Simulation of DC spacecraft power systems

A modular state-variable approach is presented for DC spacecraft power system modeling and simulation. Each modular component is treated as a multiport network, and a state model is written with the port voltages as the inputs. The state model of a component is solved independently of the other components, using its state transition matrix. The state variables of each component are updated, assuming that the inputs are constant. Network analysis principles are then utilized to calculate the component inputs     

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     

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.     

Highly variable X-ray emitting objects in the Rho Oph dark cloud

The Rho Ophiuchi dark cloud region has been the subject of an extensive guest investigation using the $\text{Einstein}$ Observatory. The set of observations comprise 14 IPC fields and 3 HRI fields. The densest part of the cloud has been observed 6 times. Forty seven sources were detected at a level > 3.5 σ and twenty more above 2 σ. The majority of these sources have optical, IR, or even radio continuum counterparts; nine are identified with known T Tauri stars, while several others are identified with stars showing H α in emission. All show a high degree of time variability; flux variations reach factors of 5 in a few hours, or 25 in a day. Apparent luminosities are in the range 10(30) – 10(31)(1) erg.s^?1. The possibility that the X-ray variability is due to flares is examined. If this interpretation is correct, one source has been the seat of the largest stellar flare ever recorded in X rays [L_x = 10(32) erg.s^?1, E_x ?10(36) ergs^-].     

Ambiguity Resolution for Satellite Doppler Positioning Systems

The implementation of satellite-based Doppler positioning systems frequently requires the recovery of transmitter position from a single pass of Doppler data. The least-squares approach to the problem yieds conjugate solutions on either side of the satellite subtrack. It is important to develop a procedure for choosing the proper solution which is correct in a high percentage of cases. A test for ambiguity resolution which is the most powerful in the sense that it maximizes the probability of a correct decision is derived. When systematic error sources are properly included in the least-squares reduction process to yield an optimal solution the test reduces to choosing the solution which provides the smaller valuation of the least-squares loss function. When systematic error sources are ignored in the least-squares reduction, the most powerful test is a quadratic form compasison with the weighting matrix of the quadratic form obtained by computing the pseudoinverse of a reduced-rank square matrix. A formula for computing the power of the most powerful test is provided. Numerical examples are included in which the power of the test is computed for situations that are relevant to the design of a satellite-aided search and rescue system.     

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.     

Results on thermal conditions of crystal growth processes in space and on earth

A special measurement technique allows to determine the stationary and dynamic temperature profiles, acting on a material sample during a Bridgman crystal growth process. It turns out that the thermal field of the furnaces at the place of the sample is modified by a number of device-related factors and by regular correlations. The investigations refer to the execution of experiments in the field of materials sciences in space in furnaces on board Salyut-stations.     

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.     

Experiences of the GDR in space sciences and technology

Following a historical review of the first activities of GDR scientists in the fields of space research, especially on astronomical and geodetical satellite-observations and in atmospheric and magnetospheric research, the growing scientific and increasingly efficient technological and economic benefits of the cooperation of the Academy of sciences and other scientific and technological institutions of the GDR within the Intercosmos-programme are described. Especially, the experiences in connection with remote sensing, of the cooperation with countries as Cuba and the Peoples Republic of Vietnam and of the common USSR - GDR manned spaceflight are discussed under the viewpoint of the mutual interests of developing and developed countries in the fields of space science and technology.