The gas production rate of periodic comet d'Arrest

Comet P/d'Arrest is a potential target for a rendezvous mission to a short period comet. Its light curve is rather peculiar, the comet being active only after perihelion passage. One apparition out of two is easy to observe from the ground. The 1995 apparition of the comet will offer a unique opportunity to characterize the outgassing properties of its nucleus

Orbital error analysis for comet Encke, 1980

Before a particular comet is selected as a flyby target, the following criteria should be considered in determining its ephemeris uncertainty: (1) A target comet should have good observability during the apparition of the proposed intercept; and (2) A target comet should have a good observational history. Several well observed and consecutive apparitions allow an accurate determination of a comet's mean motion and nongravitational parameters. Using these criteria, along with statistical and empirical error analyses, it has been demonstrated that the 1980 apparition of comet Encke is an excellent opportunity for a cometary flyby space probe. For this particular apparition, a flyby to within 1,000 km of comet Encke seems possible without the use of sophisticated and expensive onboard navigation instrumentation

Trajectory and sighting analysis for first- apparition comets

Statistical, trajectory, and sighting analysis for first-apparition comets - flight path parameters - astronom

An Exploration of the Context and Ecclesiastical Investigations of the Virgin\u27s Reported Appearance in Knock, Ireland in 1879

On August 21, 1879, the Blessed Virgin Mary, St. Joseph, St. John the Evangelist, and the Lamb of God reportedly appeared in Knock, Ireland. Ecclesiastical authorities of the Roman Catholic Church investigated this reported apparition in 1879 and again in 1936. The first chapter of this paper explores the processes by which the Church investigates alleged apparitions and considers different models for conceptualizing the Church. The second chapter unpacks the context of two nineteenth century French apparitions. The third chapter explores the Knock apparition and the immediate historical context surrounding the apparition. The analyses in the first two chapters serve as lenses for making sense of the interpretations and reception of the Knock apparition. The analysis of the Knock apparition in the third chapter suggests that the laity interpreted the Knock apparition as a sign of comfort from the Virgin Mary after experiencing much suffering during the Great Famine and the Land War. In contrast, the local bishops were more reserved in making a definitive judgment about the authenticity and meaning of the apparition. The analyses also suggest that some sort of recognition from the clergy and enthusiasm from the laity is needed in order for the fruits of an apparition to endure

Perfect partial reconstructions for multiple simultaneous sources

A major focus of research in the seismic industry of the past two decades has been the acquisition and subsequent separation of seismic data using multiple sources fired simultaneously. The recently introduced method of {\it signal apparition} provides a new take on the problem by replacing the random time-shifts usually employed to encode the different sources by fully deterministic periodic time-shifts. In this paper we give a mathematical proof showing that the signal apparition method results in optimally large regions in the frequency-wavenumber space where exact separation of sources is achieved. These regions are diamond-shaped and we prove that using any other method of source encoding results in strictly smaller regions of exact separation. The results are valid for arbitrary number of sources. Numerical examples for different number of sources (three resp.~four sources) demonstrate the exact recovery of these diamond-shaped regions. The theoretical proofs' implementation in the field is illustrated by the results of a conducted field test.Comment: 16 pages, 5 figures. Expanded Section 3 with an additional numerical experiment and the results of a field test. Added reference