The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
We present observations of three Neptune central flash events: the 20 August 1985 occultation of n39 from the European Southern Observatory (ESO), the 12 September 1988 occultation of N51 from Pic du Midi, and the 8 July 1989 occultation of N55 from ESO. From simultaneous fits to the three central flash lightcurves, we determine the shape of Neptune's limb, and show that winds near the 0.38-mbar level...
High angular resolution (adaptive optics) images taken on August 12, 1995 between 11:26 and 12:23 (UT) show a faint elongated structure apparently moving away from Saturn. The structure is consistent with light scattered by an arc of particles on a Keplerian orbit close to that of Enceladus. The orbit is slightly inclined (1.8°), and the arc is 76° ahead of the satellite. It appears to be a transient...
Telescopic observations of Mercury's sodium atmosphere were made to test the theory that two mid-latitude radar-bright spots centered near ∼345° longitude and ∼55° N and ∼25° S are sources of sodium in Mercury's atmosphere. Three important results came from these observations. (1) When the spectrograph slit was placed over, or near, the location of the radar-bright spots, notable sodium enhancements...
A spectrum of Jupiter in the 3-μm region obtained with the Infrared Space Observatory (ISO) shows evidence for the long-sought spectral signature of NH 3 ice particles in the jovian atmosphere. We calculated Jupiter 3-μm reflection spectrum, including multiple scattering by spherical cloud particles. Models containing reflection from two cloud decks along with NH 3 gas absorption reproduce...
We present and use a new rough-surface thermal model to aid in the analysis of new mid-infrared spectral measurements of Mercury from 5–12.5 μm. The model calculates spatially resolved thermal emission from slowly rotating, airless bodies. The Mercury data contain the first spectral measurements of Mercury between 5–7.5 μm, a region not accessible from ground-based telescopes, and are also the first...
We present the results of our photometric observations of 26 near-Earth asteroids (NEAs) in the range of absolute magnitudesH= 13.6–20.0 (diameters approximately 0.4–8 km). The synodic periods in the range 2.3–230 h were detected for 25 of them; 21 periods are new and in 4 cases we confirmed earlier determinations. In 20 cases the synodic periods are interpreted as being the rotation periods. Among...
Since August 1995, near-infrared images of Neptune have regularly been obtained with the University-of-Hawaii telescope. These images reveal Neptune's cloud structure with an angular resolution reaching 0.12″ in the H band.
A unique large-scale vortex, the White Tropical Oval (WTrO), was first observed in the South Tropical Zone of Jupiter, at the latitude of the Great Red Spot (GRS) in 1983. Its origin is probably related to a period of intense formation of eddies in the Southern edge of the South Equatorial Belt at latitude −20°. The WTrO survived many changes in the cloud structure of the South Equatorial Belt. However,...
The L4 and L5 points of the Earth–Sun system were imaged using the University of Hawaii 2.24-m telescope on 1994 May 5–7 and July 6–8 UT. We used a thinned Tektronix 2048 × 2048 CCD, subtending a field 7.5 arcmin on a side. Our objective in this search was to locate sub-kilometer-sized asteroids orbiting near the libration point or, failing this, to set a rough upper limit on the number density of...
Imaging polarimetry characterizes the physical nature of the lunar surface by the median size of the grains and by the roughness of the surface.A video-polarimeter was designed at Observatoire de Paris to produce at the telescope images of planetary surfaces in intensity, degree of linear polarization, flux of polarized light, and other relevant photo-polarimetric images. With these images, the median...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.