Publications

In-Space Crew-Collaborative Task Scheduling — A concept of operations, scheduling software and interplanatary internet.

On Using an Incremental Scheduler for Human Exploration Task Scheduling — A comparison of the different classes of engines and their usage.

Enabling New Operations Concepts for Lunar and Mars Exploration — An examination of possible operations concepts for Lunar and Mars Exploration to reduce time and cost.

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The planning and scheduling of human space activities is an expensive and time-consuming task that seldom provides the crew with the control, flexibility, or insight that they need. During the past thirty years, scheduling software has seen only incremental improvements; however, software limitations continue to prevent even evolutionary improvements in the “operations concept” that is used for human space missions. Space missions are planned on the ground and the crew has little input or influence on the schedule. In recent years the crew has been presented with a “job jar” of activities, but the contents of the jar is limited to tasks that do not use scarce shared resources and do not have external timing constraints. Consequently, the crew has no control over the schedule of the majority of their own tasks. As humans venture farther from earth for longer durations, it will become imperative that they have the ability to plan and schedule not only their own activities, but also the unattended activities of the systems, equipment, and robots on the journey with them. Software break-throughs are required to enable the change in the operations concept. The crew does not have the time to build or modify the schedule by hand. They only need to issue a request to schedule a task and the system should automatically do the rest. Of course, the crew should not be required to build the complete schedule. Controllers on the ground should contribute the models and schedules where they have the better knowledge. The system must allow multiple simultaneous users, some on earth and some in space. The Mission Operations Laboratory at NASA’s Marshall Space Flight Center has been researching and prototyping a modeling schema, scheduling engine, and system architecture that can enable the needed paradigm shift – it can make the crew autonomous. This schema and engine can be the core of a scheduling system that would enable multiple planners, some on earth and some in space, to build one integrated timeline. Its modeling schema can capture all the task requirements; its scheduling engine can build the schedule automatically; and its architecture can allow those (on earth and in space) with the best knowledge of the tasks to schedule them.
Presented to Space Technology & Applications International Forum (STAIF-2005) by
John Jaap (John.Jaap@nasa.gov)
Theresa Maxwell (Theresa.Maxwell@nasa.gov)
Mission Operations Laboratory
Marshall Space Flight Center
National Aeronautics and Space Administration
Cite: Jaap, J. P., and Maxwell, T. G., "Enabling New Operations Concepts for Lunar and Mars Exploration" in the proceedings of Space Technology & Applications International Forum (STAIF-2005), Albuquerque, New Mexico, 2005.

Maximally Expressive Modeling — Planning and scheduling systems organize "tasks" into a timeline or schedule…

An Enabling Technology for New Planning and Scheduling Paradigms — A future paradigm would provide a scheduling engine that accepts separate science models and hardware models...

Full paper: pdf, html
Presentation: html
The Flight Projects Directorate at NASA’s Marshall Space Flight Center is developing a new planning and scheduling environment and a new scheduling algorithm to enable a paradigm shift in planning and scheduling concepts. Over the past 33 years Marshall has developed and evolved a paradigm for generating payload timelines for Skylab, Spacelab, various other Shuttle payloads, and the International Space Station. The current paradigm starts by collecting the requirements, called “task models,” from the scientists and technologists for the tasks that are to be scheduled. Because of shortcomings in the current modeling schema, some requirements are entered as notes. Next, a cadre with knowledge of vehicle and hardware modifies these models to encompass and be compatible with the hardware model; again, notes are added when the modeling schema does not provide a better way to represent the requirements. Finally, the models are modified to be compatible with the scheduling engine. Then the models are submitted to the scheduling engine for automatic scheduling or, when requirements are expressed in notes, the timeline is built manually. A future paradigm would provide a scheduling engine that accepts separate science models and hardware models. The modeling schema would have the capability to represent all the requirements without resorting to notes. Furthermore, the scheduling engine would not require that the models be modified to account for the capabilities (limitations) of the scheduling engine.
The enabling technology under development at Marshall has three major components. (1) A new modeling schema allows expressing all the requirements of the tasks without resorting to notes or awkward contrivances. The chosen modeling schema is both maximally expressive and easy to use. It utilizes graphical methods to show hierarchies of task constraints and networks of temporal relationships. (2) A new scheduling algorithm automatically schedules the models without the intervention of a scheduling expert. The algorithm is tuned for the constraint hierarchies and the complex temporal relationships provided by the modeling schema. It has an extensive search algorithm that can exploit timing flexibilities and constraint and relationship options. (3) An innovative architecture allows multiple remote users to simultaneously model science and technology requirements and other users to model vehicle and hardware characteristics. The architecture allows the remote users to submit scheduling requests directly to the scheduling engine and immediately see the results. These three components are integrated so that science and technology experts with no knowledge of the vehicle or hardware subsystems and no knowledge of the internal workings of the scheduling engine have the ability to build and submit scheduling requests and see the results. The immediate feedback will hone the users’ modeling skills and ultimately enable them to produce the desired timeline. This paper summarizes the three components of the enabling technology and describes how this technology would make a new paradigm possible.
Presented to SpaceOps 2004 Eighth International Conference on Space Operations May 17-21, 2004 by
John Jaap (John.P.Jaap@nasa.gov)
Elizabeth Davis (Elizabeth.K.Davis@nasa.gov)
Mission Support Systems Group
Ground Systems Department
Flight Projects Directorate
Marshall Space Flight Center
National Aeronautics and Space Administration
Cite:

CDDF — Research into the enabling technologies for new planning and scheduling systems was funding from the Center Director's Discretionary Fund (CDDF).

Maximally Expressive Modeling of Operations Tasks — The models to be fed into the scheduler must describe both the complexity of the experiments and procedures…

Planning Systems for Distributed Operations — Slides regarding distributed operations presented to the Ground Systems Architecture Workshop.

Lessons Learned in Developing Multiple Distributed Planning Systems for the International Space Station — a discussion of typical problems faced during the development and coordination process, such as incompatible development schedules, difficulties in defining system interfaces, technical coordination and funding for shared tools, continually evolving planning concepts/requirements,..

Full paper: pdf
Presentation: ppt
The planning processes for the International Space Station (ISS) Program are quite complex. Detailed mission planning for ISS on-orbit operations is a distributed function. Pieces of the on-orbit plan are developed by multiple planning organizations, located around the world, based on their respective expertise and responsibilities. The “pieces” are then integrated to yield the final detailed plan that will be executed onboard the ISS. Previous space programs have not distributed the planning and scheduling functions to this extent. Major ISS planning organizations are currently located in the United States (at both the NASA Johnson Space Center (JSC) and NASA Marshall Space Flight Center (MSFC)), in Russia, in Europe, and in Japan.
Software systems have been developed by each of these planning organizations to support their assigned planning and scheduling functions. Although there is some cooperative development and sharing of key software components, each planning system has been tailored to meet the unique requirements and operational environment of the facility in which it operates. However, all the systems must operate in a coordinated fashion in order to effectively and efficiently produce a single integrated plan of ISS operations, in accordance with the established planning processes.
This paper addresses lessons learned during the development of these multiple distributed planning systems, from the perspective of the developer of one of the software systems. The lessons focus on the coordination required to allow the multiple systems to operate together, rather than on the problems associated with the development of any particular system. Included in the paper is a discussion of typical problems faced during the development and coordination process, such as incompatible development schedules, difficulties in defining system interfaces, technical coordination and funding for shared tools, continually evolving planning concepts/requirements, programmatic and budget issues, and external influences. Techniques that mitigated some of these problems will also be addressed, along with recommendations for any future programs involving the development of multiple planning and scheduling systems. Many of these lessons learned are not unique to the area of planning and scheduling systems, so may be applied to other distributed ground systems that must operate in concert to successfully support space mission operations.
Presented to SpaceOps 2002 October, 2002 by
Theresa G. Maxwell
Mission Support Systems Group
Ground Systems Department
Flight Projects Directorate
Marshall Space Flight Center
National Aeronautics and Space Administration
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Modeling of Complex Operations Sequences — Presents a view of the model methodology of the Request-Oriented Scheduling Environment as it might be used for the International Space Station. Written by a university professor.

Request-Oriented Scheduling Engine (ROSE) — Slides of a Candidate Usage Concept for the Request-Oriented Scheduling Environment as it might be applied for the International Space Station.

Web-Based Request-Oriented Scheduling Engine (ROSE) — Slides proposing that the Center Director funds the Request-Oriented Scheduling Environment from his discretionary fund.

Can Customers Schedule Their Own Payload Activities? — Customers of a spacecraft (the payload developers) can scheduling their own tasks if an appropriate modeling scheme, scheduling engine and system architecture is provided.

Putting ROSE To Work: A Proposed Application of a Request-Oriented Scheduling Engine for Space Station Operations — An alternative operations concept that is operationally viable, is low cost, provides more autonomy to payload developers and is presented for future consideration in defining the long term operations concept for ISS payload operations.

NASA/MIR Phase 1: A Lesson in Long Duration Mission Planning and Operations — An overview of the characteristics of a long duration mission timeline development and execution, a summary of applicable lessons learned, a discussion of "Gross Timelines," and a discussion of the challenges of getting the ISS Program to benefit from the NASA/Mir Phase 1 Program.

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The NASA/Mir Phase 1 Program is a precursor to the assembly and operations of the International Space Station (ISS). The Phase 1 Program covers a four-year period and encompasses over ten shuttle flights to the Mir, culminating with the flight of STS-91 in May 1998. The Mir provides an excellent environment, both onboard and on the ground, for learning and studying the characteristics associated with crew-tended operations on long duration missions. By the end of the Phase 1 Program, NASA astronauts will have accumulated over two years of continuous operations experience working and living onboard the Mir. Ground controllers, working in Russia and at remote sites in the United States, will have gained valuable experience in the generation, maintenance, and coordination of the information and products required to support the long duration crew members onboard the Mir. The experience gained by the crew and ground support personnel in the area of long duration mission operations has resulted in a number of factors that need to be considered in the definition and implementation of the processes and products for the ISS. While there are many areas in which experience has been gained, this paper focuses on the lessons learned regarding the level of detail and flexibility of crew timelines. Provided in this paper is an overview of the characteristics associated with long duration mission timeline development and execution, a summary of applicable lessons learned identified and documented through participation in the NASA/Mir Phase 1 Program, and a detailed discussion of "Gross Timelines" as an implementation which addresses the lessons learned. Also discussed are the challenges that must be overcome in getting the ISS Program to recognize, evaluate, and learn from the crew and ground controller experience gained through participation in the NASA/Mir Phase 1 Program.
Presented to Space Ops 98 Fith International Symposium on Space Mission Operations and Ground Data Systems September, 1996 by
Jeff Hagopian & Theresa Maxwell
Mission Planning Division
Mission Operations Laboratory
George C. Marshall Space Flight Center
National Aeronautics and Space Administration
Ed Nahay
Teledyne Brown Engineering
Huntsville, Alabama 35805
Cite:

Using Common Graphics Paradigms Implemented in a Java Applet to Represent Complex Scheduling Requirements — The scheduling requires a concise and comprehensive description of the experiments' requirements (to ensure a valid schedule) and a good description of the experiments' flexibilities (to effectively utilize available resources). A graphical representation promises to be an elegant solution.

Explicit and Implicit Resources: A Simplified Approach to User Requirements Modeling — The basic premise of the explicit and implicit resource concept is to hide the complexities of the station systems from the user in the definition of scheduling requirements. Explicit resources are defined within the modeling software to correspond to the physical and logical resources that a science user can relate to when defining requirements for scheduling. The requests for these explicit resources are interpreted by the modeling software.

Full paper: html
The International Space Station (ISS) program is heavily dependent on the concept of distributed planning. Within the payload planning community, the concept of distributed planning places a great deal of responsibility in the hands of the science users. This approach to planning is very different from that used within the current U.S. Space Shuttle and Spacelab programs, where much of the responsibility for planning resides with the control center personnel. In the Shuttle and Spacelab programs the control center personnel interface with the science users to obtain the requirements for the operations to be scheduled. These requirements are then translated by the scheduling experts into the format required for use by the scheduling software. Within the ISS program, the interface to the control center personnel has been radically altered. The users will assume the responsibility for submitting requirements in the format required for use by the scheduling software. Therefore, it is extremely important that requirements modeling software be provided which enables non-scheduling experts to easily and accurately define their requirements. The requirements modeling process is further complicated by the very complex nature of the ISS systems against which requirements must be defined. The concept of explicit and implicit resources has been developed to support these two key requirements. This paper defines and describes the concept of explicit and implicit resources, provides examples of scheduling requirements implemented using explicit and implicit resources, and discusses the software currently being developed to support this concept.
Presented to Space Ops 96 Fourth International Symposium on Space Mission Operations and Ground Data Systems September, 1996 by
Jeff Hagopian & Theresa Maxwell
Mission Planning Division
Mission Operations Laboratory
George C. Marshall Space Flight Center
National Aeronautics and Space Administration
Cite:

Planning in the Continous Operations Environment of the International Space Station — The planning processes developed for the International Space Station (ISS) must recognize the fact that the ISS is an on-orbit facility which will operate continuously over its ten to fifteen year lifetime. In effect, the ISS is one "mission" with an extremely long duration.

Graphical Timeline Editing — Graphical Timeline Editing is an integral part scheduling systems. Using a clipboard concept allows robust capabilities to be incorporated. The GTE Clipboard is much more than a guess-again editor in that it provides graphical assistance for conflict resolution.

The Scheduling Techniques of ESP — All task requirements are reduced to feasibility tests, windows, or backtracking rules. Which model/performance is scheduled next is determined by the selector. The checker calculates the windows, and the loader combines the windows and executes the backtracking rules.