Trajectory computation during a maneuver: Thrust estimation with the Goddard Trajectory Determination System (GTDS)

Existing thrust modeling capabilities of the Goddard Trajectory Determination System (GTDS) have been enhanced to allow calibration of the onboard propulsion system. These enhancements provide one or more thrust scale factors, based on estimation using the batch least-squares technique, for the case of along-track thrust and the case of attitude-dependent thrust. The enhancements are evaluated using simulated tracking measurements for a test spacecraft and using actual tracking measurements for the Earth Radiation Budget Satellite (ERBS). The effects of tracking measurement noise and distribution on the accuracy of the estimation are investigated and found to be significant. Results and conclusions of the analysis are presented

Energy-optimal steering of transitions through a fractal basin boundary.

We study fluctuational transitions in a discrete dy- namical system having two co-existing attractors in phase space, separated by a fractal basin boundary. It is shown that transitions occur via a unique ac- cessible point on the boundary. The complicated structure of the paths inside the fractal boundary is determined by a hierarchy of homoclinic original sad- dles. By exploiting an analogy between the control problem and the concept of an optimal fluctuational path, we identify the optimal deterministic control function as being equivalent to the optimal fluctu- ational force obtained from a numerical analysis of the fluctuational transitions between two states

Automation of orbit determination functions for National Aeronautics and Space Administration (NASA)-supported satellite missions

The Flight Dynamics Facility (FDF) at Goddard Space Flight Center (GSFC) provides spacecraft trajectory determination for a wide variety of National Aeronautics and Space Administration (NASA)-supported satellite missions, using the Tracking Data Relay Satellite System (TDRSS) and Ground Spaceflight and Tracking Data Network (GSTDN). To take advantage of computerized decision making processes that can be used in spacecraft navigation, the Orbit Determination Automation System (ODAS) was designed, developed, and implemented as a prototype system to automate orbit determination (OD) and orbit quality assurance (QA) functions performed by orbit operations. Based on a machine-resident generic schedule and predetermined mission-dependent QA criteria, ODAS autonomously activates an interface with the existing trajectory determination system using a batch least-squares differential correction algorithm to perform the basic OD functions. The computational parameters determined during the OD are processed to make computerized decisions regarding QA, and a controlled recovery process isactivated when the criteria are not satisfied. The complete cycle is autonomous and continuous. ODAS was extensively tested for performance under conditions resembling actual operational conditions and found to be effective and reliable for extended autonomous OD. Details of the system structure and function are discussed, and test results are presented

Fast Monte Carlo simulations and singularities in the probability distributions of non-equilibrium systems

A numerical technique is introduced that reduces exponentially the time required for Monte Carlo simulations of non-equilibrium systems. Results for the quasi-stationary probability distribution in two model systems are compared with the asymptotically exact theory in the limit of extremely small noise intensity. Singularities of the non-equilibrium distributions are revealed by the simulations.Comment: 4 pages, 4 figure

Analisis Bauran Pemasaran Jamur Tiram di Kota Pekanbaru

The research aims to figure out the characteristic of Oyster Mushroom in Pekanbaru, the level of belief, consumers' importance and consumers' attitude on marketing mix of Oyster Mushroom in Pekanbaru. The research was carried out on Limbungan street BPD Complex in Rumbai Pekanbaru. This research used primary data that was gained from interview and secondary data that was gained from Board of Statistic Center and other references, and then those data were analayzed by using validity and reliability test, importance and belief level, cartesian diagram, Multiattribute Fishbein. The result showed that the biggest number of consumers' chracteristicswere in productive age41-50 years old, female, mostly in S1 and High School as the educational level, and jobs were housewife and private employee, with 2-3 children, with income range between Rp. 3,000,000-Rp.5,000,000/month, and have been subscribing for 4-6 months. The attributes of Oyster Mushroom producer with above the average level of belief were the affordable price, discount, reachable location, packaging, texture, benefit, nutrients, and expiry. The attributes with below the average level of belief were the price that was cheaper than other types of mushroom, parking area, the street condition, hygiene and the place comfortability, promotion in newspaper and billboard. The attributes of Oyster Mushroom producer with above the average level of importance were affordable price, discount, reachable location, good street condition, hygiene, and the place comfortability, product availibility, texture, benefit, nutrients, and expiry. The consumers' attitude toward the Oyster Mushroom producer according to the scale score was 436.2273it was located in “a bit agree scale of measurement” (5), therefore the consumers' attitude in the research was chategorized as “a bit agree” in scale of measurement

Solution of the boundary value problem for nonlinear flows and maps

Fluctuational escape via an unstable limit cycle is investigated in stochastic flows and maps. A new topological method is suggested for analysis of the corresponding boundary value problems when the action functional has multiple local minima along the escape trajectories and the search for the global minimum is otherwise impossible. The method is applied to the analysis of the escape problem in the inverted Van der Pol oscillator and in the Henon map. An application of this technique to solution of the escape problem in chaotic maps with fractal boundaries, and in maps with chaotic saddles embedded within the basin of attraction, is discussed

Exponentially fast Monte Carlo simulations for non equilibrium systems.

A new numerical technique is demonstrated and shown to reduce exponentially the time required for Monte Carlo simulations of non-equilibrium systems. The quasi stationary probability dis- tribution is computed for two model systems, and the results are compared with the asymptotically exact theory in the limit of extremely small noise intensity. Singularities of the non-equilibrium distributions are revealed by the simulations

Dynamics importance sampling for the collection of switching events in vertical-cavity surface-emitting lasers

A numerical approach based on dynamic importance sampling (DIMS) is applied to investigate polarization switches in vertical-cavity surface-emitting lasers. A polarization switch is described as an activation process in a two-dimensional nonequilibrium system. DIMS accelerates the simulations and allows access to noise intensities that were previously forbidden, revealing qualitative changes in the shape of the transition paths with noise intensity