Chad R. Frost

Using obstacle analysis to identify contingency requirements on an unpiloted aerial vehicle

This paper describes the use of Obstacle Analysis to identify anomaly handling requirements for a safety-critical, autonomous system. The software requirements for the system evolved during operations due to an on-going effort to increase the autonomous system’s robustness. The resulting increase in autonomy also increased system complexity. This investigation used Obstacle Analysis to identify and to reason incrementally about new requirements for handling failures and other anomalous events. Results reported in the paper show that Obstacle Analysis complemented standard safety-analysis techniques in identifying undesirable behaviors and ways to resolve them. The step-by-step use of Obstacle Analysis identified potential side effects and missing monitoring and control requirements. Adding an Availability Indicator and feature-interaction patterns proved useful for the analysis of obstacle resolutions. The paper discusses the consequences of these results in terms of the adoption of Obstacle Analysis to analyze anomaly handling requirements in evolving systems.

An Architecture for Intelligent Management of Aerial Observation Missions

Apex, an elaboration of the three-tier type architecture used successfully in many autonomy applications, is designed around the concept of modular reasoning and control services (RCSs) with response-time characteristics as a primary factor in module delineation. We believe this approach reflects a valuable synthesis of requirements from diverse missions types and systems, and avoids pitfalls commonly seen in autonomy architecture design. The paper presents an overview of the architecture, its design rationale and its deployment in Unmanned Aerial Vehicles (UAVs).

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.

Identifying contingency requirements using obstacle analysis

This paper describes the use of obstacle analysis to identify anomaly-handling requirements for a safety-critical, autonomous system. The software requirements for the system evolved during operations due to an on-going effort to increase the autonomous systems robustness. The resulting increase in autonomy also increased system complexity. This investigation used obstacle analysis to identify and to reason incrementally about new requirements for handling failures and other anomalous events. Results reported in the paper show that obstacle analysis complemented standard safety-analysis techniques in identifying undesirable behaviors and ways to resolve them. The step-by-step use of obstacle analysis identified potential side effects and missing monitoring and control requirements. Adding an availability indicator and feature-interaction patterns proved useful for the analysis of obstacle resolutions. The paper discusses the consequences of these results in terms of the adoption of obstacle analysis to analyze anomaly-handling requirements in evolving systems.

LightForce Photon-pressure Collision Avoidance: Efficiency Analysis in the Current Debris Environment and Long-Term Simulation Perspective

This work provides an efficiency analysis of the LightForce space debris collision avoidance scheme in the current debris environment and describes a simulation approach to assess its impact on the long-term evolution of the space debris environment. LightForce aims to provide just-in-time collision avoidance by utilizing photon pressure from ground-based industrial lasers. These ground stations impart minimal accelerations to increase the miss distance for a predicted conjunction between two objects. In the first part of this paper we will present research that investigates the short-term effect of a few systems consisting of 20 kW class lasers directed by 1.5 m diameter telescopes using adaptive optics. The results found such a network of ground stations to mitigate more than 85 percent of conjunctions and could lower the expected number of collisions in Low Earth Orbit (LEO) by an order of magnitude. While these are impressive numbers that indicate LightForces utility in the short-term, the remaining 15 % of possible collisions contain (among others) conjunctions between two massive objects that would add large amount of debris if they collide. Still, conjunctions between massive objects and smaller objects can be mitigated. Hence, we choose to expand the capabilities of the simulation software to investigate the overall effect of a network of LightForce stations on the long-term debris evolution. In the second part of this paper, we will present the planned simulation approach for that effort. For the efficiency analysis of collision avoidance in the current debris environment, we utilize a simulation approach that uses the entire Two Line Element (TLE) catalog in LEO for a given day as initial input. These objects are propagated for one year and an all-on-all conjunction analysis is performed. For conjunctions that fall below a range threshold, we calculate the probability of collision and record those values. To assess efficiency, we compare a baseline (without collision avoidance) conjunction analysis with an analysis where LightForce is active. Using that approach, we take into account that collision avoidance maneuvers could have effects on third objects. Performing all-on-all conjunction analyses for extended period of time requires significant computer resources; hence we implemented this simulation utilizing a highly parallel approach on the NASA Pleiades supercomputer.

Heterogeneous Spacecraft Networks: General concept and case study of a cost-effective, multi-institutional Earth observation platform

In recent years the Mission Design Center (MDC) at NASA Ames Research Center has been studying mission concepts involving clusters of small spacecraft capable of providing cost-effective solutions in orbit compared to space missions involving only a single larger spacecraft. Low-cost networks of small spacecraft can be a viable alternative to large budget Earth observation or space exploration missions producing significant scientific return for often moderate development efforts and short lead times. This paper is the first in a series of 3 companion papers in which we make the point that the scientific value (and hence the cost effectiveness) of small multi-spacecraft missions can be further increased if the network of spacecraft is allowed to be heterogeneous. We define Heterogeneous Spacecraft Networks (HSNs) to be networks of spacecraft having different operators or originating from different missions that are able to communicate with each other in a low-cost manner and with low impact on overall system resources. HSN incorporates both the space segment and ground segment for an end-to-end solution. In this contribution we illustrate the strength of the HSN approach by presenting a general concept for a HSN in LEO as well as a case study showcasing the value of such a network. In particular, we present a case study where we examine the feasibility of a low-cost, multi-institutional network of small spacecraft acting as a next-generation Earth Observation (EO) platform and focusing on ad-hoc data relay to maximize throughput. In the simulation we show that the downlink throughput of an HSN can be larger by an order of magnitude compared to the conventional scenario where no networking capability exists. Other benefits of using a HSN as a next-generation increment of existing capabilities include increased revisit frequencies as well as the ability to collect correlated data simultaneously from distributed locations around the globe using either conventional or fractionated spacecraft. We list key performance requirements for a HSN in order to produce a desirable scientific return and present a concept of operations (ConOps) for the practical implementation. In the ConOps we discuss the required performance of the inter-satellite and space-to-ground links and give an overview of the associated ground station network. We give an overview of the network management techniques required to operate and control the network on a day-to-day basis and address the issues of network configuration, network discovery and security, as well as fault and performance management. The paper ends with an outlook on the paradigm shift HSNs may introduce in the domain of space operations. We also list a number of promising applications making use of the strength of the concept.

Strengthening innovation at NASA Ames Research Center by encouraging prototyping and collaboration

NASA recognizes that to achieve our mission of driving advancements in science, technology, aeronautics and space exploration, we require ingenuity and teamwork by the NASA workforce. NASA Ames Research Center has sought to support the Ames workforce in achieving the NASA mission by encouraging prototyping and collaboration to strengthen the innovation culture at the Center. In 2012, NASA Ames Research Center opened the SpaceShop Rapid Prototyping Facility, an Agency-unique workforce development facility that encourages low-fidelity prototype development. The SpaceShop is available for all Center personnel to obtain training on traditional manufacturing and computer-numerically-controlled (CNC) equipment for rapid in-house prototyping. Users are encouraged to explore and mature concepts early within the design cycle. Adjacent to the SpaceShop, NASA Ames Research Center built a complementary open workspace, the Ames Collaboratory. The Collaboratory provides the Ames workforce with a communal alternative to conventional meeting rooms by means of modern technology sharing platforms, whiteboards, modular furniture, and supplies to aid collaborative innovation. The Collaboratory also serves as an alternative work space for the workforce. This paper describes the SpaceShop Rapid Prototyping Facility and the Ames Collaboratory, including the objectives, evolving approaches, best practices, and lessons learned. The paper also proposes an initial case study and Key Performance Indicators (KPIs) that measure the adoption, engagement, and impact of the initiatives.

Evaluating UAS Autonomy Operations Software In Simulation

We describe a software simulation test bed for evaluating Concepts of Operation (CONOPS) for Unmanned Aircraft Systems (UAS) flying earth science missions. The Mission Operational Concept Evaluation Framework (MOCEF) aids in the rapid evaluation of proposed system automation designs, including intelligent controllers for vehicles, sensor payloads, and decision support systems, on a wide range of missions. Such broad evaluation is prohibitively expensive when limited to physical experiments and real missions. MOCEF allows evaluation of automation concepts in multiple mission scenarios operating in a wide range of environments. It records mission metric parameters such as the quality of sensor data obtained, flight time, stress on the vehicles, and air traffic control rules infringed or invoked. This information can be fed into specific mission metric formulas to rate performance and into the Google Earth tool for visualization.