Low-angle tracking using a multifrequency sampled aperture radar

The improvements that can be achieved in low-angle radar by using a sampled aperture radar (SAMPAR) and a maximum likelihood (ML) algorithm are discussed. The SAMPAR system described is unique in that it has a wide-ranging multifrequency capability. The ML technique is also unique because its estimation is based on the use of a highly refined signal model. It is shown, by using both simulated data and real data, that this combination, i.e., a SAMPAR system and the modified ML algorithm, provides a multiple signal resolution that exceeds any reported in the open literature. The measured data used in this study were recorded using a 32-element sampled aperture antenna on an over-water path     

PCM Frame Synchronization with a Self-Varying Threshold

An improved method for frame synchronization of PCM telemetered data is described and performance analyses are presented. This method is based on the utilization of a threshold detector whose level is selfvarying according to the characteristics of the received data. It is simple to implement and simpler from an operational point of view than the frame synchronizers currently in use in that a threshold control is altogether eliminated. Analyses show, furthermore, that a synchronizer using a self-varying threshold always has a higher probability of detecting the synchronization code no matter what the frame length, sync code length, or error level.     

Heavy ion induced changes in small intestinal parameters.

The effects on 17 different structural parameters of mouse small intestine three days after treatment with three types of heavy ion (neon, iron and niobium) are compared, the first two being of particular relevance to space flight. The data for niobium are given in full, showing that changes after niobium ion treatment are not standard and are concentrated in the epithelial compartment, with few of the parameters having a response which is dose dependent. When comparisons are made for the three types of heavy ion, the damage is greatest after neon ion irradiation, implying that the additional non-epithelial damage produced as LET rises from X rays through neutrons to neon ions is not necessarily maintained as LET continues to rise. Further understanding is therefore needed of the balance between changes affecting the vascular and absorptive components of the organ. Variation from group to group is also important, as is variation of strain or gastrointestinal status. All such factors are important in the understanding of changes in multicellular organs after exposure to heavy ion radiation.     

Atmospheric dynamics and bioregenerative technologies in a soil-based ecological life support system: initial results from Biosphere 2.

Biosphere 2 is the first man-made, soil-based, bioregenerative life support system to be developed and tested. The utilization and amendment of local space resources, e.g. martian soil or lunar regolith, for agricultural and other purposes will be necessary if we are to minimize the requirement for Earth materials in the creation of long-term off-planet bases and habitations. Several of the roles soil plays in Biosphere 2 are 1) for air purification 2) as a key component in created wetland systems to recycle human and animal wastes and 3) as nutrient base for a sustainable agricultural cropping program. Initial results from the Biosphere 2 closure experiment are presented. These include the accelerated cycling rates due to small reservoir sizes, strong diurnal and seasonal fluxes in atmospheric CO2, an unexpected and continuing decline in atmospheric oxygen, overall maintenance of low levels of trace gases, recycling of waste waters through biological regeneration systems, and operation of an agriculture designed to provide diverse and nutritionally adequate diets for the crew members.     

The benefits of using ATE systems in the testing of printed circuitboards

An industry-based pragmatic review is provided of the economic and product-quality consequences of automatic test equipment (ATE) usage in printed circuit board testing. The company selection process, the nature of the industrial participants, and the data collection process are described. The benefits obtained by users are identified. It is demonstrated that the use of ATE systems does result in definable economic and quality-level benefits     

10. The surface and interior of venus

Present ideas about the surface and interior of Venus are based on data obtained from (1) Earth-based radio and radar: temperature, rotation, shape, and topography; (2) fly-by and orbiting spacecraft: gravity and magnetic fields; and (3) landers: winds, local structure, gamma radiation. Surface features, including large basins, crater-like depressions, and a linear valley, have been recognized from recent ground-based radar images. Pictures of the surface acquired by the USSR's Venera 9 and 10 show abundant boulders and apparent wind erosion.On the Pioneer Venus 1978 Orbiter mission, the radar mapper experiment will determine surface heights, dielectric constant values and small-scale slope values along the sub-orbital track between 50°S and 75°N. This experiment will also estimate the global shape and provide coarse radar images (40–80 km identification resolution) of part of the surface. Gravity data will be obtained by radio tracking. Maps combining radar altimetry with spacecraft and ground-based images will be made. A fluxgate magnetometer will measure the magnetic fields around Venus.The radar and gravity data will provide clues to the level of crustal differentiation and tectonic activity. The magnetometer will determine the field variations accurately. Data from the combined experiments may constrain the dynamo mechanism; if so, a deeper understanding of both Venus and Earth will be gained.     

30/20 GHz Band Small Earth Station for ISSDN Experiment

The system design and operational results of a 30/20 GHz band small Earth station for integrated services satellite digital network (ISSDN) experiments are presented. The Earth station has a high efficiency offset Cassegrain antenna with elliptical beam, a high power klystron amplifier with 1 kW output power and an uncooled parametric low noise amplifier with 200 K noise temperature. Experiments were performed using the medium capacity communications satellite for experimental purposes (CS). Performance on the Earth station was high. Effective radiation power (ERP) was greater than 88.1 dBW, and the receiving figure of merit (G/T) was larger than 30.6 dB/K. Good transmission characteristics were obtained through the satellite link for demand assigned time-division multiple access (DA-TDMA) with 20 Mbit/s bit rate.     

Microcomputer-based monitoring of cardiovascular functions in simulated microgravity.

A microcomputer-based system for non-invasive monitoring of cardiovascular system in simulated microgravity is described. The system evaluates automatically, accurately and interactively heart beat intervals, beat-to-beat non-invasive finger arterial blood pressure (systolic, diastolic, mean and pulse pressure) using a Finapres device and beat-to-beat changes of thoracic blood volume using impedance changes. In addition, beat-to-beat evaluation of cardiac mechanical function including left ventricular ejection time, diastolic time, systolic time intervals, left ventricular ejection fraction estimate and several other contractility parameters, left ventricular volume, stroke volume and cardiac output estimates are performed with high degree of automaticity.