The analysis of time multiplexing systems for partial success

Time division multiplexing system analysis for partial succes

Geometric aspects of ground station/satellite communications

Geometry aspects of communications between ground station and satellite in elliptical orbi

Data Compression System with a Minimum Time Delay Unit-Patent

Minimum time delay unit for conventional time multiplexed data compression channel

Systems comparison of direct and relay link data return modes for advanced planetary missions

Advanced planetary missions using direct and relay link data return mode

An Advanced, Three-Dimensional Plotting Library for Astronomy

We present a new, three-dimensional (3D) plotting library with advanced features, and support for standard and enhanced display devices. The library - S2PLOT - is written in C and can be used by C, C++ and FORTRAN programs on GNU/Linux and Apple/OSX systems. S2PLOT draws objects in a 3D (x,y,z) Cartesian space and the user interactively controls how this space is rendered at run time. With a PGPLOT inspired interface, S2PLOT provides astronomers with elegant techniques for displaying and exploring 3D data sets directly from their program code, and the potential to use stereoscopic and dome display devices. The S2PLOT architecture supports dynamic geometry and can be used to plot time-evolving data sets, such as might be produced by simulation codes. In this paper, we introduce S2PLOT to the astronomical community, describe its potential applications, and present some example uses of the library.Comment: 12 pages, 10 eps figures (higher resolution versions available from http://astronomy.swin.edu.au/s2plot/paperfigures). The S2PLOT library is available for download from http://astronomy.swin.edu.au/s2plo

The distribution of Transverse Aeolian Ridges on Mars

Abstract not available

The Dynamical State of Barnard 68: A Thermally Supported, Pulsating Dark Cloud

We report sensitive, high resolution molecular-line observations of the dark cloud Barnard 68 obtained with the IRAM 30-m telescope. We analyze spectral-line observations of C18O, CS(2--1), C34S(2--1), and N2H+(1--0) in order to investigate the kinematics and dynamical state of the cloud. We find extremely narrow linewidths in the central regions of the cloud. These narrow lines are consistent with thermally broadened profiles for the measured gas temperature of 10.5 K. We determine the thermal pressure to be a factor 4 -- 5 times greater than the non-thermal (turbulent) pressure in the central regions of the cloud, indicating that thermal pressure is the primary source of support against gravity in this cloud. This confirms the inference of a thermally supported cloud drawn previously from deep infrared extinction measurements. The rotational kinetic energy is found to be only a few percent of the gravitational potential energy, indicating that the contribution of rotation to the overall stability of the cloud is insignificant. Finally, our observations show that CS line is optically thick and self-reversed across nearly the entire projected surface of the cloud. The shapes of the self-reversed profiles are asymmetric and are found to vary across the cloud in such a manner that the presence of both inward and outward motions are observed within the cloud. Moreover, these motions appear to be globally organized in a clear and systematic alternating spatial pattern which is suggestive of a small amplitude, non-radial oscillation or pulsation of the outer layers of the cloud about an equilibrium configuration.Comment: To appear in the Astrophysical Journal; 23 pages, 8 figures; Manuscript and higher resolution images can be obtained at http://cfa-www.harvard.edu/~ebergin/pubs_html/b68_vel.htm

Probing the inner 200 AU of low-mass protostars with the Submillimeter Array: Dust and organic molecules in NGC1333-IRAS2A

The Submillimeter Array has opened a new window to study the innermost warm and dense regions of the envelopes and disks around deeply embedded protostars. This paper presents high-angular resolution (< 2'') submillimeter observations of the class 0 young stellar object NGC1333-IRAS2A. Dust continuum emission and lines of complex organic molecules such as CH3OCH3 and CH3OCHO, high excitation CH3OH transitions, deuterated methanol CH3OD as well as lines of CO, HCN, H13CN, SO and SO2 are detected on < 200 AU scales. The observations are interpreted using detailed radiative transfer models of the physical and chemical structure, consistent with both single-dish and interferometer data. The continuum emission is explained by an extended envelope and a compact but resolved component, presumably a circumstellar disk with a diameter of 200-300 AU and a mass of a few times 0.01-0.1 M_sun. If related to the rotation of the envelope, then the size of this disk suggests a centrifugal barrier of 200-300 AU, which implies that the temperature in the envelope does not increase above 100 K. Its large size also suggests that the build-up of disks proceeds rapidly throughout the early protostellar stages. The smaller (< 100 AU) disks found around other deeply embedded protostars may be a result of tidal truncation. The high-resolution observations of SO can be explained with a simple constant abundance, ~1E-9, constrained through single-dish observations, whereas those of H13CN and the organic species require high abundances, increased by one to two orders of magnitude, or an additional compact source of emission at small scales. The compact molecular emission could originate in a hot core region of the inner envelope, but a more likely reservoir is the circumstellar disk.Comment: Accepted for publication in ApJ. 24 pages, 5 figure

Future Directions in Astronomy Visualisation

Despite the large budgets spent annually on astronomical research equipment such as telescopes, instruments and supercomputers, the general trend is to analyse and view the resulting datasets using small, two-dimensional displays. We report here on alternative advanced image displays, with an emphasis on displays that we have constructed, including stereoscopic projection, multiple projector tiled displays and a digital dome. These displays can provide astronomers with new ways of exploring the terabyte and petabyte datasets that are now regularly being produced from all-sky surveys, high-resolution computer simulations, and Virtual Observatory projects. We also present a summary of the Advanced Image Displays for Astronomy (AIDA) survey which we conducted from March-May 2005, in order to raise some issues pertitent to the current and future level of use of advanced image displays.Comment: 13 pages, 2 figures, accepted for publication in PAS

Capturing Hiproofs in HOL Light

Hierarchical proof trees (hiproofs for short) add structure to ordinary proof trees, by allowing portions of trees to be hierarchically nested. The additional structure can be used to abstract away from details, or to label particular portions to explain their purpose. In this paper we present two complementary methods for capturing hiproofs in HOL Light, along with a tool to produce web-based visualisations. The first method uses tactic recording, by modifying tactics to record their arguments and construct a hierarchical tree; this allows a tactic proof script to be modified. The second method uses proof recording, which extends the HOL Light kernel to record hierachical proof trees alongside theorems. This method is less invasive, but requires care to manage the size of the recorded objects. We have implemented both methods, resulting in two systems: Tactician and HipCam