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We present results of polarimetric, photometric, and spectral observations of the near-Earth asteroid (3200) Phaethon carried out at the 6-m BTA telescope of the Special Astrophysical Observatory and the 2.6-m and 1.25-m telescopes of the Crimean Astrophysical Observatory over a wide range of phase angles during its close approach to the Earth at the end of 2017 (19-135 deg) and in 2020 at \alpha = 52.2 deg. Using our and other available in literature data, we found that the maximum degree of linear polarization of Phaethon in the V band is 45% at the phase angle 124 deg. Using the dependence (polarimetric slope-albedo) we have found the geometric albedo of asteroid Phaethon to be 0.06. This value falls into the lower range of albedo values for asteroids determined by different methods. The mean color indices U-B=0.207 and B-V=0.639 of the asteroid are derived at heliocentric and geocentric distances 1.077 au and 0.102 au, respectively. The effective diameter of Phaethon is estimated from obtained absolute magnitude and geometrical albedo, it is equal to 6.8 km. The best fit to the observed polarimetric data was obtained with the Sh-matrix model of conjugated random Gaussian particles composed of Mg-rich silicate (90%) and amorphous carbon (10%)., Comment: 27 pages, 9 figures

There was an unprecedented opportunity to study the inner dust coma environment, where the dust and gas are not entirely decoupled, of comets 45P/Honda-Mrkos-Pajdu\u{s}\'akov\'a (45P/HMP) from Dec. 26, 2016 - Mar. 15, 2017, and 46P/Wirtanen from Nov. 10, 2018 - Feb. 13, 2019, both in visible wavelengths. The radial profile slopes of these comets were measured in the R and HB-BC filters most representative of dust, and deviations from a radially expanding coma were identified as significant. The azimuthally averaged radial profile slope of comet 45P/HMP gradually changes from -1.81 $\pm$ 0.20 at 5.24 days pre-perihelion to -0.35 $\pm$ 0.16 at 74.41 days post perihelion. Contrastingly, the radial profile slope of 46P/Wirtanen stays fairly constant over the observed time period at -1.05 $\pm$ 0.05. Additionally, we find that the radial profile of 46P/Wirtanen is azimuthally dependent on the skyplane-projected solar position angle, while that of 45P/HMP is not. These results suggest that comet 45P/HMP and 46P/Wirtanen have vastly different coma dust environments and that their dust properties are distinct. As evident from these two comets, well-resolved inner comae are vital for detailed characterization of dust environments., Comment: 21 pages, 13 figures, to be published in the Planetary Science Journal

Less than one percent of the discovered small solar system objects have highly inclined orbits ($i>60^{\circ}$), and revolve around the Sun on near-polar or retrograde orbits. The origin and evolutionary history of these objects are not yet clear. In this work we study the surface properties and orbital dynamics of selected high-inclination objects. BVRI photometric observations were performed in 2019-2020 using the 2.0m telescope at the Terskol Observatory and the 2.6m telescope at the Crimean Astrophysical Observatory. Additionally, we searched for high-inclination objects in the Sloan Digital Sky Survey and Pan-STARRS. The dynamics of the selected objects was studied using numerical simulations. We obtained new photometric observations of six high-inclination objects. All of the objects have similar $B-V$, $V-R$, $R-I$ colours, which are close to those of moderately red TNOs and grey Centaurs. The photometric data that were extracted from the all-sky surveys also correspond to moderately red surfaces of high-inclination objects. No signs of ultra-red material on the surface of high-inclination asteroids were found, which supports the results of previous works. The comet C/2018 DO4 (Lemmon) revealed some complex morphology with structures that could be associated with particles that were ejected from the cometary nucleus. For objects 2013 LU28, 2015 KZ120, and 2020 EP we estimated future and past lifetimes on their orbits. It appears that the orbits of considered objects are strongly chaotic, and with the available accuracy of the orbital elements no reliable predictions can be made about their distant past or future. The lifetimes of high-inclination objects turned out to be highly non-sensitive to the precision of the orbital elements, and to the Yarkovsky orbital drift.

We report results of polarimetric observations of comet 21P/Giacobini-Zinner made at phase angles, {\alpha}=76-78 deg, between 10 and 17 of September 2018, and compare them with previous measurements. We find significant variations in the polarimetric signals that appear consistent with those reported previously. These variations and subsequent modeling suggest that the particles in the coma are replenished within a period of approximately one day. This period is significantly shorter for highly absorbing carbonaceous particles than for non-absorbing Mg-rich silicate particles. Such a difference in the relative abundances of these components can lead to variations in the polarization response of the coma. The strong positive polarization in the subsolar direction suggests a large relative abundance of carbonaceous material, which may be an indicator of jet-type activity., Comment: 11 pages, 6 figures

We measure the degree of linear polarization of comet 46P/Wirtanen during two months, embracing the perihelion passage in 2018 December with phase angles ranging from {\alpha}=18.1 to 46.4 deg. The polarimetric response PQ obtained resembles what was previously found in comet C/1975 V1 (West). This suggests 46P/Wirtanen belongs to a group of comets with high maximum positive polarization. We conducted BVRI photometry of 46P and found either neutral or blue colour of its dust which is in good accordance with measurements of C/1975 V1 (West). While aperture-average polarimetry of 46P/Wirtanen reveals a nearly zero polarization PQ at the lowest phase angle {\alpha} = 18.1 deg, simultaneous imaging polarimetry suggests that the negative polarization (PQ<0) arises in a region of within 5000 km of the nucleus, where the negative polarization could be as strong as PQ=-(1.44 +/- 0.15) percent. This observation suggests the existence of the circumnucleus halo and that the coma is populated by at least two types of dust particles. One of those reveals a low positive polarization at side scattering and high negative polarization near backscattering. Both polarimetric features are simultaneously produced by weakly absorbing Mg-rich silicate particles. Another type of dust produces solely positive polarization that could be attributed to carbonaceous particles. This composition of 46P/Wirtanen coma appears to be similar with what was previously found in comet C/1975 V1 (West)., Comment: 12 pages, 5 figures

We measured the degree of linear polarization P of comet C/2018 V1 (Machholz-Fujikawa-Iwamoto) with the broadband Johnson V filter in mid-November of 2018. Within a radius of \r{ho}=17,000 km of the inner coma, we detected an extremely low linear polarization at phase angles from 83 to 91.2 degree and constrained the polarization maximum to Pmax = (6.8 +/- 1.8)%. This is the lowest Pmax ever measured in a comet. Using model agglomerated debris particles, we reproduced the polarimetric response of comet C/2018 V1. Four retrieved refractive indices closely match what was experimentally found in Mg-rich silicates with little or no iron content. Moreover, the size distribution of the agglomerated debris particles appears in good quantitative agreement with the in situ findings of comet 1P/Halley. The dust model of polarization of comet C/2018 V1 suggests a strongly negative polarization with amplitude |Pmin| = 5%-7%; whereas, an interpretation based on gaseous emission requires no negative polarization at small phase angles. This dramatic difference could be used to discriminate gaseous-emission and dust explanations in low-Pmax comets in future., Comment: 9 pages, 5 figures

We report photometric observations of comet 29P/Schwassmann-Wachmann 1 made on August 12, 2016 with the broadband B, V, R and I filters and the SOAR 4.1-meter telescope (Chile). We find the comet active at that time. Enhanced images obtained in all filters reveal three radial features in the 29P/ Schwassmann-Wachmann 1 coma, regardless of the image-processing algorithm. Using a high-resolution spectrum of comet 29P/Schwassmann-Wachmann 1 reported by Ivanova et al. (2018) on the same date, we estimate the relative contribution of the gaseous emission and the continuum to the total response measured with our broadband B and V filters. The gaseous-emission contribution appears to be very small 2.5%. We compute the dust production Af\r{ho} in 29P/ Schwassmann-Wachmann 1 for the four filters and find its growth with the wavelength, from 3,393 cm in the B filter to 8,561 cm in the I filter. We model the color slope of dust in Comet 29P/Schwassmann-Wachmann 1 using agglomerated debris particles. Simultaneous analysis of the color slope in the B-R and R-I pairs suggests a single dominant chemical species of 29P/Schwassmann-Wachmann 1 dust particles consisting of Fe-Mg silicates and obeying a power-law size distribution with index n=2.55. This conclusion is consistent with the previous thermal-emission study of 29P/Schwassmann-Wachmann 1., Comment: 10 pages, 7 figures

We carried out photometric and spectroscopic observations of comet 29P/Schwassmann-Wachmann 1 at the 6-m BTA telescope (SAO RAS, Russia) and the 1.6-m telescope of the National Laboratory for Astro-physics (LNA, Brazil) on February 20, 2012, and on May 31, 2011, respectively. The spectra revealed the presence of CO+ and N2+ emissions in the cometary coma at a distance of 5.25 AU from the Sun. The ratio [N2+]/[CO+] within the projected slit is 0.013. The images obtained through BVR filters showed a bright, dust coma, indicating a high level of activity. We estimated a colour index and a colour excess for the comet. The parameter Af\r{ho}, which is used as an indicator of a cometary activity, was measured to be 2584 cm in the reference optical aperture of \r{ho}=10^4 km. The dust production constituted 33 kg/s and 9.3*10^3 kg/s, it was obtained using different methods. We also investigated the morphology of the comet using image enhancement techniques and found two jets in the coma., Comment: 8 pages, 6 figures

Comet-centaur 29P/Schwassmann-Wachmann 1 was observed in CO+ emission and contin-uum during 2007-2009 using the 6-m Big Telescope Alt-azimuth at the Special Astrophysical Observatory of the Russian Academy of Sciences. We analysed the morphology of the CO+ and dust coma. The distributions of dust and CO+ ions in the coma are not similar and vary depending on the level of comet activity. CO+ ions are more concentrated towards the nucleus than the dust continuum. The column density of the CO+ was derived and found to vary from 3.7*10^9 to 4.3*10^10 ions cm^-2. The production rate of CO+ was estimated to be from (7.01)*10^24 to (1.15)*10^26 ions s^-1. We discuss possible mechanisms for the ionization of cometary material and show that impact ionization by solar wind particles is probably the main ionization mechanism at large heliocentric distances., Comment: 7 pages, 5 figures

Photometric observations of asteroid (596) Scheila were obtained during and after its 2010 outburst. The estimated radius of the body (spherical approximation of the asteroidal body) was 51.2 km and 50.67 km for different methods. The ejected dust mass from the asteroid ranged from 2.5*10e7 to 3.4*10^7 kg for different methods. An impact mechanism for triggering Scheila's activity is discussed. A few days before the impact, Scheila passed through the corridors of two potential cometary streams., Comment: 6 pages, 3 figures, 3 tables

Results of astrometric and BVRI photometric observations of the active asteroid (596) Scheila are presented. The observations were carried out at the Zeiss 1000 telescope of the Sanglokh International Astro-nomical Observatory of the Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan on June 16 and 17 and from July 30 to August 1, 2017. The coordinates of the object and its orbit were determined; and the apparent brightness in four filters, the absolute brightness in the V and R filters, and the color indices were obtained. The light curves suggest that no substantial changes in the brightness of asteroid occurred during the observations. The absolute brightness of the asteroid in the V and R filters was 9.1 mag and 8.8 mag, respectively. The mean value of the asteroid diameter was 119 km. The mean values of the color indices B-V=0.72 mag, V-R=0.29 mag, and R-I=0.31 mag agree well with the values for asteroids of the P and D types and its averages. The rotation period of the asteroid estimated from photometric observations was 16.1 h. The analysis of the data has shown that the asteroid continues to exhibit the same values of absolute brightness and other characteristics as those before the collision with a small body in December 2010, though the latter resulted in the outburst event and cometary activity of the asteroid. Most likely, the collision of asteroid (596) Scheila with a small body did not lead to catastrophic changes in the surface of the asteroid or to its compete breakup., Comment: 10 pages, 5 figures. arXiv admin note: text overlap with arXiv:2012.06833

Astrometric and photometric observations of the comet 29P/Schwassmann-Wachmann 1 were performed at the Zeiss-1000 telescope of the International Astronomical Observatory Sanglokh (IAOS) of the Institute of Astrophysics, Academy of Sciences of the Republic of Tajikistan in July and August 2017. Although the comet has a short period of revolution it is regarded to be an object of the Centaurs group. Comet was exhibited a new activity this period which we used for analysis of its features. The coordinates of comet were determined and the orbit was calculated, the apparent and absolute magnitudes in BVRI bands were determined, as well the comet color indices and the estimation of nucleus diameter were obtained., Comment: 7 pages, 5 figures

The main aim of photometrical observations of the asteroid 3200 Phaethon was searching for its low-level cometary activity (possible coma and/or dust tail) in the pre-perihelion passage. We performed observational runs with telescopes ranging from 0.61-m to 2-m and BVR color imaging. Three longer photometric series were used for modeling of the 3D shape of Phaethon. The color indices and size of the asteroid were estimated., Comment: 6 pages, 2 figures, 1 table

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft, and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively `well behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit-to-orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends -- in this paper we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies., Comment: Author prepared version; final published version available at journal. 22 pages