The eccentric ringlet at 1.29 RS

1984 ◽  
Vol 75 ◽  
pp. 259-262
Author(s):  
C. Porco ◽  
N. Borderies ◽  
G.E. Danielson ◽  
P. Goldreich ◽  
J.B. Holberg ◽  
...  
Keyword(s):  
Gravity Field ◽  
Geometric Distortion ◽  
Data Sets ◽  
Radio Science ◽  
Preliminary Results ◽  
Stellar Occultations ◽  
Major Planet

We present preliminary results of an examination of the eccentric ringlet near 1.29 R, in Saturn's inner C ring. Situated near the Titan 1:0 apsidal resonance, this feature provides an opportunity to study the behavior of a ring under the influence of both the gravity field of a major planet and the potential of an external satellite.The data sets used for this analysis consisted of seven Voyager images of this ringlet, ranging in resolution from 60 to 5 km/pixel, plus data obtained from three UVS stellar occultations and one Radio Science occultation. Three observations occurred within a day of Voyager 1 closest approach and seven within 5 days of Voyager 3 closest approach. The Voyager encounters were separated by 286 days. Of the seven Voyager images used, only the three highest resolution frames were corrected for geometric distortion. Therefore, the results presented here must be considered preliminary.

Human aorta: preliminary results with virtual endoscopy based on three-dimensional MR imaging data sets.

Radiology ◽  
1996 ◽  
Vol 199 (1) ◽  
pp. 37-40 ◽  
Author(s):  
C P Davis ◽  
M E Ladd ◽  
B J Romanowski ◽  
S Wildermuth ◽  
J F Knoplioch ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Three Dimensional ◽  
Virtual Endoscopy ◽  
Human Aorta ◽  
Data Sets ◽  
Imaging Data ◽  
Preliminary Results

scholarly journals An http data-federation ecosystem with caching functionality using DPM and Dynafed

2019 ◽  
Vol 214 ◽  
pp. 04041 ◽  
Author(s):  
Davide Michelino ◽  
Silvio Pardi ◽  
Guido Russo ◽  
Bernardino Spisso
Keyword(s):  
Data Distribution ◽  
Controlled Environment ◽  
Data Sets ◽  
Preliminary Results ◽  
Computing Model ◽  
Data Federation ◽  
Belle Ii ◽  
New Feature ◽  
Grid Storage ◽  
Computing Infrastructure

The implementation of cache systems in the computing model of HEP experiments enables to accelerate access to hot data sets by scientists, opening new scenarios of data distribution and enable to exploit the paradigm of storage-less sites. In this work, we present a study for the creation of an http data-federation ecosystem with caching functionality. We created plug-in integrated in the logic of a DPM Storage, able to reproduce a cache behaviour, taking advantage from the new feature introduced in the last version of Disk Pool Manager, called volatile-pool. Then we used Dynafed as lightweight federation system to aggregate a set of standard Grid Storage together with the caching system. With the designed setup, clients asking for a file present on the Data-Grid are automatically redirected to the cache, if the cache is the closest storage, thanks to the action of the geo-plugin run by Dynafed. As proof of the concept, we tested the whole system in a controlled environment within the Belle II computing infrastructure using a set of files located in production Storage Elements. Preliminary results demonstrate the proper functionality of the logic and encourage continuing the work.

Radio Science Investigations of the Saturn System with Voyager 1: Preliminary Results

Science ◽  
1981 ◽  
Vol 212 (4491) ◽  
pp. 201-206 ◽  
Author(s):  
G. L. TYLER ◽  
V. R. ESHLEMAN ◽  
J. D. ANDERSON ◽  
G. S. LEVY ◽  
G. F. LINDAL ◽  
...  
Keyword(s):  
Radio Science ◽  
Preliminary Results ◽  
Science Investigations

scholarly journals A variant of gravitational classification

2014 ◽  
Vol 51 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Tomasz Górecki ◽  
Maciej Luczak
Keyword(s):  
Gravity Field ◽  
Error Rate ◽  
Simulation Method ◽  
General Idea ◽  
Classification Error ◽  
Data Sets ◽  
Classification Error Rate ◽  
Motion Problem ◽  
The Mean ◽  
Parameter Values

Summary In this article there is proposed a new two-parametrical variant of the gravitational classification method. We use the general idea of objects' behavior in a gravity field. Classification depends on a test object's motion in a gravity field of training points. To solve this motion problem, we use a simulation method. This classifier is compared to the 1NN method, because our method tends towards it for some parameter values. Experimental results on different data sets demonstrate an improvement in efficiency and that this approach outperforms the 1NN method by providing a significant reduction in the mean classification error rate.

Didymos Gravity Science Investigations through Ground-based and Inter-Satellite Links Doppler Tracking

2021 ◽  
Author(s):  
Paolo Tortora ◽  
Marco Zannoni ◽  
Edoardo Gramigna ◽  
Riccardo Lasagni Manghi ◽  
Sebastien Le Maistre ◽  
...  
Keyword(s):  
Gravity Field ◽  
Low Frequency ◽  
Imaging Data ◽  
Satellite Link ◽  
Asteroid Impact ◽  
Radio Science ◽  
Combining Data ◽  
Planetary Defense ◽  
Global Mapping ◽  
Range Rate

<p>The Asteroid Impact and Deflection Assessment (AIDA) is an international collaboration supported by ESA and NASA to assess the feasibility of the kinetic impactor technique to deflect an asteroid, combining data obtained from NASA’s DART and ESA’s Hera missions. Together the missions represent the first humankind’s investigations of a planetary defense technique. In 2022, DART will impact Dimorphos, the secondary of the binary near-Earth asteroid (65803) Didymos.  After 4 years, Hera will follow-up with a detailed post-impact survey of Didymos, to fully characterize and validate this planetary defense technique. In addition, Hera will deploy two CubeSats around Didymos once the Early Characterization Phase has completed, to augment the observations of the mother spacecraft. Juventas, the first Cubesat, will complete a low-frequency radar survey of the secondary, to unveil its interior. Milani, the second Cubesat, will perform a global mapping of Didymos and Dimorphos, with a focus on their compositional difference and their surface properties. One of the main objectives of Hera is to determine the binary system’s mass, gravity field, and dynamical state using radio tracking data in combination with imaging data. The gravity science experiment includes classical ground-based radiometric measurements between Hera and ground stations on Earth by means of a standard two-way X-band link, onboard images of Didymos, and spacecraft-to-spacecraft inter-satellite (ISL) radiometric tracking between Hera and the Cubesats. The satellite-to-satellite link is a crucial add-on to the gravity estimation of low-gravity bodies by exploiting the Cubesats’ proximity to the binary, as the range-rate measurements carried out by the inter-satellite link contain information on the dynamics of the system, i.e., masses and gravity field of Didymos primary and secondary.</p><p>We will describe the updated mission scenario for the Hera radio science experiment to be jointly carried out by the three mission elements, i.e., Hera, Juventas and Milani. To conclude, our updated analysis and latest results, as well as the achievable accuracy for the estimation of the mass and gravity field of Didymos and Dimorphos, are presented.</p>

scholarly journals Direct comparisons of GOMOS and SAGE III NO<sub>3</sub> vertical profiles

2012 ◽  
Vol 5 (1) ◽  
pp. 1497-1514
Author(s):  
J. Hakkarainen ◽  
J. Tamminen ◽  
J. R. Moore ◽  
E. Kyrölä
Keyword(s):  
Data Sets ◽  
Vertical Profiles ◽  
Median Difference ◽  
Comparison Results ◽  
Stellar Occultations ◽  
Ozone Monitoring ◽  
Stratospheric Aerosols

Abstract. In this paper we present first global comparisons between the two unique satellite-borne data sets of NO3 vertical profiles retrieved from the GOMOS (Global Ozone Monitoring by the Occultation of Stars) stellar occultations and the SAGE III (Stratospheric Aerosols and Gas Experiment) lunar occultations. The comparison results indicate that between the altitudes 25 km and 45 km the median difference between these two data sets is within &amp;pm;25%. The study of zonal median profiles shows agreement between these data sets. The agreement is at its best in tropics and slightly deviating towards the poles.

The Measured Gravity and Global Geophysical Properties of (101955) Bennu

2020 ◽  
Author(s):  
Daniel Scheeres ◽  
Andrew French ◽  
Pasquale Tricarico ◽  
Steven Chesley ◽  
Yu Takahashi ◽  
...  
Keyword(s):  
Gravity Field ◽  
Parent Body ◽  
Equatorial Region ◽  
The Body ◽  
Particle Migration ◽  
Constant Density ◽  
Radio Science ◽  
California Institute Of Technology ◽  
Institute Of Technology ◽  
Rubble Pile

&lt;p&gt;&lt;strong&gt;Introduction:&lt;/strong&gt;&amp;#160; Estimates of asteroid (101955) Bennu&amp;#8217;s gravity have been determined based on a series of independent solutions from different teams involved on the OSIRIS-REx mission. In addition to classical radio science techniques for estimating a body's gravity field coefficients, the discovery of particles ejected from Bennu that persist in orbit for multiple revolutions provides a unique opportunity to probe the gravity field to higher degree and order than possible by using conventional spacecraft tracking [1]. However, the non-gravitational forces acting on these particles must also be characterized, and their impact on solution accuracy must be assessed, requiring the different gravity field estimates to be compared and reconciled.&lt;/p&gt; &lt;p&gt;Given the measured gravity field of Bennu, rigorous constraints on its internal density heterogeneity can be found by comparing the measured field with the constant density field computed from the asteroid shape. These results in turn provide unique insight into the global geophysical processes that drive the external and internal morphology of small rubble-pile asteroids such as Bennu.&lt;/p&gt; &lt;p&gt;Finally, definitive results on the surface and close-proximity force environment of Bennu can be derived and updated from the initial analysis based on the total mass and constant density shape. Several aspects of the environment are highly sensitive to the gravity field and have changed from earlier results [2, 3, 4].&lt;/p&gt; &lt;p&gt;We will present the current gravity field solutions and uncertainties, update the surface and proximity environment models, and provide the geophysical implications and interpretations of these measurements. &amp;#160;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;Geophysical Models:&lt;/strong&gt;&amp;#160; The estimated gravity field solutions are compared with the constant density shape model to constrain models of the internal density variation. We find that these differences are consistent with Bennu having an under-dense core and equatorial ridge. The degree to which these are under-dense cannot be specifically constrained, but feasible ranges for these values can be determined.&lt;/p&gt; &lt;p&gt;An under-dense equator could be consistent with transport of material to the equator without compaction. Given the slope transition at the Roche lobe, this would also be consistent with the ballistic transport of material into the equatorial region. Estimates of the rate of particle migration do not seem to be enough to account for the overall equatorial bulge of Bennu, however, implying that this feature could be older and not due to the more recent transport of material to the equator.&lt;/p&gt; &lt;p&gt;The lower-density interior is consistent with a period of rapid spin and failure of the interior of the body [5]. This could also be consistent with the raised equatorial bulge. This interior failure could have occurred in an earlier epoch of YORP-induced rapid rotation or could trace to the initial formation of Bennu as a distinct rubble-pile body [6]. Tests of this hypothesis require additional simulations of how rubble-pile asteroids coalesce after the catastrophic disruption of their parent body.&amp;#160;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Acknowledgements:&lt;/strong&gt; This material is based upon work supported by NASA under Contract NNM10AA11C issued through the New Frontiers Program. Part of this research was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. We are grateful to the entire OSIRIS-REx Team for making the encounter with Bennu possible.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt; [1] Lauretta D.S. &amp; Hergenrother C.W. et al. (2019) Science 366, eaay3544. [2] Scheeres D.J. et al. (2019) Nature Astronomy 3, 352-361. [3] Barnouin O.S. et al. 2019. Nature Geoscience 12, 247-252. [4] Tricarico P. et al. (2019) EPSC-DPS Abstract #2019-547-1. [5] Scheeres D.J. et al. (2016) Icarus 276, 116-140. [6] Michel P. et al. (2018) AGU Fall Meeting 2018 Abstract #P33C-P33850.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt;

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