Lightweight (AlGaAs)GaAs/CuInSe2 tandem junction solarcells for space applications

Mechanically stacked tandem cells consisting of GaAs thin-film upper cells and CuInSe₂ thin-film lower cells have been developed to meet the increasing power needs projected for future spacecraft. The authors report the fabrication of the first highly efficient lightweight GaAs/CuInSe₂ tandem cell on a 2-mil thick substrate, update recent performance improvements in thin-film GaAs/CuInSe₂ tandem cells, and discuss their application to space power systems. The efficiency of 4-cm² cells has improved to 21.6% AM0, the highest ever reported for a thin-film photovoltaic cell. Lightweight 4-cm² tandem cells have been successfully fabricated with efficiencies as high as 20.8%. These cells weighed about 180 mg without optimized substrate trimming. Radiation and operating temperature effects on GaAs/CuInSe₂ tandem cells are also discussed, and an interconnect scheme to form a voltage-matched string is described     

Sensor compensation for vehicle magnetic signatures

Most land vehicles whose positions need to be tracked are made primary of steel. The problem considered is that of finding locations within or on land vehicles where magnetic sensors can be mounted to measure heading accurately and of finding compensation methods that minimize the effect of the vehicle magnetic signature. Results obtained with various types of vehicles in several world locations are given. Advantages and disadvantages of pendulous mounting are considered, and vehicle magnetic changes caused by driving in areas of extremely strong magnetic fields such as those generated by DC-powered trains are discussed     

Electrical power distribution on space based radar satellites

The radar payload on a space-based radar (SBR) satellite could require tens of kilowatts of power distributed to many small loads over a large area. This poses special problems for the power distribution and control system (PDCS). A study that examined the power requirements of an SBR spacecraft is reported. A baseline prime power system, generating about 30 kW, was derived. The proposed distribution network would transmit 240 V at 20 kHz. The voltage would be downconverted in one converter for about 100 transmit/receive modules. The design considerations are discussed, and the baseline PDCS is described     

Physical interpretation of interdisciplinary solar/interplanetary observations relevant to the 27–29 June 1980 SMY/STIP event no. 5

A sequence of six well defined interplanetary structures (magnetic clouds) was identified in the solar wind and magnetic field measurements of Helios-1 from 29 June-01 July, 1980. (location 0.64–0.67 AU, C. Long. ～165°, C. Lat. ～5.8°). These structures were characterized by a large northward directed solar wind flow; by well defined directional discontinuities of mainly the ‘tangential-type’ at their beginnings and ends; by some increase in proton and by very pronounced increases in alpha particle number densities - each accompanied by sudden temperature decreases (or in one case by an increase); by some times an increase in magnetic field strength and by values of Nα/Np typical of the inner solar atmosphere. These structures are suggested to have been ejections from a succession (27–29 June, 1980) of Type II producing flares in Hale Region 16923 which coronagraph and X-ray (GOES) data indicate constituted a family of transient producing events. Only two interplanetary shocks were identified in the relevant Helios-1 records. It is suggested on the basis of observations of the directionality of certain of the flare related Type II bursts that some of these shocks could have been missed by the spacecraft. This implies that, in the absence of directional information, correlation of an observed interplanetary shock wave with a solar Type II burst may not always lead to a unique result.     

The role of antiprotons in cosmic-ray physics

Though success eluded experimentalists from detecting cosmic-ray antiprotons over a long period of time, the study of cosmic-ray antiprotons has now become a fascinating field of research. In this review, we have attempted to elucidate the excitement in this area of research since the discovery of antiprotons in the laboratory. We have described the experiments carried out so far to measure the energy spectrum of antiprotons, from about 200 MeV to about 15 GeV, and summarised the results. The observed spectrum, with the limited data, appears to be very hard and is different from other components of cosmic radiation. Upper limits to the fraction of antiprotons in cosmic-rays have also been derived at higher energies, using the observed spectra of cosmic-ray primary and secondary particles at different depths in the atmosphere. We have described various physical processes by which antiprotons could be produced, such as high-energy interactions, neutron oscillations, evaporation of Mini Black Holes, decay of super symmetric particles, etc. The energy spectrum of antiprotons, which are produced through the above processes, undergoes modifications during propagation in the Galaxy. We have examined in detail the propagation models which have been employed to explain the observed data. It is shown that no single model could predict correctly the observed energy spectrum of antiprotons over the entire energy region. However, many models are able to explain the data at relativistic energies. It is difficult at this stage to make a choice among these models. The implications of these models for other components of cosmic-rays, such as positrons, deuterium, and He, have been discussed. We have examined the production of gamma rays in the Galaxy from sources, which produce the observed antiprotons through high-energy interactions. We have also briefly indicated the effect of possible re-acceleration during their confinement in the Galaxy. We finally emphasized the need for more detailed measurements of the spectral shape of cosmic-ray antiprotons to further refine speculations of their origin. Similarly, we have shown that detailed observation of the energy spectra of positrons, deuterium, and He at relativistic energies are crucial to test various propagation models.     

Signatures of troposphere-stratosphere momentum coupling: Implications for global atmospheric angular momentum and earth rotation budgets

During January–August 1978, the global atmospheric angular momentum (M) exhibits distinct patterns of short term momentum interchange across latitudes. In the northern hemisphere winter-spring season, 30–50 day modulations of M are present in which momentum $\text{enhancements}$ at mid-latitudes (20–30°) are closely matched by momentum $\text{depressions}$ at high latitudes (50–60°). During the same interval there are no corresponding variations in M evident in the southern hemisphere. Conversely, during southern hemisphere fall-winter, similar anticorrelations in monthly scale momentum excursions are evident between mid and high latitudes. In the northern hemisphere, the winter-spring momentum signatures are detected throughout the atmosphere, from the lower troposphere to the stratosphere. During the southern hemisphere fall-winter, the modulation patterns are not evident at the higher altitudes. Structural details of the momentum signatures indicate that the coupling is sometimes effective on very short time scales, e.g. 1–2 days, or less. The evidence of distinct anti-correlation between large regions has interesting implications for studies of global atmospheric circulation, and also for studies of the excitation of variations in earth rotation in response to short term modulations of M.     

Equatorial F-region ionization differences between March and September, 1979

Ionospheric total electron content and the F-region maximum electron density at a number of stations in the equatorial region, during the recent solar activity maximum period 1979 to 1980, show significant differences between the two equinoctial periods. Ionization during the month of March is higher than in September, irrespective of the station location both in northern and southern hemispheres, and in different longitude sectors. The observed pattern is compared with those predicted by different models, in particular with one of the authors which includes processes such as ionization production, loss, electrodynamic drifts, winds and global composition changes involved in the equatorial ionosphere. It is found that a change in the neutral composition is primarily responsible for the observed F-region density differences between March and September.     

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.     

Synoptic studies of the middle atmosphere using balloons

During the Middle Atmosphere Program, 1982–1985, balloons will play a central role in gathering stratospheric, chemical, and dynamical data. This paper discusses some of the unique aspects of balloons as tools for probing the middle atmosphere, and suggests some directions for future projects and enhanced capabilities that would improve their utility in future investigations.     

Recognition and Self-Organization of Nodes into DTDMA Nets

An effective relay management solution applicable to multiple terminal ground-to-ground or ground-to-air line-of-sight communication environments is described. Algorithms are developed which enable terminals first to recognize the existence or availability of other terminals, and second, to self-organize a community of terminals rapidly into local nets without the need for a master control terminal. Computer simulation results show how a static or dynamically changing user geometry can be managed. Network connectivity is provided automatically and the system protects itself against the loss of a master user by not requiring one.