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

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

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)

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

Surveys, Astrometric Follow-up & Population Statistics

Asteroid surveys are the backbone of asteroid science, and with this in mind we begin with a broad review of the impact of asteroid surveys on our field. We then provide a brief history of asteroid discoveries so as to place contemporary and future surveys in perspective. Surveys in the United States have discovered the vast majority of the asteroids and this dominance has been consolidated since the publication of Asteroids III. Our descriptions of the asteroid surveys that have been operational since that time are focussed upon those that have contributed the vast majority of asteroid observations and discoveries. We also provide some insight into upcoming next-generation surveys that are sure to alter our understanding of the small bodies in the inner solar system and provide evidence to untangle their complicated dynamical and physical histories. The Minor Planet Center, the nerve center of the asteroid discovery effort, has improved its operations significantly in the past decade so that it can manage the increasing discovery rate, and ensure that it is well-placed to handle the data rates expected in the next decade. We also consider the difficulties associated with astrometric follow-up of newly identified objects. It seems clear that both of these efforts must operate in new modes in order to keep pace with expected discovery rates of next-generation ground- and space-based surveys.Comment: Chapter to appear in the book ASTEROIDS IV, (University of Arizona Press) Space Science Series, edited by P. Michel, F. DeMeo and W. Bottk

The Thousand Asteroid Light Curve Survey

We present the results of our Thousand Asteroid Light Curve Survey (TALCS) conducted with the Canada-France-Hawaii Telescope in September 2006. Our untargeted survey detected 828 Main Belt asteroids to a limiting magnitude of g'~22.5 corresponding to a diameter range of 0.4 km <= D <= 10 km. Of these, 278 objects had photometry of sufficient quality to perform rotation period fits. We debiased the observations and light curve fitting process to determine the true distribution of rotation periods and light curve amplitudes of Main Belt asteroids. We confirm a previously reported excess in the fraction of fast rotators but find a much larger excess of slow rotating asteroids (~15% of our sample). A few percent of objects in the TALCS size range have large light curve amplitudes of ~1 mag. Fits to the debiased distribution of light curve amplitudes indicate that the distribution of triaxial ellipsoid asteroid shapes is proportional to the square of the axis-ratio, (b/a)^2, and may be bi-modal. Finally, we find six objects with rotation periods that may be less than 2 hours with diameters between 400 m and 1.5 km, well above the break-up limit for a gravitationally-bound aggregate. Our debiased data indicate that this population represents <4% of the Main Belt in the 1-10 km size range.Comment: Accepted to Icarus. Full tables to appear there in electronic format, or contact autho

Shape-Driven Selection Effects for Aspherical Near-Earth Objects in Systematic Surveys

The apparent magnitude of elongated small bodies is time-dependent over their rotation phase. Therefore, previously undiscovered aspherical minor planets may experience a shape-driven selection effect in systematic surveys versus their spherical counterparts. In this study, we conduct injection-recovery exercises of synthetic asteroid lightcurves using a simple model to quantify the effect of varying axial ratio on detection efficiencies. We find that high-amplitude lightcurves are confronted with adverse selection effects for survey cadences and discovery thresholds for constructing tracklets that are representative of modern and proposed future NEO searches. Furthermore, we illustrate the possible hazards of drawing population-level inferences on an underlying reservoir of elongated small bodies. If physical size and characteristic axial ratios are correlated, then size-frequency distributions may require revision at small diameters. In particular, this effect could alter the estimated populations of near-Earth objects. We conclude by discussing the applicability of our results to various other classes of solar system minor planets and interstellar interlopers, as well as discuss future work that may further interrogate this detection bias.Comment: 21 pages, 10 figure, 1 table. Accepted for publication in Icarus. (small typo fixed in v2