Lick Observatory Optical SETI: targeted search and new directions

Lick Observatory's Optical SETI (search for extraterrestrial intelligence) program has been in regular operation for 4.5 years. We have observed 4,605 stars of spectral types F-M within 200 light-years of Earth. Occasionally, we have appended objects of special interest, such as stars with known planetary systems. We have observed 14 candidate signals ("triple coincidences"), all but one of which are explained by transient local difficulties. Additional observations of the remaining candidate have failed to confirm arriving pulse events. We now plan to proceed in a more economical manner by operating in an unattended drift scan mode. Between operational and equipment modifications, efficiency will more than double.     

Magnifying our world: Why we must extend civilization to the Moon

Since the completion of its original prehistoric migration some 10 000 years ago, humankind has had nowhere else on Earth to go. The Space Age has produced the wherewithal for a new off-Earth human migration to restart, with the Moon as the clear initial destination. As insurance against cataclysmic and human-induced natural disasters, as a means of creating new commercial industrial–financial opportunities at a time of fundamental change in the global economy, and as a way for the USA to regain some international political influence, it should pursue Moon settlement vigorously and soon. However, the developing US space exploration program being designed by NASA for such an undertaking is too narrowly confined to the pursuit of natural-science objectives. There must be fundamental involvement of the private sector and of a much wider range of professionals and federal departments therein.     

Theory and Modeling for the Magnetospheric Multiscale Mission

The Magnetospheric Multiscale (MMS) mission will provide measurement capabilities, which will exceed those of earlier and even contemporary missions by orders of magnitude. MMS will, for the first time, be able to measure directly and with sufficient resolution key features of the magnetic reconnection process, down to the critical electron scales, which need to be resolved to understand how reconnection works. Owing to the complexity and extremely high spatial resolution required, no prior measurements exist, which could be employed to guide the definition of measurement requirements, and consequently set essential parameters for mission planning and execution. Insight into expected details of the reconnection process could hence only been obtained from theory and modern kinetic modeling. This situation was recognized early on by MMS leadership, which supported the formation of a fully integrated Theory and Modeling Team (TMT). The TMT participated in all aspects of mission planning, from the proposal stage to individual aspects of instrument performance characteristics. It provided and continues to provide to the mission the latest insights regarding the kinetic physics of magnetic reconnection, as well as associated particle acceleration and turbulence, assuring that, to the best of modern knowledge, the mission is prepared to resolve the inner workings of the magnetic reconnection process. The present paper provides a summary of key recent results or reconnection research by TMT members.     

The space-developed dynamic vertical cutoff rigidity model and its applicability to aircraft radiation dose.

We have developed a dynamic geomagnetic vertical cutoff rigidity model that predicts the energetic charged particle transmission through the magnetosphere. Initially developed for space applications, we demonstrate the applicability of this library of cutoff rigidity models for computing aircraft radiation dose. The world grids of vertical cutoff rigidities were obtained by particle trajectory tracing in a magnetospheric model. This reference set of world grids of vertical cutoff rigidities calculated for satellite altitudes covers all magnetic activity levels from super quiet to extremely disturbed (i.e., Kp indices ranging from 0 to 9+) for every three hours in universal time. We utilize the McIlwain "L" parameter as the basis of the interpolation technique to reduce these initial satellite altitude vertical cutoff rigidities to cutoff rigidity values at aircraft altitudes.     

Large-scale impact cratering on the terrestrial planets

Impact cratering as a geologic process on the terrestrial planets is addressed. The crater densities on the Earth and Moon form the basis for a standard flux-time curve, which can be used to date unsampled planetary surfaces and constrain the temporal history of endogenic geologic processes. The attached uncertainties and the shape of the flux curve (a rapid exponential decay for the period 4.6 – 4.0 by, followed by the establishment of a constant fluid by 3.5 – 3.0 by which continues more or less to the present) are such that only very old (3.8 by) and very young ( 1.0 by) surfaces can be dated with some confidence. Dating of intermediate-aged surfaces is more imprecise; a problem which is most significant for the geologic history of Mars.

The cratering mechanics of simple craters are fairly well understood. A transient cavity of roughly parabolic cross-section results from the combined excavation and displacement of the target rocks by the cratering flow-field, which can be approximated by the Z-model derived from shallow-buried explosive events. The walls of the transient crater are unstable and slump inwards, resulting in a final bowl-shaped crater partially filled by breccia. The formation process of larger, shallow complex structures is less well understood. Recent models favor the complete collapse of the initial cavity, with the dynamic uplift of the excavated cavity floor. Regardless of the driving force for uplift, yield strength of the target rocks must be drastically reduced during cavity modification by an, as yet, imprecisely known process.

The formation of large impact basins had a profound effect on planetary evolution. They define the basic tectonic and stratigraphic framework of the Moon and their secondary effects lasted for 10⁸ y. The evidence is less compelling from other planets, but a general feature appears to be the concentration of later endogenic activity in and around basins. On Earth, it is possible that basin-formation contributed to the establishment of the dichotomy between proto-continental and proto-oceanic crusts. The effects of impact continue into recent geologic history and may be linked to major biological changes on Earth, such as at the Cretaceous-Tertiary boundary.     

The accuracy of ionogram-derived N(h) profiles

At the Millstone Hill station the Incoherent Scatter Radar (ISR) and a Digisonde 256 are simultaneously operating. Some characteristic true heights determined by both instruments are compared with each other, possible reasons for observed difference are indicated.     

New line profiles of Li–H2 for brown dwarfs

In order to calculate the opacity of a gas it is necessary to consider how its constituent atoms are perturbed by the surrounding medium. This is required both in order to calculate the equation of state, and in order to determine the profiles of the spectrum lines. In this work we report new theoretical Li line profiles perturbed by H₂ and their dependence with temperature.     

Statistical Measurements of Phase-Locked Receivers

Test instrumentation is described for use in the measurement of threshold sensitivities and noise bandwidths of narrow-band phase-locked receivers. The method is statistical in nature with the data being recorded digitally by a counter and printer. Scale factors can be selected for convenient relation of the data to the standard deviations, 1,2, or 3 sigma. Curves are included showing the results of a typical experiment.     

The United Kingdom Atomic Energy Authority RIPPLE Program

This paper reviews the work carried out at the Atomic Energy Research Establishment (AERE) since 1963 in connection with the development of isotope-powered thermoelectric generators, known as RIPPLEs. It outlines the criteria considered for the selection of strontium 90 as the radioisotope, the design of the generators, the choice of material for the biological shield, and the development of the thermal insulation. It briefly discusses the voltage conversion system employed and states safety design considerations. The paper concludes by discussing the effect of efficiency on the cost of generators and shows typical costs curves.     

Profiling of flow passage in axial radial-flow compressor impellers

A procedure of calculating an axial radial-flow centrifugal stage is considered. Using the gas-dynamically expedient load ratio distribution in profile, the process of impeller flow passage profiling is described. Also given are some techniques for decreasing or eliminating a wake zone as well as a graph of loss dependence on the divergence factor and velocity deceleration on the rarefaction side of the blade channel at the impeller outlet.