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Journal ArticleDOI

Observational detection of eclipses of J5 Amalthea by the Galilean satellites

01 Nov 2010-Astronomy and Astrophysics (EDP Sciences)-Vol. 522

AbstractAims. We carried out observations of the small jovian satellite Amalthea (J5) as it was being eclipsed by the Galilean satellites near the 2009 equinox of Jupiter in order to apply the technique of mutual event photometry to the astrometric determination of this satellite’s position. Methods. The observations were carried out during the period 06/2009−09/2009 from the island of Maui, Hawaii and Siding Spring, Australia with the 2m Faulkes Telescopes North and South respectively. We observed in the near-infrared part of the spectrum using a PanStarrs-Z filter with Jupiter near the edge of the field in order to mitigate against the glare from the planet. Frames were acquired at rates >1/min during eclipse times predicted using recent JPL ephemerides for the satellites. Following subtraction of the sky background from these frames, differential aperture photometry was carried out on Amalthea and a nearby field star. Results. We have obtained three lightcurves which show a clear drop in the flux from Amalthea, indicating that an eclipse took place as predicted. These were model-fitted to yield best estimates of the time of maximum flux drop and the impact parameter. These are consistent with Amalthea’s ephemeris but indicate that Amalthea is slightly ahead of, and closer to Jupiter than, its predicted position by approximately half the ephemeris uncertainty in these directions. We argue that a ground-based campaign of higher-cadence photometry accurate at the 5% level or better during the next season of eclipses in 2014-15 should yield positions to within 0. �� 05 and affect a corresponding improvement in Amalthea’s ephemeris.

Topics: Jupiter (57%), Ephemeris (55%), Jovian (53%), Eclipse (51%)

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Citations
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Journal ArticleDOI
Abstract: Radio tracking and astrometric data obtained by the JUICE mission, using the PRIDE, 3GM and JANUS instruments, will allow the dynamics of the Galilean moons to be measured to unprecedented accuracy. As a result, the dynamical models used for creating ephemerides from these data will most likely require the inclusion of various heretofore neglected physical effects. To determine which effects will need to be included, we perform a sensitivity analysis of the influence on the dynamics of the system for a wide array of gravitational, tidal and rotational characteristics of the system. We estimate the dynamics of the Galilean moons with a given perturbation turned off, using ideal three-dimensional measurements of the satellites' positions generated with these perturbations turned on. In doing so, we assess the capabilities of the nominal dynamical model to absorb the influence of this perturbations. We analyze the dynamical behaviour over a period of five years, and limit our analysis to effects that may be observable from JUICE radio tracking and optical astrometry data. Our simulations comprise a short-period (5 years) sensitivity analysis of the dynamics of the moons, and not a simulation of the tracking data inversion for JUICE. Our analysis indicates that the nominal dynamical model of the Galilean satellites can very efficiently absorb the influence of the current uncertainties in most of the physical parameters of the Jovian system, to a level where these uncertainties will not be influential for JUICE-derived ephemerides. An important exception is the influence of tidal dissipation: the k 2 / Q of Io will be clearly observable by JUICE tracking data, which will be strongly correlated with the weaker effect of Jupiter's k 2 / Q . The dissipation inside Europa may also be weakly constrained by JUICE tracking data. Without improvements in the Jovian gravity field from the Juno mission, the estimation of Jupiter zonal gravity field coefficients at degrees 2, 3 and 5 should be included in the ephemerides generation. The influence of the deviation from perfect tidal locking of the moons' rotation is at the limit of observability. Furthermore, we have verified that the present uncertainty in the a priori ephemeris of Jupiter will not influence the (Jupiter-centered) dynamics of the Galilean moons at an observable level.

16 citations


Journal ArticleDOI
TL;DR: The goal of this paper is to show that some phenomena occurring during the equinox on the giant planets are worth to be observed, and to encourage observations in the next future especially for planetary systems for which no space mission is planned.
Abstract: Astrometry of Solar system objects needs to perform observations regularly since the motions are fast and the dynamical models need sample of data on long intervals of time. The goal of this paper is to show that some phenomena occurring during the equinox on the giant planets are worth to be observed. Past experience has shown the interest of such observations which should be continued in the future due to their relevant contribution to improve the dynamical models. Using the best ephemerides of the natural planetary satellites, we calculate the next phenomena to occur in order to prepare the future observational campaigns. We provide in this paper the tables of the dates of the next phenomena as their observational conditions which depends on the opposition and the declination of the planet. Past observations provided particularly accurate data, better than all the other ground based observations and we encourage observations in the next future especially for planetary systems for which no space mission is planned.

5 citations


Journal ArticleDOI
Abstract: Aims. During the 2014–2015 campaign of mutual events, we recorded ground-based photometric observations of eclipses of Amalthea (JV) and, for the first time, Thebe (JXIV) by the Galilean moons. We focused on estimating whether the positioning accuracy of the inner satellites determined with photometry is sufficient for dynamical studies.Methods. We observed two eclipses of Amalthea and one of Thebe with the 1 m telescope at Pic du Midi Observatory using an IR filter and a mask placed over the planetary image to avoid blooming features. A third observation of Amalthea was taken at Saint-Sulpice Observatory with a 60 cm telescope using a methane filter (890 nm) and a deep absorption band to decrease the contrast between the planet and the satellites. After background removal, we computed a differential aperture photometry to obtain the light flux, and followed with an astrometric reduction.Results. We provide astrometric results with an external precision of 53 mas for the eclipse of Thebe, and 20 mas for that of Amalthea. These observation accuracies largely override standard astrometric measurements. The (O − C)s for the eclipse of Thebe are 75 mas on the X -axis and 120 mas on the Y -axis. The (O − C)s for the total eclipses of Amalthea are 95 mas and 22 mas, along the orbit, for two of the three events. Taking into account the ratio of (O − C) to precision of the astrometric results, we show a significant discrepancy with the theory established by Avdyushev and Ban’shikova in 2008, and the JPL JUP 310 ephemeris.

3 citations


Cites background from "Observational detection of eclipses..."

  • ...The inner moons were observed during the previous mutual event season (Christou et al. 2010)....

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Journal ArticleDOI
Abstract: Progress in astrometry and orbital modelling of planetary moons in the last decade enabled better determinations of their orbits. These studies need accurate positions spread over extended periods. We present the results of the 2014–2015 Brazilian campaign for 40 mutual events from 47 observed light curves by the Galilean satellites plus one eclipse of Amalthea by Ganymede. We also reanalysed and updated results for 25 mutual events observed in the 2009 campaign. All telescopes were equipped with narrow-band filters centred at 889 nm with a width of 15 nm to eliminate the scattered light from Jupiter. The albedos’ ratio was determined using images before and after each event. We simulated images of moons, umbra, and penumbra in the sky plane, and integrated their fluxes to compute albedos, simulate light curves and fit them to the observed ones using a chi-square fitting procedure. For that, we used the complete version of the Oren-Nayer reflectance model. The relative satellite positions mean uncertainty was 11.2 mas ( ~ 35 km) and 10.1 mas ( ~ 31 km) for the 2014–2015 and 2009 campaigns respectively. The simulated and observed ascii light curve files are freely available in electronic form at the Natural Satellites DataBase (NSDB). The 40/25 mutual events from our 2014–2015/2009 campaigns represent a significant contribution of 17%/15% in comparison with the PHEMU campaigns lead by the IMCCE. Besides that, our result for the eclipse of Amalthea is only the 4th such measurement ever published after the three ones observed by the 2014–2015 international PHEMU campaign. Our results are suitable for new orbital/ephemeris determinations for the Galilean moons and Amalthea.

1 citations


Journal ArticleDOI
Abstract: During the 2014-2015 campaign of mutual events, we recorded ground-based photometric observations of eclipses of Amalthea (JV) and, for the first time, Thebe (JXIV) by the Galilean moons. We focused on estimating whether the positioning accuracy of the inner satellites determined with photometry is sufficient for dynamical studies. We observed two eclipses of Amalthea and one of Thebe with the 1 m telescope at Pic du Midi Observatory using an IR filter and a mask placed over the planetary image to avoid blooming features. A third observation of Amalthea was taken at Saint-Sulpice Observatory with a 60 cm telescope using a methane filter (890 nm) and a deep absorption band to decrease the contrast between the planet and the satellites. After background removal, we computed a differential aperture photometry to obtain the light flux, and followed with an astrometric reduction. We provide astrometric results with an external precision of 53 mas for the eclipse of Thebe, and 20 mas for that of Amalthea. These observation accuracies largely override standard astrometric measurements. The (O-C)s for the eclipse of Thebe are 75 mas on the X-axis and 120 mas on the Y-axis. The (O-C)s for the total eclipses of Amalthea are 95 mas and 22 mas, along the orbit, for two of the three events. Taking into account the ratio of (O-C) to precision of the astrometric results, we show a significant discrepancy with the theory established by Avdyushev and Ban'shikova in 2008, and the JPL JUP 310 ephemeris.

References
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Journal ArticleDOI
07 Mar 2003-Science
TL;DR: Findings on Jupiter's zonal winds, convective storms, low-latitude upper troposphere, polar stratosphere, and northern aurora are reported, including previously unseen emissions arising from Io and Europa in eclipse, and a giant volcanic plume over Io's north pole are described.
Abstract: The Cassini Imaging Science Subsystem acquired about 26,000 images of the Jupiter system as the spacecraft encountered the giant planet en route to Saturn. We report findings on Jupiter's zonal winds, convective storms, low-latitude upper troposphere, polar stratosphere, and northern aurora. We also describe previously unseen emissions arising from Io and Europa in eclipse, a giant volcanic plume over Io's north pole, disk-resolved images of the satellite Himalia, circumstantial evidence for a causal relation between the satellites Metis and Adrastea and the main jovian ring, and information on the nature of the ring particles.

457 citations


Journal ArticleDOI
01 Sep 1994-Icarus
Abstract: Full-disk albedo spectra of the jovian planets and Titan were derived from observations at the European Southern Observatory in July 1993. The spectra extend from 300- to 1000-nm wavelength at 1-nm resolution. The signal-to-noise ratio is approximately 1000 in the visible. The accuracy is 2% for relative and 4% for absolute ulbedos. Colors and magnitudes were also determined. Some 40-60 Raman scattering features are visible in the spectrum of each jovian planet. A Raman scattering model with five parameters adjusted for each planet can explain these features. A methane absorption spectrum is given which fits methane features in the spectra of the jovian planets and Titan. It differs from room-temperature laboratory spectra but it is consistent with some limited laboratory data at cold temperatures. Three new, weak methane bands were detected in the spectra of Uranus and Neptune. A strong absorption hand in Jupiter's spectrum is possibly due to water, confirming a strong depletion of oxygen in the probed part of Jupiter's atmosphere.

363 citations


"Observational detection of eclipses..." refers background or methods in this paper

  • ...This is a broadband filter (FWHM: 104 nm) centred at 870 nm; as it contains the 890 nm methane absorption feature in Jupiter’s spectrum (Karkoschka 1994), it increases the contrast of the satellite against the scattered light from Jupiter....

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  • ...These include: utilising methane absorption bands in Jupiter’s spectrum (Karkoschka 1994), coronagraphy and post-processing (Nicholson & Matthews 1991; Kulyk et al. 2002; Kulyk & Jockers 2004; Veiga & Vieira Martins 2005; Kulyk 2008)....

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Journal ArticleDOI
14 May 1999-Science
TL;DR: Observations by the Galileo spacecraft and the Keck telescope showed that Jupiter's outermost (gossamer) ring is actually two rings circumscribed by the orbits of the small satellites Amalthea and Thebe, suggesting that faint rings may accompany all small inner satellites of the other jovian planets.
Abstract: Observations by the Galileo spacecraft and the Keck telescope showed that Jupiter's outermost (gossamer) ring is actually two rings circumscribed by the orbits of the small satellites Amalthea and Thebe. The gossamer rings' unique morphology-especially the rectangular end profiles at the satellite's orbit and the enhanced intensities along the top and bottom edges of the rings-can be explained by collisional ejecta lost from the inclined satellites. The ejecta evolves inward under Poynting-Robertson drag. This mechanism may also explain the origin of Jupiter's main ring and suggests that faint rings may accompany all small inner satellites of the other jovian planets.

228 citations


"Observational detection of eclipses..." refers background in this paper

  • ...The remaining two, Amalthea and Thebe, fulfil the same function in relation to the so-called Gossamer rings (Burns et al. 1999; de Pater et al. 1999; Ockert-Bell et al. 1999; de Pater et al. 2008; Showalter et al. 2008)....

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Journal ArticleDOI
01 Apr 1999-Icarus
Abstract: The jovian ring system was observed during four orbits of Galileo's nominal mission, when 25 clear-filter images of the rings were taken at spatial resolutions of 23 to 134 km/pixel; the ring appeared fortuitously in an additional 11 images. The tenuous jovian ring system (normal optical depths<10−5) has three components: the halo, main ring, and gossamer ring. The innermost component, atoroidal halo, extends radially from approximately 92,000 to about 122,500 km (near the 3 : 2 Lorentz resonance) and has a full-width, half-maximum thickness of 12,500 km; its brightness decreases with height off the equatorial plane and decreases as the planet is approached. Themain ringreaches from the halo's outer boundary across 6440 to 128,940 km, just interior to Adrastea's orbit (128,980 km); at its outer edge, the main ring takes nearly 1000 km to develop its full brightness. The ring's brightness noticeably decreases around 127,850 km in the vicinity of Metis' semimajor axis (127,980 km). The precise location and nature of the main ring's outer periphery may shift slightly from image to image; the same is true for the “notch” near Metis. The main ring has a faint, vertically extended component that thickens as the halo region is approached. Brightness variations of ±10% are visible in the central main ring and may be due to vertical corrugations, density clumps, or “spokes” in the ring. Unexplained differences between the near- and far-arm brightnesses are visible. We have discovered that thegossamer ring, lying exterior to the main ring, has two primary components, each of which is fairly uniform: one originates just interior to Amalthea's orbit (181,366 km) while the other is situated radially interior to Thebe's orbit (221,888 km). Very faint material continues past Thebe, blending into the background at 250,000 km. The gossamer rings have thicknesses that are comparable to the maximum elevations of these satellites off Jupiter's equatorial plane; from Galileo's nearly equatorial view, the gossamer rings present rectangular end-profiles with greater intensities along their top and bottom surfaces. The rings seem to be derived from the satellites.

103 citations


"Observational detection of eclipses..." refers background in this paper

  • ...The remaining two, Amalthea and Thebe, fulfil the same function in relation to the so-called Gossamer rings (Burns et al. 1999; de Pater et al. 1999; Ockert-Bell et al. 1999; de Pater et al. 2008; Showalter et al. 2008)....

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Journal ArticleDOI
01 Apr 1999-Icarus
Abstract: We imaged the jovian ring system at a wavelength of 2.27 μm with the 10-m W. M. Keck telescope on August 14 and 15, 1997, when the ring plane was almost edge-on (opening angle β=0.17°) and near opposition (phase angle α≈1.1°). The resolution in the images is 0.6″=0.025 R J . We obtained the first images of the jovian halo and gossamer ring in back-scattered light, and the best ground-based images to date of Jupiter's main ring. The main ring is radially confined between 1.70 and 1.82 R J (where 1 R J =71398 km), with a maximum (after inversion) at 1.79 R J , in agreement with the Voyager findings. The halo extends inward from the main ring (at 1.71 R J ) down to 1.40 R J , apparently bounded by the locations of Lorentz resonances. Roughly 50% of the halo's intensity originates from a region within ∼700 km from the equatorial plane, although it is visible up to ∼10,000 km above and below the plane. Although the vertical extent agrees with Voyager findings, the halo's intensity relative to that of the main ring in the Keck images is much less than in forward-scattered Voyager images, which we attribute to a predominance of micrometer-sized particles, which scatter visible light preferentially in the forward direction. The gossamer ring is found to have two components, with steep dropoffs in brightness at the orbits of Amalthea and Thebe. The first, Amalthea's gossamer ring, is visible between the main ring's periphery and ∼2.55 R J ; it is relatively uniform in brightness and has a vertical thickness (FWHM) of 0.06 R J , clearly broader than the FWHM of the main ring (0.045 R J ) and the image resolution. The other component, Thebe's gossamer ring, is a factor of five fainter than Amalthea's ring and about twice as broad vertically (FWHM≈0.12 R J ). This ring extends outward to 3.11 R J , but additional material is visible, albeit barely, out to ∼3.6 R J , near the edge of our images. The vertical extent of both the Thebe and Amalthea rings decreases with decreasing distance to the planet.

53 citations