Search

Your search keyword '"Oberst, J."' showing total 745 results
Start Over Author "Oberst, J."
745 results on '"Oberst, J."'

1. Mars moon ephemerides after 14 years of Mars Express data

Author

Lainey, V., Pasewaldt, A., Robert, V., Rosenblatt, P., Jaumann, R., Oberst, J., Roatsch, T., Willner, K., Ziese, R., and Thuillot, W.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

The Mars Express (MEX) mission has been successfully operated around Mars since 2004. Among many results, MEX has provided some of the most accurate astrometric data of the two Mars moons, Phobos and Deimos. In this work we present new ephemerides of Mars' moons benefitting from all previously published astrometric data to the most recent MEX SRC data. All in all, observations from 1877 until 2018 and including spacecraft measurements from Mariner 9 to MEX were included. Assuming a homogeneous interior, we fitted Phobos' forced libration amplitude simultaneously with the Martian tidal k2/Q ratio and the initial state of the moons. Our solution of the physical libration 1.09 +/- 0.01 degrees deviates notably from the homogeneous solution. But considering the very low error bar, this may essentially suggest the necessity to consider higher order harmonics, with an improved rotation model, in the future. While most data could be successfully fitted, we found a disagreement between the Mars Reconnaissance Orbiter and the Mars Express astrometric data at the kilometer level probably associated with a biased phase correction. The present solution precision is expected at the level of a few hundreds of meters for Phobos and several hundreds of meters for Deimos for the coming years. The real accuracy of our new ephemerides will have to be confirmed by confrontation with independent observational means., Comment: accepted for publication in Astronomy and Astrophysics

Published
2020
Full Text
View/download PDF

3. Automated detection of block falls in the north polar region of Mars

Author

Fanara, L., Gwinner, K., Hauber, E., and Oberst, J.

Subjects
Computer Science - Computer Vision and Pattern Recognition
Abstract

We developed a change detection method for the identification of ice block falls using NASA's HiRISE images of the north polar scarps on Mars. Our method is based on a Support Vector Machine (SVM), trained using Histograms of Oriented Gradients (HOG), and on blob detection. The SVM detects potential new blocks between a set of images; the blob detection, then, confirms the identification of a block inside the area indicated by the SVM and derives the shape of the block. The results from the automatic analysis were compared with block statistics from visual inspection. We tested our method in 6 areas consisting of 1000x1000 pixels, where several hundreds of blocks were identified. The results for the given test areas produced a true positive rate of ~75% for blocks with sizes larger than 0.7 m (i.e., approx. 3 times the available ground pixel size) and a false discovery rate of ~8.5%. Using blob detection we also recover the size of each block within 3 pixels of their actual size.

Published
2018

4. Observations of meteors in the Earth's atmosphere: Reducing data from dedicated double-station wide-angle cameras

Author

Margonis, A., Christou, A., and Oberst, J.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

Meteoroids entering the Earth's atmosphere can be observed as meteors, thereby providing useful information on their formation and hence on their parent bodies. We developed a data reduction software package for double station meteor data from the SPOSH camera, which includes event detection, image geometric and radiometric calibration, radiant and speed estimates, trajectory and orbit determination, and meteor light curve recovery. The software package is designed to fully utilise the high photometric quality of SPOSH images. This will facilitate the detection of meteor streams and studies of their trajectories. We have run simulations to assess the performance of the software by estimating the radiants, speeds, and magnitudes of synthetic meteors and comparing them with the a priori values. The estimated uncertainties in radiant location had a zero mean with a median deviation between 0.03$^{\circ}$ and 0.11$^{\circ}$ for the right ascension and 0.02$^{\circ}$ and 0.07$^{\circ}$ for the declination. The estimated uncertainties for the speeds had a median deviation between 0.40 and 0.45 km s$^{-1}$. The brightness of synthetic meteors was estimated to within +0.01m. We have applied the software package to 177 real meteors acquired by the SPOSH camera. The median propagated uncertainties in geocentric right ascension and declination were found to be of 0.64$^{\circ}$ and 0.29$^{\circ}$, while the median propagated error in geocentric speed was 1.21 km $s^{-1}$.

Published
2018
Full Text
View/download PDF

10. Direct observations of asteroid interior and regolith structure: Science measurement requirements

Author

Herique, A., Agnus, B., Asphaug, E., Barucci, A., Beck, P., Bellerose, J., Biele, J., Bonal, L., Bousquet, P., Bruzzone, L., Buck, C., Carnelli, I., Cheng, A., Ciarletti, V., Delbo, M., Du, J., Du, X., Eyraud, C., Fa, W., Gil Fernandez, J., Gassot, O., Granados-Alfaro, R., Green, S.F., Grieger, B., Grundmann, J.T., Grygorczuk, J., Hahnel, R., Heggy, E., Ho, T-M., Karatekin, O., Kasaba, Y., Kobayashi, T., Kofman, W., Krause, C., Kumamoto, A., Küppers, M., Laabs, M., Lange, C., Lasue, J., Levasseur-Regourd, A.C., Mallet, A., Michel, P., Mottola, S., Murdoch, N., Mütze, M., Oberst, J., Orosei, R., Plettemeier, D., Rochat, S., RodriguezSuquet, R., Rogez, Y., Schaffer, P., Snodgrass, C., Souyris, J-C., Tokarz, M., Ulamec, S., Wahlund, J-E., and Zine, S.

Published
2018
Full Text
View/download PDF

12. The BepiColombo Laser Altimeter

Author

Thomas, N., Hussmann, H., Spohn, T., Lara, L. M., Christensen, U., Affolter, M., Bandy, T., Beck, T., Chakraborty, S., Geissbuehler, U., Gerber, M., Ghose, K., Gouman, J., HosseiniArani, S., Kuske, K., Peteut, A., Piazza, D., Rieder, M., Servonet, A., Althaus, C., Behnke, T., Gwinner, K., Hüttig, C., Kallenbach, R., Lichopoj, A., Lingenauber, K., Lötzke, H.-G., Lüdicke, F., Michaelis, H., Oberst, J., Schrödter, R., Stark, A., Steinbrügge, G., del Togno, S., Wickhusen, K., Castro, J. M., Herranz, M., Rodrigo, J., Perplies, H., Weigel, T., Schulze-Walewski, S., Blum, S., Casciello, A., Rugi-Grond, E., Coppoolse, W., Rech, M., Weidlich, K., Leikert, T., Henkelmann, R., Trefzger, B., and Metz, B.

Published
2021
Full Text
View/download PDF

16. Results from the Mars Pathfinder Camera

Author

Smith, P. H., Bell, J. F., Bridges, N. T., Britt, D. T., Gaddis, L., Greeley, R., Keller, H. U., Herkenhoff, K. E., Jaumann, R., Johnson, J. R., Kirk, R. L., Lemmon, M., Maki, J. N., Malin, M. C., Murchie, S. L., Oberst, J., Parker, T. J., Reid, R. J., Sablotny, R., Soderblom, L. A., Stoker, C., Sullivan, R., Thomas, N., Tomasko, M. G., Ward, W., and Wegryn, E.

Published
1997

17. PIXEL-RESOLUTION DTM GENERATION FOR THE LUNAR SURFACE BASED ON A COMBINED DEEP LEARNING AND SHAPE-FROM-SHADING (SFS) APPROACH

Author

Chen, H., Hu, X., and Oberst, J.

Abstract

High-resolution Digital Terrain Models (DTMs) of the lunar surface can provide crucial spatial information for lunar exploration missions. In this paper, we propose a method to generate high-quality DTMs based on a synthesis of deep learning and Shape from Shading (SFS) with a Lunar Reconnaissance Orbiter Narrow Angle Camera (LROC NAC) image as well as a coarse-resolution DTM as input. Specifically, we use a Convolutional Neural Network (CNN)-based deep learning architecture to predict initial pixel-resolution DTMs. Then, we use SFS to improve the details of DTMs. The CNN-model is trained based on the dataset with 30, 000 samples, which are formed by stereo-photogrammetry derived DTMs and orthoimages using LROC NAC images as well as the Selenological and Engineering Explorer and LRO Elevation Model (SLDEM). We take Chang’E-3 landing site as an example, and use a 1.6 m resolution LROC NAC image and 5 m resolution stereo-photogrammetry derived DTM as input to test the proposed method. We evaluate our DTMs with those from stereo-photogrammetry and deep learning. The result shows the proposed method can generate 1.6 m resolution high-quality DTMs, which can clearly improve the visibility of details of the initial DTM generated from the deep learning method.

Published
2022
Full Text
View/download PDF

27. The Phobos information system

Author

Karachevtseva, I.P., Oberst, J., Zubarev, A.E., Nadezhdina, I.E., Kokhanov, A.A., Garov, A.S., Uchaev, D.V., Uchaev, Dm.V., Malinnikov, V.A., and Klimkin, N.D.

Published
2014
Full Text
View/download PDF

28. Mars Express investigations of Phobos and Deimos

Author

Witasse, O., Duxbury, T., Chicarro, A., Altobelli, N., Andert, T., Aronica, A., Barabash, S., Bertaux, J.-L., Bibring, J.-P., Cardesin-Moinelo, A., Cichetti, A., Companys, V., Dehant, V., Denis, M., Formisano, V., Futaana, Y., Giuranna, M., Gondet, B., Heather, D., Hoffmann, H., Holmström, M., Manaud, N., Martin, P., Matz, K.-D., Montmessin, F., Morley, T., Mueller, M., Neukum, G., Oberst, J., Orosei, R., Pätzold, M., Picardi, G., Pischel, R., Plaut, J.J., Reberac, A., Pardo Voss, P., Roatsch, T., Rosenblatt, P., Remus, S., Schmedemann, N., Willner, K., and Zegers, T.

Published
2014
Full Text
View/download PDF

30. Phobos and Deimos cartography

Author

Wählisch, M., Stooke, P.J., Karachevtseva, I.P., Kirk, R., Oberst, J., Willner, K., Nadejdina, I.A., Zubarev, A.E., Konopikhin, A.A., and Shingareva, K.B.

Published
2014
Full Text
View/download PDF

31. The future Global Geodetic Observing System

Author

Rothacher, M., Beutler, G., Behrend, D., Donnellan, A., Hinderer, J., Ma, C., Noll, C., Oberst, J., Pearlman, M., Plag, H.-P., Richter, B., Schöne, T., Tavernier, G., Woodworth, P. L., Plag, Hans-Peter, editor, and Pearlman, Michael, editor

Published
2009
Full Text
View/download PDF

39. The Deep Space 1 Encounter with Comet 19P/Borrelly

Author

Boice, D. C., Soderblom, L. A., Britt, D. T., Brown, R. H., Sandel, B. R., Yelle, R. V., Buratti, B. J., Hicks, M. D., Nelson, R. M., Rayman, M. D., Oberst, J., Thomas, N., Boehnhardt, H., editor, Combi, M., editor, Kidger, M. R., editor, and Schulz, R., editor

Published
2003
Full Text
View/download PDF

40. GAUSS - genesis of asteroids and evolution of the solar system: A sample return mission to Ceres

Author

Ministerio de Ciencia e Innovación (España), European Research Council, European Commission, Shi, X., Castillo-Rogez, J., Hsieh, H., Hui, H., Ip, W. H., Lei, H., Li, J. Y., Tosi, F., Zhou, L., Agarwal, J., Barucci, A., Beck, P., Bagatin, A. C., Capaccioni, F., Coates, A. J., Cremonese, G., Duffard, René D., Grande, M., Jaumann, R., Jones, G. H., Kallio, E., Lin, Y., Mousis, O., Nathues, A., Oberst, J., Sierks, H., Ulamec, S., Wang, M., Ministerio de Ciencia e Innovación (España), European Research Council, European Commission, Shi, X., Castillo-Rogez, J., Hsieh, H., Hui, H., Ip, W. H., Lei, H., Li, J. Y., Tosi, F., Zhou, L., Agarwal, J., Barucci, A., Beck, P., Bagatin, A. C., Capaccioni, F., Coates, A. J., Cremonese, G., Duffard, René D., Grande, M., Jaumann, R., Jones, G. H., Kallio, E., Lin, Y., Mousis, O., Nathues, A., Oberst, J., Sierks, H., Ulamec, S., and Wang, M.

Abstract

The goal of Project GAUSS (Genesis of Asteroids and evolUtion of the Solar System) is to return samples from the dwarf planet Ceres. Ceres is the most accessible candidate of ocean worlds and the largest reservoir of water in the inner Solar System. It shows active volcanism and hydrothermal activities in recent history. Recent evidence for the existence of a subsurface ocean on Ceres and the complex geochemistry suggest past habitability and even the potential for ongoing habitability. GAUSS will return samples from Ceres with the aim of answering the following top-level scientific questions:What is the origin of Ceres and what does this imply for the origin of water and other volatiles in the inner Solar System?What are the physical properties and internal structure of Ceres? What do they tell us about the evolutionary and aqueous alteration history of dwarf planets?What are the astrobiological implications of Ceres? Is it still habitable today?What are the mineralogical connections between Ceres and our current collections of carbonaceous meteorites? © 2023 Elsevier B.V., All rights reserved.

Published
2022

46. Numerical Simulation of Illumination and Thermal Conditions at the Lunar Poles Using LOLA DTMs

Author

Glaser, P, Glaser, D, Oberst, J, Neumann, G. A, Mazarico, E, and Siegler, M. A

Subjects
Space Sciences (General)
Abstract

We are interested in illumination conditions and the temperature distribution within the upper two meters of regolith near the lunar poles. Here, areas exist receiving almost constant illumination near areas in permanent shadow, which were identified as potential exploration sites for future missions. For our study a numerical simulation of the illumination and thermal environment for lunar near-polar regions is needed. Our study is based on high-resolution, twenty meters per pixel and 400 x 400 km large polar Digital Terrain Models (DTMs), which were derived from Lunar Orbiter Laser Altimeter (LOLA) data. Illumination conditions were simulated by synthetically illuminating the LOLA DTMs using the horizon method considering the Sun as an extended source. We model polar illumination for the central 50 x 50 km subset and use it as an input at each time-step (2 h) to evaluate the heating of the lunar surface and subsequent conduction in the sub-surface. At surface level we balance the incoming insolation with the subsurface conduction and radiation into space, whereas in the sub-surface we consider conduction with an additional constant radiogenic heat source at the bottom of our two-meter layer. Density is modeled as depth-dependent, the specific heat parameter as temperature-dependent and the thermal conductivity as depth- and temperature-dependent. We implemented a fully implicit finite-volume method in space and backward Euler scheme in time to solve the one-dimensional heat equation at each pixel in our 50 x 50 km DTM. Due to the non-linear dependencies of the parameters mentioned above, Newton's method is employed as the non-linear solver together with the Gauss-Seidel method as the iterative linear solver in each Newton iteration. The software is written in OpenCL and runs in parallel on the GPU cores, which allows for fast computation of large areas and long time scales.

Published
2017

47. Aspects of small-sizemeteor parameters determination

Author

Efremov, V, Popova, O. P., Glazachev, D. O., Margonis, A., Oberst, J., and Kartashova, A. P.

Abstract

A model of the interaction of small meteoroid bodies with the Earth’s atmosphere, using the saturated vapor pressure of the meteoroid, was applied to analyze the light curves of meteors, making it possible to estimate the parameters of meteoroids. An automated method for estimating meteoroid body parameters was developed. The effect of uncertainty in the dependence of the saturated vapor pressure on the meteoroid body parameters is analyzed, the limitations and features of the model are discussed. Модель взаимодействия мелких метеорных тел с атмосферой Земли, использующая давление насыщенного пара вещества метеороида, была использована для анализа кривых блеска метеоров, что позволило оценить параметры метеороидов. Был разработан автоматизированный метод оценки параметров метеорного тела. Проанализировано влияние неопределенности в зависимости давления насыщенного пара от температуры на параметры метеорного тела, обсуждаются ограничения и особенности модели.

Published
2022

Catalog

Books, media, physical & digital resources
See catalog results