Ionospheric refraction effects on TOPEX orbit determination accuracy using the Tracking and Data Relay Satellite System (TDRSS)

This investigation concerns the effects on Ocean Topography Experiment (TOPEX) spacecraft operational orbit determination of ionospheric refraction error affecting tracking measurements from the Tracking and Data Relay Satellite System (TDRSS). Although tracking error from this source is mitigated by the high frequencies (K-band) used for the space-to-ground links and by the high altitudes for the space-to-space links, these effects are of concern for the relatively high-altitude (1334 kilometers) TOPEX mission. This concern is due to the accuracy required for operational orbit-determination by the Goddard Space Flight Center (GSFC) and to the expectation that solar activity will still be relatively high at TOPEX launch in mid-1992. The ionospheric refraction error on S-band space-to-space links was calculated by a prototype observation-correction algorithm using the Bent model of ionosphere electron densities implemented in the context of the Goddard Trajectory Determination System (GTDS). Orbit determination error was evaluated by comparing parallel TOPEX orbit solutions, applying and omitting the correction, using the same simulated TDRSS tracking observations. The tracking scenarios simulated those planned for the observation phase of the TOPEX mission, with a preponderance of one-way return-link Doppler measurements. The results of the analysis showed most TOPEX operational accuracy requirements to be little affected by space-to-space ionospheric error. The determination of along-track velocity changes after ground-track adjustment maneuvers, however, is significantly affected when compared with the stringent 0.1-millimeter-per-second accuracy requirements, assuming uncoupled premaneuver and postmaneuver orbit determination. Space-to-space ionospheric refraction on the 24-hour postmaneuver arc alone causes 0.2 millimeter-per-second errors in along-track delta-v determination using uncoupled solutions. Coupling the premaneuver and postmaneuver solutions, however, appears likely to reduce this figure substantially. Plans and recommendations for response to these findings are presented

Atmospheric drag model calibrations for spacecraft lifetime prediction

Although solar activity prediction uncertainty normally dominates decay prediction error budget for near-Earth spacecraft, the effect of drag force modeling errors for given levels of solar activity needs to be considered. Two atmospheric density models, the modified Harris-Priester model and the Jacchia-Roberts model, to reproduce the decay histories of the Solar Mesosphere Explorer (SME) and Solar Maximum Mission (SMM) spacecraft in the 490- to 540-kilometer altitude range were analyzed. Historical solar activity data were used in the input to the density computations. For each spacecraft and atmospheric model, a drag scaling adjustment factor was determined for a high-solar-activity year, such that the observed annual decay in the mean semimajor axis was reproduced by an averaged variation-of-parameters (VOP) orbit propagation. The SME (SMM) calibration was performed using calendar year 1983 (1982). The resulting calibration factors differ by 20 to 40 percent from the predictions of the prelaunch ballistic coefficients. The orbit propagations for each spacecraft were extended to the middle of 1988 using the calibrated drag models. For the Jaccia-Roberts density model, the observed decay in the mean semimajor axis of SME (SMM) over the 4.5-year (5.5-year) predictive period was reproduced to within 1.5 (4.4) percent. The corresponding figure for the Harris-Priester model was 8.6 (20.6) percent. Detailed results and conclusions regarding the importance of accurate drag force modeling for lifetime predictions are presented

Anterior segment optical coherence tomography changes with introduction and discontinuation of tamsulosin

published_or_final_versio

Theory of the Hunter-Covey Interface

We established mathematical models and explored the role of a learned response (avoidance behavior) to understand and manage the hunter-covey interface. Furthermore, we examined the dynamic nature of the probability of flush, given encounter, in a population that learned to avoid hunters as time passed. Learning rate was defined as the proportion of a covey that leaves the naive population and enters the experienced population per unit of hunter-covey contact. The conditional probability of flushing and shooting at a covey, given a covey encounter, declined through the season. This is because the probability of flushing was lower for experienced than for naive coveys and the population of experienced coveys grew with exposure. Thus, quality of hunting declined at a faster rate than quail population; i.e., birds became more wary as the hunting season progresses. The birds\u27 ability to avoid hunters provided an explanation of the sudden reappearance of bobwhites contributing to reproduction in areas where hunters were unsuccessful the previous hunting season. Management can use our models to manipulate the interface and obtain a desired population following the hunting season

Evaluation of advanced geopotential models for operational orbit determination

To meet future orbit determination accuracy requirements for different NASA projects, analyses are performed using Tracking and Data Relay Satellite System (TDRSS) tracking measurements and orbit determination improvements in areas such as the modeling of the Earth's gravitational field. Current operational requirements are satisfied using the Goddard Earth Model-9 (GEM-9) geopotential model with the harmonic expansion truncated at order and degree 21 (21-by-21). This study evaluates the performance of 36-by-36 geopotential models, such as the GEM-10B and Preliminary Goddard Solution-3117 (PGS-3117) models. The Earth Radiation Budget Satellite (ERBS) and LANDSAT-5 are the spacecraft considered in this study

Subaru Spectroscopy and Spectral Modeling of Cygnus A

We present high angular resolution ($\sim$0.5$^\prime$$^\prime$) MIR spectra of the powerful radio galaxy, Cygnus A, obtained with the Subaru telescope. The overall shape of the spectra agree with previous high angular resolution MIR observations, as well as previous Spitzer spectra. Our spectra, both on and off nucleus, show a deep silicate absorption feature. The absorption feature can be modeled with a blackbody obscured by cold dust or a clumpy torus. The deep silicate feature is best fit by a simple model of a screened blackbody, suggesting foreground absorption plays a significant, if not dominant role, in shaping the spectrum of Cygnus A. This foreground absorption prevents a clear view of the central engine and surrounding torus, making it difficult to quantify the extent the torus attributes to the obscuration of the central engine, but does not eliminate the need for a torus in Cygnus A

Method for Simultaneous Monitoring of Uterine Contractions and Abdominal Pushing in a Childbirth

Effective and safe labour requires good cooperation of all the physiological systems. A proper synchronization of uterine and abdominal muscles is necessary for labour progression. Therefore, a new method for simultaneous monitoring of uterine activities and parturient’s pushing efforts is presented. A high sampled, rectified electrohysterographic signal is divided into a low, uterine passband (0.1-3.00Hz) and a high, muscular (40-100Hz) one. The time-dependent mean frequencies arse estimated for each passband separately. At the moments of uterine contraction the time-dependent LOW mean frequency was locally increased. During parturient’s pushing effort the HIGH mean frequency was increased in the manner typical for the skeletal muscles. It seems that the proposed method would be less sensitive to a measuring noise than the previously published RMS based estimators. Moreover, the proposed method enables to monitor fatigue of a uterus or abdominal muscles during the prolonged 2nd stage of a labour. It can be helpful to make a decision of Caesarean section

Contribuição da bracatinga (Mimosa scabrella) para a produção de serapilheira em sistema silvipastoril agroecológico.

O presente trabalho teve por objetivo analisar a produção e o conteúdo de nutrientes da serapilheira produzida por árvores de bracatinga em uma área de pastagem agroecológica, localizada no CPRA ? Centro Paranaense de Referência em Agroecologia. As coletas de material foram efetuadas mensalmente, entre fevereiro de 2010 e julho de 2012. Com base na quantidade de matéria seca e dos teores de N, P, K, Ca e Mg foi obtida a estimativa da quantidade destes elementos aportados à pastagem pela serapilheira. A produção média de serapilheira foi de 2.006 kg de matéria seca por hectare por ano, correspondendo a uma incorporação ao solo de 30 kg de N, 0,4 kg de P, 3,8 kg de K, 7,4 kg de Ca e 3,2 kg de Mg

Inertial Focusing of Particles in Curved Micro-channels

Inertial focusing is the migration of particles in flow laterally across a channel into well-defined equilibrium positions. In microfluidic channels, inertial focusing takes advantage of hydrodynamic interactions even at high flow speeds. Particle isolation through inertial focusing is a high throughput method of processing biological samples for point-of-care diagnostics. While photos provide qualitative analyses of inertial focusing, we desired quantitative characterization of these systems. In this study, we ran flow experiments, first with fluorescent polystyrene beads and later with cells in solution, through curved micro-channels at controlled rates using a syringe pump. Our results from polystyrene bead experiments confirmed previous studies on flow through curved micro-channels, in which particles are focused along both sides of the channel at low flow rates and transition towards the center of the channel as the flow rate increases. FWHM analysis also showed that the streamline width is minimized at an intermediate flow rate, indicating inertial focusing is optimized under that condition. As this method of analysis was confirmed with polystyrene beads, we further used this analysis method to characterize the focusing of cells in solution. To maximize both throughput and purity, microfluidic devices must be designed to operate at the highest flow rate at which effective separation from bulk fluid can occur. The device presented in this report indeed isolates the desired target cells to be studied in downstream characterization.http://deepblue.lib.umich.edu/bitstream/2027.42/169578/1/Honors_Capstone_Anna_Kaehr.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/169578/2/Kaehr_Anna_Capstone_Poster.pptxhttp://deepblue.lib.umich.edu/bitstream/2027.42/169578/3/Capstone_Presentation_Video_Anna_Kaehr.mp

Sistemas silvipastoriles agroecológicos con espécies nativas como estratégia de conservassem de la biodiversidad.

IUFROLAT 2013. Disponibilizado online. Resumen