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Schaffer, Steve

Publications and source records attributed to Schaffer, Steve.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Sailing Towards an Expressive Scheduling Language for Europa Clipper

The mission planners for NASA's Europa Clipper deep-space mission use automated scheduling software to generate activity plans and command sequences for multiple instruments and subsystems before sending the sequences for execution on board. Both science and engineering planners must translate their intents into expressions of mission constraints, goals, and preferences that the scheduling engine understands. This paper describes the ongoing development of a dedicated domain-specific java-embedded language that can efficiently and accurately capture such concerns for the Europa Clipper mission, along with a user-interface companion for the language.

Schaffer, Steve↗
NASA NTRS2018

Integrated Planning and Execution for a Self-Reliant Mars Rover

Planetary rovers exploring the surface of Mars face a challenging operational environment that requires close cooperation between deliberative planning and behavioral execution in order to most efficiently leverage the robot’s capabilities into science value returned to earth. The Self-Reliant Rovers project envisions future rover missions that require only occasional high-level direction from human controllers to successfully conduct detailed in-situ studies of its Martian environs. To achieve this high degree of autonomy, this work leverages a spectrum of planning and execution techniques that allow the rover to respond appropriately to both opportunity and adversity it encounters. Small perturbations are accommodated at first by behavioral adaptation, with more and more extensive disruptions handled in turn by executive administration of plan flexibility, heuristic-guided plan repair strategies, and finally comprehensive replanning from science campaign goals. The integrated system has been deployed and tested on a terrestrial rover in an environment and under scenarios that anticipate those faced by future Mars rovers. This paper recounts complexities of planning and execution coordination faced in the rover domain and the practical solutions employed to address them. Particular emphasis is given to lessons from the field and foibles ripe for remedy by future advances in planning and execution research.

Gaines, Daniel↗
NASA NTRS2018

Self-Reliant Rover Design for Increasing Mission Productivity

Achieving consistently high levels of productivity has been a challenge for Mars surface missions. While the rovers have made major discoveries and dramatically increased our understanding of Mars, they often require a great deal of effort from the operations teams, and achieving mission objectives can take longer than anticipated. The objective of this work is to identify changes to flight software and ground operations that enable high levels of productivity with reduced reliance on ground interactions. This will enable the development of Self-Reliant Rovers: rovers that make use of high-level guidance from operators to select their own situational activities and respond to unexpected conditions, all without dependence on ground intervention. In this paper we describe the system we are developing and illustrate how it enables increased mission productivity.

Vasavada, Ashwin↗
NASA NTRS2018

Self-Reliant Rover Design for Increasing Mission Productivity

Achieving consistently high levels of productivity has been a challenge for Mars surface missions. While the rovers have made major discoveries and dramatically increased our understanding of Mars, they often require a great deal of effort from the operations teams, and achieving mission objectives can take longer than anticipated. The objective of this work is to identify changes to flight software and ground operations that enable high levels of productivity with reduced reliance on ground interactions. This will enable the development of Self-Reliant Rovers: rovers that make use of high-level guidance from operators to select their own situational activities and respond to unexpected conditions, all without dependence on ground intervention. In this paper we describe the system we are developing and illustrate how it enables increased mission productivity.

Vasavada, Ashwin↗
NASA NTRS2018

Validation of Fault-Tolerant Plans for Europa Clipper

The Europa Clipper mission will explore that icy moon in a series of brief flybys through the Jovian radiation belts. A single event upset in the spacecraft flight computer during these critical scientific periods could jeopardize the success of the mission. Rather than safing and awaiting operator intervention, the Clipper mission envisions limited onboard autonomy that can restore spacecraft state sufficiently to resume the encounter observation plan as rapidly as possible. The contingency plan is contained in an Activity Restart Timeline (ART) that is transmitted in parallel with the nominal plan, which must be co-validated jointly against all spacecraft state and resource constraints amid unpredictable fault timing. A prototype validation tool was built that leverages declarative spacecraft models and automated search techniques to find such potential inconsistencies in the unified contingent mission plan. Early validation results within motivating scenarios are presented.

Ferguson, Eric↗
NASA NTRS2017

Initial Results of Heuristic Guided Orbit Selection for a Low Frequency Radio Interferometric Spacecraft Constellation

A constellation of radio telescope spacecraft can leverage interferometry to accurately image distant objects throughout the universe, but mission design must balance among many interrelated constraints. In particular, the number of craft and the selection of time-varying orbital parameters play a pivotal role in determining what interferometric baselines are feasible with respect to different targets, and thus drives the breadth and quality of data available to the constellation. The large combinatorial orbit configuration space and competing concerns present a challenging problem that is not well addressed by traditional mission design processes. This paper describes application of automated optimization methods to help direct mission design effort to the most promising dynamic constellation geometries: those that achieve broad interferometric coverage but remain cost-effective and resilient to failures. Several automatic heuristic-driven optimization algorithms representing complementary search strategies were created to explore among concrete constellation configuration plans. Evaluation of each candidate constellation plan was accelerated by efficiently combining precomputed caches of orbital and interferometric data. Results indicate that leveraging automated optimization for constellation mission design is both practical and illuminating: generated solutions provided both evidence for existing design intuitions as well as fresh insights into novel configurations.

Hernandez, Sonia↗
NASA NTRS2017

Expressing Campaign Intent to Increase Productivity of Planetary Exploration Rovers

Achieving consistently high levels of productivity has been a challenge for Mars surface missions. While the rovers have made major discoveries and dramatically increased our understanding of Mars, they often require a great deal of effort from the operations teams and achieving mission objectives can take longer than anticipated. Missions have begun investigating ways to enhance productivity by increasing the amount of decision-making performed onboard the rovers. Our work focuses on the use of goal-based commanding as a means of more productively operating rovers. In particular, we are working on ways to convey the intent that operations team use to conduct science campaigns to the rover so that it can guide the rover in creating high quality plans and in identifying its own goals based on operator guidance. In addition to informing future surface exploration missions, this work is relevant for a wide range of applications in which operators must interact with limited communication opportunities.

Gaines, Daniel↗
NASA NTRS2017

A Case Study of Productivity Challenges in Mars Science Laboratory Operations

Achieving consistently high levels of productivity has been a challenge for Mars surface missions. While the rovers have made major discoveries and dramatically increased our understanding of Mars, they often require a great deal of effort from the operations teams and achieving mission objectives can take longer than anticipated. We conducted an in-depth case study of Mars Science Laboratory operations in order to identify the productivity challenges facing surface missions. In this paper, we describe how we performed the case study and analyzed the data. We present and discuss the significant productivity challenges we identified during the study. In addition to informing future surface exploration missions, the study is relevant for a wide range of applications in which operators must interact with a robotic system with limited communication opportunities.

Gaines, Daniel↗
NASA NTRS2017

Autonomous Science Restart for the Planned Europa Mission with Lightweight Planning and Execution

In this paper we present MEXEC - a lightweight on-board planning and execution system that monitors spacecraft state to robustly respond to current conditions. In addition it projects the remaining plan forward in time to detect conflicts and revise the plan. Most current planetary missions use sequence based commanding from the ground,which limits the ability to respond to on-board state varying from planned for state. This results in planning for worst-case execution time, power utilization, data volume and other resources and leads to under utilization of the spacecraft capability. It also limits the ability to respond to faults. Due to the high radiation environment at Jupiter the probability of flight software resets is high. Therefore, of particular interest to the planned Europa Mission is the capability to restart the science plan after flight software resets. In this paper we present results from running Europa flyby scenarios with flight software resets in the Europa flight software test environment. Preliminary results with the prototype scenario show MEXEC takes less than a tenth of a second to respond to resets. The development was done as part of Europa-focused flight software, but MEXEC was designed to be applicable to landers and rovers as well.

Joshi, Rajeev↗
NASA NTRS2017

CARACaS multi-agent maritime autonomy for unmanned surface vehicles in the Swarm II harbor patrol demonstration

This paper describes new autonomy technology that enabled a team of unmanned surface vehicles (USVs) to execute cooperative behaviors in the USV Swarm II harbor patrol demonstration and provides a description of autonomy performance in the event. The new developments extend the NASA Jet Propulsion Laboratory’s CARACaS (Control Architecture for Robotic Agent Command and Sensing) autonomy architecture, which pro- vides foundational software infrastructure, core executive functions, and several default robotic technology mod- ules. In Swarm II, CARACaS demonstrated higher levels of autonomy and more complex cooperation than previous on-water exercises, using full-sized vehicles and real-world sensing and communication. The core au- tonomous behaviors to support the harbor patrol scenario included Patrol, Track, Inspect, and Trail, providing the capability of finding all vessels entering the patrol area, keeping track of them, inspecting them to infer intent, and trailing suspect vessels. Significantly, CARACaS assumed responsibility for not only executing tasks safely and efficiently but also recognizing what tasks needed to be accomplished, given the current state of the world. Since the heterogeneous USV teams shared world model that evolved, such as due to (dis)appearance of vessels in the area or a change in health or availability of a USV, CARACaS replanned to generate and reallocate the new task list. Thus, human intervention was never required in the loop to task USVs during mission execution, though a supervisory role was supported in the autonomy system for mission monitoring and exception handling. Finally, CARACaS also ensured the USVs avoided hazards and obeyed the applicable rules of the road, using its local motion planning modules.

Sandoval, Michael↗