Galilean Satellites Of Jupiter Research Articles

Astrometry for the Galileo mission. 1: Asteroid encounters

view Abstract Citations (8) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Astrometry for the Galileo Mission. I. Asteroid Encounters Monet, A. K. B. ; Stone, R. C. ; Monet, D. G. ; Dahn, C. C. ; Harris, H. C. ; Leggett, S. K. ; Pier, J. R. ; Vrba, F. J. ; Walker, R. L. Abstract Optical Charge Coupled Device (CCD) astrometry was done at the U.S. Naval Observatory Flagstaff Station (NOFS) to obtain positions of solar system bodies to be encountered by the Galileo spacecraft. The objects observed were the minor planets 951 Gaspra and 243 Ida, discussed in this paper, and the Galilean satellites of Jupiter, to be discussed in Paper II. Observations of Gaspra were made from April through August 1991, and Ida was observed from 1991 November through 1993 May. Each observing campaign was followed by a successful encounter. The instrumentation, techniques, analysis methods, and astrometric results are described. Publication: The Astronomical Journal Pub Date: June 1994 DOI: 10.1086/117036 Bibcode: 1994AJ....107.2290M Keywords: Asteroids; Astrometry; Astronomical Observatories; Charge Coupled Devices; Galileo Spacecraft; Astronomical Catalogs; Very Long Base Interferometry; Astronomy; MINOR PLANETS; SPACE PROBES full text sources ADS |

Video techniques applied to astrometry

In this work we report on the application of video techniques to the astrometry of fast moving objects in the Solar System. Various phenomena may be observed for astrometric purposes, and two-dimensional photometry is well adapted for this. In this paper we describe in particular the method used to acquire and analyse such observations and we also give the first results obtained concerning two observations of mutual phenomena of the Galilean satellites of Jupiter which occurred during the last (1985) campaign of observations.

Pulkovo Programme for the Photographic Observations of Satellites of Planets

The satellites of Mars, the Galilean satellites of Jupiter and the first eight satellites of Saturn have been observed with the 26-inch refractor, the normal astrograph at Pulkovo and with the luni-planet telescope at the Ordubad station of the Pulkovo observatory since 1972.

Validation of Sagnier's theory by its application to the major planets

In this paper, the theory of Sagnier was applied to the major planets, in order to have a first evaluation of this theory which was built, primarily, to study the galilean satellites of Jupiter. In this application we included the first order of the intermediary solution and the solution of the linear variational equations. Results from other theories, mainly those of Simon and Bretagnon, have been used as basis for comparisons. The results and their comparisons are shown by means of tables of coefficients and proper frequencies and graphs of variations of the orbital elements.

The effect of the dynamical parameters in the motion of the Galilean satellites of Jupiter

The construction of an analytical theory of the motion of the Galilean satellites of Jupiter requires that we keep track of the dynamical parameters, that is, the masses of the satellites, and the harmonic coefficients of the potential of the planet J2 and J4. This is realized here. But as in other theories the solution becomes partly numerical from the resolution of an autonomous system. The aim of this paper is to present a method to obtain developped solutions of this autonomous system. In these solutions the proper motions of the pericenters and nodes are obtained as short series developped in the neighbourhood of a numerical solution. We have used these results to obtain complementary terms in the general solution which give a complete representation of the motions with respect to the dynamical parameters.

Charge-Coupled Device Television Camera For Nasa's Galileo Mission To Jupiter

The slow-scan television camera being built for NASA's Galileo Jupiter Orbiter spacecraft consists of a 1500 mm focal-length telescope coupled to a camera head housing a newly developed 800 x 800 element charge-coupled device (CCD) detector based on "virtual-phase" charge transfer technology. This detector results in a broadband sensitivity over 100 times that of a comparable vidicon-tube camera while also yielding improved resolution, linearity, geometric fidelity, and spectral range. In the near-Jovian radiation belts, interactions of high-energy particles with the silicon CCD result in the production of unwanted charge, and special techniques have been implemented (e.g., tantalum and quartz shielding, rapid image readout, and 2 x 2 picture-element on-chip averaging) to ensure adequate signal-to-noise performance for images acquired as close to Jupiter as five planetary radii. The images returned from Galileo will provide high-resolution (approximately 1 km) mapping coverage of most of the surface of the four large Galilean satellites of Jupiter with coverage of selected targets at resolutions as good as about 20 m. The broad spectral range of the instrument (0.4 to 1.1 Am) and the use of special methane-absorption-band filters in the near-infrared will allow study of the Jovian atmospheric structure and dynamics. Excellent off-axis light rejection and high sensitivity of the instrument will permit study of low-light-level phenomena such as lightning and aurorae on Jupiter and the Jovian ring.

VLA observations of the Galilean satellites

Jupiter's Galilean satellites I–IV, Io, Europa, Ganymede, and Callisto have been observed with the VLA at 2 and 6 cm. The Jovian system was about 4.46 AU from the Earth at the time the observations were taken. The flux densities for satellites I–IV at 2 cm are 15 ± 2, 5.6 ± 1.2, 22.3 ± 2.0, and 26.0 ± 2.5 mJy, respectively, which corresponds to disk brightness temperatures of 92 ± 13, 47 ± 10, 67 ± 6, and 92 ± 9°K, respectively. At 6 cm flux densities of 1.10 ± 0.2, 0.55 ± 0.12, 2.0 ± 0.2, and 3.15 ± 0.2 mJy were found, corresponding to temperatures of 65 ± 11, 44 ± 10, 55 ± 6, and 105 ± 7°K, respectively. The radio brightness temperatures are lower than the infrared, the latter generally being consistent with the temperature derived from equilibrium with absorbed insolation. The radio temperature are qualitatively consistent with the equilibrium temperature for fast rotating bodies considering the high radio reflectivity (low emissivity) as determined from radar measurements by S. J. Ostro (1982). In Satellites of Jupiter (D. Morrison, Ed.). Univ. of Arizona Press, Tucson).

Perturbation of an orbiter of a Galilean satellite by the other satellites

In this paper the perturbation of an orbiter of one of the Galilean Satellites by the other Galilean Satellites of Jupiter is investigated. The attraction of a perturbing Satellite is averaged over one revolution assuming a circular orbit. The perturbation can then easily be represented by elliptic integrals. The first-order Lagrange equations are solved by the stroboscopic method. The solution is obtained up to the fourth term in the power expansion of the ratio of the mean motions of the satellite and the orbiter.

A Collection of Galilean Satellite Eclipses 1652–1982

It is known that early (i.e. 17th-l8th century) visual observations of Jupiter's Galilean satellites are approximately as accurate as modern visually observed eclipses (Lieske 1982). In the early days the clocks were the primary source of error while in present days problems related to the Earth's and Jupiter's atmospheres have become the primary limiting factor. The early observations were generally made in local apparent time (i.e. related to the real hour angle of the sun). After the development by Huygens in 1656 of the pendulum clock, these early observations, when reduced to a modern UT system, have been shown to be quite accurate.

Comparison of Sampson-Lieske theory of the Galilean satellites of Jupiter with observations

The aim of the present work is to compare photographic observations of the Galilean satellites of Jupiter with the theory developed by Sampson at the beginning of the century and corrected and implemented recently by Lieske.

Floquet Reference Solutions for the Lunar Theory and the Jovian Moons

Reference solutions are constructed for lunar theory and Jupiter's Galilean satellites, consisting of a periodic orbit and associated Floquet modes. Although these solutions are obtained numerically, they introduce a full set of literal variables for perturbation work. In the Jovian problem, difficulties with resonances are avoided, since perturbations are expanded in the Poincar£ exponents, not the Keplerian frequencies. The modes for the inner three Jovian satellites are discussed in detail.

Secular effects in the orbits of the Galilean satellites

This paper presents the results of an investigation into the secular behavior of the orbits of the Galilean satellites of Jupiter. Kamel's perturbation method is used to remove all the explicitly periodic variables from the differential equations that describe the long period behavior of the orbits to third order in the masses, and the resulting differential equations for the secular behavior are then solved. Several numerical examples are given to illustrate the sensitivity of the solution to variations in the masses of the satellites.

Tectonic patterns on a tidally distorted planet

Tidal deformation of the lithosphere of a synchronously rotating planet or satellite produces stresses that may result in a distinctive tectonic pattern. The lithosphereis treated as a thin elastic shell which maintains the equilibrium shape of a tidally distorted body. Stresses develop as the equilibrium shape changes during orbital evolution. E. M. Anderson's theory of faulting is used to translate this stress pattern into a tectonic pattern of faults on the planet's surface ( The Dynamics of Faulting, Oliver & Boyd, Edinburgh, 1951). On a body such as the Moon, which has receded from the Earth, an originally large tidal bulge has collapsed. The predicted tectonic pattern includes N-S striking thrust faults over an area extending roughly 30° in latitude and longitude around the sub-Earth point and its antipode. The polar regions above roughly 70° latitude exhibit normal faults striking from the near side of the Moon toward the far side. Strike slip faults, with offsets consistent with east-west compression, occur near the limbs. Stress differences are largest at the equator on the limbs, and may have reached several hundreds bars over the last few billion years of the Moon's history. The existence of such a tectonic pattern on the Moon can only be resolved by photogeologic mapping. At present, there is little evidence of this pattern; however, the crucial evidence probably lies in the poorly mapped lunar polar regions. These tectonic patterns, which could provide geologic evidence for large tidal distortions, may also be present on the Galilean satellites of Jupiter.

Orbital and solar resonance in the Jovian Moon system

The periodic orbit representing the motion of the inner three Galilean satellites of Jupiter is constructed in a rotating frame. Stability analysis indicates linear instability; but the repeated Poincare exponents are associated with time and rotational symmetries, and it is concluded that the system is orbitally stable. Analysis of system frequencies reveals two resonances with the Sun. The rotation rate of the reference frame is close to 89∶10 the mean motion of Jupiter, and the period of the reference orbit is nearly 17∶10446 the period of Jupiter. The 89∶10 resonance is investigated via the method of averaging. The Jovian system currently circulates just outside the capture boundary with a period of about 117000 year, but with rotation rate of the reference frame varying by over an order of magnitude. Including tidal interaction, the system is evolving towards temporary capture in this resonance.

Reflectance polarimetry of Callisto and the evolution of the Galilean

Telescopic inspection and polarization, and albedo measurements indicate that Callisto differs from the other three Galilean satellites of Jupiter in that its surface consists of a layer of exposed rocks; also, the polarization characteristics reveal that the leading hemisphere (in its orbital motion phase-locked to Jupiter) is characteristic of a lunar-type regolith, whereas the following hemisphere is characteristic of clean, dust-free rock. This suggests that the leading hemisphere has been bombarded by meteoroids, whereas the following hemisphere has not. This bombardment asymmetry can best be explained by assuming that the dominant bombardment of Callisto has been by the meteoroids in orbit around Jupiter. As Callisto may have an icy crust above a liquid water mantle, the presence of an upper layer of rocks could be explained if the crust consisted of ice with stones embedded in it: as the exposed surface of ice slowly evaporated, rocks would become exposed at the surface. This explanation implies that the initial accretion product was a mixture of ice and rocks, and that the upper crust has never melted completely. The satellite Ganymede has a surface characteristic of ice or snow patches, probably because it has a crust of ice and rocks thinner than that of Callisto. The crust is more easily broken by impacts, which might therefore cause extrusion of water to form an ice field on the surface. The satellite Europa is almost entirely covered with ice; the absence of silicates on its surface may be explained by the ice crust having been at some time completely melted, or broken, by impacts.

Astrometric observations of the satellites of the outer planets. I - The Galilean satellites in 1977

Astrometric observations of the Galilean satellites of Jupiter performed around the opposition of 1977 with a 67-cm photovisual refractor are reported. The measurements are reduced to absolute and intersatellite positions by two different methods: a linear least-squares plate-constant solution to the AGK3 reference-star frame and the trail-scale method of Pascu (1977). Results of a plate-constant reduction are also presented for two observations of JV (Amalthea). Comparison of the data with Liske's (1978) theoretical predictions for the intersatellite positions indicates no systematic bias in the data; a probable scatter of about 15 arcsec in both right ascension and declination is estimated.

Io-phase motion and jovian decametre source locations

Io, Jupiter's innermost Galilean satellite, plays a major part in determining when jovian decametre storms are observed1. Specifically, as a result of beaming of the radiation at a preferred angle to the local magnetic field, the most favourable satellite locations for the reception of emission are approximately 90° and 240° γIo (departure of Io from superior geocentric conjunction). Recently a second-order effect has been noted—a periodic displacement in the particular γIo phase at which the reception probabilities are observed to peak2–4. The modulation has a peak-to-peak magnitude of 5° to 10°, a period of about 12 yr, and is most pronounced in the case of the jovian decametre storm sources Io–B and Io–C. (There is not yet general agreement as to the behaviour of Io–A.) The effect has been tentatively correlated with the ±3.5° variation in the jovicentric declination of the Earth, DE; however, it has also been considered3 that it may be a consequence of changes intrinsic to the jovian activity cycle. Here we interpret this phenomenon simply in terms of the latitudinal variations inherent in the Earth–Jupiter viewing geometry as defined by the 12-yr cycle in DE. Furthermore, we show that the phase of the Io–B and Io–C displacements relative to DE phase uniquely defines the hemisphere, north or south, from which the radiation associated with each source is beamed. The results agree with, and lend credence to, the source positions as inferred from polarimetry5,6 and more recently from considerations of planetary-limb shadowing7.

Masses of the Galilean Satellites of Jupiter

Numerical data derived from the observation of the four great satellites of Jupiter are compared with the values obtained through Sampson's theory by using the new JPL (Jet Propulsion Laboratory) system of masses. It is not possible to fit the coefficient of the free oscillation in the longitude of Ganymede, whose argument is l(3) - omega(4) (the mean longitude of Ganymede referred to the proper apse of Callisto), and the mass of Callisto derived from the path of Pioneer 10.

On the inversion of mutual occultation light curves

The extent to which mutual occultation light curves, of the type that occur among the Galilean satellites of Jupiter, can be inverted to produce albedo maps of the surfaces has been investigated. Model calculations have been done utilizing the Earth's own moon as the object of study. It is found that the inversion process can be successfully accomplished even in the presence of amounts of random noise typical of routine high-quality photometry of the Galilean satellites. The inversion process is also reasonably tolerant of systematic errors in the light curves, such as those due to photometric nonlinearity. Unless the limb-darkening distribution is pathological or the geometric elements adopted are seriously in error it should be possible to produce fairly high resolution maps of at least some of the Galilean satellites.

On the Laplace Relation among the Satellites of Uranus

Three of Uranus' satellites are involved in an interaction similar to the Laplace relation among the Galilean satellites of Jupiter. However, there are no pair-wise commensurabilities in the Uranus system as there are among the Galilean satellites. Thus analysis by Fourier expansion of disturbing functions becomes too unwieldy for practical calculation. Instead, the unexpanded perturbations are numerically averaged over a time scale short compared to the important variations in the Laplace relation. Perturbations of Miranda's orbit are estimated to be of observable magnitude for reasonable masses of Ariel and Umbriel.