Some practical strategies for reducing intermodulation in satellitecommunications

Various heuristic procedures for obtaining practical solutions to the general one-level carrier frequency assignment problem are described. The problem treated is general in the sense that it accommodates the case where L of the N slots may be explicitly designated as prohibited and unavailable for assignment. This problem occurs in satellite transmission with many small carriers accessing the same transponder where, due to multipath and TV interference from crosspolarized transponders of the same satellite and from copolarized transponders of the adjacent satellites, some portions of the bandwidth of the considered transponder cannot be used. To permit comparison with respect to the intermodulation advantage and central-processing-unit time required, the case without prohibited slots is considered. The sequential insertion procedure in which, starting with two carriers at the two end slots, one additional carrier at a time is optimally inserted into one of the unassigned slots is found best when the ratio between the available bandwidth and the total carrier bandwidth is greater than about 125%. All the heuristic procedures produced assignments whose intermodulation advantages are all greater than the bandwidth ratio     

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     

Detection of Projectiles by Electric Field Measurements

A number of various physical mechanisms cause aircraft, missiles, and projectiles to he electrically charged during free flight. The electric charge is in the 10-6 C range for aircraft and in the 10-10 C range for projectiles. The electric field thus transported provides information by which measuring the position and velocity of a projectile is possible. A measuring device is described to determine the position of a projectile in free flight while it is passing a target plane. The electric field distribution is measured by means of three electrodes in the manner of metal plates which are positioned in the proximity of the trajectory of the projectile. A mathematical formula can be derived to describe the coherence between the values measured of the electric field strength and the coordinates of the projectile. This measuring device consists of the target plane, 1 × 1 m2 in size, and the electric device controlled by a microprocessor. The measuring system has been tested with projectiles of the 4-30 mm caliber range and at velocities within the 50-1100 m/s range. The accuracy of the coordinates measured was found to be ± 7.5 mm.     

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.     

Three-Axes Attitude Determination of Spacecraft Using a Laser

A new method for attitude determination of spacecraft is proposed. The distinctive feature of this method is the ability to determine with high accuracy three elementary angles of the attitude by detection of the electromagnetic wave transmission from a single point. The system consists of a transmitter of a linearly polarized laser beam on the earth (or spacecraft) and receiving equipment on a relevant spacecraft. When the system is used for geosynchronous satellites, the possible accuracies of determination are 10-4 rad or higher for the angles which correspond to roll and pitch, and 10-2 rad or higher for the angle which corresponds to yaw, with the period of 1 s. The system margin for atmospheric attenuation is estimated to be about 50 dB (midnight) to about 20 dB (midday) on the basis of commercially available components. Consequently, it becomes possible to orient antennas or detectors toward arbitrary points around the laser transmitting point on the earth with a high pointing accuracy.     

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.     

Comments on `Existence and uniqueness of GPS solutions' by J.S.Abel and J.W. Chaffee

The commenter points out that a direct Global Positioning System (GPS) algorithm together with discussions on the existence and uniqueness of the solution appeared in his paper (J. Guidance, Control, and Dynamics, vol.9, p.715-17, Nov./Dec. 1986). Since the GPS solution is reduced to solving a quadratic equation, the existence and uniqueness can be easily tested. J.S. Abel and J.W. Chaffee, in the above-titled paper (ibid., vol.26, no.6, p.748-53, Sept. 1990), show that the GPS solution problem is similar to the hyperbolic-fix problem. The commenter notes that it can be inferred from his later work (ibid., vol.26. no.5, p.748-53, Sept. 1990) that the two solutions exist if and only if the four GPS satellites are coplanar, in which case the two solutions are mirror-symmetric with respect to the GPS plane     

LET dependence of cell death, mutation induction and chromatin damage in human cells irradiated with accelerated carbon ions.

We investigated the LET dependence of cell death, mutation induction and chromatin break induction in human embryo (HE) cells irradiated by accelerated carbon-ion beams. The results showed that cell death, mutation induction and induction of non-rejoining chromatin breaks detected by the premature chromosome condensation (PCC) technique had the same LET dependence. Carbon ions of 110 to 124keV/micrometer were the most effective at all endpoints. However, the number of initially induced chromatin breaks was independent of LET. About 10 to 15 chromatin breaks per Gy per cell were induced in the LET range of 22 to 230 keV/micrometer. The deletion pattern of exons in the HPRT locus, analyzed by the polymerase chain reaction (PCR), was LET-specific. Almost all of the mutants induced by 124 keV/micrometer beams showed deletion of the entire gene, while all mutants induced by 230keV/micrometer carbon-ion beams showed no deletion. These results suggest that the difference in the density distribution of carbon-ion track and secondary electron with various LET is responsible for the LET dependency of biological effects.     

Blood and clonogenic hemopoietic cells of newts after the space flight.

Ribbed newts were used for studying the effect of space flight on board of the biosatellite (Cosmos-2229) on blood and clonogenic hemopoietic cells. In blood of newts of the flight group, the relative proportion of neutrophils increased, whereas that of lymphocytes and eosinophils decreased. Space flight did not result in loss of the ability of newt blood cells to incorporate H3-thymidine. Analysis of clonogenic hemopoietic cells was performed using the method of hemopoietic colony formation on cellulose acetate membranes implanted into the peritoneal cavity of irradiated newts. To analyze reconstitution of hemopoiesis after irradiation donor hemopoietic cells from flight or control newts were transplanted into irradiated newts whose hemopoietic organs were investigated. The newt can be considered an adequate model for studying hemopoiesis under the conditions of the space flight.