution engines that were not necessarily intended to be
operated by a planner. The Mission Data System has been designed from the onset to have both an execution and planning engine
and provides a framework for defining state-based models that can be used to coordinate planning and execution. The models provide a basis
for ensuring the consistency of assumptions made by the execution engine and planner, and a basis for run-time communications
between the planner and execution engines.
International Conference on Automated Planning and Scheduling (ICAPS).
Monterey, CA.
June
A Unifying Framework for Systems Modeling, Control Systems Design, and System Operation
ABSTRACT - Current engineering practice in the analysis and design of large-scale multi-disciplinary control systems is typified by some form
of decomposition -- whether functional or physical or discipline-based -- that enables multiple teams to work in parallel and in relative
isolation. Too often, the resulting system after integration is an awkward marriage of different control and data mechanisms with
poor end-to-end accountability. System of systems engineering, which faces this problem on a large scale, cries out for a unifying
framework to guide analysis, design, and operation. This paper describes such a framework for semi-autonomous control systems that
guides analysis and modeling, shapes control system software design, and directly specifies operational intent. This paper
illustrates the key concepts in the context of a large-scale, concurrent, globally-distributed system of systems: NASA's proposed
array-based Deep Space Network.
IEEE System, Man, and Cybernetics Conference.
Kona, HI.
October
Achieving Control and Interoperability Through Unified Model-Based Engineering and Software Engineering
ABSTRACT - This paper describes the control challenge faced by future exploration systems and outlines a realistic approach to solving it, based upon a unified, principled architectural approach to both software and systems engineering. It concludes by suggesting the steps necessary to put this capability in place for exploration systems.
AIAA Infotech@Aerospace Conference.
Arlington, VA.
September
Data Management in the Mission Data System
ABSTRACT - As spacecraft systems evolve from simple embedded devices to become more sophisticated computing platforms with complex behaviors it is increasingly necessary to model and manage the flow of data, and to provide uniform models for managing data that promote adaptability, yet pay heed to the physical limitations of the embedded and space environments. The Mission Data System (MDS) defines a software architecture in which both control theory and end-to-end data management provide the primary guiding principles. This paper describes how the MDS architecture facilitates data accountability and storage resource management.
IEEE System, Man, and Cybernetics Conference.
Kona, HI.
October
Mission Planning and Execution Within the Mission Data System
ABSTRACT - Not only has the number of launched spacecraft per year exploded recently, but spacecraft are also getting progressively
more complex as flyby missions give way to remote orbiters, which in turn give way to rovers and other in situ explorers. To address
the software issues in this expanding mission set JPL started the Mission Data System (MDS) project -- an effort to make flight software
engineering more straightforward and less prone to error through the explicit modeling of spacecraft state. This paper presents how
MDS performs mission planning and execution in the context of explicitly managing spacecraft state.
International Workshop on Planning and Scheduling for Space.
Darmstadt, Germany.
June
Project Golden Gate: Toward Real Time Java in Space Missions
ABSTRACT - Planetary science missions, such as those that explore Mars and Saturn, employ a variety of spacecraft such as orbiters, landers,
probes, and rovers. Each of these kinds of spacecraft depend on embedded real-time control systems -- systems that are increasingly being
asked to do more as challenging new mission concepts are proposed. For both systems engineers and software engineers the large
challenges are in analysis, design, and verification of complex control systems that can run on relatively limited processors. Project
Golden Gate -- a collaboration among NASA's Jet Propulsion Laboratory, Sun Microsystems Laboratory, and Carnegie Mellon University--
is exploring those challenges in the context of real time Java applied to space mission software. This paper describes the problem
domain and our experimentation with the first commercial implementation of the Real Time Specification for Java. The two main
issues explored in this report are: (1) the effect of RTSJ's non-heap memory on the programming model, and (2) performance benchmarking
of RTSJ/Linux relative to C++/VxWorks.
IEEE Symposium on Object-Oriented Real Time Distributed Computing (ISORC'04).
Vienna, Austria.
May
Planning for V&V of the Mars Science Laboratory Rover Software
ABSTRACT - NASA's Mars Science Laboratory (MSL) rover mission is planning to make use of advanced software technologies in order to support fulfillment of its ambitious science objectives. The mission plans to adopt the Mission Data System (MDS) as the mission software architecture, and plans to make significant use of on-board autonomous capabilities (e.g., path planning, obstacle avoidance) for the rover software. The use of advanced software technologies embedded in an advanced mission software architecture represents a turning point in software for space missions. While prior flight experiments (notably the Deep Space One Remote Agent Experiment) have successfully demonstrated aspects of autonomy enabled by advanced software technologies, and MDS has been tested in ground experiments (e.g., on-earth tests on rover hardware), MSL will be the first science mission to rely on this combination. The success of the MSL mission is predicated upon our ability to adequately verify and validate the advanced software technologies, the MDS architectural elements, and the integrated system as a whole. Because MSL is proposing a shift from traditional approaches to flight software, approaches to verification and validation (V&V) require scrutiny to determine whether traditional methods are adequate, and where they need adjustment and/or augmentation to handle the new challenges. This paper presents a study of the V&V needs and opportunities associated with MSL's novel approach to mission software, and provides an assessment of V&V techniques, both current and emerging, vis-a-vis their adequacy and suitability for V&V of the MSL rover software.
IEEE Aerospace Conference.
Big Sky, MT.
March
Engineering Complex Embedded Systems with State Analysis and the Mission Data System
ABSTRACT - It has become clear that spacecraft system complexity is reaching a threshold where customary methods of control are no
longer affordable or sufficiently reliable. At the heart of this problem are the conventional approaches to systems and software
engineering based on subsystem-level functional decomposition, which fail to scale in the tangled web of interactions typically
encountered in complex spacecraft designs. Furthermore, there is a fundamental gap between the requirements on software specified
by systems engineers and the implementation of these requirements by software engineers. Software engineers must perform the
translation of requirements into software code, hoping to accurately capture the systems engineer's understanding of the system
behavior, which is not always explicitly specified. This gap opens up the possibility for misinterpretation of the systems
engineer's intent, potentially leading to software errors. This problem is addressed by a systems engineering methodology
called State Analysis which provides a process for capturing system and software requirements in the form of explicit models.
This paper describes how requirements for complex aerospace systems can be developed using State Analysis and how these
requirements inform the design of the system software, using representative spacecraft examples.
AIAA Intelligent Systems Technical Conference.
Chicago, IL.
September
Generating Requirements for Complex Space Systems Using State Analysis
ABSTRACT - It has become clear that spacecraft system complexity is reaching a threshold where customary methods of control are no
longer affordable or sufficiently reliable. At the heart of this problem are the conventional approaches to systems and software
engineering based on subsystem-level functional decomposition, which fail to scale in the tangled web of interactions typically
encountered in complex spacecraft designs. Furthermore, there is a fundamental gap between the requirements on software specified
by systems engineers and the implementation of these requirements by software engineers. Software engineers must perform the
translation of requirements into software code, hoping to accurately capture the systems engineer's understanding of the system
behavior, which is not always explicitly specified. This gap opens up the possibility for misinterpretation of the systems
engineer's intent, potentially leading to software errors. This problem is addressed by a systems engineering methodology
called State Analysis which provides a process for capturing system and software requirements in the form of explicit models.
This paper describes how requirements for complex aerospace systems can be developed using State Analysis and how these
requirements inform the design of the system software, using representative spacecraft examples.
International Astronautical Federation Congress.
Vancouver, Canada.
October
Modelling Relationships Using Graph State Variables
ABSTRACT - The Mission Data System is a unified flight, ground, simulation, and test software system for space missions. Currently,
its first application will be the Mars Smart Lander mission, where common MDS software frameworks will be adapted for use in interplanetary
cruise, entry-descent-landing, and rover operations. A key architectural theme of MDS is explicit modeling of states. This provides
a sound foundation for estimation, control, and data analysis. Certain essential states are relative rather than absolute. Relative
states are defined in graph state variables (GSVs) as relationships between nodes in a graph. GSVs are a general graph-based state
representation that (1) derives a state's value by combining relationships, (2) produces different results for different derivation
paths, (3) handles changes to topology and relationships between nodes, and (4) represents dependencies between relationships (e.g.,
correlations). This paper shows example GSV representations for spacecraft orientation, location, trajectories, dynamics, and
kinematics.
IEEE Aerospace Conference.
Big Sky, MT.
March
State Knowledge Representation in the Mission Data System
ABSTRACT - The possible states of a system, be it a spacecraft, rover, or ground station, are what system engineers identify and
specify, what software engineers design for, and what operators monitor and control. Many activities inside mission software are
directly concerned with state, whether planning it, estimating it, controlling it, reporting it, or simulating it. The cause of
several mission failures can be traced to inadequate or inconsistent representations of state. Consequently, the concept of 'state'
and its representation occupy a prominent role in mission software architecture. The Mission Data System (MDS), presently under
development by NASA to provide multi-mission flight and ground software for the next generation of deep space systems, addresses
this fundamental need. This paper describes the MDS approach to state knowledge representation, covering state variables,
state functions, state estimates, and state constraints, emphasizing design patterns that reduce sources of human error.
IEEE Aerospace Conference.
Big Sky, MT.
March
Goal-Based Fault Tolerance for Space Systems Using the Mission Data System
ABSTRACT - In anticipating in-situ exploration and other circumstances with environmental uncertainty, the present system
for space system fault tolerance breaks down. The perplexities of fault-tolerant behavior, once confined to infrequent
episodes, must now extend to the entire operational model. To address this dilemma we need an operational approach to robust
behavior that includes fault tolerance as an intrinsic feature. This requires an approach capable of measuring operators' intent
in the light of present circumstances, so that actions are derived by reasoning, not by edict. The Mission Data System (MDS),
presently under development by NASA, is one realization of this paradigm -- part of a larger effort to provide multi-mission
flight and ground software for the next generation of deep space systems. This paper describes the MDS approach to fault
tolerance, contrasting it with past efforts, and offering motivation for the approach as a general recipe for similar efforts.
IEEE Aerospace Conference.
Big Sky, MT.
March
Software Architecture Themes in JPL's Mission Data System
ABSTRACT - Describes 13 themes that shape the MDS control system architecture.
IEEE Aerospace Conference.
Big Sky, MT.
March
The MDS Autonomous Control Architecture
ABSTRACT - We describe the autonomous control architecture for the JPL Mission Data System (MDS). MDS is a comprehensive new software infrastructure for supporting unmanned space exploration. The autonomous control architecture is one component of MDS designed to enable autonomous operations.
World Automation Conference.
Maui, HI.
June
Energy Management of the Multi-Mission Space Exploration Vehicle using a Goal-Oriented Control System
ABSTRACT -
Safe human exploration in space missions requires careful management of limited resources such as breathable air and stored electrical energy. Daily activities for astronauts must be carefully planned with respect to such resources, and usage must be monitored as activities proceed to ensure that the can be completed while maintaining safe resource margins. Such planning and monitoring can be complex because they depend on models of resource usage, the activities being planned, and uncertainties. This paper describes a system -- and the technology behind it -- for energy management of the NASA-Johnson Space Center's Multi-Mission Space Exploration Vehicles (SEV), that provides, in an onboard advisory mode, the situational awareness to astronauts and real-time guidance to mission operators. This new capability was evaluated during this year's Desert RATS (Research and Tecnhology Studies) planetary exploration analog test in Arizona. This software aided ground operators and crew members in modifying the day's activities based on the real-time execution of the plan and on energy data received from the rovers.
IEEE Aerospace Conference 2011.
Big Sky, MT.
.
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