Properties of the neutral density and composition in the thermosphere

Measurements of the density and composition of the thermosphere between 150 and 500 km, which were obtained by the S3-1 satellite, have been compared with the Jacchia and MSIS models. The measurements of the densities of O, N₂, N and Ar show some differences from the current models which should be considered during the preparation of the next CIRA model. The Ar measurements are particularly useful in examining the response of the neutral atmosphere to geomagnetic heating. These results are useful in establishing the appropriate lower boundary conditions for modeling of the thermosphere.     

Quasi-Complementary Sequences

A method of constructing digital phase reversal codes which have few nonzero sidelobes and which are available in frequent lengths is given. This is particularly important in the area of longer codes. The codes are a form of combined sequence and, hence, have the desirable property of bandwidth reduction for the outer code. However, only two member codes are required. A major usage of these codes may be in addressing.     

Measurements of the earth radiation budget from satellites during the first garp global experiment

Two special measurements of the energy exchange between earth and space were made in connection with the FGGE. A global monitoring program using wide-field-of-view and scanner detectors from NASA's NIMBUS-7 satellite successfully returned measurements during the entire FGGE. This experiment system also used a black cavity detector to measure the total energy output of the sun to very high precision. A second set of high frequency time and space estimates of the radiation budget were determined from selected geostationary satellite data. Preliminary results from both radiation budget data sets and the solar “constant” measurements will be presented.     

Physical determinants of radiation sensitivity in bacterial spores.

Several factors modifying radiation sensitivity in dry bacterial spores are described and discussed. Vacuum inducing the loss of critical structural water, very low dose rates of radiation from which the cell may recover, radiations of high linear energy transfer, and the action of temperature over long periods of time on previously irradiated cells are recognized from extensive laboratory work as important in determining survival of spores exposed to low radiation doses at low temperatures for long periods of time. Some extensions of laboratory work are proposed.     

Beam-plasma discharge in near rocket region

The model of beam-plasma discharge near the rocket following electron beam injection into the ionosphere is presented. The dependence of discharge plasma density on neutral atmosphere concentration and beam parameters is found. Radioemission and luminiscence intensities from discharge are estimated. The model is consistent with the data of ARAKS and “Zarnitsa-2” experiments.     

Wave measurements in active experiments on plasma beam injection

The paper presents the results and discussion of VLF wave measurements carried out in the course of two rocket experiments on injection of a dense cesium ion beam into the ionosphere at the heights of 165–240 km. The injection was accompanied by enhancement of the broad-band noise by several orders of magnitude. The wave measurements in the frequency range of 1–11 kHz revealed two pronounced frequencies somewhat exceeding that of the lower-hybrid resonance oscillations in the background plasma and the cesium beam. The oscillations were modulated by frequencies close to the ion-cyclotron frequencies of the background plasma.     

Exact Detection Performance for Broadband Correlators

The detection of a broadband plane wave in an isotropic noise field is considered. The detection statistic used is the cross correlation of the sampled output from two sensors where the sampling rate equals the Nyquist rate and the time delay is an integer multiple of the sampling period. By restricting the number of points in the cross correlation to be even, the detection and false-alarm probbilities are obtained in closed form. Numerical results are presented for several special cases.     

Measurements of LET spectra and comparison to models.

We present measurements of LET spectra for near earth orbits with various inclinations and altitudes. A comparison with calculated LET spectra shows that the contribution from direct ionizing galactic cosmic rays is well described by the models. An additional contribution to the spectra originates from stopping protons and from nuclear interactions of particles with material. In the case of an interaction a large amount of energy is deposited in a small volume by target recoils or target fragments. These events will be called short range (SR) events. For a low inclination orbit radiation belt protons are the main source of these events while galactic protons become more important when increasing the inclination to near polar orbits. We show that the contribution of SR events for orbits with low altitude (324 km) and 57 degrees inclination is comparable to that for an orbit with 28 degrees inclination at a high altitude (510 km).     

Review of basic medical results of the Salyut-7--Soyuz-T 8-month manned flight.

This paper presents the results of medical investigations performed in the Salyut-7 8-month mission in which a professional physician took part. The paper contains anthropometric measurements, results of investigating the vestibular function, cardiovascular function at rest and in response to multi-step tests (with emphasis on echocardiographic measurements), metabolic parameters and hormonal status. It also discusses medical aspects of the extravehicular activity. The medical investigations, although some new methods were applied, provided the continuity of methodical approaches and data accumulated in previous missions.     

Advanced communications satellite technology

Technology drivers for commercial communications satellites are examined based on the efficient use of spacecraft mass which is to be accomplished by increasing the efficiency of the microwave power amplifiers and antenna feed systems used for communications satellites, such as the INTELSAT series. The history of the INTELSAT series of satellites, the late 1980s market and available technology, and future directions of development are considered. Emphasis is on multibeam solid-state antennas, microwave switch matrices, solid-state power amplifiers, and the use of several filter modes in one physical cavity. By using quasimonolithic solid state techniques in a class B amplification mode they have achieved 40-60% efficiencies, compared with 20% for the conventional travelling wavetube amplifiers. It is concluded that technology directed towards improving the economics of satellite communications will continue to be a major driver of future communications satellite payloads. Through their use and their extension, the authors foresee more than doubling the telephone channels per satellite from the current 80000 to perhaps 200000 by the turn of the century