Edward F. Tedesco

THE STATISTICAL ASTEROID MODEL. I. THE MAIN-BELT POPULATION FOR DIAMETERS GREATER THAN 1 KILOMETER

We describe the creation of a model of the main asteroid belt whose purpose is to describe the main-belt asteroid size frequency distribution and simulate the number of main-belt asteroids and their fluxes at visual through mid-infrared (~0.3–70 μm) wavelengths in any area of sky for an arbitrary date. This model is based on a population of ~1.9 × 106 asteroids obtained from the complete known asteroid sample, plus extrapolation of the size-frequency distributions of 15 asteroid dynamical families and three background populations, to a diameter limit of 1 km. The model is compared with data and other models, example applications are given, planned refinements and extensions to the model are presented, and some implications of the resulting size frequency distribution are discussed.

Linking Very Large Telescope asteroid observations

Space Science Center, Univ. New Hampshire, 39 College Road, Durham, NH 03824, USAAbstract. A novel method for the preliminary identification of asteroids at discovery and a fewdays thereafter is being developed in Helsinki. Having two different sets of asteroid observations,the goal is to identify all possible pairs of objects between the sets. An arbitrary asteroid caneither remain unidentified, or be preliminary linked to one or more asteroids. In the case of am-biguity, the final decision must usually be based on additional observations. We use a multistepapproach, during which possible pairs of objects are first selected by comparing ephemeridesthat have been generated for three common epochs. The method has been successfully testedusing both Very Large Telescope observations, and simulated observations of near-Earth andmain-belt objects. Identification results of simulated observations indicate that the observingstrategy promoted by the Minor Planet Center might not be the best one, at least for the pur-poses of identification. The ultimate goal is to produce a real-time asteroid identification tool forESA’s astrometric space observatory Gaia, the Lowell Observatory Near-Earth-Object Search,the Near-Earth Space Surveillance mission, and the Nordic Near-Earth Object Network. Thetool could also benefit large-scale surveys done with the Large Synoptic Survey Telescope, andthe Discovery Channel Telescope.Keywords. Celestial mechanics, methods: numerical, methods: statistical, asteroids, surveys

Rationale and orbital options for a dedicated space-based observatory for NEOs

Abstract We present a concept for a dedicated space-based observatory for NEO physical characterization and discovery of objects belonging to orbital classes difficult to observe from the ground (Atens, lEOs). The purpose of such a mission is to derive NEO sizes and albedos using the radiometric technique, and to discover a large fraction of the existing Atens and lEOs during an operational lifetime of a few years. Intrinsic advantages of a space-based platform for reaching the above objectives are discussed, as well as several options for the choice of the satellite orbit. It seems likely that current technology is sufficiently mature to field a relatively inexpensive mission, in which most of the thermal constraints are met by means of passive cooling. The thermal load on the system is greatly reduced if the spacecraft orbits far from the most intense sources of heat, e.g., in the L2 Lagrangian points of the Earth or Venus. Based upon preliminary simulations presented herein the Earth L2 option is the better choice.

Albedo and size of (99942) Apophis from polarimetric observations

We have obtained the first accurate determination of the albedo of (99942) Apophis, by means of polarimetric observations carried out at the VLT. The observations allowed us to obtain the slope of the polarization – phase curve of this object, from which an albedo estimate of 0.33± 0.04 could be obtained. From our observations we also obtained a new estimate of the absolute magnitude:H = 19.7±0.2 (assuming G=0.25, which applies to Sand Q-type asteroids). Based on these results, we derive for the size of Apophis a value of 270±30 meters. The accuracy of this size estimate is mostly related to uncertainties in H, whereas the obtained albedo value should be considered more robust. Our observations convincingly show that polarimetry is an effective and efficient tool to obtain accurate albedos and sizes for small and faint potentially hazardous asteroids.

DIVISION III / COMMISSION 15 / WORKING GROUP PHYSICAL STUDY OF MINOR PLANETS

The meeting of the Physical Properties of the Minor Planets Working Group of IAU Commission 15 took place on 24 August, and was devoted to purely scientific matters, since other topics (organization of the Minor Planet WG, need of a new web page, election of the new chairman) had been already discussed during the business meeting of Commission 15, on 22 August. A brief summary of the talks given during the meeting is given in what follows.