Robert S. French

SETI Institute · Carl Sagan Center

Some of the small inner moons of Uranus have very closely-spaced orbits. Multiple numerical studies have found that the moons Cressida and Desdemona, within the Portia subgroup, are likely to collide in less than 100 Myr. The subsequent discovery of three new moons (Cupid, Perdita, and Mab) made the system even more crowded. In particular, it has b...

Some of the small inner moons of Uranus have very closely-spaced orbits. Multiple numerical studies have found that the moons Cressida and Desdemona, within the Portia sub-group, are likely to collide in less than 100 Myr. The subsequent discovery of three new moons (Cupid, Perdita, and Mab) made the system even more crowded. In particular, it has...

We report integrated orbital fits for the inner regular moons of Neptune based on the most complete astrometric data set to date, with observations from Earth-based telescopes, Voyager 2, and the Hubble Space Telescope covering 1981-2016. We summarize the results in terms of state vectors, mean orbital elements, and orbital uncertainties. The estim...

We report integrated orbital fits for the inner regular moons of Neptune based on the most complete astrometric data set to date, with observations from Earth-based telescopes, Voyager 2, and the Hubble Space Telescope covering 1981–2016. We summarize the results in terms of state vectors, mean orbital elements, and orbital uncertainties. The estim...

During its 1989 flyby, the Voyager 2 spacecraft imaged six small moons of Neptune, all with orbits well interior to that of the large, retrograde moon Triton¹. Along with a set of nearby rings, these moons are probably younger than Neptune itself; they formed shortly after the capture of Triton and most of them have probably been fragmented multipl...

Before images from the Cassini spacecraft can be analyzed, errors in the published pointing information (up to ~110 pixels for the Imaging Science Subsystem Narrow Angle Camera) must be corrected so that the line of sight vector for each pixel is known. This complicated and labor-intensive process involves matching the image contents with known fea...

We report on a new analysis of Hubble Space Telescope (HST) images of the Neptune system spanning 2004 to 2016. This expands upon an initial analysis we presented in 2013 (Showalter et al., DPS Meeting #45, abstract 206.01), based on HST images from 2004-2009. At that time we reported (1) the discovery of Neptune’s fourteenth moon, S/2004 N 1, whic...

The thirteen inner moons of Uranus form a densely-packed and possibly chaotic system. Numerical simulations show that several groups of moons exhibit complex resonant interactions, and Mab shows as-yet unexplained variations in its orbit. However, the masses of these moons are currently unknown, limiting the insights that can be gained from numeric...

Analysis of optical remote sensing (ORS) data from the Cassini spacecraft is a complicated and labor-intensive process. First, small errors in Cassini’s pointing information (up to ~40 pixels for the Imaging Science Subsystem Narrow Angle Camera) must be corrected so that the line of sight vector for each pixel is known. This process involves match...

Numerical integrations of the closely-packed inner Uranian satellite system show that variations in semi-major axes can take place simultaneously between three or four consecutive satellites. We find that the three-body Laplace angle values are distributed unevenly and have histograms showing structure, if the angle is associated with a resonant ch...

Saturn's F ring is well known for its unique and dynamic features that change on timescales from hours to months. Among these features are clumps, localized bright areas spanning ~3-30 degrees in longitude. 34 clumps tracked in Voyager images (Showalter 2004, Icarus, 171, 356-371) were found to live for several months and have a ~100 km spread in s...

We report on observations of Neptune’s rings, arcs and inner moons as obtained by the Hubble Space Telescope during 2004-2009. These are the only Earth-based observations of the ring system obtained at visual wavelengths, permitting direct photometric comparison with the Voyager images. This allows us to determine quantitatively how the arcs have e...

CBET 3586 available at Central Bureau for Astronomical Telegrams.

Saturn’s F ring is unusual in that it is subject to dynamic structural changes over short periods - anywhere from days to months. Images from the Voyager and Cassini spacecraft have revealed phenomena such as kinks, fans, channels, streamers, and clumps, all of which change over these short time intervals. While the causes of some of these features...

Saturn’s F ring exhibits dramatic radial and longitudinal variation, ranging from the kinks and clumps (diffuse bright features around 5-20 degrees in longitudinal extent) found by Voyager to the more recently discovered kinematic spirals, fans, streamers, and channels. These features change over short time spans ranging from hours to months. While...

Image photometry reveals that the F ring is approximately twice as bright during the Cassini tour as it was during the Voyager flybys of 1980 and 1981. It is also three times as wide and has a higher integrated optical depth. We have performed photometric measurements of more than 4800 images of Saturn’s F ring taken over a 5-year period with Cassi...

We have continued our exploration of the stability of the inner Uranian satellites (French & Showalter 2011, DDA abstract) using simulations based on recent observational data. We find that the moon subsets Cressida/Desdemona/Juliet and Cupid/Belinda/Perdita are unstable in isolation, crossing orbits in 106-107 years. The presence of the other inne...

We have explored the stability of the inner Uranian satellites using simulations based on the most recent observational data. We find that, across a wide range of mass assumptions, the system is chaotic, resulting in the eventual crossing of orbits. Cupid and Belinda are usually the first satellites to cross orbits, and they do so on a time scale o...

A method and system for processing a data flow in a multi-channel, multiservice environment is described. In one embodiment, a socket is dynamically allocated, the socket including a dynamically allocated service. Further, the server processes the data flow based upon the type of data being processed.

A method and system for processing a data flow in a multi-channel, multi-service environment is described. In one embodiment, a socket is dynamically allocated, the socket including a dynamically allocated service. Further, the server processes the data flow based upon the type of data being processed.

A method and an apparatus for retiming in a network of multiple context processing elements in a network of multiple context processing elements are provided. A programmable delay element is configured to programmably delay signals between a number of multiple context processing elements of an array without requiring a multiple context processing e...

A system and method for creating run time executables in a configurable processing element array is disclosed. This system and method includes the step of partitioning a processing element array into a number of defined sets of hardware accelerators, which in one embodiment are processing elements called “bins”. The system and method then involves...

A method and apparatus for providing local control of processing elements in a network of multiple context processing elements (MCPEs). A MCPE stores configuration memory contexts and maintains data of a current configuration. State information is received from at least one other MCPE. A configuration control signal is generated in response to the...

A system and method for executing previously created run time executables in a configurable processing element array is disclosed. In one embodiment, this system and method begins by identifying at least one subset of program code. The method may then generate at least one set of configuration memory contexts that replaces each of the at least one...

A method and an apparatus for configuration of multiple context processing elements (MCPEs) are described. The method and an apparatus is capable of selectively transmitting data over a bidirectional shared bus network including a plurality of channels between pairs of MCPEs in the networked array. The method and an apparatus then selectively trans...

A method and system for processing a data flow in a multi-channel, multi-service environment is described. In one embodiment, a socket is dynamically allocated, the socket including a dynamically allocated service. Further, the server processes the data flow based upon the type of data being processed.

A method and apparatus for debugging are described. In one embodiment, a target construct is selected for debugging. Data related to an operation of the target construct is accessed by a debug construct in real time. At least a portion of this data is retrieved without disturbing the operation of the target construct to debug the target construct.

A method and apparatus for providing local control of processing elements in a network of multiple context processing elements (MCPEs). A MCPE stores configuration memory contexts and maintains data of a current configuration. State information is received from at least one other MCPE. A configuration control signal is generated in response to the...

A method and an apparatus for configuration of multiple context processing elements (MCPEs)are described. According to one aspect of the invention, the structure that joins the MCPE cores into a complete array in one embodiment is actually a set of several mesh-like interconnect structures. Each interconnect structure forms a network, and each netw...

A system and method for executing previously created run time executables in a configurable processing element array is disclosed. In one embodiment, this system and method begins by identifying at least one subset of program code. The method may then generate at least one set of configuration memory contexts that replaces each of the at least one...

A method and apparatus for providing local control of processing elements in a network of multiple context processing element are provided. A multiple context processing element is configured to store a number of configuration memory contexts. This multiple context processing element maintains data of a current configuration. State information is r...

A method and an apparatus for retiming in a network of multiple context processing elements are provided. A programmable delay element is configured to programmably delay signals between a number of multiple context processing elements of an array without requiring a multiple context processing element to implement the delay. The output of a first...

A method and apparatus for providing local control of processing elements in a network of multiple context processing element are provided. A multiple context processing element is configured to store a number of configuration memory contexts. This multiple context processing element maintains data of a current configuration. State information is r...

A method and an apparatus for position independent reconfiguration in a network of multiple context processing elements are provided. Wach multiple context processing element in a networked array of multiple context processing elements has an assigned physical identification. Virtual identifications may also be assigned to a number of the multiple...

A method and an apparatus for retiming in a network of multiple context processing elements are provided. A programmable delay element is configured to programmably delay signals between a number of multiple context processing elements of an array without requiring a multiple context processing element to implement the delay. The output of a first...

A method and apparatus for providing local control of processing elements in a network of multiple context processing element are provided. A multiple context processing element is configured to store a number of configuration memory contexts. This multiple context processing element maintains data of a current configuration. State information is r...

Like many architectural techniques that originated with mainframes. the use of multiple processors in a single computer is becoming popular in workstations and even personal computers. Multiprocessors constitute a significant percentage of recent workstation sales, and highly affordable multiprocessor personal computers are available in local compu...

Compiler infrastructures that support experimental research are crucial to the advancement of high-performance computing. New compiler technology must be implemented and evaluated in the context of a complete compiler, but developing such an infrastructure requires a huge investment in time and resources. We have spent a number of years building th...

We present a new approach to event-driven simulation that does not use a centralized run-time event queue, yet is capable of handling arbitrary models, including those with unclocked feedback and nonunit delay. The elimination of the event queue significantly reduces run-time overhead, resulting in faster simulation. We have implemented our algorit...

Compiler infrastructures that support experimental research are crucial to the advancement of high-performance computing. New compiler technology must be implemented and evaluated in the context of a complete compiler, but developing such an infrastructure requires a huge investment in time and resources. We have spent a number of years building th...

Supervised by Thomas F. Knight. Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1990. Includes bibliographical references (leaves 48-49).

The Educational On-line System (EOS) is a suite of programs which enables students and lecturers to exchange course materials within the Project Athena environment at the Massachusetts Institute of Technology in Cambridge, MA. Early versions of this software used a command-line interface. This paper outlines the implementation of a user interface t...

Computational origami is a parallel-processing concept in which a regular array of processors can be folded along any dimension so that it can be simulated by a smaller number of processors. The problem of assigning functions to each of the processors is very much like the generalized electrical circuit layout problem. This paper presents a simple,...

Zephyr is a notice transport and delivery system under development at Project Athena.1 Zephyr is for use by network-based services and applications with a need for immediate, reliable and rapid communication with their clients. Zephyr meets the high- throughput, high fan-out communications requirements of large-scale workstation environments. It is...