Colleen McGhee-French

Wellesley College · Department of Astronomy

Using the complete set of stellar and radio occultation data from the Cassini mission, we fit a multimode model to the outer edge of Saturn’s A ring, similar to that previously applied to the B ring edge by Spitale and Porco (2010) and Nicholson et al. (2014a). Our model takes into account the coorbital libration of the satellite Janus, whose 7:6 L...

Saturn's rings act as a system of innumerable test particles that are remarkably sensitive to periodic disturbances in the planet's gravitational field. We identify 15 additional density and bending waves in Saturn's C ring driven by the planet's internal normal mode oscillations. Taking advantage of a highly accurate absolute radius scale for the...

Saturn’s rings act as a system of innumerable test particles that are remarkably sensitive to periodic disturbances in the planet’s gravitational field. We identify 15 additional density and bending waves in Saturn’s C ring driven by the planet’s internal normal mode oscillations. The collective response of the rings to Saturn’s oscillations result...

We unveil a two-dimensional visualization of the Mimas 5:3 density wave in Saturn’s rings, created directly from 31 radial optical depth profiles of the rings obtained between 2005 and 2008 from Cassini Radio Science Subsystem (RSS) occultation observations, assuming only its predicted pattern speed and taking advantage of its evident four-armed st...

We identify several unusual one-armed density waves in Saturn's Cassini Division, using occultation observations from the Cassini RSS and VIMS instruments. In the inner Cassini Division, we identify outward-propagating density waves with wavenumber m = 1 located near 118,050 km (W118.05), 118,400 km (W118.40), and 118,530 km (W118.53). From Cassini...

We investigate waves driven in Saturn's rings by planetary normal modes, concentrating on the previously unexplored inner C ring. In this region, the known waves all have exceptionally short wavelengths, which has proven problematic for previous studies that depended on the accurate estimate of wave phases for wave identification. However, detailed...

We present a comprehensive solution for the geometry of Saturn’s ring system, based on orbital fits to an extensive set of occultation observations of 122 individual ring edges and gaps. We begin with a restricted set of very high quality Cassini VIMS, UVIS, and RSS measurements for quasi-circular features in the C and B rings and the Cassini Divis...

The eccentric Maxwell ringlet in Saturn's C ring is home to a prominent wavelike structure that varies strongly and systematically with true anomaly, as revealed by nearly a decade of high-SNR Cassini occultation observations. Using a simple linear "accordion" model to compensate for the compression and expansion of the ringlet and the wave, we der...

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 200 m on...

Careful study of the edges of many of the gaps and narrow ringlets in Saturn's rings has revealed not only eccentric and resonantly-perturbed features (Spitale & Porco 2009, 2010; French etal. 2011; Nicholson etal. 2011), but a wide variety of what appear to be spontaneously-generated radial distortions with a range of azimuthal wavenumbers, m, and...

We present the results of six soundings of the atmosphere of Titan by the radio occultation technique using the Cassini spacecraft currently in orbit around Saturn. These occultations occurred during four separate targeted Titan encounters in both the Prime and Equinox missions of Cassini over 3 years. They cover a wide range of latitude from 75°S...

Although Saturn's rings appear at first glance to be axisymmetric, more precise measurements reveal that many of the gap edges and narrow ringlets within the rings are noncircular, a characteristic they share with the narrow uranian rings. A careful study of these features is of interest for several reasons: (i) resonantly-forced perturbations are...

Likely evidence of nearly six centuries old collision of captured cometary material with Saturn's Ring C is uncovered in recent Cassini Radio Science ring observations. Three Cassini ring occultation experiments were especially designed so that radio signals transmitted by Cassini to the Earth pass through the rings when the rings are nearly closed...

We present results from the two radio occultations of the Cassini spacecraft by Titan in 2006, which probed mid-southern latitudes. Three of the ingress and egress soundings occurred within a narrow latitude range, 31-34°S near the surface, and the fourth at 52.8°S. Temperature-altitude profiles for all four occultation soundings are presented, and...

Quasi-periodic ring structure of mean wavelength ? ? 1.3 km is uncovered in Cassini radio occultation optical depth (? ) profiles of the innermost region of Ring C (∼74,480-77,740 km). The structure is characterized by two interfering "tones" separated in ? by few 100 meters. The mean ? increases slowly with ring radius. The observed behavior is co...

This paper presents a new, much improved method to analyze in combination many rings occultations profiles using the nonlinear theory.

We present preliminary results from a comprehensive study of noncircular features in the Cassini Division, based on occultation data from the Cassini mission. A companion paper presents our results for features in the C ring.

This paper discusses our determination of the Saturn's pole orientation and precession using a combination of Earthbased and spacecraft based observational data. From our model of the polar motion and the observed precession rate we obtain a value for Saturn's polar moment of inertia.

A series of near-equatorial radio occultations of Cassini by Saturn occurred in 2005 and again in 2009-2010. Comparison of the temperature-pressure profiles obtained from the two sets of occultations shows evidence of a descending pattern in the stratosphere that is similar to those associated with equatorial oscillations in Earth's middle atmosphe...

Rappaport et al. (2009) designed a procedure to analyze RSS ring optical depth profiles. Recently we have designed an improved method. Two common concepts of the two approaches are that they use the nonlinear theory of density waves and that they rely on a combination of multiple optical depth profiles. The main differences are summarized in Table...

Voyager radio occultation of Saturn's F-Ring revealed a single strand about 1 km wide. The strand was clearly detectable at 3.6 and 13 cm wavelengths (X-and S-band), indicating pres-ence of a population of particle sizes exceeding about 10 cm radius. Yet, in 25 Cassini radio occultations of the F-Ring collected during the Cassini 4-year Nominal Mis...

Cassini radio science experiments have provided multiple occultation optical depth profiles of Saturn's rings that can be used in combination to analyze density waves. This paper establishes an accurate procedure of inversion of the wave profiles to reconstruct the wave kinematic parameters as a function of semi-major axis, in the nonlinear regime....

The outer edge of Saturn's B ring is strongly affected by the nearby 2:1 inner Lindblad resonance of Mimas and is distorted approximately into a centered elliptical shape, which at the time of the Voyager 1 and 2 encounters was oriented with its periapse toward Mimas. Subsequent observations have shown that the actual situation is considerably more...

Saturn's B ring demarcates the inner edge of the dynamically fascinating Cassini Division, replete with eccentric and circular ringlets and gaps. We present kinematical models for ringlets and gaps in the Cassini Division, and the outer edge of the B ring, from more than 100 individual Cassini occultations using RSS, VIMS, and UVIS instruments. Rec...

The outer edge of Saturn's B ring has long been known to be affected by the nearby Mimas 2:1 resonance, resulting in an m=2 centered elliptical shape with a variation of +/- 70 km from a mean radius of about 117,580 km. Voyager occultation and imaging observations indicated that the minimum radius of the ring edge was aligned with Mimas, and that t...

Upon completion of Cassini's Prime Mission on July 1, 2008, the Radio Science team obtained twenty-four separate occultation observations taken between 2005 and 2008. Here, we present measurements of ring features in a subset of multiwavelength diametric occultations in Revs 7, 8, 10, and 12. Our ultimate goal is to obtain accurate kinematic models...

Occultation observations of Saturn's rings during the Cassini mission provide exquisite radial profiles of the rings at sub-km scale, making it possible to measure the orbital properties and internal structure of narrow ringlets and gap edges. Two of the most prominent among these are the Titan and Maxwell ringlets, first measured from Voyager imag...

Four out of six Radio Science bistatic scattering (bistatic-radar) observations of Titan's surface completed during the Cassini nominal mission yielded detectable quasi-specular 3.6 cm-lambda (X-band) surface echoes, making Titan the most distant solar system object for which bistatic echoes have been successfully detected. Right circularly polariz...

Cassini provided many radio occultation profiles of the rings, in particular diametric occultation profiles at the beginning of the nominal mission. Those have been corrected for diffraction effect. Using simulations, we established a procedure to analyze linear and non-linear density waves. This procedure recovers the wave kinematic parameters. It...

A series of 11 radio occultations beginning in December 2007 and concluding July 2008 probed the atmosphere of Saturn at mid-latitudes. Four covered northern latitudes from 18 - 33 degrees, and 7 covered southern latitudes from 20 - 70 degrees. We present the temperature - pressure profiles obtained from the radio occultation data for this series o...

Twenty-four one-sided Cassini radio occultation observations have been successfully completed. Two types of observations provide information about physical ring properties. The first is differential extinction of three sinusoidal signals simultaneously transmitted through the rings (0.94, 3.6, and 13 cm-wavelength). The observations reveal remarkab...

Six radio occultations of Cassini by Saturn have occurred or will occur in 2007, on May 10, June 11, June 26, October 24, December 3, and (after this meeting) on December 19. Unlike the 2005 series of occultations that were diametric and within 10 degrees of the equator, this series of occultations covered a wide range of latitudes from ~ 66 S to ~...

Eight vertical profiles of the electron density in Titan's ionosphere were derived from the Cassini radio occultations of March 26, and May28, 2007 (T27 and T31), as well as those of March 19, 2006 (T12), and May 20,2006 (T14) . The 2006 occultations occurred at low Southern latitudes of 14.7S, 36.2S, 19.8S, and 21.9S. The 2007 occultations were ne...

Cassini radio occultation observations of the extinction and near-forward scattering of 0.94, 3.6, and 13 cm- wavelengths sinusoidal signals have shed much new light on the structure and physical properties of Saturn's main ring system, especially enigmatic Ring B. As of June 2007, the occultations covered 15 distinct ring longitudes and roughly tw...

Eight vertical profiles of the electron density in Titan's ionosphere were derived from the Cassini radio occultations of March 26, and May28, 2007 (T27 and T31), as well as those of March 19, 2006 (T12), and May 20,2006 (T14) . The 2006 occultations occurred at low Southern latitudes of 14.7S, 36.2S, 19.8S, and 21.9S. The 2007 occultations were ne...

The four radio occultations during the Cassini prime mission have provided soundings in northern winter at eight mid- and high-latitude locations: 74 S, 69 S, 53 S, 34 S, 33 S, 31 S, 53 N, and 73 N. In the lower troposphere, the meridional contrast in temperature is muted, and temperatures in the lowest two kilometers differ by only 1.5 K, except f...

The many radio occultation profiles of Saturn's rings obtained during the Cassini mission allow one to analyze accurately any nonlinear (or linear) density wave from multiple optical depth profiles. There are several motivations to analyze density waves. The first one is to verify the theoretical model and its assumptions for nonlinear density wave...

Radio occultations of Saturn's rings during the Cassini prime mission fall into three main groups, depending on the rings opening angle B. The first is a set of eight diametric occultations completed early in the mission (March-September/2005) when |B| was relatively large (19.5 to 23.5°). They permitted multiple-longitude profiling of relatively o...

Two radio occultations of Cassini by Titan occurred during 2007, the last occultations during the Cassini primary mission. Both 2007 occultations profiled the atmosphere of Titan at higher latitudes than the initial two Titan occultations in 2006. The orbit 41 occultation that occurred on March 26, 2007 (T27), probed the atmosphere at 69 S on ingre...

From 378 Hubble Space Telescope WFPC2 images obtained between 1996–2004, we have measured the detailed nature of azimuthal bright-ness variations in Saturn's rings. The extensive geometric coverage, high spatial resolution (∼300 km px −1), and photometric precision of the UBVRI images have enabled us to determine the dependence of the asymmetry amp...

A series of eight Cassini radio occultation observations were completed from May 3 to September 5, 2005. Four were ingress-egress occultations and four were either ingress or egress occultation, for a total of 12 full cuts of the ring system. Diffraction reconstructed optical depth profiles reveal significant wealth of information about ring struct...

On 2005 January 14, the Saturn system was observed at true opposition with the planetary camera of the Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telescope. This was the culmination of nearly a decade of similar UBVRI observations, yielding a uniform set of over 400 high spatial resolution and photometrically accurate radial profiles...

We report results on Titan's ionosphere from the Cassini radio occultation of March 26, 2007 (T27), as well as those of March 19, 2006 (T12), and May 20,2006 (T14) . The 2006 occultations occurred at low Southern latitudes of 14.7S, 36.2S, 19.8S, and 21.9S. The 2007 occultation was nearly polar, at latitudes of 81S and 59N. The solar zenith angles...

A fortuitous Cassini radio occultation by Enceladus plume occurs on September 15, 2006. The occultation track (the spacecraft trajectory in the plane of the sky as viewed from the Earth) has been designed to pass behind the plume (to pass above the south polar region of Enceladus) in a roughly symmetrical geometry centered on a minimum altitude abo...

Cassini conducted the first two Radio Science bistatic scattering observations of Titan's surface on March 18 (T12) and May 20 (T14), 2006. The experiment was designed to search for mirror-like (quasi-specular) reflections from relatively flat surface regions. Three sinusoidal signals (0.94, 3.6, and 13 cm-wavelength; Ka-, X-, and S-band) transmitt...

Planetary rings provide a remarkable laboratory for the investigation of a wide range of dynamical effects, including resonance-driven density and bending waves, satellite wakes, shepherding of narrow ringlets, and non-circular edges of gaps. Careful quantitative examination of these features requires a very accurate absolute radius scale and plane...

We report results on Titan s ionosphere from the first two Titan radio occultations of the Cassini spacecraft on March 19 and May 20 2006 The latitudes of the occultations were 29 S on entry and 49 S on exit for the first one and 32 S and 34 S for the second one The Cassini radio science system is unprecedented in having three frequencies that can...

The first two Cassini radio occultations of Titan's atmosphere occurred on March 18 (T12) and May 20 (T14), 2006. The atmosphere was probed on the ingress and egress sides, yielding observations at four mid-southern latitudes. Titan's surface was also probed using bistatic-scattering during the inbound period on T12 and the inbound and outbound per...

Much new knowledge about Ring B has been acquired by a series of eight Cassini radio occultations completed from May 3 to September 5, 2005. The optimized occultation geometry and the relatively large ring opening angle (19 to 23.6 degrees) allowed detailed structure profiling, revealing remarkable variability with radius. Four regions of distinct...

Saturn's ring system is an elegant celestial mechanical laboratory for studying the interactions between a host of small and large moons, and the rings themselves. Resonances between the satellites and the ring particles result in spiral density waves whose detailed characteristics can be used to determine the physical properties of the rings. Over...

The well-known quadrupole brightness asymmetry of Saturn's rings is a natural consequence of the competition between the tendency of particles to clump gravitationally and the frustration of this process by tidal shearing interior to the Roche limit. The resulting Julian-Toomre wake structures are tilted by about 23 degrees relative to circular rin...

Highly accurate astrometric positions of 14 of Saturn's satellites have been obtained from 444 Hubble Space Telescope images taken with the Wide Field Planetary Camera 2 (WFPC2) between 1996 and 2005. In all, 1036 satellite positions were measured in Planetary Camera (PC) frames, with a typical uncertainty of σPC=0.014" (80 km at Saturn), and 1403...

Eight completed Cassini radio occultation observations of Saturn s rings have yielded high spatial resolution 1 km X-band 3 6 cm-wavelength optical depth profiles at twelve distinct ring longitudes The profiles provide a rich resource of information about radial ring structure and its azimuthal variability Additional acquired Ka- and S-band 0 94 an...

By contrast with the Voyager mission, Cassini provides us with many different radio optical depths profiles of Saturn's main rings. This provides us with new constraints which open the possibility to quantify in a much better way the physics of the ring-satellite interaction on the one hand, and the ring rheology on the other. To this purpose, we h...

A suite of dozens of occultation observations over the course of the Cassini tour should eventually yield extremely precise measurements of the geometry of Saturn s ring system A series of high-SNR multiwavelength RSS diametric ring occultations between May and September 2005 has been completed and the first of many planned UVIS and VIMS stellar oc...

From a long series of Hubble Space Telescope WFPC2 observations of Saturn s rings from 1996-2004 we have obtained precise UBVRI measurements of the reflectivity of the rings I F at high spatial resolution sim 300 km over the full range of solar phase angles and ring opening angles visible from the Earth A distinctive feature of these measurements i...

The Cassini Radio Science Team conducted a set of optimized diametric occultations by Saturn and its rings from May to September 2005, providing 11 separate probes of Saturn's ionosphere and atmosphere, and 12 optical depth profiles of the complete ring system. Each event was observed by the stations of the Deep Space Net (DSN) at three radio frequ...

The Cassini spacecraft completed a set of eight radio occultation observations of Saturn's rings during the period May 2 to September 5, 2005. The observation geometry was optimized to provide multiple ring longitude measurements at three radio wavelengths (0.94, 3.6, 13 cm; Ka-, X-, and S-band, respectively). A normal optical depth profile, a phas...

Eight Cassini radio occultations of Saturn's rings were conducted between May 3 and September 5, 2005. During any given occultation, Cassini transmits through the rings three coherent sinusoidal radio signals of wavelength 0.94, 3.6, and 13 cm (Ka-, X-, and S-band, respectively). Spectral analysis of the signals received at the NASA Deep Space Netw...

We present results from 12 ingress and egress soundings done within 10 degrees of Saturn's equator. Above the 100-mbar level, near the tropopause, the vertical profiles of temperature are marked by undulatory structure that may be associated with vertically propagating waves. We determine the properties and spectra of these waves, and speculate on...

Cassini orbits around Saturn were designed to provide eight optimized radio occultation observations of Saturn's rings during summer, 2005. Three monochromatic radio signals (0.94, 3.6, and 13 cm-wavelength) were transmitted by Cassini through the rings and observed at multiple stations of the NASA Deep Space Network. A rich data set has been colle...

On May 3, 2005, the first of a series of eight nearly diametric occultations by Saturn's rings and atmosphere took place, observed by the Cassini Radio Science (RSS) team. Simultaneous high SNR measurements at the Deep Space Network (DSN) at S, X, and Ka bands (lambda = 13, 3.6, and 0.9 cm) have provided a remarkably detailed look at the radial str...

Eight Cassini radio occultations of Saturn's rings were conducted from May 3 to September 5, 2005. During any given occultation, Cassini transmits Ka-, X-, and S-band sinusoidal signals (0.94, 3.6, and 13 cm-wavelength) through the rings. Spectral analysis of the perturbed signals received at stations of the Deep Space Network (DSN) reveals two dis...

The opposition surge of Saturn's rings has been measured from a long-term, uniform series of observations with the Hubble Space Telescope's (HST) Wide Field and Planetary Camera 2 (WFPC2). Extending from 1996--2005, the measurements spanned nearly the full range of ring opening (3o

On May 3, 2005 occurred the first of a series of seven occultations of Cassini by Saturn which have taken or will take place during the spring and summer of 2005. These near diametric occultations cover a latitude range of between 8 N and 10 S planetocentric latitude, and will give us a detailed look at the structure of the low latitude neutral atm...

We present preliminary results expected from the first planned Cassini radio occultation observation of Saturn's rings, to be conducted on May 3rd, 2005. The path of Cassini as seen from Earth (the occultation track) has been designed to cross the rings from the west to the east ansa almost diametrically, allowing for occultation of all major ring...

As part of a long-term study of Saturn's rings, we have used the Hubble Space Telescope's (HST) Wide Field and Planetary Camera (WFPC2) to obtain several hundred high resolution images from 1996 to 2004, spanning the full range of ring tilt and solar phase angles accessible from the Earth. Using these multiwavelength observations and HST archival d...

Hubble Space Telescope (HST) Wide-Field Planetary Camera (WFPC2) observations at phase angles in the range α=0.26°–6.4° obtained at every opposition and near quadrature between October 1996 and December 2002 reveal the opposition effect of Enceladus. We present a photometric analysis of nearly 200 images obtained through the five broadband UVBRI fi...

skip 0.5cm Two major explanations for the opposition brightening of Saturn's rings are i) the intrinsic brightening of particles due to coherent backscattering, and ii) the reduced mutual shadowing as the phase angle alpha -> 0o. Both mechanisms are likely to be important but to what degree is currently unclear. Here we utilize the extensive set of...

On July 1, 2005 at 01:12 SCET-UTC, Cassini started the engine burn required to insert the spacecraft into orbit around Saturn (SOI). Almost 30 minutes later, Cassini was occulted by Saturn's rings as seen from the Earth. The geometric ring occultation covered all main ring features, starting at the outer edge of Ring A at 01:42 and ending at the in...

For nearly a decade, the Hubble Space Telescope has provided stunning views of the Saturn system, including hundreds of images of Pandora and Prometheus, two small moons that straddle the F ring. In spite of technological advances in large ground-based telescopes since the launch of the HST, Hubble's WFPC2 is the only near-Earth instrument capable...

In April, 2004, the cameras aboard the Cassini spacecraft will at last rival the superb resolution of the Hubble Space Telescope's Wide Field Planetary Camera (WFPC2). For the past ten years, we have monitored the positions of Saturn's satellites with an accuracy of about 0.02" using WFPC2. One of our key findings was that tiny Prometheus and Pando...

Spokes in Saturn's B ring were first seen clearly during the Voyager encounters in 1980 and 1981, and since that time have been observed only intermittently from Earth. We have obtained images of dozens of spoke complexes, using the Hubble Space Telescope's WFPC2 camera. By virtue of the the high photometric precision and broad wavelength coverage...

As part of a long-term program to study Saturn's rings over the full range of inclination and phase angles accessible from Earth, we have accumulated over 300 high resolution images of Saturn and its rings with the Hubble Space Telescope's WFPC2 from 1996-2002. Using these images, we have obtained highly accurate measurements of the positions of Sa...

Due to their proximity to the bright A ring, the innermost of Saturn's classical satellites have historically proven challenging targets for the Earth-based observer. Since the ring plane crossings in 1995 and 1996 and in preparation for the upcoming Cassini mission in 2004, the Hubble Space Telescope has been monitoring the Saturn system with the...

Saturn’s narrow F ring is flanked by two nearby small satellites, Prometheus and Pandora, discovered in Voyager images taken in 1980 and 1981 (Synnott et al., 1983, Icarus 53, 156–158). Observations with the Hubble Space Telescope (HST) during the ring plane crossings (RPX) of 1995 led to the unexpected finding that Prometheus was ∼19° behind its p...

Saturn's moons Prometheus and Pandora, the putative shepherds of the F Ring, orbit Saturn at rates that differ significantly from the rates at the time of the Voyager flybys in 1980/1981 (C. A. McGhee et al., Icarus 152, 282--315, 2001). Specifically, Prometheus is running slow, and Pandora is running fast. Soon after Prometheus' lag was discovered...

Spokes, the transient streaks on Saturn's B ring, were revealed during the Voyager flybys. Their photometric properties have been interpreted in terms of small dust particles that become charged and interact with Saturn's magnetic field and plasma environment. From an examination of seven spokes in the Voyager images, Doyle and Grün (1990, Icarus 8...

The Uranian rings were discovered nearly a quarter century ago, and since that time, a rich set of Earthbased and Voyager occultation observations have made it possible to determine the orbits of the rings to remarkable precision. During the 1980's, Uranus' orbit traversed the rich star field of the Milky Way, as seen from the Earth, providing many...

Saturn's moons Prometheus and Pandora, the putative shepherds of the F Ring, orbit Saturn at rates that differ significantly from the rates at the time of the Voyager flybys in 1980/1981 (C. A. McGhee et al., Icarus 152, 282-315, 2001). Specifically, Prometheus is running slow, and Pandora is running fast. Soon after Prometheus' lag was discovered,...

Prometheus and Pandora, the wayward small satellites orbiting on either side of Saturn's F ring, continue to surprise us with their deviant wanderings. Observations with the Hubble Space Telescope (HST) WFPC2 obtained from 1994--2000 revealed that both satellites were lagging behind their predicted orbital longitudes based on the Synnott et al. ([1...

In May, August, and November 1995, Hubble Space Telescope (HST) observations during Saturn's ring-plane crossings allowed us to view saturnian satellites normally hidden to Earth-based observers in the glare of the rings. New measurements of Janus, Epimetheus, Prometheus, and Pandora have been combined to form revised orbital solutions using all th...

Saturn's narrow F ring is flanked by two nearby small satellites, Prometheus and Pandora, discovered in Voyager images taken in 1980/81 (Synnott et al., [1983] Icarus 53, 156). Observations with the HST during the ring plane crossings (RPX) of 1995 led to the unexpected finding that Prometheus was ~19o behind its predicted orbital longitude, based...

In 1994, humankind had the unique opportunity to witness directly the collisions between Jupiter and the ~20 separate fragments of Comet P/Shoemaker-Levy 9. From Palomar observatory, we obtained high-resolution (λ/Δλ ~= 2000) and low-resolution (λ/Δλ ~= 100) spectra of Jupiter in the 8-14 μm spectral region from July 16 to July 24. We were able to...

Saturn's irregular F Ring is flanked by the small satellites Prometheus and Pandora, discovered in Voyager images taken in 1980/81 (Synnott et al., [1983] Icarus 53, 156). Observations with HST during the ring plane crossings in 1995 led to the surprising discovery that Prometheus lagged behind its predicted position by some 19 deg in longitude (Bo...

The first near-infrared (0.9 μm) photometric observations of Saturn's five medium-sized satellites were obtained during the August 1995 ring plane crossing with Palomar Observatory's 60-in. telescope. The albedos of the satellites are very high, indicating that a very low fraction of dark opaque contaminants is present on their icy surfaces. The ge...

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 Neptun...

Saturn's ring--plane crossings in May, August and November 1995 presented an opportunity to study the faint inner satellites of Saturn, usually overpowered by the glare of Saturn's normally bright rings. Orbit fits for these satellites have been published for each separate HST data set, (Nicholson et\ al.; Bosh and Rivkin 1996, Science 272, 509; 51...

One of the most surprising results from the 1995 Saturn RPX campaign was the discovery that Prometheus lagged some 19(deg) behind its predicted position based on an ephemeris derived from Voyager 1 and 2 observations (Nicholson et\ al.; Bosh and Rivkin 1996, Science 272, 509; 518). The most likely explanation seemed to be that a previously-undetect...

We observed the 6 September 1996 Neptune occultation of N72 (m_K=10.9) as part of an ongoing campaign to detect ring material in the vicinity of the known ring arcs. The geometry of this occultation was particularly favorable for studying both the rings and atmosphere of Neptune. To provide as much coverage as possible of the ring region, we obtain...

The satellites of Saturn were observed with the 60-inch telescope at Palomar Mountain during the Saturn Ring Plane Crossing (RPX) on August 9-12, 1995. Observations were obtained with a 1024 square CCD and a methane filter to reduce light from Saturn. During the four nights more than 250 images were obtained. These images enable a rare opportunity...