@misc{GutscheLaeuterSchmidt2016, author = {Gutsche, Philipp and L{\"a}uter, Matthias and Schmidt, Frank}, title = {Parameter-dependent Parallel Block Sparse Arnoldi and D{\"o}hler Algorithms on Distributed Systems}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-58202}, year = {2016}, abstract = {We summarize the basics and first results of the analyses within our ZIB Bridge Project and give an outlook on further studies broadening the usage of hardware acceleration within the Finite Element Method (FEM) based solution of Maxwell's equations.}, 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} } @article{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 = {Varying water activity and momentum transfer on comet 67P/Churyumov-Gerasimenko from its non-gravitational forces and torques}, volume = {690}, journal = {Astronomy and Astrophysics}, arxiv = {http://arxiv.org/abs/2408.10877}, doi = {10.1051/0004-6361/202450728}, pages = {A82}, year = {2024}, abstract = {Aims. We investigate the ability of a simultaneous fitting of comet 67P/Churyumov-Gerasimenko's non-gravitational forces, torques, and total water-outgassing rate, as observed by Rosetta, to constrain complex thermophysical models of cometary material. Methods. We extend the previous work of fitting geographically defined surface outgassing models to the Rosetta observations by testing the effects of a more detailed geomorphological mapping, the resolution of the shape-model used, self-heating by neighbouring facets on the shape-model, thermal inertia in the outgassing solution, and the variation in the momentum coupling between the gas and the nucleus. We also directly compare the non-gravitational acceleration curves available in the literature. Results. We correct an error in the calculation of pole-orientation in the previous paper. We find that, under the assumptions of the model, 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. Conclusions. Consolidated terrain facing south on 67P/Churyumov-Gerasimenko has a high outgassing flux, a steep response to insolation, and a large gas momentum transfer coefficient. Instead, that facing north behaves differently, producing little to no water outgassing, and with a lower momentum transfer efficiency. Dusty terrain also has a lower outgassing rate and momentum transfer efficiency, and either depletes its volatile component or is buried in fall-back as the comet approaches the Sun. Momentum transfer appears correlated with insolation, likely due to an increased enhancement in the gas temperature as the dust it flows through is heated.}, 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} } @article{LaeuterKramer2025, author = {L{\"a}uter, Matthias and Kramer, Tobias}, title = {Rotation dynamics and torque efficiency of cometary nuclei}, volume = {699}, journal = {Astronomy \& Astrophysics}, arxiv = {http://arxiv.org/abs/2507.06036}, doi = {10.1051/0004-6361/202553845}, pages = {A75}, year = {2025}, abstract = {The dynamics of a rigid cometary nucleus is described by the evolutions of its center-of-mass and of its rotation state. Solar irradiation that reaches the surface of a cometary nucleus causes the sublimation of volatiles that form the coma around the nucleus. The sublimation process transfers linear momentum and rotational angular momentum from the nucleus to the surrounding space, and thus affects the dynamics via nongravitational forces and nongravitational torques. With the exception of close approaches to planets, these torques exert the dominant influence on the rotation states of cometary nuclei. The Rosetta mission 2014-2016 accompanying comet 67P/Churyumov-Gerasimenko provides the longest continuous observational data to track its rotation state. In particular, the data set encompasses the direction of the angular velocity, denoted by ω, and the angular frequency |ω|over a time period of approximately 700 days. The observed change of the rotation state is not explained by a low heat conductivity thermophysical model in combination with a homogeneous surface ice coverage of comet 67P. Spatially and/or temporally varying weights for effective active fraction with respect to a prescribed set of surface regions provide a potential solution to this problem. Here, we present a methodology for classifying the surface based on vectorial efficiency of the torque. On any cometary surface without geometric symmetry, the methodology highlights the decomposition into eight characteristic regions that encode the signs of torque efficiency with respect to all vector components. This decomposition is divided into two subsets of four regions each of which is located in one of both hemispheric regions. We analyze in detail rotation states close to lowest energy and different thermophysical models, and we discuss how the uncertainties of observations affect the model parameters. We study the occurrence of these regions for an oblate ellipsoid, a nearprolate ellipsoid, a bilobed shape, and a shape model analogous to that of comet 67P. The sensitivity analysis for comet 67P indicates that the observations constrain only one of the eight weights uniquely. The other directions are poorly constrained and show the limitation of the rotational data to determine the regional activity on comet 67P.}, language = {en} } @article{GroussinJordaAttreeetal.2025, author = {Groussin, Olivier and Jorda, L. and Attree, N. and Birch, S.P.D. and B{\"u}rger, Johanna and Guti{\´e}rrez, Pedro and Jindal, Abhinav S. and Keller, H.U. and Kramer, Tobias and Lasagni Manghi, Riccardo and L{\"a}uter, Matthias and Markkanen, J. and Marschall, R. and Schuckart, C.}, title = {Thermal environment and erosion of comet 67P/Churyumov-Gerasimenko}, volume = {694}, journal = {Astronomy and Astrophysics}, doi = {10.1051/0004-6361/202452260}, pages = {A21}, year = {2025}, abstract = {Aims. This paper focuses on how insolation affects the nucleus of comet 67P/Churyumov-Gerasimenko over its current orbit. We aim to better understand the thermal environment of the nucleus, in particular its surface temperature variations, erosion, relationship with topography, and how insolation affects the interior temperature for the location of volatile species (H2O and CO2). Methods. We have developed two thermal models to calculate the surface and subsurface temperatures of 67P over its 6.45-year orbit. The first model, with high resolution (300 000 facets), calculates surface temperatures, taking shadows and self-heating into account but ignoring thermal conductivity. The second model, with lower resolution (10 000 facets), includes thermal conductivity to estimate temperatures down to ∼3 m below the surface. Results. The thermal environment of 67P is strongly influenced by its large obliquity (52◦), which causes significant seasonal effects and polar nights. The northern hemisphere is the coldest region, with temperatures of 210-300 K. H2O is found in the first few centimetres, while CO2 is found deeper (∼2 m) except during polar night around perihelion, when CO2 accumulates near the surface. Cliffs erode 3-5 times faster than plains, forming terraces. The equatorial region receives maximum solar energy (8.5×109 J m-2 per orbit), with maximum surface temperatures of 300-350 K. On the plains, H2O is found in the first few centimetres, while CO2 is found deeper (∼2 m) and never accumulates near the surface. In the southern hemisphere, a brief intense perihelion heating raises temperatures to 350-400 K, which is followed by a 5-year polar night when surface temperatures drop to 55 K. Here H2O remains in the first few centimetres, while CO2 accumulates shallowly during polar night, enriching the region. Erosion is maximal in the southern hemisphere and concentrated on the plains, which explains the observed overall flatness of this hemisphere compared to the northern one. Over one orbit, the total energy from self-heating is 17\% of the total energy budget, and 34\% for thermal conduction. Our study contributes to a better understanding of the surface changes observed on 67P.}, 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{BrookFullerSwinburneetal.2022, author = {Brook, Glenn and Fuller, Douglas and Swinburne, John and Christgau, Steffen and L{\"a}uter, Matthias and Rodrigues Pel{\´a}, Ronaldo and Lewin, Stein and Christian, Tuma and Steinke, Thomas}, title = {An Early Scalability Study of Omni-Path Express}, address = {Hamburg}, organization = {ISC 2022 IXPUG}, doi = {10.13140/RG.2.2.21353.57442}, pages = {8}, year = {2022}, abstract = {This work provides a brief description of Omni-Path Express and the current status of its development, stability, and performance. Basic benchmarks that highlight the gains of OPX over PSM2 are provided, and the results of an initial performance and scalability study of several applications are presented.}, 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} }