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1.
Apostolos A. Christou 《Earth, Moon, and Planets》2004,95(1-4):425-431
Based on the number of planet-approaching cometary orbits at Mars and Venus relative to the Earth, there should be ample opportunities
for observing meteor activity at those two planets. The ratio of planet-approaching Jupiter family comets (JFCs) at Mars,
Earth, and Venus is 4:2:1 indicating that JFC-related outbursts would be more frequent at Mars than the Earth. The relative
numbers of planet-approaching Halley-type comets (HTCs) implies that the respective levels of annual meteor activity at those
three planets are similar. We identify several instances where near-comet outbursts (Jenniskens, P.: 1995, Astron. Astrophys. 295, 206–235) may occur. A possible double outburst of this type at Venus related to 45P/Honda-Mrkos-Padjusakova may be observable
by the ESA Venus Express spacecraft in the summer of 2006. Similarly, the Japanese Planet-C Venus orbiter may observe an outburst related to 27P/Crommelin’s perihelion passage in July 2011. Several additional opportunities
exist to observe such outbursts at Mars from 2019 to 2026 associated with comets 38P/Stephan-Oterma, 13P/Olbers and 114P/Wiseman-Skiff. 相似文献
2.
M Grande R BrowningN Waltham D ParkerS.K Dunkin B KentB Kellett C.H PerryB Swinyard A PerryJ Feraday C HoweG McBride K PhillipsJ Huovelin P MuhliP.J Hakala O VilhuJ Laukkanen N ThomasD Hughes H AlleyneM Grady R LundinS Barabash D BakerP.E Clark C.D MurrayJ Guest I CasanovaL.C d'Uston S MauriceB Foing D.J Heather V FernandesK Muinonen S.S RussellA Christou C OwenP Charles H KoskinenM Kato K SipilaS Nenonen M HolmstromN Bhandari R ElphicD Lawrence 《Planetary and Space Science》2003,51(6):427-433
The D-CIXS Compact X-ray Spectrometer will provide high quality spectroscopic mapping of the Moon, the primary science target of the ESA SMART-1 mission. D-CIXS consists of a high throughput spectrometer, which will perform spatially localised X-ray fluorescence spectroscopy. It will also carry a solar monitor, to provide the direct calibration needed to produce a global map of absolute lunar elemental abundances, the first time this has been done. Thus it will achieve ground breaking science within a resource envelope far smaller than previously thought possible for this type of instrument, by exploiting two new technologies, swept charge devices and micro-structure collimators. The new technology does not require cold running, with its associated overheads to the spacecraft. At the same time it will demonstrate a radically novel approach to building a type of instrument essential for the BepiColombo mission and potential future planetary science targets. 相似文献
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David Asher Mark Bailey Apostolos Christou John McFarland Mark Muir Paul Rafferty 《Astronomy& Geophysics》2002,43(2):2.19-2.21
A possible naked-eye comet that may have been important in early cometary theory is announced by D J Asher , M E Bailey , A Christou , J McFarland , M F Muir and P P Rafferty .
Early indications sugest that Comet C/2002 (Ikeya-Zhang), discovered on 1 February 2002, may brighten to naked-eye visibility in late March 2002. It has also been suggested that it may be identical to one of the brighter comets of the 16th or 17th centuries, namely C/1532 R1 or C/1661 C1. The first of these, observed for more than 100 days towards the end of 1532, played an important role in the development of cometary theory. The second, although identified by Halley as having an orbit similar to that of the comet C/1532 R1, was not seen on its predicted return in 1788/1789 and so was presumably unrelated. Here we present long-term orbital integrations of C/2002 C1 which suggest that it orginated from the Oort cloud, and will be ejected again, within ˜0.3 Myr. There is a chance of 10–20% that it will end its life by falling into the Sun during a Halley-type phase of cometary evolution. The discovery of Ikeya-Zhang so closeto perigee by two amateur astonomers highlights the need for surveys covering both hemispheres to discover long-period and intermediate-period comets on Earth-crossing orbits. 相似文献
Early indications sugest that Comet C/2002 (Ikeya-Zhang), discovered on 1 February 2002, may brighten to naked-eye visibility in late March 2002. It has also been suggested that it may be identical to one of the brighter comets of the 16th or 17th centuries, namely C/1532 R1 or C/1661 C1. The first of these, observed for more than 100 days towards the end of 1532, played an important role in the development of cometary theory. The second, although identified by Halley as having an orbit similar to that of the comet C/1532 R1, was not seen on its predicted return in 1788/1789 and so was presumably unrelated. Here we present long-term orbital integrations of C/2002 C1 which suggest that it orginated from the Oort cloud, and will be ejected again, within ˜0.3 Myr. There is a chance of 10–20% that it will end its life by falling into the Sun during a Halley-type phase of cometary evolution. The discovery of Ikeya-Zhang so closeto perigee by two amateur astonomers highlights the need for surveys covering both hemispheres to discover long-period and intermediate-period comets on Earth-crossing orbits. 相似文献
6.
Armagh Observatory installed a sky monitoring system consisting of two wide angle (90° × 52°) and one medium angle (52° × 35°)
cameras in July 2005. The medium angle camera is part of a double station setup with a similar camera in Bangor, ∼73 km ENE
of Armagh. All cameras use UFOCapture to record meteors automatically; software for off-line photometry, astrometry and double
station calculations is currently being developed. The specifications of the cameras and cluster configuration are described
in detail. 2425 single station meteors (1167, 861 and 806 by the medium-angle and the wide-angle cameras respectively) and
547 double station meteors were recorded during the months July 2005 to Dec 2006. About 212 double station meteors were recorded
by more than one camera in the cluster. The effects of weather conditions on camera productivity are discussed. The distribution
of single and double station meteor counts observed for the years 2005 and 2006 and calibrated for weather conditions are
presented. 相似文献
7.
Watershed morphometric analysis of Wadi Baish Dam catchment area using integrated GIS-based approach
The integration of Remote Sensing (RS) and Geographic Information Systems (GIS) constitutes a powerful tool for the evaluation of watershed morphometric parameters. The benefits of this integration include saving time and effort as well as improving the accuracy of the analysis. Moreover, this technique is appropriate for describing the watershed and its streams. In this study, a detailed morphometric analysis of the Wadi Baish catchment area has been performed using the Shuttle Radar Topography Mission (SRTM). The performed morphometric analysis includes linear, areal, and relief aspects. The results of the morphometric analysis reveal that the catchment can be described as of eighth stream order and consists of an area of 4741.07 km2. Additionally, the basin is characterized by a relatively high mean value of bifurcation (4.012), indicative of the scarcity of permeable rocks with high slope in the area. This value of bifurcation ratio is consistent with the high drainage density value of 2.064 km/km2 and confirms the impermeability of the subsurface material and mountainous relief. The hypsometric integral of the catchment is 47.4%, and the erosion integral of the catchment is 52.6%, both were indications of a mature catchment area. 相似文献
8.
Corey A Cohn Christopher E Pedigo Shavonne N Hylton Sanford R Simon Martin AA Schoonen 《Geochemical transactions》2009,10(1):8-9
Background
Given the importance of highly reactive oxygen species (hROS) as reactants in a wide range of biological, photochemical, and environmental systems there is an interest in detection and quantification of these species. The extreme reactivity of the hROS, which includes hydroxyl radicals, presents an analytical challenge. 3'-(p-Aminophenyl) fluorescein (APF) is a relatively new probe used for measuring hROS. Here, we further evaluate the use of APF as a method for the detection of hydroxyl radicals in particle suspensions. 相似文献9.
J. C. Christou 《Experimental Astronomy》1991,2(1):27-56
The extended Knox-Thompson reduction scheme currently in use at Kitt Peak National Observatory and Steward Observatory for the reduction of infrared speckle interferometry is described in detail. Applications of this algorithm and the less computationally intensive shift-and-add analysis to both simulated and real binary star data is presented demonstrating that the latter may be successfully used for image reconstruction by using a separately measured point source. The performance of both techniques is shown to improve by application of an iterative deconvolution algorithm to apply a priori image constraints without degradation of photometric information.Operated by the Association of Universities for Research in Astronomy Inc. (AURA) under cooperative agreement with the National Science Foundation 相似文献
10.
Alexander Smirnov Douglas Hausner Richard Laffers Daniel R Strongin Martin AA Schoonen 《Geochemical transactions》2008,9(1):1-20
Experiments with dinitrogen-, nitrite-, nitrate-containing solutions were conducted without headspace in Ti reactors (200°C), borosilicate septum bottles (70°C) and HDPE tubes (22°C) in the presence of Fe and Ni metal, awaruite (Ni80Fe20) and tetrataenite (Ni50Fe50). In general, metals used in this investigation were more reactive than alloys toward all investigated nitrogen species. Nitrite and nitrate were converted to ammonium more rapidly than dinitrogen, and the reduction process had a strong temperature dependence. We concluded from our experimental observations that Hadean submarine hydrothermal systems could have supplied significant quantities of ammonium for reactions that are generally associated with prebiotic synthesis, especially in localized environments. Several natural meteorites (octahedrites) were found to contain up to 22 ppm Ntot. While the oxidation state of N in the octahedrites was not determined, XPS analysis of metals and alloys used in the study shows that N is likely present as nitride (N3-). This observation may have implications toward the Hadean environment, since, terrestrial (e.g., oceanic) ammonium production may have been supplemented by reduced nitrogen delivered by metal-rich meteorites. This notion is based on the fact that nitrogen dissolves into metallic melts. 相似文献