Interference Immunity Effects in CPSK Systems with Hard-Limiting Transponders

Transmission characteristics are described for M-ary coherent phase-shift keyed (CPSK) systems with N-stage hard-limiting transponders where noise and multiple continuous wave (CW) interference sources are additively combined in each link. A general expression for the probability density function of the composite phase at the final link is derived; the overall error probability is then obtained from this general expression. Comparisons with N-cascaded linear amplifier systems clearly show the noise and interference immunity that result from the use of bandpass hard limiters (BPHLs). The BPHL system's error probability improvement versus interference sources is shown to be much larger than the improvement versus noise.     

Real-time stereoscopic applications using the goes operational satellites

We have investigated the use of real and synthetic stereo satellite images and stereo graphics in applications such as cloud-tracked winds, severe storm cloud analysis, and general meteorological interpretation. We have concluded that a stereo meteorological presentation is possible and desirable in an operational environment. Synthetic stereo could be used immediately in cloud-tracked wind operations. The presentation allows one to appreciate the interrelations between cloud motions and cloud structures, especially in multi-layered situations. Reprocessing of FGGE tropical wind sets with a synthetic stereo presentation showed some improved yields of low-level vectors, a significant increase in mid-level vectors, and very little change in the high-level vectors. Severe local storm real-stereo presentations are possible operationally because the 15 minute RISOP operations of GOES-East allow simultaneous scanning of both geosynchronous satellites twice per hour. The real-stereo height measurements of overshooting turrets are an improvement over infrared heights and can be used to monitor the strength of the thunderstorm updraft. Synthetic stereo presentations of thunderstorm tops can be presented in a non-linear fashion which stretches out the cloud top features. The synthetic stereo presentation is easier for most people to see. We recommend the use of a hybrid system where the viewing is done on the synthetic stereo image and the quantitative measurements are done on the real-stereo pairs.     

On the quasi-biennial oscillation in equatorial stratospheric temperatures and total ozone

The results of a cross-spectral analysis between monthly mean temperatures at 100 mb, 50 mb and 30 mb over the equator and the corresponding monthly mean BUV total ozone at different latitude zones are presented for the period 1970–1977. Significant squared coherences between total ozone and 50 mb equatorial temperatures at 26 months are only found between 5 degrees on each side of the equator, between 45 deg N and 55 deg N and at 45 deg S. At latitudes were the QBO in stratospheric temperature diminishes so does the QBO in total ozone (i.e. close to 35 deg N and 15 deg S). Over subtropical latitudes there is a tendency towards a more biennial oscillation in total ozone (not correlated with the equatorial QBO in stratospheric temperatures) and at 65 deg N and 65 deg S total ozone oscillates at periods greater than the equatorial QBO.     

The sensitivity of the earth's radiation budget to changes in cloudiness

Cloudiness modulates the radiation budget at the top of the Earth-atmosphere system. For radiation balance studies, for climate diagnostic studies, and for climate modeling studies, it is important to know the sensitivity of both the outgoing longwave radiation and the net (absorbed solar minus outgoing longwave) radiation of the system to changes in cloudiness on a global basis. Based on a 45 month series of NOAA satellite scanning radiometer observations, estimates of the global distribution of these sensitivity parameters are obtained.     

Dominance in space — a new means of exercising global power?

Sustained criticism of the strategy of nuclear deterrence and technological developments in the military uses of space suggest that nuclear weapons may soon be replaced by control of outer space as the USA and USSR's primary instrument of global power. This article traces the change in perceptions of nuclear weapons policy and assesses the potential of outer space as a means of control, and the plans of the two superpowers for its exploitation, especially in the military sphere. The consequences for Western Europe of a shift from nuclear to space-based weapons as the primary guarantor of national security are also discussed.     

LIPS III-a solar cell test bed in space

The LIPS III satellite, which was launched into a 1100-km circular orbit of 60° inclination in the spring of 1987, is discussed. LIPS III is a member of the living-plume-shield class of spacecraft, all of which were built around a simple sheet metal plume deflector. The purpose of LIPS III was to provide a testbed for space power sources. An overview of the LIPS III system is given, and the experiments submitted for it, all but one of which were photovoltaic in nature, are described     

Design of nonparametric truncated sequential detectors withparallel linear boundaries

A design method is proposed for a class of nonparametric truncated sequential detectors. These detectors test nonparametric statistics against two parallel linear boundaries with an abrupt truncation at some sample size. The proposed method obtains the asymptotic relative efficiencies (ARE) of these tests with respect to their corresponding fixed-sample-size (FSS) tests in terms of some parameters of the tests. There parameters are then chosen to optimize the ARE. This (asymptotically) optimal set of parameters is used to design the thresholds of the sequential tests. Numerical results are obtained and design examples are presented, using the sum of the signs of the observations as the test statistic. The method can be used for nonparametric sequential detectors and for robust and parametric sequential detectors as well     

An algorithm for detection of moving optical targets

An algorithm is described for detecting moving optical targets against spatially nonstationary Poisson background and noise. The algorithm has applications in optical detection of objects such as meteors, asteroids, and satellites against a stellar background. A maximum-likelihood approach is used which results in reducing interference from stars. It is shown that by choosing a detection threshold to provide a constant false alarm rate, the resulting algorithm is independent of the signal strength of the target. An analysis of this algorithm is presented, showing the probability of detection for several false-alarm rates     

Algol, Beta Lyrae, and W Serpentis: Some new results for three well studied eclipsing binaries

The properties of the eclipsing binaries Algol, Beta Lyrae, and W Serpentis are discussed and new results are presented. The physical properties of the components of Algol are now well determined. High resolution spectroscopy of the H-alpha feature by Richards et al. and by Gillet et al. and spectroscopy of the ultraviolet resonance lines with the International Ultraviolet Explorer satellite reveal hot gas around the BBV primary. Gas flows also have been detected apparently originating from the low mass, cooler secondary component and flowing toward the hotter star through the Lagrangian L1 point. Analysis of 6 years of multi-bandpass photoelectric photometry of Beta Lyrae indicates that systematic changes in light curves occur with a characteristic period of -275 ± 25 days. These changes may arise from pulsations of the B8II star or from changes in the geometry of the disk component. Hitherto unpublished u, v, b, y, and H-alpha index light curves of W Ser are presented and discussed. W Ser is a very complex binary system that undergoes complicated, large changes in its light curves. The physical properties of W Ser are only poorly known, but it probably contains one component at its Roche surface, rapidly transfering matter to a component which is embedded in a thick, opaque disk. In several respects, W Ser resembles an upscale version of a cataclysmic variable binary system.