A Libration Model for Enceladus Based on Geodetic Control Point Network Analysis

Nadezhdina, I.; Zubarev, A. E.; Brusnikin, E.S.; Oberst, J.

doi:10.5194/isprsarchives-xli-b4-459-2016

Cited by 4 publications

(8 citation statements)

References 7 publications

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“…We recovered a quadrupole gravity field with J 3 and a forced libration amplitude of 0.091° ± 0.009° (3σ). This libration estimate is lower than the previously estimated values from Thomas et al (2016) and Nadezhdina et al (2016). We believe this difference is likely due to the use of different Enceladus and spacecraft ephemerides, the span of data arcs, and the techniques for extracting the libration amplitude.…”

Section: Discussioncontrasting

confidence: 59%

“…The result shows a robust recovery of the forced libration amplitude with the resulting value of −0.091° ± 0.009° (3-σ). Table 6 also shows two previous forced libration amplitude estimates from analyzing the Cassini imaging data (Nadezhdina et al, 2016;Thomas et al, 2016).…”

Section: Rotational Modelmentioning

confidence: 99%

“…Where appropriate, we added terms to account for long period mean motion librations. We also included a term in the prime meridian expression to account for the observed forced libration (Nadezhdina et al, 2016;Thomas et al, 2016) and ignore the potential biasing impact of deformation over the orbital timescale (Berne et al, 2023;Van Hoolst et al, 2016).…”

Section: Rotational Modelmentioning

confidence: 99%

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The Global Shape, Gravity Field, and Libration of Enceladus

Park,

Mastrodemos,

Jacobson

et al. 2024

JGR Planets

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In order to improve our understanding of the interior structure of Saturn's small moon Enceladus, we reanalyze radiometric tracking and onboard imaging data acquired by the Cassini spacecraft during close encounters with the moon. We compute the global shape, gravity field, and rotational parameters of Enceladus in a reference frame consistent with the International Astronomical Union's definition, where the center of the Salih crater is located at −5° East longitude. We recover a quadrupole gravity field with J3 and a forced libration amplitude of 0.091° ± 0.009° (3‐σ). We also compute a global shape model using a stereo‐photoclinometry technique with a global resolution of 500 m, although some local maps have higher resolutions ranging from 25 to 100 m. While our overall results are generally consistent with previous studies, we infer a thicker 27–33 km mean ice shell, a thinner 21–26 km mean ocean thickness, and a mean core density range of 2,270–2,330 kg/m3.

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Section: Discussioncontrasting

confidence: 59%

Section: Rotational Modelmentioning

confidence: 99%

Section: Rotational Modelmentioning

confidence: 99%

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The Global Shape, Gravity Field, and Libration of Enceladus

Park,

Mastrodemos,

Jacobson

et al. 2024

JGR Planets

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“…With the arrival of Cassini in the Saturn system, new global control networks (Oberst et al, ) and global mosaics were completed (Roatsch et al, , ; Zubarev et al, ; and see global color products by P. Schenk, e.g., Planetary Photojournal, https://photojournal.jpl.nasa.gov/catalog/PIA18435). Cassini‐based control networks have now also been extensively utilized to evaluate Enceladus' rotation, including its libration (Giese et al, ; Nadezhdina et al, ; Thomas et al, ) and obliquity (Giese, ).…”

Section: Introduction Motivation and Overviewmentioning

confidence: 99%

A New Enceladus Global Control Network, Image Mosaic, and Updated Pointing Kernels From Cassini's 13‐Year Mission

Bland

Becker

Edmundson

et al. 2018

Earth and Space Science

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NASA's Cassini spacecraft spent 13 years exploring the Saturn system, including 23 targeted flybys of the small, geologically active moon Enceladus. These flybys provided a wealth of image data from Cassini's Imaging Science Subsystem. To improve the usability of the Enceladus data set, we created a new, global photogrammetric control network for Enceladus that enabled compilation of a versatile cartographic package to support geologic mapping and other investigations. The network used 586 images in four image filters with a pixel scale generally between 50 and 500 m per pixel and a phase angle less than 120° and consisted of 10,362 tie points and 173,704 individual image measures, averaging nearly 17 measures per tie point. Least squares bundle adjustment resulted in a root‐mean‐square residual of 0.45 pixel, corresponding to root‐mean‐square ground point uncertainties of 66, 51, and 46 m in latitude, longitude, and radius, respectively. Using our geodetic control network, we created new global image mosaics, coregistered flyby mosaics to support geologic mapping, and updated pointing kernels for every image used in the solution. These products, including the updated pointing kernels, are available to the community through NASA's Planetary Data System Imaging Annex. The bundle adjustment solution also yielded independently determined shape information, resulting in radii within the stated uncertainty of International Astronomical Union values. The challenges of the data set, and the technical methodology described here are applicable to bodies imaged during multiple flybys with variable viewing and illumination geometry, including other midsized satellites of Saturn, and the Europa Clipper mission.

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“…Additionally, the small angle method is limited by the measuring distance and angle, and when the measured distance is 100 m, the angle measurement accuracy is 2", and the mean square error is about 2 mm, the accuracy is low. Some studies adopt the method of a geodetic control network for deformation monitoring [12,13]. During these studies, one total station is used to observe the control network manually, adjust the control network and correct the displacement value of the working basis.…”

Section: Introductionmentioning

confidence: 99%

External Deformation Monitoring and Improved Partial Least Squares Data Analysis Methods of High Core Rock-Fill Dam (HCRFD)

Cheng

Zhou

et al. 2020

Sensors

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External deformation monitoring of high core rock-fill dams (HCRFDs) is an important and difficult part of safety monitoring. The traditional method of external deformation monitoring and data analysis for HCRFDs is to use a total station for small angle observations and establish a regression model to analyze the results. However, the small angle method has low accuracy and a low automation degree, and there is multicollinearity between the independent variables, which affects the parameter estimation and leads to the failure of model establishment. The angle forward intersection method is adopted in this paper for observation, and an improved partial least squares method (IPLS) is proposed to eliminate the multicollinearity of the independent variables. Compared to the traditional method, the improved observation method exhibits high accuracy and a high automation degree. The new data analysis method can not only eliminate multicollinearity but also improve the interpretation ability of the model. The data from the initial stage of water storage shows that the displacement increases with the increase in the upstream water level and time, and the speed of water storage is proportional to the displacement. The water level and time are the main influencing factors. This conclusion provides a theoretical basis for reservoir management departments to control water levels and gate opening and closing. The method in this paper can be applied to arch dams, gravity dams, and other types of waterpower engineering systems.

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A Libration Model for Enceladus Based on Geodetic Control Point Network Analysis

Cited by 4 publications

References 7 publications

The Global Shape, Gravity Field, and Libration of Enceladus

The Global Shape, Gravity Field, and Libration of Enceladus

A New Enceladus Global Control Network, Image Mosaic, and Updated Pointing Kernels From Cassini's 13‐Year Mission

External Deformation Monitoring and Improved Partial Least Squares Data Analysis Methods of High Core Rock-Fill Dam (HCRFD)

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