The Orbital and Absolute Magnitude Distributions of Main Belt Asteroids

We have developed a model-independent analytical method for debiasing the four-dimensional (a,e,i,H) distribution obtained in any asteroid observation program and have applied the technique to results obtained with the 0.9m Spacewatch Telescope. From 1992 to 1995 Spacewatch observed ~3740 deg^2 near the ecliptic and made observations of more than 60,000 asteroids to a limiting magnitude of V~21. The debiased semi-major axis and inclination distributions of Main Belt asteroids in this sample with 11.5<= H <16 match the distributions of the known asteroids with H <11.5. The absolute magnitude distribution was studied in the range 8< H <17.5. We have found that the set of known asteroids is complete to about absolute magnitudes 12.75, 12.25 and 11.25 in the inner, middle and outer regions of the belt respectively. The number distribution as a function of absolute magnitude cannot be represented by a single power-law (10^{alpha H}) in any region. We were able to define broad ranges in H in each part of the belt where alpha was nearly constant. Within these ranges of H the slope does not correspond to the value of 0.5 expected for an equilibrium cascade in self-similar collisions (Dohnanyi, 1971). The value of alpha varies with absolute magnitude and shows a `kink' in all regions of the belt for H~13. This absolute magnitude corresponds to a diameter ranging from about 8.5 to 12.5 km depending on the albedo or region of the belt.Comment: 33 pages, 6 figures, 6 tables. published in Icaru

Partizipation und Kooperation zur Realisierung von Naturschutzprojekten im Biosphärenreservat Rhön

Naturschutzmanagement kann mit zwei gegensätzlichen Ansätzen verfolgt werden (STOLL-KLEEMANN 2002): Die „ecology-first“-Perspektive sieht ihre Prioritäten strikt in der Dominanz ökologischer Prinzipien. Dagegen stellt die „people-included“-Perspektive die Menschen vor Ort in das Zentrum eines nachhaltigen Ressourcenmanagements, sie geht von einer Wechselwirkung zwischen der Integrität von Ökosystemen und nachhaltigen Lebens- und Wirtschaftsweisen der lokalen Bevölkerung aus. Ressourcenmanagement ist umfassend zu verstehen: Es schließt die biotischen Ressourcen (Biodiversität)ein. Der Begriff des Managements meint nicht allein die Steuerung der direkten wirtschaftlichen Nutzung von Ressourcen, sondern auch von Nichtnutzung, die erforderlich ist, um bestimmte Ressourcen zu erhalten – wie für den Erhalt natürlicher Prozesse und davon abhängiger Biodiversität (Wildnisschutz)

Impact cratering on Mercury: consequences for the spin evolution

Impact basins identified by Mariner 10 and Messenger flyby images provide us a fossilized record of the impactor flux of asteroids on Mercury during the last stages of the early Solar System. The distribution of these basins is not uniform across the surface, and is consistent with a primordial synchronous rotation (Wieczorek et al. 2012). By analyzing the size of the impacts, we show that the distribution for asteroid diameters D < 110 km is compatible with an index power law of 1.2, a value that matches the predicted primordial distribution of the main-belt. We then derive a simple collisional model coherent with the observations, and when combining it with the secular evolution of the spin of Mercury, we are able to reproduce the present 3/2 spin-orbit resonance (about 50% of chances), as well as a primordial synchronous rotation. This result is robust with respect to variations in the dissipation and collisional models, or in the initial spin state of the planet.Comment: 6 pages, 3 tables, 2 figure

Rhön im Fluss - ein Projekt zur Revitalisierung von Fließgewässern

Unter dem Titel RHÖN IM FLUSS startete die Zoologische Gesellschaft Frankfurt e.V. (ZGF)am 1. Juni 2003 gemeinsam mit den drei Verwaltungsstellen des Biosphärenreservats in Bayern, Hessen und Thüringen sowie der länderübergreifenden informellen Arbeitsgemeinschaft Artenschutz im Biosphärenreservat Rhön ein Projekt zur Revitalisierung von Fließgewässern. Die Initiative für das Vorhaben entstand aus dem Projekt „Artenschutz im Biosphärenreservat Rhön“, welches die ZGF seit 1996 fördert. Projektziel ist, in der Landschaft zahlreiche Exempel zu setzen, um zu zeigen, was zu tun ist und wie dieses bewerkstelligt werden kann. Längerfristig soll das Projekt zum „Selbstläufer“ werden. Es bleibt zu hoffen, dass die „Welle“ der positiven Beispiele auch zu den vielen anderen Fließgewässern in der Rhön schwappt und vielfältige Nachahmung erfährt

Efficient intra- and inter-night linking of asteroid detections using kd-trees

The Panoramic Survey Telescope And Rapid Response System (Pan-STARRS) under development at the University of Hawaii's Institute for Astronomy is creating the first fully automated end-to-end Moving Object Processing System (MOPS) in the world. It will be capable of identifying detections of moving objects in our solar system and linking those detections within and between nights, attributing those detections to known objects, calculating initial and differentially-corrected orbits for linked detections, precovering detections when they exist, and orbit identification. Here we describe new kd-tree and variable-tree algorithms that allow fast, efficient, scalable linking of intra and inter-night detections. Using a pseudo-realistic simulation of the Pan-STARRS survey strategy incorporating weather, astrometric accuracy and false detections we have achieved nearly 100% efficiency and accuracy for intra-night linking and nearly 100% efficiency for inter-night linking within a lunation. At realistic sky-plane densities for both real and false detections the intra-night linking of detections into `tracks' currently has an accuracy of 0.3%. Successful tests of the MOPS on real source detections from the Spacewatch asteroid survey indicate that the MOPS is capable of identifying asteroids in real data.Comment: Accepted to Icaru

The population of natural Earth satellites

Peer reviewe

Identifying Near Earth Object Families

The study of asteroid families has provided tremendous insight into the forces that sculpted the main belt and continue to drive the collisional and dynamical evolution of asteroids. The identification of asteroid families within the NEO population could provide a similar boon to studies of their formation and interiors. In this study we examine the purported identification of NEO families by Drummond (2000) and conclude that it is unlikely that they are anything more than random fluctuations in the distribution of NEO osculating orbital elements. We arrive at this conclusion after examining the expected formation rate of NEO families, the identification of NEO groups in synthetic populations that contain no genetically related NEOs, the orbital evolution of the largest association identified by Drummond (2000), and the decoherence of synthetic NEO families intended to reproduce the observed members of the same association. These studies allowed us to identify a new criterion that can be used to select real NEO families for further study in future analyses, based on the ratio of the number of pairs and the size of strings to the number of objects in an identified association.Comment: Accepted for publication in Icarus. 19 pages including 11 figure