@inproceedings{Kramer2020, author = {Kramer, Tobias}, title = {Transient capture of electrons in magnetic fields, or: comets in the restricted three-body problem}, volume = {1612}, booktitle = {Journal of Physics: Conference Series}, edition = {Symmetries in Science XVIII}, arxiv = {http://arxiv.org/abs/1912.08593}, doi = {10.1088/1742-6596/1612/1/012019}, pages = {012019}, year = {2020}, abstract = {The motion of celestial bodies in astronomy is closely related to the orbits of electrons encircling an atomic nucleus. Bohr and Sommerfeld presented a quantization scheme of the classical orbits to analyze the eigenstates of the hydrogen atom. Here we discuss another close connection of classical trajectories and quantum mechanical states: the transient dynamics of objects around a nucleus. In this setup a comet (or an electron) is trapped for a while in the vicinity of parent object (Jupiter or an atomic nucleus), but eventually escapes after many revolutions around the center of attraction.}, language = {en} } @inproceedings{LaeuterKramerRubinetal.2020, author = {L{\"a}uter, Matthias and Kramer, Tobias and Rubin, Martin and Altwegg, Kathrin}, title = {Gas production for 14 species on comet 67P/Churyumov-Gerasimenko from 2014-2016}, volume = {14}, booktitle = {Europlanet Science Congress}, publisher = {Europlanet Science Congress}, doi = {10.5194/epsc2020-319}, pages = {EPSC2020-319}, year = {2020}, abstract = {During a two year period between 2014 and 2016 the coma of comet 67P/Churyumov-Gerasimenko (67P/C-G) has been probed by the Rosetta spacecraft. Density data for 14 gas species was recorded with the COmet Pressure Sensor (COPS) and the Double Focusing Mass Spectrometer (DFMS) being two sensors of the ROSINA instrument. The combination with an inverse gas model yields emission rates on each of 3996 surface elements of a surface shape for the cometary nucleus. The temporal evolution of gas production, of relative abundances, and peak productions weeks after perihelion are investigated. Solar irradiation and gas production are in a complex relation revealing features differing for gas species, for mission time, and for the hemispheres of the comet. This characterization of gas composition allows one to correlate 67P/C-G to other solar and interstellar comets, their formation conditions and nucleus properties, see [Bodewits D., et al., 2020 Nature Astronomy].}, language = {en} } @inproceedings{KramerLaeuter2020, author = {Kramer, Tobias and L{\"a}uter, Matthias}, title = {Non-gravitational force model vs observation: the trajectory and rotation-axis of comet 67P/Churyumov-Gerasimenko}, volume = {14}, booktitle = {Europlanet Science Congress}, publisher = {Europlanet Science Congress}, doi = {10.5194/epsc2020-403}, pages = {EPSC2020-403}, year = {2020}, abstract = {The determination of non-gravitational forces based on precise astrometry is one of the main tools to establish the cometary character of interstellar and solar-system objects. The Rosetta mission to comet 67P/C-G provided the unique opportunity to benchmark Earth-bound estimates of non-gravitational forces with in-situ data. We determine the accuracy of the standard Marsden and Sekanina parametrization of non-gravitational forces with respect to the observed dynamics. Additionally we analyse the rotation-axis changes (orientation and period) of 67P/C-G. This comparison provides a reference case for future cometary missions and sublimation models for non-gravitational forces.}, language = {en} } @inproceedings{KramerLaeuter2024, author = {Kramer, Tobias and L{\"a}uter, Matthias}, title = {Benchmarking the rotating jet model of cometary activity with the trajectory of comet 67P/Churyumov-Gerasimenko}, volume = {17}, booktitle = {EPSC Abstracts}, doi = {10.5194/epsc2024-207}, year = {2024}, abstract = {An important tool to assess the composition and the spatial origin of cometary material is the analysis of its trajectory reflecting gravitational acceleration due to solar system bodies complemented by non-gravitational accelerations (NGA).}, language = {en} } @inproceedings{AttreeGutierrezGroussinetal.2024, author = {Attree, Nicholas and Guti{\´e}rrez, Pedro and Groussin, Olivier and B{\"u}rger, Johanna and Keller, Horst Uwe and Kramer, Tobias and Lasagni Manghi, Riccardo and L{\"a}uter, Matthias and Lemos, Pablo and Markkanen, Johannes and Marschall, Raphael and Schuckart, Christian}, title = {The Results of ISSI Team \#547: Understanding the Activity of Comets Through 67P's Dynamics}, volume = {17}, booktitle = {EPSC Abstracts}, doi = {10.5194/epsc2024-82}, year = {2024}, abstract = {Understanding cometary activity gives us an insight into the materials properties, and therefore formation and evolution processes of these relatively pristine protoplanetary objects. We will present the results of an International Space Science Institute project to investigate the phenomenon through the effects of the outgassing activity on the orbit and spin-state of comet 67P/Churymov-Gerasimenko, e.g. its non-gravitational dynamics. This International Team gathered experts in orbital dynamics and trajectory reconstruction together with thermophysical modellers and comet observationalists, in order to compare the available extractions of 67P's non-gravitational acceleration (NGA) from its trajectory. The team then fitted a combination of the NGA, the non-gravitational torque (NGT), and the total water-outgassing rate with a thermophysical activity model. The results of this model will be presented. In particular, it was found that: non-gravitational forces and torques are driven by water sublimation from the nucleus; thermal inertia and self-heating have only minor effects; spatially uniform activity cannot explain 67P's non-gravitational dynamics; spatially uniform momentum transfer cannot explain 67P's non-gravitational dynamics; and different terrain types have different instantaneous responses to insolation. The implications of these findings for the modelling of cometary material and the variety of surface types seen on 67P will be discussed.}, language = {en} } @inproceedings{LaeuterKramerRubinetal.2022, author = {L{\"a}uter, Matthias and Kramer, Tobias and Rubin, Martin and Altwegg, Kathrin}, title = {Determination of the ice composition near the surface of comet 67P/Churyumov-Gerasimenko}, booktitle = {Europlanet Science Congress}, doi = {10.5194/epsc2022-826}, pages = {EPSC2022-826}, year = {2022}, abstract = {During the apparition of comet 67P/Churyumov-Gerasimenko (67P/C-G) solar irradiation causes varying rates for sublimation of volatile species from the cometary nucleus. Because sublimation processes take place close to the cometary surface, the relative abundance of volatiles in the coma and the ice composition are related to each other. To quantify this relation we assume a model for the expansion of a collisionless gas from the surface into the surrounding space. We use an inverse model approach to relate the in situ measurements of gas densities from the two Rosetta instruments COPS (COmet Pressure Sensor) and DFMS (Double Focusing Mass Spectrometer) at the positions of the spacecraft to the locations of surface gas emissions during the Rosetta mission 2014-2016. We assume the temporally integrated gas emissions to be representative for the ice composition close to the surface. Our analysis shows characteristic differences in the ice compositions between both hemispheres of 67P/C-G. In particular CO2 ice has a reduced abundance on the northern hemisphere. In contrast to the hemispherical differences, the two lobes do not show significant differences in terms of their ice composition.}, language = {en} } @inproceedings{KramerLaeuter2022, author = {Kramer, Tobias and L{\"a}uter, Matthias}, title = {The near nucleus gas and dust environment around comet 67P/Churyumov-Gerasimenko}, booktitle = {Europlanet Science Congress}, doi = {10.5194/epsc2022-281}, pages = {EPSC2022-281}, year = {2022}, abstract = {The Rosetta mission to comet 67P/C-G provided a detailed view of the near nucleus environment of an active Jupiter family comet. The continuous monitoring of the gas pressure with the ROSINA experiment at the location of the Rosetta spacecraft in combination with the images of the dust environment acquired by the OSIRIS cameras allows one to test different hypotheses about the origin of the dust and gas emissions. In addition the orbital elements and the rotation axis and spin rate of the nucleus are affected by the gas release.}, language = {en} } @inproceedings{BuergerGundlachBlumetal.2022, author = {B{\"u}rger, Johanna and Gundlach, Bastian and Blum, J{\"u}rgen and Hayne, Paul and L{\"a}uter, Matthias and Kramer, Tobias}, title = {Lunar regolith properties derived from LRO/Diviner data and thermophysical modelling}, booktitle = {Europlanet Science Congress}, doi = {10.5194/epsc2022-92}, pages = {EPSC2022-92}, year = {2022}, abstract = {The Moon as our nearest celestial object is one of the most important bodies for space resource exploration and planetary science. However, knowledge of the physical properties of the lunar regolith is required for the exploitation of lunar resources and for understanding the Moon's geologic history. This knowledge comes mainly from Apollo in-situ experiments and returned samples, but the global distribution of these properties is still poorly understood. Remote sensing measurements offer the opportunity to derive properties of unsampled areas with the help of models. In our study, a microphysical thermal model for the lunar regolith was developed and the simulated surface temperatures were compared with thermal emission measurements from the Diviner radiometer on board the Lunar Reconnaissance Orbiter (LRO) to derive regolith properties. This work expands upon previous investigations of lunar regolith properties using Diviner data, by more directly simulating physical properties such as particle size and porosity.}, language = {en} } @inproceedings{BuergerHayneGundlachetal.2023, author = {B{\"u}rger, Johanna and Hayne, Paul and Gundlach, Bastian and L{\"a}uter, Matthias and Kramer, Tobias and Blum, J{\"u}rgen}, title = {Investigating the Latitudinal Dependence of Lunar Regolith Properties Using LRO/Diviner Data and a Microphysical Thermal Model}, volume = {55}, booktitle = {Bulletin of the AAS}, number = {8}, year = {2023}, abstract = {Regolith is formed through weathering of the local rock by meteorite bombardment, space weathering (Pieters \& Noble, 2016) and thermal erosion (Delbo et al., 2014). In the case of the Moon, the space weathering effects and diurnal temperature variations are reduced towards the poles. The aim of this study is to investigate whether the lunar regolith properties derived from the comparison of regolith temperatures measured by the Diviner radiometer (Paige et al., 2010) on board the Lunar Reconnaissance Orbiter (LRO) with simulated temperatures derived from a microphysical thermal model show a latitudinal dependence. The developed microphysical thermal model expands upon previous models by more directly simulating regolith properties, such as grain radius and volume filling factor.}, language = {en} } @inproceedings{LaeuterKramer2023, author = {L{\"a}uter, Matthias and Kramer, Tobias}, title = {Non-gravitational acceleration and torque on comet 67P/Churyumov-Gerasimenko}, volume = {55}, booktitle = {Bulletin of the AAS}, number = {8}, year = {2023}, abstract = {From August 2014 to September 2016, the ESA operated the Rosetta spacecraft mission alongside with comet 67P/Churyumov-Gerasimenko (67P). The mission provided valuable long-term data on the comet's nucleus, including its volume, mass, tensor of inertia, spatial position of the orbital trajectory, and rotational state.}, language = {en} } @inproceedings{KramerLaeuter2021, author = {Kramer, Tobias and L{\"a}uter, Matthias}, title = {Matching the activity of comet 67P/Churyumov-Gerasimenko with long-term ground-based astrometry}, volume = {15}, booktitle = {Europlanet Science Congress}, publisher = {Europlanet Science Congress}, doi = {10.5194/epsc2021-337}, pages = {EPSC2021-337}, year = {2021}, abstract = {50 years of astrometric data for comet 67P/C-G (orbital period about 6.45 years) provides a unique opportunity to benchmark non-gravitational acceleration models to the in situ measurements of the volatile release performed from the Rosetta rendezvous mission (2014-2016). Taken together, the Earth-bound and in-situ data yields lower fit errors and serves as a test-case for our ability to deduce thermophysical quantities of cometary nuclei from the Earth-bound observations.}, language = {en} } @inproceedings{LaeuterKramerRubinetal.2018, author = {L{\"a}uter, Matthias and Kramer, Tobias and Rubin, Martin and Altwegg, Kathrin}, title = {Gas production of comet 67P/Churyumov-Gerasimenko reconstructed from DFMS/COPS data}, volume = {12}, booktitle = {Europlanet Science Congress}, publisher = {Europlanet Science Congress}, pages = {EPSC2018-515-1}, year = {2018}, abstract = {We reconstruct the temporal evolution of surface emissions for the four major gas species H2O, CO2, CO, and O2 emitted during the 2015 apparition of comet 67P/Churyumov-Gerasimenko (67P/C-G). Measurements from the Double Focusing Mass Spectrometer (DFMS) of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) and the COmet Pressure Sensor (COPS) are used to determine the gas sources on the surface with an inverse gas model for the entire coma. For all species, peak production rates and integrated production rates per orbit are evaluated separately for the northern and the southern hemisphere. Complemented with the total mass production, this allows us to estimate the dust-to-gas ratio of the emitted material.}, language = {en} }