We consider scattering and absorption of light in planetary regoliths composed of sparsely or densely packed nonspherical particles. For the particles, we incorporate sizes and refractive indices and generate sample regolith geometries using varying packing algorithms for particles and their clusters. To ensure computational eUiciency, we make use of average elementary scattering and...
The photometric observations of an asteroid can be used to derive the reduced magnitudes at different phase angles, V(α). A photometric function can be used to fit the magnitudes at different phase angles and to predict the behavior into the exact backscattering geometry at V(0), giving the absolute magnitude H of the object. In 2012 IAU adopted the H,G1,G2 photometric function which is an...
The absolute magnitude H of asteroids is a fundamental property.
It is a proxy to diameter, it is required to predict apparent magnitude, and it is the only way to measure colors whenever filters are not observed (near-)simultaneously.
Major ephemerides computation centers like the Minor Planet Center (MPC), the Jet Propulsion Laboratory (JPL), the Asteroid Dynamical Site (AstDyS), and...
The Minor Planet Center (MPC) collects astrometric and photometric data on minor planets, with its catalog currently containing over 450 million data points for nearly 1.4 million objects. Photometric measurements are submitted in various bands and converted to the Johnson-Cousins V-band using band-specific conversion constants. The absolute magnitude H, a proxy for object size, is calculated...
ESA's Planetary Defence Office has traditionally focused most of its observational activities to astrometry, in order to provide high-precision measurements for the orbit determination and impact monitoring processes that form a significant component of our activities.
Although most of our observations are still designed to optimize the astrometric output, during the last year we have...
Asteroid phase curves provide insights into their surface properties. In particular, the surge of brightness towards low phase angles (opposition effect) and the change in brightness with change in phase angle (photometric slope) are function of the surface composition and particle properties. This dependence opens up phase curves to taxonomic classification of asteroids, a process that has...
We run a long-term project of time-resolved (lightcurve) photometric observations of near-Earth and main-belt asteroids. While our primary scientific interest is to determine other physical parameters of the studied objects (e.g., their spin rates and states, or binary nature), we also, as a by-product, obtain estimates of their absolute magnitudes. We run most of the observations at the...
Most current and planned NEO surveys are ground-based and carried out in the visible wavelength range. However, this approach has some limitations, such as (1) weather dependency, (2) that only a portion of the night sky is visible from any given location on Earth, (3) NEOs are difficult to detect at low galactic latitudes and (4) that visible-light surveys can only determine the motion and...
The Institute of Astronomy, School of Science, University of Tokyo, is promoting the TAO (The University of Tokyo Atacama Observatory) project to construct a 6.5-m telescope at an altitude of 5,640 m in Atacama, Chile. This will be the highest astronomical observatory on Earth, providing exceptionally clear skies for infrared observations at wavelengths up to 38 μm. Scientific observations are...
The thermal emission from an asteroid is a consequence of its surface temperatures, and the object’s size can be directly estimated from observations in the infrared. Accurately estimating the surface temperature distribution, which depends on several factors, can improve the precision of these size measurements. Key factors include the asteroid’s shape, spin, and thermophysical properties...
The radiometric method has proven highly effective in determining the sizes and albedo of asteroids and near-Earth objects (NEOs). This technique involves measuring the heat flux from these objects in the thermal infrared using telescopes, and modeling these observations as a function of size and other physical parameters. The values of these parameters are constrained by achieving the best...
Polarimetry is an effective tool for remote sensing of asteroid surfaces, mainly for assessing their albedo and surface texture, and searching for surface peculiarities. The main advantage of the polarimetric method of albedo determination is that albedo can be derived directly from polarimetric measurements using simple empirical relationships between polarimetric parameters and albedos....
Polarimetric observations of NEOs are important for a number of reasons:
• Determination of the geometric albedo and hence possible derivation of diameter
• Determination of some surface regolith properties
• For taxonomic classification purposes
• Because it is useful to identify special classes of objects having anomalous compositions
• Because it is useful to identify objects...
The Two-Channel-Focal-Reducer Rozhen (FoReRo2) was delivered to the Bulgarian National Astronomical Observatory (BNAO) Rozhen based on a contract between the Max-Planck Institute for Solar System Research and the Institute of Astronomy and National Astronomical Observatory (IA and NAO) in 2004. Since then, the FoReRo2 has been used at the f/8 Ritchey-Chrétien focus of the 2m...
Polarization observations are a key tool for swiftly determining the size of a NEO, and consequently, their potential threat to Earth. The degree of linear polarization is inversely proportional to the albedo of the scattering surface of an asteroid. This relation is better constrained at high phase angles at which NEOs are usually observed and where polarization is more significant. This...
The degree of linear polarization of sunlight scattered by an asteroid contains valuable information for rapid characterization of the surface properties of Near-Earth objects (NEOs). In the case of atmosphereless bodies the state of linear polarization varies as a function of the phase angle (α) and is described using the so-called Pr parameter.
The properties of the phase-polarization...
The polarization of light reflected by asteroids can be used to constrain the albedo of the asteroid's surface, and probe mineralogical surface properties such as grain size and index of refraction. Depending on the specific mineral components of the body these surface properties are expected to change with wavelength, and so observations of the polarization beyond the visible provide...
Photometric observations of near-Earth asteroids (NEAs) using the TRAPPIST telescopes are regularly performed notably to support shape modeling using radar data as well as an effort to calibrate the relation between the albedo and the polarization displayed by NEAs. These two methods allow to obtain accurate size determination for these objects.
The TRAPPIST telescopes are two twin 60-cm...
The European Space Agency’s Flyeye telescopes will play a crucial role in global efforts to detect and track near-Earth objects (NEOs). Inspired by the compound vision of a fly, the unique design of Flyeye-1 divides its field of view into 16 subfields, enabling the telescope to scan a wide area of the sky every night.
This talk will explore the design and development of the Flyeye-1, focusing...
Determining the size of an asteroid is scientifcally interesting, but also particularly relevant in the case of
those objects that are considered as potential impactors: together with the distance to Earth, is one of the
two criteria used to classify an asteroid as Potentially Hazardous. There are several ways to compute this
physical property, some of them based on the acquisition of...
