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A new model of asteroid shapes is proposed for simulation of asteroid lightcurves using sparse observational data. The shape model uses logarithmic 3-foci ellipsoids and has four free parameters for describing body shapes with both convex and concave elements of global topography, as well as binary systems. We demonstrate the applicability of the model for asteroids 1580 Betulia and 8567 1996 HW1. A ray-tracing method incorporating Akimov's disk function was used to calculate the flux scattered by each elementary surface element. The simulations provide good fits to observational data, revealing the possibility for wide use of the approach.

We introduce a constrained nonlinear least-squares algorithm to be used in estimating the parameters in the H, G1, G2 phase function. As the algorithm works directly in the magnitude space, it will surpass the possible bias problem that may be present in the existing H , G 1 , G 2 fit procedure when applied to low-accuracy observations with large magnitude variations. With constraints on the photometric phase-curve shape parameters G1 and G2, it guarantees a physically reasonable phase-curve estimate. With a new data set of 93 asteroids, we re-assess the two-parameter version of the H , G 1 , G 2 function. Finally, we introduce a one-parameter version of the phase function that can give a suggestion of the asteroids taxonomic group based only on its phase curve. A statistical model selection procedure is presented that can automatically select between the different versions of the photometric phase functions. An online tool that implements these algorithms is introduced.

Our photometric observations of 18 main-belt binary systems in more than one apparition revealed a strikingly high number of 15 having positively re-observed mutual events in the return apparitions. Our simulations of the survey showed that it cannot be due to an observational selection effect and that the data strongly suggest that poles of mutual orbits between components of binary asteroids in the primary size range 3–8 km are not distributed randomly: The null hypothesis of an isotropic distribution of the orbit poles is rejected at a confidence level greater than 99.99%. Binary orbit poles concentrate at high ecliptic latitudes, within 30° of the poles of the ecliptic. We propose that the binary orbit poles oriented preferentially up/down-right are due to either of the two processes: (i) the YORP tilt of spin axes of their parent bodies toward the asymptotic states near obliquities 0° and 180° (pre-formation mechanism) or (ii) the YORP tilt of spin axes of the primary components of already formed binary systems toward the asymptotic states near obliquities 0° and 180° (post-formation mechanism). The alternative process of elimination of binaries with poles closer to the ecliptic by dynamical instability, such as the Kozai effect due to gravitational perturbations from the Sun, does not explain the observed orbit pole concentration. This is because for close binary asteroid systems, the gravitational effects of primary’s irregular shape dominate the solar-tide effect.

We investigate the photometric system consisting of the AZT-8 telescope BVRI filters, and IMG 1024S CCD-camera. The coefficients of the transformation from the instrumental values of magnitudes and color indexes to the standard Johnson-Cousins system for the BVRI bands are derived.

The long time photometric observations were carried out for eight asteroids: (122) Gerda, (153) Hilda, (190) Ismene, (221) Eos, (411) Xanthe, (679) Pax, (700) Auravictrix, (787) Moskva. New rotation periods have been determined for the asteroids (153) Hilda (5.959 h) and (411) Xanthe (11.408 h), and known rotation periods for some of the others have been confirmed. Using our data and others data we have estimated new pole coordinates for the observed asteroids.

The results of 1993–2005 photometric observations for 24 main-belt asteroids: 24 Themis, 51 Nemausa, 89 Julia, 205 Martha, 225 Henrietta, 387 Aquitania, 423 Diotima, 505 Cava, 522 Helga, 543 Charlotte, 663 Gerlinde, 670 Ottegebe, 693 Zerbinetta, 694 Ekard, 713 Luscinia, 800 Kressmania, 1251 Hedera, 1369 Ostanina, 1427 Ruvuma, 1796 Riga, 2771 Polzunov, 4908 Ward, 6587 Brassens and 16541 1991 PW18 are presented. The rotation periods of nine of these asteroids have been determined for the first time and others have been improved.

Photometric CCD observations of the small main-belt asteroid 11 264 Claudiomaccone, carried out with the 0.7-m telescope at Chuguev Observation Station (Kharkiv, Ukraine) in November 2004 and the 1-m telescope at Simeiz Observatory (Crimea, Ukraine) in December 2004, have shown the presence of two different periods in asteroid brightness variations. A short period of 3.1872±0.0006 h and long one of 15.11±0.01 h were determined. The analysis of lightcurves allowed us to suppose that asteroid 11264 Claudiomaccone is an asynchronous binary system in the main belt. The short period is interpreted as a rotational period of the larger (primary) body. The long period component has sharp dips characteristic of mutual eclipse phenomena and is therefore interpreted as the orbital period of the secondary. The parameters of the system are estimated to be: the ratio of the secondary to primary diameters is ⩾0.31, based on the depth of the apparently partial eclipses, the ratio of the orbital radius to the primary's diameter is about 1.5 and a bulk density of the primary body is ρp⩾1.2 g/cm3. We obtained the asteroid phase curve parameters H = 14.30 , G = 0.10 and measured color index V - R = 0.52 . These data allow to suppose that the asteroid belongs to S (or Q) type and to estimate effective diameter of the system to be 4.2 km, based on the average albedo of objects of these taxonomic classes.

Albedos for 57 asteroids were determined using diameters obtained from stellar occultations. For 18 objects, the occultation albedos were determined to accuracies better than 5%. The effect on the occultation albedo due to errors in the asteroid absolute magnitude is discussed and correlations between the occultation albedos and IRAS and polarimetric albedos are presented. The higher-quality occultation albedos presented here are suitable for calibrating albedos obtained by indirect methods.

The regular CCD observations of near-Earth asteroids (NEAs) in the Institute of Astronomy of Kharkiv National University were initiated in 1995 within the framework of asteroid hazard problem in collaboration with the DLR, Institute of Planetary Research (Berlin). The main aim of the study is a determination of rotation periods and shapes of NEAs as well as astrometry of newly discovered objects. We also carry out the absolute photometry of NEAs inBVRIbands in order to put constraints on surface properties and to estimate their diameters. The observations are carried out with 0.7-m telescope of the Institute of Astronomy (Kharkiv) and with 1-m telescope of the Crimean Astrophysical Observatory (Simeiz) in the standard Johnson-Cousins photometric system. Some observations were made as an optical support of radar observation of NEAs. We present the results of photometric observations of 21 NEAs obtained in 2004-2006 which include asteroid rotation properties, diameters and shapes.

We present new polarimetric and photometric observations of high-albedo E-type Asteroid 44 Nysa in the BVRI wavebands at phase angles ranging from 0.41° to 7.49° during the 2005 opposition. A bimodal phase-angle dependence of polarization was found for Nysa in the V band. The polarization opposition effect was revealed in the form of a secondary minimum of negative polarization with amplitude ∼0.3% centered at a phase angle ∼0.8°. It is superimposed on the regular negative polarization branch with minimal polarization −0.30% at a phase angle 5.8°. We analyzed all available polarimetric data for E-type Asteroids 44 Nysa, 64 Angelina, and 214 Ashera and confirmed the presence of the polarization opposition effect for high-albedo asteroids at phase angle ∼1° with an amplitude ∼0.35%. The magnitude–phase curves reveal the presence of spike-like opposition effect of brightness for 44 Nysa in the BVRI spectral bands. 44 Nysa is the second high-albedo asteroid after 64 Angelina for which both the polarization opposition effect and the brightness opposition effect are detected. The differences between the parameters of the opposition effects for silicate surfaces (44 Nysa, 64 Angelina, Io) and icy surfaces (Europa, Ganymede, Iapetus, Saturn's rings) are discussed. The specific morphological parameters of opposition effects, in particular the angular width of the polarization opposition effect is comparable to that of the brightness opposition effect, provide almost unequivocal evidence that they are caused by coherent backscattering. One of unexpected results of our investigation is that 44 Nysa becomes bluer with increasing phase angle, while 64 Angelina shows phase reddening.

We present new observations and models of the shapes and rotational states of the eight near-Earth Asteroids (1580) Betulia, (1627) Ivar, (1980) Tezcatlipoca, (2100) Ra-Shalom, (3199) Nefertiti, (3908) Nyx, (4957) Brucemurray, and (5587) 1990 SB. We also outline some of their solar phase curves, corrected to common reference geometry with the models. Some of the targets may feature sizable global nonconvexities, but the observable solar phase angles were not sufficiently high for confirming these. None is likely to have a very densely cratered surface. We discuss the role of the intermediate topographic scale range in photometry, and surmise that this scale range is less important than large or small scale lengths.

The first results of the observational program devoted to simultaneous investigation of asteroid polarimetric and photometric opposition phenomena are presented. UBVRI polarimetric and V-band photometric observations of the S-type Asteroid 20 Massalia and the E-type Asteroids 214 Aschera and 620 Drakonia were carried out in 1996–1999 down to phase angles of 0.08°, 0.7°, and 1.2°, correspondingly. The S-type Asteroid 20 Massalia is characterized by the pronounced brightness opposition surge with an amplitude larger than that observed for the E-type asteroids. A sharp peak of negative polarization at small phase angles was not observed for this asteroid. The value of polarization degree at phase angle α

The results of photometric observations of seven E-type asteroids 64 Angelina, 214 Aschera, 1025 Riema, 1103 Sequoia, 1251 Hedera, 2035 Stearns, and 2248 Dwornik are presented. New rotation periods have been determined for asteroids 1025 Riema (6.557±0.001 h ) , 1251 Hedera (15.015±0.010 h ) , 2035 Stearns (85.0±0.1 h ), and 2048 Dwornik (3.664±0.001 h ) . Two new poles have been estimated for 214 Aschera (274±8°; 64±4°) and 1025 Riema (141±10°, 11±6°) and pole has been redefined for 64 Angelina (138±10°, 31±5°). Using all available data on rotation periods, the spin rates of E-type asteroids have been analyzed. The distribution of the spin rates has maximum corresponding to the period of about 6.2 h . The shapes of E-asteroids are more elongated than the shapes of small-size S-asteroids. The average values of color indexes, albedo and G parameter for E-type asteroids have also been determined.

Lightcurve observations of 16 near-Earth objects (NEOs) and 2 Mars-crossers in 1996–1999 from three observational sites are presented. Eight objects were observed shortly after their discovery within the follow-up program of NEO observations. We were able to determine rotation periods for 14 asteroids. For 8 objects (5626, 5732, 1998 FM5, 1998 FX2, 1998 UT18, 1998 VO33, 1999 RQ36, 1999 US3) our determinations constitute new results while in the remaining 6 cases (3200, 4341, 7025, 7822, 11066, 1992 QN) we could improve or confirm previously published periods. We also put constraints on the spin vector of 3200 Phaethon.

The results of photometric observations of seven main-belt asteroids with moderate surface albedos are presented. New magnitude-phase dependences were obtained for these asteroids: 5 Astraea (down to a phase angle of 0.3°, S type), 75 Eurydike (0.1°, M), 77 Frigga (0.9°, M), 105 Artemis (0.3°, C), 119 Althaea (0.3°, S), 124 Alkeste (0.1°, S), and 201 Penelope (0.5°, M). The parameters of approximating functions and the amplitudes of the opposition effect of these asteroids were determined. The obtained data allowed us to improve values of the rotation periods for some of them: 5 Astraea (16.815±0.002 h), 105 Artemis (18.56±0.01 h), 119 Althaea (11.466±0.001 h), and 124 Alkeste (9.907±0.001 h).