Alternative mathematical programming formulations for FSS synthesis

A variety of mathematical programming models and two solution strategies are suggested for the problem of allocating orbital positions to (synthesizing) satellites in the Fixed Satellite Service. Mixed integer programming and almost linear programming formulations are presented in detail for each of two objectives: (1) positioning satellites as closely as possible to specified desired locations, and (2) minimizing the total length of the geostationary arc allocated to the satellites whose positions are to be determined. Computational results for mixed integer and almost linear programming models, with the objective of positioning satellites as closely as possible to their desired locations, are reported for three six-administration test problems and a thirteen-administration test problem

The role of service areas in the optimization of FSS orbital and frequency assignments

A relationship is derived, on a single-entry interference basis, for the minimum allowable spacing between two satellites as a function of electrical parameters and service-area geometries. For circular beams, universal curves relate the topocentric satellite spacing angle to the service-area separation angle measured at the satellite. The corresponding geocentric spacing depends only weakly on the mean longitude of the two satellites, and this is true also for alliptical antenna beams. As a consequence, if frequency channels are preassigned, the orbital assignment synthesis of a satellite system can be formulated as a mixed-integer programming (MIP) problem or approximated by a linear programming (LP) problem, with the interference protection requirements enforced by constraints while some linear function is optimized. Possible objective-function choices are discussed and explicit formulations are presented for the choice of the sum of the absolute deviations of the orbital locations from some prescribed ideal location set. A test problem is posed consisting of six service areas, each served by one satellite, all using elliptical antenna beams and the same frequency channels. Numerical results are given for the three ideal location prescriptions for both the MIP and LP formulations. The resulting scenarios also satisfy reasonable aggregate interference protection requirements

Engineering calculations for communications satellite systems planning

An extended gradient search code for broadcasting satellite service (BSS) spectrum/orbit assignment synthesis is discussed. Progress is also reported on both single-entry and full synthesis computational aids for fixed satellite service (FSS) spectrum/orbit assignment purposes

Broadcasting satellite service synthesis using gradient and cyclic coordinate search procedures

Two search techniques are considered for solving satellite synthesis problems. Neither is likely to find a globally optimal solution. In order to determine which method performs better and what factors affect their performance, we design an experiment and solve the same problem under a variety of starting solution configuration-algorithm combinations. Since there is no randomization in the experiment, we present results of practical, rather than statistical, significance. Our implementation of a cyclic coordinate search procedure clearly finds better synthesis solutions than our implementation of a gradient search procedure does with our objective of maximizing the minimum C/I ratio computed at test points on the perimeters of the intended service areas. The length of the available orbital arc and the configuration of the starting solution are shown to affect the quality of the solutions found

Engineering calculations for communications satellite systems planning

Progress is reported on a computer code to improve the efficiency of spectrum and orbit utilization for the Broadcasting Satellite Service in the 12 GHz band for Region 2. It implements a constrained gradient search procedure using an exponential objective function based on aggregate signal to noise ratio and an extended line search in the gradient direction. The procedure is tested against a manually generated initial scenario and appears to work satisfactorily. In this test it was assumed that alternate channels use orthogonal polarizations at any one satellite location

Beable trajectories for revealing quantum control mechanisms

The dynamics induced while controlling quantum systems by optimally shaped laser pulses have often been difficult to understand in detail. A method is presented for quantifying the importance of specific sequences of quantum transitions involved in the control process. The method is based on a ``beable'' formulation of quantum mechanics due to John Bell that rigorously maps the quantum evolution onto an ensemble of stochastic trajectories over a classical state space. Detailed mechanism identification is illustrated with a model 7-level system. A general procedure is presented to extract mechanism information directly from closed-loop control experiments. Application to simulated experimental data for the model system proves robust with up to 25% noise.Comment: Latex, 20 pages, 13 figure

Dynamics and hysteresis in square lattice artificial spin-ice

Dynamical effects under geometrical frustration are considered in a model for artificial spin ice on a square lattice in two dimensions. Each island of the spin ice has a three-component Heisenberg-like dipole moment subject to shape anisotropies that influence its direction. The model has real dynamics, including rotation of the magnetic degrees of freedom, going beyond the Ising-type models of spin ice. The dynamics is studied using a Langevin equation solved via a second order Heun algorithm. Thermodynamic properties such as the specific heat are presented for different couplings. A peak in specific heat is related to a type of melting-like phase transition present in the model. Hysteresis in an applied magnetic field is calculated for model parameters where the system is able to reach thermodynamic equilibrium.Comment: Revised versio

Variabilidad infrarroja del núcleo activo en NGC 2992

There are galaxies in the Universe that harbour an active nucleus and present variability in the type of emission, varying in their Seyfert type classification, and in their nuclear magnitude. In this work, a photometric study of the galaxy NGC 2992 is presented. In the latest decades, this galaxy has gone through episodes of variability in the optical, infrared, and X-ray ranges. In this contribution, nuclear magnitudes in J band are reported from observations carried on in January 2022 and the magnitude obtained in a 3" aperture is compared with previous reports, finding a variation of 0.8±0.3 magnitudes with respect to 1998.Hay galaxias en el Universo que albergan un núcleo activo y presentan variabilidad en el tipo de emisión, variando en su clasificación tipo Seyfert, y en su magnitud nuclear. En este trabajo se presenta un estudio fotométrico de la galaxia NGC 2992. En las últimas décadas, esta galaxia ha atravesado episodios de variabilidad en los rangos óptico, infrarrojo y de rayos X. En esta contribución se reportan magnitudes nucleares en la banda J a partir de observaciones realizadas en enero de 2022 y se compara la magnitud obtenida en una apertura de 3" con informes anteriores, encontrando una variación de 0,8±0,3 magnitudes con respecto a 1998.Fil: Levis, Selene. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Gaspar, G.. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaFil: Diaz, Carlos Gonzalo. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Mast, D.. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaFil: Diaz, R. J.. Gemini Observatory; Estados Unido

Variabilidad infrarroja del núcleo activo en NGC 2992

There are galaxies in the Universe that harbour an active nucleus and present variability in the type of emission, varying in their Seyfert type classification, and in their nuclear magnitude. In this work, a photometric study of the galaxy NGC 2992 is presented. In the latest decades, this galaxy has gone through episodes of variability in the optical, infrared, and X-ray ranges. In this contribution, nuclear magnitudes in J band are reported from observations carried on in January 2022 and the magnitude obtained in a 3" aperture is compared with previous reports, finding a variation of 0.8±0.3 magnitudes with respect to 1998.Hay galaxias en el Universo que albergan un núcleo activo y presentan variabilidad en el tipo de emisión, variando en su clasificación tipo Seyfert, y en su magnitud nuclear. En este trabajo se presenta un estudio fotométrico de la galaxia NGC 2992. En las últimas décadas, esta galaxia ha atravesado episodios de variabilidad en los rangos óptico, infrarrojo y de rayos X. En esta contribución se reportan magnitudes nucleares en la banda J a partir de observaciones realizadas en enero de 2022 y se compara la magnitud obtenida en una apertura de 3" con informes anteriores, encontrando una variación de 0,8±0,3 magnitudes con respecto a 1998.Fil: Levis, Selene. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Gaspar, G.. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaFil: Diaz, Carlos Gonzalo. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Mast, D.. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaFil: Diaz, R. J.. Gemini Observatory; Estados Unido