Aerospace & Aviation

Contributions of new mexico to space program

Optimum control of processes described by differential equations

Electron microprobe analysis of rare minerals in norton county, kansas achondrite

This paper discusses the design and characteristics of ruby traveling-wave masers operating at 4 gc. These masers, characterized by an average gain of ≈35 db over a bandwidth of 25 mc, are equipped with waveguide input transmission lines, rather than the previously employed coaxial cables. This change results in an over-all noise temperature of 3.5°K for these devices, rather than the 10°K exhibited by earlier masers. The maser noise temperature now closely approximates sky temperatures, which set the ultimate limit on earthbound receiver sensitivity. The improvements to be had by further reduction in amplifier noise are therefore almost negligible. A less well known maser property, i.e., its freedom from distortion, even when driven well into gain saturation, is discussed.

To limit the 4080-mc local oscillator signal power input to the beat oscillator modulator of the Telstar satellite communications repeater, a subsidiary absorption limiter was used which consisted of an optically polished sphere of single-crystal yttrium iron garnet (YIG), placed in a resonant transmission cavity between the amplified 4080-mc output of the traveling-wave tube and the BO modulator input. The limiter holds the output power nearly constant above a given input threshold; below this threshold the YIG is linear and introduces only a small loss. The threshold is determined, for a given sample at a given frequency, by the external magnetic bias field. Temperature compensation over the desired range was obtained by orienting the crystal with the dc magnetic field along a [100] or “hard” axis. The total weight of the limiter package, including the bias magnet and cavity, is 13 ounces.

Objectives in development of the solar plant for the Telstar spacecraft were to provide a power source which would withstand launching stresses and the expected space environment, with optimum end-of-life performance. Radiation damage to the silicon solar cells is the primary factor limiting their useful life; the effect of energetic protons or electrons is the generation of recombination centers in the silicon which reduce the minority-carrier diffusion length and therefore the long-wave response of the cell. The spacecraft solar cells use the n-on-p structure, in preference to conventional p-on-n structure, to obtain a factor of 3 to 10 increased life expectancy. Response to light in the 0.4 to 0.7 micron range is enhanced by using a thin n-layer (about 0.5 micron) and an antireflection coating with minimum reflectance at 0.55 micron wavelength. Early estimates of electron and proton fluxes in the satellite orbit showed that even the best cells would not give sufficient life without radiation shielding. Therefore the cells are protected against electrons of energy up to 1 Mev by 0.3 gm/sq. cm sapphire cover plates. The cell mountings are designed to withstand peak vibration stresses of 200 g and repeated temperature cycles from +65°C to −100°C. The 3600-cell solar power plant is composed of 300 twelve-cell groups of 1 cm × 2 cm cells, yielding a nominal initial power of 14 watts at 28 volts for any spin-axis orientation relative to the sun. Telemetry information on performance of the solar plant indicates degradation of the shielded solar cells equal to that measured in the laboratory on unshielded cells with a 1-Mev normal incidence flux of 6 × 10^(12) electrons/(sq. cm day). From this comparison it is estimated that the plant will degrade to 68 per cent of its initial output after two years in orbit.

The electronics system of the Telstar satellite is described from the point of view of philosophy of design and construction rather than that of circuit details. The reliability is emphasized, and steps taken to preserve the inherent reliability of the components are discussed. The physical construction of modules, subsystems, and finally the entire system is described, including the foam encapsulation and the eventual hermetic sealing of the canister.

Role of magnetohydrodynamics, magnetic fields, and conductive plasma instabilities in solar flare origin

Spectral normal emittance of materials under simulated space environment

Spectral emittance of opaque and transparent materials from 40- to 200-deg c

Calorimeter for measuring total hemispherical emittance in low temperature range

Multiplier-type photometer with wide dynamic range for absorption spectroscopy

Heated cavity reflectometer for thermal reflectance measurements of opaque surface

Thermocouple and radiation thermometry above 900 deg k

NASA Special Publication SP-32 is being published in accordance with the cooperative agreement executed on July 27, 1961 between the National Aeronautics and Space Administration and the American Telephone and Telegraph Company for the development and experimental testing of active communications satellites. This report consists of four volumes. The first three are composed of papers originally published together as a regular issue of the Bell System Technical Journal. The fourth volume, to be published at a later date, will contain pertinent papers contributed by various authors at the NASA Goddard Space Flight Center; the General Post Office of the United Kingdom; the Centre National d'Etudes des Telecommunications, France; and Telespazio, Italy.