Engineering topics

Powers, Edward I.

Publications and source records attributed to Powers, Edward I..

43 records · Page 3

NASA NTRS2000

Automation and Upgrade of Thermal System for Large 38-Year-Young Test Facility

The Goddard Space Flight Center's Space Environment Simulator (SES) facility has been improved by the upgrade of its thermal control hardware and software. This paper describes the preliminary design process, funding constraints, and the proposed enhancements as well as the installation details, the testing difficulties, and the overall benefits realized from this upgrade. The preliminary design process was discussed in a paper presented in October 1996 and will be recapped in this paper to provide background and comparison to actual product. Structuring the procurement process to match the funding constraints allowed Goddard to enhance its capabilities in an environment of reduced budgets. The installation of the new system into a location that has been occupied for over 38 years was one of the driving design factors for the size of the equipment. The installation was completed on time and under budget. The tuning of the automatic sequences for the new thermal system to the existing shroud system required more time and ultimately presented some setbacks to the vendor and the final completion of the system. However, the end product and its benefits to Goddard's thermal vacuum test portfolio will carry the usefulness of this facility well into the next century.

Webb, Andrew T.↗

NASA NTRS2000

Using Model-Based Reasoning for Autonomous Instrument Operation

Multiprobe missions are an important part of NASA's future: Cluster, Magnetospheric Multi Scale, Global Electrodynamics and Magnetospheric Constellation are representatives from the Sun-Earth Connections Theme. To make such missions robust, reliable, and affordable, ideally the many spacecraft of a constellation must be at least as easy to operate as one spacecraft is today. To support this need for scalability, science instrumentation must become increasingly easy to operate, even as this same instrumentation becomes more capable and advanced. Communication and control resources will be at a premium for future instruments. Many missions will be out of contact with ground operators for extended periods either to reduce operations cost or because of orbits that limit communication to weekly perigee transits. Autonomous capability is necessary if such missions are to effectively achieve their operational objectives. An autonomous system is one that acts given its situation in a mission appropriate manner without external direction to achieve mission goals. To achieve this capability autonomy must be built into the system through judicious design or through a built-in intelligence that recognizes system state and manages system response. To recognize desired or undesired system states, the system must have an implicit or explicit understanding of its expected states given its history and self observations. The systems we are concerned with, science instruments, can have stringent requirements for system state knowledge in addition to requirements driven by health and safety concerns. Without accurate knowledge of the system state, the usefulness of the science instrument may be severely limited. At the same time, health and safety concerns often lead to overly conservative instrument operations further reducing the effectiveness of the instrument. These requirements, coupled with overall mission requirements including lack of communication opportunities and tolerance of environmental hazards, frame the problem of constructing autonomous science instruments. we are developing a model of the Low Energy Neutral Atom instrument (LENA) that is currently flying on board the Imager for Magnetosphere-to-Aurora Global Exploration (IMAGE) spacecraft. LENA is a particle detector that uses high voltage electrostatic optics and time-of-flight mass spectrometry to image neutral atom emissions from the denser regions of the Earth's magnetosphere. As with most spacecraft borne science instruments, phenomena in addition to neutral atoms are detected by LENA. Solar radiation and energetic particles from Earth's radiation belts are of particular concern because they may help generate currents that may compromise LENA's long term performance. An explicit model of the instrument response has been constructed and is currently in use on board IMAGE to dynamically adapt LENA to the presence or absence of energetic background radiations. The components of LENA are common in space science instrumentation, and lessons learned by modelling this system may be applied to other instruments. This work demonstrates that a model-based approach can be used to enhance science instrument effectiveness. Our future work involves the extension of these methods to cover more aspects of LENA operation and the generalization to other space science instrumentation.

Johnson, Mike↗

NASA NTRS2000

Upgrade of The Thermal Vacuum Data System at NASA/GSFC

The Goddard Space Flight Center's new thermal vacuum data acquisition system is a networked client-sever application that enables lab operations crews to monitor all tests from a central location. The GSFC thermal vacuum lab consists of eleven chambers in Building 7 and one chamber in Building 10. The new data system was implemented for several reasons. These included the need for centralized data collection, more flexible and easier to use operator interface, greater data accessibility, a reduction in testing time and cost, and increased payload and personnel safety. Additionally, a new data system was needed for year-2000 compliance. This paper discusses the incorporation of the Thermal Vacuum Data System (TVDS) within the thermal vacuum lab at GSFC, its features and capabilities and lessons learned in its implementation. Additional topics include off-center (Internet) capability for remote monitoring and the role of TVDS in the efforts to automate thermal vacuum chamber operations.

Palmer, John↗

NASA NTRS2000

Ground Data System Risk Mitigation Techniques for Faster, Better, Cheaper Missions

With the advent of faster, cheaper, and better missions, NASA Projects acknowledged that a higher level of risk was inherent and accepted with this approach. It was incumbent however upon each component of the Project whether spacecraft, payload, launch vehicle, or ground data system to ensure that the mission would nevertheless be an unqualified success. The Small Explorer (SMEX) program's ground data system (GDS) team developed risk mitigation techniques to achieve these goals starting in 1989. These techniques have evolved through the SMEX series of missions and are practiced today under the Triana program. These techniques are: (1) Mission Team Organization--empowerment of a closeknit ground data system team comprising system engineering, software engineering, testing, and flight operations personnel; (2) Common Spacecraft Test and Operational Control System--utilization of the pre-launch spacecraft integration system as the post-launch ground data system on-orbit command and control system; (3) Utilization of operations personnel in pre-launch testing--making the flight operations team an integrated member of the spacecraft testing activities at the beginning of the spacecraft fabrication phase; (4) Consolidated Test Team--combined system, mission readiness and operations testing to optimize test opportunities with the ground system and spacecraft; and (5). Reuse of Spacecraft, Systems and People--reuse of people, software and on-orbit spacecraft throughout the SMEX mission series. The SMEX ground system development approach for faster, cheaper, better missions has been very successful. This paper will discuss these risk management techniques in the areas of ground data system design, implementation, test, and operational readiness.

Catena, John J.↗

NASA NTRS2000

An Evaluation of the High Level Architecture (HLA) as a Framework for NASA Modeling and Simulation

The High Level Architecture (HLA) is a current US Department of Defense and an industry (IEEE-1516) standard architecture for modeling and simulations. It provides a framework and set of functional rules and common interfaces for integrating separate and disparate simulators into a larger simulation. The goal of the HLA is to reduce software costs by facilitating the reuse of simulation components and by providing a runtime infrastructure to manage the simulations. In order to evaluate the applicability of the HLA as a technology for NASA space mission simulations, a Simulations Group at Goddard Space Flight Center (GSFC) conducted a study of the HLA and developed a simple prototype HLA-compliant space mission simulator. This paper summarizes the prototyping effort and discusses the potential usefulness of the HLA in the design and planning of future NASA space missions with a focus on risk mitigation and cost reduction.

Reid, Michael R.↗

NASA NTRS2000

A Matrix Approach to Software Process Definition

The Software Engineering Laboratory (SEL) is currently engaged in a Methodology and Metrics program for the Information Systems Center (ISC) at Goddard Space Flight Center (GSFC). This paper addresses the Methodology portion of the program. The purpose of the Methodology effort is to assist a software team lead in selecting and tailoring a software development or maintenance process for a specific GSFC project. It is intended that this process will also be compliant with both ISO 9001 and the Software Engineering Institute's Capability Maturity Model (CMM). Under the Methodology program, we have defined four standard ISO-compliant software processes for the ISC, and three tailoring criteria that team leads can use to categorize their projects. The team lead would select a process and appropriate tailoring factors, from which a software process tailored to the specific project could be generated. Our objective in the Methodology program is to present software process information in a structured fashion, to make it easy for a team lead to characterize the type of software engineering to be performed, and to apply tailoring parameters to search for an appropriate software process description. This will enable the team lead to follow a proven, effective software process and also satisfy NASA's requirement for compliance with ISO 9001 and the anticipated requirement for CMM assessment. This work is also intended to support the deployment of sound software processes across the ISC.

Schultz, David↗

NASA NTRS1999

The Submillimeter-Wave Astronomy Satellite: On-Orbit Thermal Performance and Design Retrospective

A large telescope aperture, stringent thermal stability and temperature range requirements, and a passively-cooled 150 K module presented major challenges in thermal design and hardware fabrication of this Small Explorer satellite. This paper reviews briefly the thermal design of the SWAS science instrument, and examines the first three months of on-orbit thermal history. Measured temperatures for both the science payload and the spacecraft module and solar arrays are compared with those predicted by the correlated analytical model. Similarities and differences are interpreted in terms of the major uncertainties remaining after thermal-balance testing, especially those of MLI performance and telescope aperture properties. Review of the thermal model adequacy and thermal design verification are included to suggest improvements in the thermal design process for future missions.

Boyd, David A.↗