Capillary brazing under microgravity (TEXUS-II) and 1g conditions

Experiments of vacuum brazing under both microgravity and 1-g conditions show the effect of hydrostatic pressure on ga-filling. The absence of buoyancy forces under microgravity affects the microstructure of the solidified braze in the joint.     

Recent developments in space-borne zodiacal light photometry

The 1985 International Solar Polar Mission will provide the first opportunity to perform measurements from out of the ecliptic and from above the solar poles. Included in this mission is the Zodiacal Light/Background Starlight Experiment of the Ruhr-University Bochum, FRG (in collaboration with the State University of New York at Albany). The experiment is based on the use of a multicolor, sky-scanning photopolarimeter, which will be carried on the NASA S/C.The scientific objectives of the experiment are to investigate the intensity, polarization, and color of the diffuse sky brightness and determine the spatial distribution and physical properties of the interplanetary dust, including a possible interstellar component, as a function of S/C position in and out of the ecliptic.The instrument will allow simultaneous measurements in two separate wavelength bands. Measurements will be performed at 180, 220, 240, 280, 320, 350, 360, 440, 540, 640, 800 nm, including the state of polarization. Two different fields-of-view (1 sq deg and 5.6 sq deg) can be selected.The use of a microprocessor system in the instrument electronics will provide flexibility in measurement sequences and programs, on-board data processing and data quality control.     

Quadrature Sampling with High Dynamic Range

Many radio and sonar systems require signal outputs in complex low-pass form. To achieve this, it is possible to use uniform sampling of the bandpass signal, together with computation of the quadrature component by way of a Hilbert transform. The bandpass to low-pass translation is accomplished by undersampling. A hardware implementation is described which achieves 70 dB spurious-free dynamic range and a bandwidth of 30 kHz.     

Absolute IR-spectra from the measurement of Fourier-spectrometers aboard Meteor 25 and 28

It is well known that temperature- and watervapour-profiles, ozone concentration, other atmospheric constituents and the surface-radiation of the Earth can be determined by remote sensing in the IR radiation range with the aid of a satellite.

The narrow-band radiation measurements for remote sensing of the atmosphere and the Earth-surface can be realized either by various radiometers working in selected frequency channels or, continuously in a given frequency range, by spectrometers with fixed spectral resolution.

Fourier-spectrometers (FS) have been used in Earth-orbit only four times up to now: Nimbus 3, Nimbus 4, Meteor 25 and Meteor 28.

The most important technical parameters, the working regime and some aspects of date processing of the FSs working aboard of Meteor 25 and Meteor 28 are given. For the determination of calibrated absolute spectra a method is used that is based on the experience of the first experiment and on the long time stability of the spectrometers. The results obtained in laboratory calibration tests and in the orbit are described.     

Reliability of the Station-Keeping Activator Subsystem of a Geostationary Satellite

The reliability of the station-keeping activator subsystem of a geostationary satellite using electric thrusters is analyzed by modeling the probabilistic behavior of the system as a homogeneous Markov process. The method is applied to the particular case of a 400-kg satellite using 1.5-mN cesium contact electric thrusters. lt is shown that certain system configurations offer a mass improvement without loss of reliability.     

Steady State Analysis of the Rectified Superconducting Alternator

Equations are derived to predict the electrical behavior of a three-phase superconducting alternator connected to a full-wave bridge rectifier. This is accomplished by expanding a previous analysis for conventional rectified alternators and adding computational impovements. The significance of the work is that it provides a means of calculating certain critical variables such as the ac current in the superconducting field winding and the ac voltage harmonics at the rectified output. A numerical example based on a machine designed for airborne applications is included.     

Computation of Optimal Earth-Mars and Earth-Venus Trajectories

Accurate solutions of minimal time Earth-Mars and Earth-Venus heliocentric trajectories are calculated with a shooting-Newton method. The flight times are less and the steering histories are diferent than those presented in [1], thus contradicting the optimality claims in [1].     

Planetary radio astronomy experiment for Voyager missions

The planetary radio astronomy experiment will measure radio spectra of planetary emissions in the range 1.2 kHz to 40.5 MHz. These emissions result from wave-particle-plasma interactions in the magnetospheres and ionospheres of the planets. At Jupiter, they are strongly modulated by the Galilean satellite Io.As the spacecraft leave the Earth's vicinity, we will observe terrestrial kilometric radiation, and for the first time, determine its polarization (RH and LH power separately). At the giant planets, the source of radio emission at low frequencies is not understood, but will be defined through comparison of the radio emission data with other particles and fields experiments aboard Voyager, as well as with optical data. Since, for Jupiter, as for the Earth, the radio data quite probably relate to particle precipitation, and to magnetic field strength and orientation in the polar ionosphere, we hope to be able to elucidate some characteristics of Jupiter auroras.Together with the plasma wave experiment, and possibly several optical experiments, our data can demonstrate the existence of lightning on the giant planets and on the satellite Titan, should it exist. Finally, the Voyager missions occur near maximum of the sunspot cycle. Solar outburst types can be identified through the radio measurements; when the spacecraft are on the opposite side of the Sun from the Earth we can identify solar flare-related events otherwise invisible on the Earth.     

Computerized Model Demonstrating Magnetic Submarine Localization

A modet is described which consists of an aircraft with flux gate magnetometers mounted on the wing tips and a submarine containing a magnet to simulate the induced and permanent fields of an actual submarine. Equations are developed which enable a minicomputer sampling the magnetometers to calculate the location, depth, and heading of the submarine as the aircraft travels towards it. The real time plotted results are presented.     

Modified Barker and Huffman Sequences in Combination Codes

lt is possible that usable combination codes can be obtained if Barker and Huffman sequences are chosen as the inner and outer codes. lt is shown that an improvement in either energy efficiency or time sidelobe structure will result either from a modification of a Huffman sequence or from a modification of a Barker sequence. Results are given for a combination code of length 91, with inner and outer codes of length 7 and 13.