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We extracted physical atmospheric parameters from a 23 July 2008 single-chord stellar occultation of the star USNO-B1.0 0759-0739128 (I-band magnitude of 12.60) by Neptune using a light curve model fitting technique. We observed the occultation using the Agile CCD camera mounted on the Astrophysical Research Consortium 3.5m telescope at Apache Point Observatory. We found isothermal temperatures of...
A new Hubble Space Telescope observation of the 7:4 resonant transneptunian binary system (385446) Manwë has shown that, of two previously reported solutions for the orbit of its satellite Thorondor, the prograde one is correct. The orbit has a period of 110.18±0.02days, semimajor axis of 6670±40km, and an eccentricity of 0.563±0.007. It will be viewable edge-on from the inner Solar System during...
We present the analysis of high angular resolution observations of the triple Asteroid (87) Sylvia collected with three 8–10m class telescopes (Keck, VLT, Gemini North) and the Hubble Space Telescope. The moons’ mutual orbits were derived individually using a purely Keplerian model. We computed the position of Romulus, the outer moon of the system, at the epoch of a recent stellar occultation which...
In July 2007, we observed a stellar occultation by Pluto from three sites in New Zealand and Australia. From these occultation observations, we find that Pluto’s atmospheric pressure is still at the increased level measured in 2002 and 2006 with a pressure at a radius of 1275km of 2.09±0.09μbar. One of the sites, Mt. John Observatory, was ∼70km from the shadow center and we recorded the first central-flash...
We present a comprehensive survey of sharp-edged features in Saturn’s C ring, using data from radio and stellar occultation experiments carried out by the Cassini spacecraft over a period of more than five years. Over 100 occultations are included in the combined data set, enabling us to identify systematic radial perturbations as small as 200m on the edges of ringlets and gaps. We systematically...
In this work, we investigate the equilibrium figures of a dumb-bell-shaped sequence with which we are still not well acquainted. Studies have shown that these elongated and nonconvex figures may realistically replace the classic “Roche binary approximation” for modeling putative peanut-shaped or contact binary asteroids. The best-fit dumb-bell shapes, combined with the known rotational period of the...
We observed two stellar occultations on UT 4 May 2013 and UT 9 September 2012, with the aim of measuring Pluto’s atmospheric parameters. Both of these events were observed by world-wide collaborations of many observers, and both occurred within 1month of Pluto’s stationary points. The PC20120909 event was observed at the McDonald Observatory (MONET 1.2-m), and Olin Observatory (the Ortega 0.8-m);...
Pluto’s lower atmosphere has been observed to evolve since the first definitive occultation detection in 1988. Possibilities for explaining the lower atmospheric structure include a steep thermal gradient and/or extinction, the latter of which can be characterized as a dependence between occultation flux and wavelength. On 2011 June 23, a 14.43 UCAC magnitude star (R=13.64) was occulted by Pluto as...
Combining stellar occultation observations probing Pluto’s atmosphere from 1988 to 2013, and models of energy balance between Pluto’s surface and atmosphere, we find the preferred models are consistent with Pluto retaining a collisional atmosphere throughout its 248-year orbit. The occultation results show an increasing atmospheric pressure with time in the current epoch, a trend present only in models...
Pluto’s tenuous atmosphere exhibits remarkable seasonal change as a result of the planet’s substantial obliquity and highly eccentric orbit. Over the past two decades, occultations have revealed that the atmospheric pressure on Pluto has increased substantially, perhaps by a factor as large as 2 to 4, as the planet has moved from equinox towards solstice conditions. These data have also shown variations...
The Pluto system passed in front of a 15th magnitude star on 12 June 2006. We observed this occultation from the 3.9m Anglo-Australian Telescope (AAT), and took photometric observations every 100ms for 3h. Our three-hour baseline of data provides among the longest and highest-quality occultation dataset of the Pluto system ever taken. Results on Pluto’s atmospheric structure from these data have been...
We present an analysis of the VIMS solar occultations dataset, which allows us to extract vertically resolved information on the characteristics of Titan’s atmosphere between ∼100 and 700km with a vertical resolution of ∼10km. After a series of data treatment procedures to correct problems in pointing stability and parasitic light, 4 occultations out of 10 are retained. This sample covers different...
We determine the first altitude profiles of O2 in the important photochemical region below 120km in the atmosphere of Mars by analyzing Mars Express/SPICAM ultraviolet observations of six occultations of stars by the atmosphere. Over the range of 90–130km the altitude-averaged mixing ratio of O2 relative to the major constituent CO2varies in space and time in the range of 3.1×10-3–5.8×10-3, with a...
On 29 November 2011 UT, 2060 Chiron occulted a R=14.9-mag star; data were successfully obtained at the 3-m NASA Infrared Telescope Facility (IRTF) on Mauna Kea and 2-m Las Cumbres Observatory Global Telescope Network (LCOGT) Faulkes Telescope North (FTN) at Haleakala. The MORIS lightcurve shows a solid-body detection of Chiron’s nucleus with a chord duration of 16.0±1.4s, corresponding to a chord...
The Voyager 1 and 2 Ultraviolet Spectrometer (UVS) solar and stellar occultation dataset represents one of the primary, pre-Cassini sources of information that we have on the neutral upper atmosphere of Saturn. Despite its importance, however, the full set of occultations has never received a consistent, nor complete, analysis, and the results derived from the initial analyses over thirty years ago...
We retrieved the density and temperature profiles in Saturn’s thermosphere from 26 stellar occultations observed by the Cassini/UVIS instrument. These results expand upon and complement the previous analysis of 15 Cassini/UVIS solar occultations by Saturn’s upper thermosphere. We find that the exospheric temperatures based on the stellar occultations agree with the solar occultations and range from...
Benzene is an important molecule in Titan’s atmosphere because it is a potential link between the gas phase and the organic solid phase. We measured photoabsorption in the ultraviolet by benzene gas at temperatures covering the range from room temperature to 215K. We derived benzene absorption cross sections and analyzed them in terms of the transitions observed. No significant variation with measurement...
We have conducted a comprehensive survey of 22 sharp-edged ringlets and gaps in the Cassini Division of Saturn’s rings, making use of nearly 200 high-SNR stellar and radio occultation chords obtained by the Cassini VIMS, UVIS, and RSS instruments between 2005 and 2013. We measure eccentricities from as small as ae=80 m to nearly 30 km, free normal modes with amplitudes from ∼ 0.1 to 4.1 km, and detectable...
SPICAV IR, a channel of the SPICAV/SOIR suite of instruments onboard Venus Express spacecraft measured spectra in nadir and solar occultation modes in the range of 0.65–1.7μm. We report results from 222 solar occultations observed from May 2006 to November 2014. The vertical resolution of measurements varies from 1 to 25km depending on the distance of the spacecraft to the limb of Venus. The vertical...
In 1988 Rosen and Lissauer identified an unusual wavelike feature in Saturn’s inner C ring as a bending wave driven by a nodal resonance with Titan (Science 241, 690). This is sometimes referred to as the −1:0 resonance since it occurs where the local nodal regression rate is approximately equal to −nT, where nT=22.577∘d−1 is Titan’s orbital mean motion. We have used a series of 44 stellar occultation...
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