Escaping near-relativistic electron beams from the solar corona

Processes in the solar corona are prodigious accelerators of energetic ions, and electrons. The angular distribution, composition, and spectra of energetic particles observed near Earth gives information on the acceleration mechanisms. A class of energetic particle observations particularly useful in understanding the solar acceleration is the near-relativistic impulsive beam-like electron events. During five years of operation the Advanced Composition Explorer (ACE) has measured well over 400 electron events. Approximately 25% of these electron events are impulsive beam-like events that are released onto interplanetary field lines predominantly from western solar longitudes. We extend our initial 3 year study during the rise to solar maximum (Haggerty and Roelof, 2002; Simnett et al., 2002) to a five year statistical analysis of these beam-like energetic electron events in relationship to optical flares, microwave emission, soft X-ray emission, metric and decametric type-III radio bursts, and coronal mass ejections.     

Microgravity particle research on the space station: the Gas-Grain Simulation Facility.

In the gravitational field on Earth, the large settling rate of micron-sized particles and the effects of gravity-induced convection prohibit many interesting studies of phenomena such as coagulation, collisions, and mutual interactions of droplets, dust grains and other particles. Examples of exobiology experiments involving these phenomena are the simulation of organic aerosol formation in Titan's atmosphere, studies of the role of comets in prebiotic chemical evolution, and simulations of carbon grain interactions in various astrophysical environments. The Gas-Grain Simulation Facility (GGSF) is a proposed Earth-orbital laboratory that will allow present ground-based experimental programs which study processes involving small particles and weak interactions to be extended to a new domain. Physics issues that scientists wishing to propose GGSF experiments must consider are reviewed in this paper. Specifically, coagulation, motion in gases and vacua, and wall deposition of particles in a microgravity environment are discussed.     

Spending without results: lessons from the space station program

The US spent all of the funds originally estimated for the initial development of its orbital space station without producing any significant amount of flight hardware. This article shows how a project with large design costs and significant “non-prime” outlays can quickly deplete program funds. The authors recount the way in which budgetary politics, congressional micro-management, and technological risk conspired to produce this result.     

Mobile Satellite Plans and Status

A variety of new communication functions will become available near the end of the decade when mobile satellite services (MSS) are introduced commercially in the United States and Canada. Mobile radios, hand carried radios and small fixed transponders will communicate directly through satellites into the telephone network or to private base stations. Voice, data, and position fixing services will be distance insensitive with good performance in difficult terrain and remote locations. Experiments with NASA satellites and studies in the U.S. and Canada demonstrated the technical feasibility and practical applications of mobile satellites. In 1983 Mobile Satellite Corporation, followed by Skylink Corporation, applied to the FCC for authorization to build and operate a land and aeronautical mobile satellite system for the United States. Canada had advanced its plans for an MSAT system. In response to these initiatives, the FCC issued a ``Notice of Proposed Rulemaking' that proposed the allocation of radio spectrum for the new service and asked for applications from prospective providers. Twelve applications were received. The shortage of radio spectrum in the U.S. has resulted in much contention over the proposed allocations, and the numerous applications have introduced competing systems concepts. The paper describes a likely system implementation, its services and markets, and the current regulatory status.     

An approach to knowledge-aided covariance estimation

This paper introduces a parametric covariance estimation scheme for use with space-time adaptive processing (STAP) methods operating in heterogeneous clutter environments. The approach blends both a priori knowledge and data observations within a parameterized model to capture instantaneous characteristics of the cell under test (CUT) and reduce covariance errors leading to detection performance loss. We justify this method using both measured and synthetic data. Performance potential for the specific operating conditions examined herein include: 1) averaged behavior within roughly 2 dB of the optimal filter, 2) 1 dB improvement in exceedance characteristic relative to the optimal filter, highlighting improved instantaneous capability, and 3) impervious ness to corruptive target-like signals in the secondary data (no additional signal-to-interference-plus-noise ratio (SINK) loss, compared with 10 dB or greater loss for the standard STAP implementation), with corresponding detections comparable to the optimal filter case     

A root moisture sensor for plants in microgravity.

Development of components for bioregenerative life-support systems is a vital step toward long-term space exploration. The culturing of plants in a microgravity environment may be optimized by the use of appropriate sensors and controllers. This paper describes a sensor developed for determining the amount of fluid (nutrient solution) available on the surface of a porous ceramic nutrient delivery substrate to the roots of conventional crop plants. The sensor is based on the change in thermal capacitance and thermal conductance near the surface as the moisture content changes. The sensor could be employed as a data acquisition and control sensor to support the automated monitoring of plants grown in a microgravity environment.     

Accuracy of predicted earth's artificial satellite orbits

The accuracy of predicted satellite positions depends on many factors: the accuracy of initial conditions (observations), the accuracy of the adopted force model, the accuracy of the theory used in calculations and the time interval. The paper proposes an analytical algorithm for the inverse transformation from osculating to mean orbital elements and presents some results of an analysis of the influence of geopotential errors on predicted satellite position errors.     

Monitoring power supply current and using a neural network routineto diagnose circuit faults

As a circuit is tested, the current drawn from a power supply can vary as different functions are invoked by the test. The current draw can be plotted against time, showing a characteristic trace for the test performed. Sensors in the ATS power supply can be used to monitor the current flow during test execution. Defective components can be classified using a Neural Network according to the pattern of variation from the “trace” of a good card. This can be performed as a background function, with the network gaining in accuracy over time. This paper discusses the Neural Network Routine for diagnosing circuit faults using monitored power supply current