Phobos control point network, rotation, and shape

Willner, Konrad; Oberst, J.; Hußmann, H.; Giese, B.; Hoffmann, H.; Matz, Klaus-Dieter; Roatsch, Thomas; Duxbury, T. C.

doi:10.1016/j.epsl.2009.07.033

Cited by 92 publications

(86 citation statements)

References 16 publications

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“…However, heterogeneities inside Phobos cannot be ruled out based on the measured libration angle by Willner et al (2010). Assuming Phobos is made of a mixture of porosity (macro-porosity or micro-porosity), Rosenblatt et al (2011) have proposed models of heterogeneous internal mass distribution inside Phobos, which can fit its bulk density and librational angle.…”

Section: Phobos Interiormentioning

confidence: 99%

“…Here, we investigate the rotational motion of Phobos by using a numerical integration to explore couplings that are non-linear or generally neglected from the analytical developments. In addition, we used both the recent determination of the moments of inertia based on MEX images (Willner et al 2010) and the numerical ephemerides of Lainey et al (2007).…”

Section: Predicting High-resolution Measurements Of Phobos' Rotationmentioning

confidence: 99%

“…The rotational motion of Phobos was first determined in 1981 by Duxbury and Callahan by using Viking orbiter images, which led to dynamical studies of Phobos' librations (Borderies & Yoder 1990;Chapront-Touzé 1990;Pesek 1991). Recently Willner et al (2010) have increased the number of control points by using Mars EXpress (MEX) high-resolution images. These authors determined the libration amplitude at 1.20 degree (deg) with an accuracy of about 0.15 deg.…”

Section: Introductionmentioning

confidence: 99%

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Rotational motion of Phobos

Rambaux

Castillo‐Rogez

Maistre

et al. 2012

A&A

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Context. Phobos is in synchronous spin-orbit resonance around Mars, like our Moon around the Earth. As a consequence, the rotational period of Phobos is equal in average to its orbital period. The variations of its rotational motion are described by oscillations, called physical librations, which yield information of its interior structure. The largest libration of Phobos rotational motion was first detected in 1981 and the determination of this libration has recently been improved using Mars EXpress observations. Aims. The objective of this paper is to present the spectrum of Phobos' librations by using recent orbital ephemerides and geophysical knowledge of this Martian satellite. The analysis of the librational spectrum highlights the relationship between dynamical and geophysical properties of the body, but is also useful for cartographic and geodetic purposes for future space missions dedicated to Phobos. Methods. We developed a numerical model of Phobos' rotation that includes the point-mass Mars acting on the dynamical shape of Phobos, expanded to the third degree, and the effect of Mars' oblateness. The forced librations spectrum is extracted through a frequency analysis. Results. We find that the libration in longitude presents a quadratic term that coincides with the secular acceleration of Phobos falling onto Mars. The primary libration in longitude has a period equal to the anomalistic mean motion, whereas the primary libration in latitude has a period equal to the draconic mean motion (node to node). Both librations have amplitudes of about one degree leading to a surface displacement of about 200 m. These two components dominate the libration spectrum by a factor one hundred. Phobos' third degree gravity harmonics and Mars' oblateness affect the librations amplitude at 10 −4 degree. This is small but detectable from long-term tracking of a lander. The determination of the librational spectrum would bring strong constraints on the principal torques acting on the Martian moon, as well as on the possible presence of lateral variations in density predicted by certain geophysical models of the Stickney crater formation. We also investigate the obliquity variations of Phobos and find that their amplitudes are larger than the mean value of the obliquity. Conclusions. Phobos exhibits a rich and varied set of librational oscillations. The main librations and the librations close to the proper frequencies are the most sensitive to the interior structure. On the other hand, the superimposed effect of large amplitude oscillations is likely to make the determination of the mean obliquity challenging.

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Section: Phobos Interiormentioning

confidence: 99%

Section: Predicting High-resolution Measurements Of Phobos' Rotationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Rotational motion of Phobos

Rambaux

Castillo‐Rogez

Maistre

et al. 2012

A&A

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“…A new set of cartographic products based on the integration of data from multiple orbits was produced and published recently (Gwinner, et al, 2016). Controlled images and ortho-image mosaics were also produced and published for Phobos (Wä hlisch et al, 2010(Wä hlisch et al, , 2014Willner et al, 2010Willner et al, , 2014, or the Icy Saturnian Satellites (4) (Roatsch et al, 2009). For Ceres and Vesta, global mosaics serve as base map for different atlas collections (5) (e.g.…”

Section: Institutes and Facilitiesmentioning

confidence: 99%

Planetary Cartography and Mapping: Where We Are Today, and Where We Are Heading For?

Naß

Elgner

et al. 2017

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:Planetary Cartography does not only provides the basis to support planning (e.g., landing-site selection, orbital observations, traverse planning) and to facilitate mission conduct during the lifetime of a mission (e.g., observation tracking and hazard avoidance). It also provides the means to create science products after successful termination of a planetary mission by distilling data into maps. After a mission's lifetime, data and higher level products like mosaics and digital terrain models (DTMs) are stored in archives -and eventually into maps and higher-level data products -to form a basis for research and for new scientific and engineering studies. The complexity of such tasks increases with every new dataset that has been put on this stack of information, and in the same way as the complexity of autonomous probes increases, also tools that support these challenges require new levels of sophistication. In planetary science, cartography and mapping have a history dating back to the roots of telescopic space exploration and are now facing new technological and organizational challenges with the rise of new missions, new global initiatives, organizations and opening research markets. The focus of this contribution is to summarize recent activities in Planetary Cartography, highlighting current issues the community is facing to derive the future opportunities in this field. By this we would like to invite cartographers/researchers to join this community and to start thinking about how we can jointly solve some of these challenges. * Corresponding author. This is useful to know for communication with the appropriate person in cases with more than one author.

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“…While the former is based on Phobos' control-point network, the latter is founded on Phobos' gridded shape model. In the implementation of these methods we used the latest versions of both models by Willner et al (2010Willner et al ( , 2014. The coordinates of control points are believed to be given with respect to the Phobos center of mass (COM) as defined by the MAR080 ephemeris.…”

Section: Phobos Com Measurementsmentioning

confidence: 99%

Astrometric observations of Phobos with the SRC on Mars Express

Pasewaldt

Oberst

Willner

et al. 2015

A&A

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Aims. From April 2008 to August 2011 Mars Express carried out 74Phobos flybys at distances between 669 and 5579 km. Images taken with the Super Resolution Channel (SRC) were used to determine the spacecraft-centered right ascension and declination of this Martian moon. Methods. Image positions of Phobos were measured using the limb-fit and control-point measurement techniques. Camera pointing and pointing drift were controlled by means of background star observations that were compared to corresponding positions from reference catalogs. Blurred and noisy images were restored by applying an image-based point spread function in a Richardson-Lucy deconvolution.Results. Here, we report on a set of 158 Phobos astrometric observations with estimated accuracies between 0.224 and 3.405 km circular w.r.t. the line of sight to the satellite. Control point measurements yield slightly more accurate results than the limb fit ones. Our observations are in good agreement with the current Phobos ephemerides by the Jet Propulsion Laboratory (JPL) and the Royal Observatory of Belgium (ROB) with mean offsets of up to 335 m. Our data can be used for the maintenance and update of these models.

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Phobos control point network, rotation, and shape

Cited by 92 publications

References 16 publications

Rotational motion of Phobos

Rotational motion of Phobos

Planetary Cartography and Mapping: Where We Are Today, and Where We Are Heading For?

Astrometric observations of Phobos with the SRC on Mars Express

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