Recent Experiences of the NASA Engineering and Safety Center (NESC) GN and C Technical Discipline Team (TDT)

The NASA Engineering and Safety Center (NESC), initially formed in 2003, is an independently funded NASA Program whose dedicated team of technical experts provides objective engineering and safety assessments of critical, high risk projects. The GN&C Technical Discipline Team (TDT) is one of fifteen such discipline-focused teams within the NESC organization. The TDT membership is composed of GN&C specialists from across NASA and its partner organizations in other government agencies, industry, national laboratories, and universities. This paper will briefly define the vision, mission, and purpose of the NESC organization. The role of the GN&C TDT will then be described in detail along with an overview of how this team operates and engages in its objective engineering and safety assessments of critical NASA projects. This paper will then describe selected recent experiences, over the period 2007 to present, of the GN&C TDT in which they directly performed or supported a wide variety of NESC assessments and consultations

A Survey of the Spacecraft Line-Of-Sight Jitter Problem

Predicting, managing, controlling, and testing spacecraft Line-of-Sight (LoS) jit- ter due to on-board internal disturbance sources is a challenging multi- disciplinary systems engineering problem, especially for those observatories hosting extremely sensitive optical sensor payloads with stringent requirements on allowable LoS jitter. Some specific spacecraft jitter engineering challenges will be introduced and described in this survey paper. Illustrative examples of missions where dynamic interactions have to be addressed to satisfy demanding payload instrument LoS jitter requirements will be provided. Some lessons learned and a set of recommended rules of thumb are also presented to provide guidance for analysts on where to initiate and how to approach a new spacecraft jitter design problem. These experience-based spacecraft jitter lessons learned and rules of thumb are provided in the hope they can be leveraged on new space system development projects to help overcome unfamiliarity with previously identified jitter technical pitfalls and challenges

Present Challenges, Critical Needs, and Future Technological Directions for NASA's GN and C Engineering Discipline

The National Aeronautics and Space Administration (NASA) is currently undergoing a substantial redirection. Notable among the changes occurring within NASA is the stated emphasis on technology development, integration, and demonstration. These new changes within the Agency should have a positive impact on the GN&C discipline given the potential for sizeable investments for technology development and in-space demonstrations of both Autonomous Rendezvous & Docking (AR&D) systems and Autonomous Precision Landing (APL) systems. In this paper the NASA Technical Fellow for Guidance, Navigation and Control (GN&C) provides a summary of the present technical challenges, critical needs, and future technological directions for NASA s GN&C engineering discipline. A brief overview of the changes occurring within NASA that are driving a renewed emphasis on technology development will be presented as background. The potential benefits of the planned GN&C technology developments will be highlighted. This paper will provide a GN&C State-of-the-Discipline assessment. The discipline s readiness to support the goals & objectives of each of the four NASA Mission Directorates is evaluated and the technical challenges and barriers currently faced by the discipline are summarized. This paper will also discuss the need for sustained investments to sufficiently mature the several classes of GN&C technologies required to implement NASA crewed exploration and robotic science missions

Recent Experiences of the NASA Engineering and Safety Center (NESC) Guidance Navigation and Control (GN and C) Technical Discipline Team (TDT)

The NASA Engineering and Safety Center (NESC) is an independently funded NASA Program whose dedicated team of technical experts provides objective engineering and safety assessments of critical, high risk projects. NESC's strength is rooted in the diverse perspectives and broad knowledge base that add value to its products, affording customers a responsive, alternate path for assessing and preventing technical problems while protecting vital human and national resources. The Guidance Navigation and Control (GN&C) Technical Discipline Team (TDT) is one of fifteen such discipline-focused teams within the NESC organization. The TDT membership is composed of GN&C specialists from across NASA and its partner organizations in other government agencies, industry, national laboratories, and universities. This paper will briefly define the vision, mission, and purpose of the NESC organization. The role of the GN&C TDT will then be described in detail along with an overview of how this team operates and engages in its objective engineering and safety assessments of critical NASA

Spacecraft Hybrid (Mixed-Actuator) Attitude Control Experiences on NASA Science Missions

There is a heightened interest within NASA for the design, development, and flight implementation of mixed-actuator hybrid attitude control systems for science spacecraft that have less than three functional reaction wheel actuators. This interest is driven by a number of recent reaction wheel failures on aging, but what could be still scientifically productive, NASA spacecraft if a successful hybrid attitude control mode can be implemented. Over the years, hybrid (mixed-actuator) control has been employed for contingency attitude control purposes on several NASA science mission spacecraft. This paper provides a historical perspective of NASA's previous engineering work on spacecraft mixed-actuator hybrid control approaches. An update of the current situation will also be provided emphasizing why NASA is now so interested in hybrid control. The results of the NASA Spacecraft Hybrid Attitude Control Workshop, held in April of 2013, will be highlighted. In particular, the lessons learned captured from that workshop will be shared in this paper. An update on the most recent experiences with hybrid control on the Kepler spacecraft will also be provided. This paper will close with some future considerations for hybrid spacecraft control

The NASA Engineering and Safety Center (NESC) GN and C Technical Discipline Team (TDT): Its Purpose, Practices and Experiences

This paper will briefly define the vision, mission, and purpose of the NESC organization. The role of the GN&C TDT will then be described in detail along with an overview of how this team operates and engages in its objective engineering and safety assessments of critical NASA projects. This paper will then describe key issues and findings from several of the recent GN&C-related independent assessments and consultations performed and/or supported by the NESC GN&C TDT. Among the examples of the GN&C TDT s work that will be addressed in this paper are the following: the Space Shuttle Orbiter Repair Maneuver (ORM) assessment, the ISS CMG failure root cause assessment, the Demonstration of Autonomous Rendezvous Technologies (DART) spacecraft mishap consultation, the Phoenix Mars lander thruster-based controllability consultation, the NASA in-house Crew Exploration Vehicle (CEV) Smart Buyer assessment and the assessment of key engineering considerations for the Design, Development, Test & Evaluation (DDT&E) of robust and reliable GN&C systems for human-rated spacecraft

The interrelation of process techniques and space radiation effects in metal-insulator-semiconductor structures Final report, 21 Apr. 1966 - 31 Jul. 1967

Interrelation of process techniques and space radiation effects in metal oxide semiconductor

Varietal Preferences of Erythroneura Leafhoppers (Homoptera: Cicadellidae) Feeding on Grapes in New York

Species composition of Erythroneura leafhoppers infesting the 3 major classes of grapes grown in New York was investigated. Eastern grape leafhopper, E. comes (Say), comprised 74-100% of populations collected on the native American (Vitis labrusca Bailey) cultivars ‘Concord', ‘Niagara', ‘Catawba' and ‘Delaware'. On interspecific hybrid (Vitis sp.) and Vitis vinifera L. cultivars, E. comes was largely absent, and 97-100% of leafhoppers collected were 2 cryptic species, E. bistrata McAtee and E. vitifex Fitch. On the native American variety ‘Elvira', a V. labrusca X V riparia Michaux hybrid, field populations were 24% E. comes and 74% the E. bistrata/vitifex complex. E. vitis (Harris), E. tricinta Fitch, and E. vulnerata Fitch were also present in commercial grapes, but never exceeded 20% of the populations sampled. Populations on wild V. riparia adjacent to vineyards were comprised of 24% E. comes, 47% E. histrata/vitifex, 19% E. vitis, and 10% E. tricinta. Dissection revealed that proportions of E. bistrata and E. vitifex in field collections, varied from 97% E. bistrata to 61% E. vitifex. Oviposition of E. comes and E. bistrata on V. vinifera, interspecific hybrid, and native American cultivars was compared in greenhouse choice tests and field no-choice tests. In choice tests, E. comes laid more eggs on Concord and Elvira than on the interspecific hybrid ‘Seyval blanc', or the V. vinifera cultivar ‘White Riesling'. E. bistrata did not oviposit on Concord when paired with either Elvira, Seyval blanc or White Riesling. When caged to grape leaves in no-choice tests, E. comes laid the most eggs on native American cultivars and the fewest on V. vinifera and interspecific hybrids; E. bistrata laid the most eggs on hybrid and V. vinifera cultivars, and very few eggs on three native American cultivars. These results show that E. bistrata and E. vitifex are the principal pest species on V. vinifera and many interspecific hybrid cultivars in New York, and that E. comes is the principal leafhopper pest on native American V. labrusca cultivar

Influence of Temperature-Driven Phenology and Photoperiodic Induction of Reproductive Diapause on Population Dynamics of Erythroneura comes (Homoptera: Cicadellidae)

The influence of degree-day accumulations and photoperiodic induction of diapause on the phenology of Erythroneura Comes (Say) was investigated. In growth chamber experiments, nymphs reared at photoperiods of 710 degree days (DD) before 1 August are required to produce a 2nd generation of E. comes under climatic conditions in New York.Variationsin temperature-driven development are hypothesized to strongly influence year-to-year variability in leafhopper abundance. Degree-day accumulations by 30 June correlated well with degree-days by 1 August and may provide a useful early-warningsystem for predicting years in which leafhopper population densities are above averag

NASA Workshop on Hybrid (Mixed-Actuator) Spacecraft Attitude Control

At the request of the Science Mission Directorate Chief Engineer, the NASA Technical Fellow for Guidance, Navigation & Control assembled and facilitated a workshop on Spacecraft Hybrid Attitude Control. This multi-Center, academic, and industry workshop, sponsored by the NASA Engineering and Safety Center (NESC), was held in April 2013 to unite nationwide experts to present and discuss the various innovative solutions, techniques, and lessons learned regarding the development and implementation of the various hybrid attitude control system solutions investigated or implemented. This report attempts to document these key lessons learned with the 16 findings and 9 NESC recommendations