2,099 research outputs found
Kalman Filter for Calibrating a Telescope Focal Plane
The instrument-pointing frame (IPF) Kalman filter, and an algorithm that implements this filter, have been devised for calibrating the focal plane of a telescope. As used here, calibration signifies, more specifically, a combination of measurements and calculations directed toward ensuring accuracy in aiming the telescope and determining the locations of objects imaged in various arrays of photodetectors in instruments located on the focal plane. The IPF Kalman filter was originally intended for application to a spaceborne infrared astronomical telescope, but can also be applied to other spaceborne and ground-based telescopes. In the traditional approach to calibration of a telescope, (1) one team of experts concentrates on estimating parameters (e.g., pointing alignments and gyroscope drifts) that are classified as being of primarily an engineering nature, (2) another team of experts concentrates on estimating calibration parameters (e.g., plate scales and optical distortions) that are classified as being primarily of a scientific nature, and (3) the two teams repeatedly exchange data in an iterative process in which each team refines its estimates with the help of the data provided by the other team. This iterative process is inefficient and uneconomical because it is time-consuming and entails the maintenance of two survey teams and the development of computer programs specific to the requirements of each team. Moreover, theoretical analysis reveals that the engineering/ science iterative approach is not optimal in that it does not yield the best estimates of focal-plane parameters and, depending on the application, may not even enable convergence toward a set of estimates
Solid particle erosion of environmental barrier coatings and ceramic matrix composites
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Adaptive Deadband Synchronization for a Spacecraft Formation
A paper discusses general problems in estimation and control of the states (positions, attitudes, and velocities) of spacecraft flying in formation, then addresses the particular formation-flying-control problem of synchronization of deadbands. The paper presents a deadband synchronization algorithm for the case in which the spacecraft are equipped with pulse-width-modulated thrusters for maintaining their required states. The algorithm synchronizes thruster-firing times across all six degrees of freedom of all the spacecraft. The algorithm is scalable, inherently adapts to disturbances, and does not require knowledge of spacecraft masses and disturbance forces. In this algorithm, one degree of freedom of one spacecraft is designated the leader, and all other degrees of freedom of all spacecraft as followers. The Cassini adaptive optimum deadband drift controller is the subalgorithm for control in each degree of freedom, and the adaptation is run until each spacecraft achieves a specified drift period. The adaptation is critical because a different disturbance affects each different degree of freedom. Then the leader communicates its thruster-firing starting times to the followers. Then, for each follower, a deadband-synchronization subalgorithm determines the shift needed to synchronize its drift period with that of the leader
Optimization of State Revenues through the Introduction of Casino Gambling
Thesis advisor: Richard McGowanThis thesis will try to determine whether any state could benefit from the introduction of casino gambling, and if so, how much extra funds could be expected. Massachusetts residents spend an estimated 726 million at out-of-state gambling facilities each year. If this sum were to be spent in-state, Massachusetts would be able to reap a significant percentage of that amount for its state revenues. The same can be said for Rhode Island. West Warwick, Rhode Island is merely 45 minutes away from Foxwoods, and Mohegan Sun is about an hour away, and for a state with a huge deficit, the profit that RI could reap from an instate casino could make the introduction of casinos a worthwhile venture.Thesis (BA) — Boston College, 2003.Submitted to: Boston College. Carroll School of Management.Discipline: Operations and Strategic Management.Discipline: College Honors Program
Air-data estimation for air-breathing hypersonic vehicles
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1996.Includes bibliographical references (p. 194-198).by Bryan Heejin Kang.Ph.D
Air data and surface pressure measurement for hypersonic vehicles
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1989.Includes bibliographical references (leaves 96-97).by Bryan H. Kang.M.S
Advanced materials development under NASA\u27s Hybrid Thermally Efficient Core (HyTEC) project
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Effect of tDCS on aberrant functional network connectivity in refractory hallucinatory schizophrenia: A pilot study
A Comparison of Cosmological Hydrodynamic Codes
We present a detailed comparison of the simulation results of various
cosmological hydrodynamic codes. Starting with identical initial conditions
based on the Cold Dark Matter scenario for the growth of structure, we
integrate from redshift to to determine the physical state within
a representative volume of size where . Five
independent codes are compared: three of them Eulerian mesh based and two
variants of the Smooth Particle Hydrodynamics "SPH" Lagrangian approach. The
Eulerian codes were run at cells,
the SPH codes at and particles. Results were then rebinned
to a grid with the expectation that the rebinned data should converge,
by all techniques, to a common and correct result as . We
find that global averages of various physical quantities do, as expected, tend
to converge in the rebinned model, but that uncertainties in even primitive
quantities such as , persists
at the 3\%-17\% level after completion of very large simulations. The two SPH
codes and the two shock capturing Eulerian codes achieve comparable and
satisfactory accuracy for comparable computer time in their treatment of the
high density, high temperature regions as measured in the rebinned data; the
variance among the five codes (at highest resolution) for the mean temperature
(as weighted by ) is only 4.5\%. Overall the comparison allows us to
better estimate errors, it points to ways of improving this current generation
of hydrodynamic codes and of suiting their use to problems which exploit their
individually best features.Comment: 20p plaintex to appear in The Astrophysical Journal on July 20, 199
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