Structural analysis of the comet 45P/Honda based on isophote modeling

The work focuses on using the isophote method to construct a 45P/Honda comet model. At the same time, important problems were solved for modeling the physical surface of a comet and studying the structure of the cometary nucleus. This is due to the fact that, on the basis of modern studies of meteoroids, complex internal processes and dynamic phenomena on their surface have been discovered. The study of comet nuclei is of great importance, since, according to the theory of their formation, they were formed from the matter of the protoplanetary disk. Thus, modeling and analysis of the structure of various comets make it possible to create a more accurate theory of their evolution. This made it possible to evaluate the structural parameters more accurately and reliably. This allowed for the evaluation of the structural parameters more accurately and reliably. Isophotes of the nucleus, coma and tail of comet 45P/Honda were determined. Depending on the point where the comet is located on the trajectory of its orbit, one can see structural changes in the comet’s brightness from the nucleus to the peripheral region. Near the cometary nucleus, the isophotes are circular in shape. If in the center of the model the isophotes have a shape close to narrow rings, then elongations in the direction of the cometary tail and thickening of their structure appear towards the peripheral regions. Large and small tail rays can be distinguished, and the nucleus is well marked. In the future, the author’s method for modeling isophotes, developed in this work, will allow studying the structure of various cometary objects, and, based on the results, determine the degree of comet activity. On the other hand, about the development of the theory of dynamic processes and the evolution of the Solar system, one can use the data on changes in cometary activity in the process of its movement around the Sun.

Statistical analysis of the accelerated H2O ions above 1 keV: the comet 67P/Churyumov–Gerasimenko observed by the Rosetta spacecraft.

<p>The ESA/Rosetta spacecraft has studied the comet 67P/Churyumov-Gerasimenko for two years. Rosetta Plasma Consortium's Ion Composition Analyser (RPC/ICA) detected comet-origin water ions that are accelerated to > 100 eV.<span>  </span>Majority of them are interpreted as ordinary pick-up acceleration<span>  </span>by the solar wind electric field perpendicular to the magnetic field during low comet activity [1,2]. As the comet approaches the sun, a comet magnetosphere is formed, where solar winds cannot intrude.</p><p>However,  some water ions are accelerated to > 1 keV even in the magnetosphere [3]. Using RPC/ICA data during two years [4], we investigate the acceleration events > 1 keV where solar winds are not observed, and classify dispersion events with respect to the directions of the sun, the comet, and the magnetic field.<span>  </span>Majority of these water ions show reversed energy-angle dispersion. <span>Results of the investigation also show that these ions are flowing along the (enhanced) magnetic field, indicating that the parallel acceleration occurs in the magnetosphere.</span></p><p>In this meeting, we show a statistical analysis and discuss a possible acceleration mechanism.</p><p><strong>References</strong></p><p>[1] H. Nilsson et al., MNRAS 469, 252 (2017), doi:10.1093/mnras/stx1491</p><p>[2] G. Nicolau et al., MNRAS 469, 339 (2017), doi:10.1093/mnras/stx1621</p><p>[3] T. Kotani et al., EPSC, EPSC2020-576 (2020), https://doi.org/10.5194/epsc2020-576</p><p>[4] H. Nilsson et al., Space Sci. Rev., 128, 671 (2007), DOI: 10.1007/s11214-006-9031-z </p>

Comets: Seeing The Bigger Picture – Maximising the Contribution of Amateurs

<p>The Rosetta Mission invited amateur astronomers to be part of a ground-based observing campaign for Comet 67P/Churyumov–Gerasimenko.  Amateurs, with greater access to telescope time and wider geographical coverage, can add important temporal coverage and wider scale observations to complement those of professional astronomers. They add the bigger picture. This allows for greater multi-scale analysis of comet activity.</p> <p>This campaign followed on from campaigns in support of the Halley-related and Deep Impact Missions, as well as general comet observing campaigns such as for Comet C/2012 S1 ISON. </p> <p>With 67P coming back shortly, and future comet missions such as Comet Interceptor being planned, there is an opportunity to consider the effectiveness of the 67P amateur campaign, a related 46P/Wirtanen schools’ observing campaign, and draw lessons from these and previous comet and other Pro-Am campaigns to inform good practice for future campaigns.</p> <p>Feedback has been sought, via 3 surveys, from those who took part in the 67P and 46P campaigns, and from amateur astronomers who might be encouraged to take part in future campaigns. The survey results will be presented, along with reflections from some of amateurs involved, and a discussion of how future campaigns may be made most effective.</p>

Could the space probe Philae© be energized remotely?

Space probes suffer from a fundamental problem, which is the limited energy available for their operation. Energy supply is essential for continuous operation and ultimately the most important sub-system for its sustainable functioning. Considering, for instance, the last space probe put on Comet 67P/Churyumov–Gerasimenko, called “Philae”, which was sent by Rosetta (http://www.esa.int/Our_Activities/Space_Science/Rosetta), to operate and to monitor comet activity, its operation was jeopardized due to the fact that it landed on a shadowed zone (no direct sunlight). Since its operational energy was only based on solar harvesters, the energy for its operation was limited by solar energy availability. In this paper a study on a viable alternative based on wireless power transmission is presented and discussed at the system level. It is proved that, using current technology, it is possible to create alternatives or supplement to existing power sources such as solar panels to power up these important space probes and to secure their operation.

Results from the EPOXI and StardustNExT Missions – A Changing View of Comet Volatiles and Activity

Within a period of ~3 months there were two extended mission flybys of comets. Both encounters have provided an exciting new view of comet activity and volatile composition that is changing our paradigm of these small early solar system remnants. The EPOXI mission flew past the nucleus of comet 103P/Hartley 2 on 4 Nov. 2010. This small nucleus was known to be exceptionally active prior to the encounter, by virtue of a very large water production rate relative to its surface area. Both the encounter and ground-based data showed that comet Hartley 2fs perihelion activity was dominated by sub-surface CO2 outgassing rather than by water, suggesting our classic comet formation picture is not correct. The gas flow carried large grains (up to >10 cm in diameter) from the nucleus, and the icy grains contributed to the large observed water production. The CO2 abundance relative to water varies with rotation between 10-20% between the two lobes of the nucleus. The bi-lobed nucleus is rotating in an excited state, with a period that varied rapidly from ~16.5 hrs to longer than 18.5 hrs over 3 months. The nucleus morphology was different from that of other nuclei visited by space craft, with some regions of rough topography in which surface ice was visible. On 2011 Feb. 14 the Stardust-NExT spacecraft flew past the nucleus of comet 9P/Tempel 1, the target of the Deep Impact (DI) experiment in July 2005. The mission goal was to look at the nucleus after and intervening perihelion passage, extending the surface area imaged during the DI encounter and also image the 2005 impact site. The layering seen during the DI flyby was exhibited over the areas newly imaged in the NExT flyby, and it was found that 30% of the nucleus was covered by smooth deposits that were likely caused by eruption of subsurface materials. Although it has long been known that comets lose on average ~ a meter of their surface per perihelion passage, it was surprising to see that in the regions imaged by both DI and NExT there was little change in the surface photometric properties and morphology with the exception of the prominent smooth flow edges. As seen from both the spacecraft and ground-based campaign, the comet continued its trend of decreasing activity from previous perihelion passages. We will present highlights from both missions and discuss implications for formation scenarios.