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...
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...
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...
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...
Nowadays, we are experiencing a revolution in astronomical surveys. Thanks to ground-based and orbiting telescopes, millions of observations of asteroids in various photometric filters are available. The main objective of our project is to develop tools for reading, processing, and analyzing large volumes of data. We’ve successfully determined phase curves for thousands of asteroids in orange...
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...
Most Potentially Hazardous and Near-Earth Objects are not observed by specific
photometric follow-up telescopes. The only estimate on their physical parameters is
therefore made based on the discovery observations and their follow-up submitted to the
MPC. Those observations usually only include low-accuracy photometry.
Recent studies show that these observations also contain systematic...
The NEOCC Aegis Orbit Determination and Impact Monitoring system currently uses the H-G model by Bowell et al. 1989 to determine the absolute magnitude H from photometry data. Typically, it is not possible to determine both the absolute magnitude H and the slope parameter G, therefore G is often fixed to a nominal value of 0.15. However, several studies have shown that the slope parameter may...
