The Solution of Some Problems of Optimizing the Processes of a Flexible Correction of Motion of Satellite Systems: I

The first of a series of problems of the optimization of correction of satellite systems, moving over near-circular orbits, is considered. The correction is accomplished by means of low-thrust engines and is supposed to be flexible, where only the parameters of the relative motion of satellites must be corrected. The problem has a large dimension, but is invariant with respect to renumbering of satellites. This allows us to decompose the problem, i.e., to find new variables, linearly dependent on old ones, in which the problem breaks down into a series of independent subproblems of low dimension. The decomposition is accomplished by means of the technique [1] based on the theory of linear representations of groups.     

Bubble detector characterization for space radiation

In light of the importance of the neutron contribution to the dose equivalent received by space workers in the near-Earth radiation environment, there is an increasing need for a personal dosimeter that is passive in nature and able to respond to this neutron field in real time. Recent Canadian technology has led to the development of a bubble detector, which is sensitive to neutrons, but insensitive to low linear energy transfer (LET) radiation. By changing the composition of the bubble detector fluid (or “superheat”), the detectors can be fabricated to respond to different types of radiation. This paper describes a preliminary ground-based research effort to better characterize the bubble detectors of different compositions at various charged-particle accelerator facilities, which are capable of simulating the space radiation field.     

Raman imagery: a new approach to assess the geochemical maturity and biogenicity of permineralized precambrian fossils

Laser-Raman imagery is a non-intrusive, non-destructive analytical technique, recently introduced to Precambrian paleobiology, that can be used to demonstrate a one-to-one spatial correlation between the optically discernible morphology and kerogenous composition of permineralized fossil microorganisms. Made possible by the submicron-scale resolution of the technique and its high sensitivity to the Raman signal of carbonaceous matter, such analyses can be used to determine the chemical-structural characteristics of organic-walled microfossils and associated sapropelic carbonaceous matter in acid-resistant residues and petrographic thin sections. Here we use this technique to analyze kerogenous microscopic fossils and associated carbonaceous sapropel permineralized in 22 unmetamorphosed or little-metamorphosed fine-grained chert units ranging from approximately 400 to approximately 2,100 Ma old. The lineshapes of the Raman spectra acquired vary systematically with five indices of organic geochemical maturation: (1) the mineral-based metamorphic grade of the fossil-bearing units; (2) the fidelity of preservation of the fossils studied; (3) the color of the organic matter analyzed; and both the (4) H/C and (5) N/C ratios measured in particulate kerogens isolated from bulk samples of the fossil-bearing cherts. Deconvolution of relevant spectra shows that those of relatively well-preserved permineralized kerogens analyzed in situ exhibit a distinctive set of Raman bands that are identifiable also in hydrated organic-walled microfossils and particulate carbonaceous matter freed from the cherts by acid maceration. These distinctive Raman bands, however, become indeterminate upon dehydration of such specimens. To compare quantitatively the variations observed among the spectra measured, we introduce the Raman Index of Preservation, an approximate measure of the geochemical maturity of the kerogens studied that is consistent both with the five indices of organic geochemical alteration and with spectra acquired from fossils experimentally heated under controlled laboratory conditions. The results reported provide new insight into the chemical-structural characteristics of ancient carbonaceous matter, the physicochemical changes that accompany organic geochemical maturation, and a new criterion to be added to the suite of evidence by which to evaluate the origin of minute fossil-like objects of possible but uncertain biogenicity.     

Surreal estate: addressing the issue of ‘Immovable Property Rights on the Moon’

At a time when scientific and commercial interest in the Moon is being reinvigorated it is becoming fashionable for ordinary individuals to ‘buy’ plots on the lunar surface, with the ‘vendors’ arguing that an absence of specific prohibition of individual private activity in space makes such action legal. It is therefore time for the legal community to address this situation by investigating just how legal such activity is—and bringing their findings to the attention of governments. This can be done through an examination of the relationship between national law and international space law, of the provisions of international space law—especially Article 2 of the Outer Space Treaty—and by answering any claims to private ownership of immovable property. Aside from the fact that individuals appear to be being duped, the pursuit of property claims on the Moon could impede future activities aimed at benefiting society.     

On the breakdown of wave fronts of characteristics in an ideal dissociating gas

Using the method of characteristics, the problem of breaking or non-breaking of waves is studied in a plane cylindrically or spherically symmetric flow of an ideal dissociating gas. It is investigated as to how the effects of dissociation and that of the wave front curvature influence the breaking or non-breaking of waves. In a symmetrical converging gas motion a remarkable difference between the behaviours of cylindrical and spherical waves is discovered.     

Economy of modular low-technology launch vehicles

The paper comprises an assessment of the design and the economics of so-called “low-cost” simple modular launch vehicles. It is shown that the performance is very marginal and that the cost per launch cannot compete with technically more advanced fully reusable vehicles. Especially a private-funded development cannot be amortized economically in case of an expendable launch vehicle.     

Energy Spectrum of Galactic 10–100 MeV Protons in Quiet Sun Periods

The dynamics of the proton energy spectrum during the solar cycle is studied. The spectra were determined by 1–100 MeV particle fluxes measured by different instruments mounted aboard the Earth's IMP-8 satellite for more than one hundred quiet-time intervals in the period between 1974 and 1991. The galactic branch of the spectra (E _p > 10 MeV) constructed for every quiet interval was fitted by a power law function, J =CE . The theory predicts that in the 1–100 MeV energy range, where the adiabatic cooling of particles is dominant, = 1, while we have derived a double-peak distribution. The main maximum has the mean value = 1.35. The mean value of the second, much weaker maximum, is = 0.95. Within the main maximum, values are distributed in accordance with the Gaussian law with a standard deviation D/ = 0.12. The substantial difference of from unity requires the elaboration of a new model of modulation processes in the inner heliosphere. The values corresponding to the second maximum show that modulation processes correspond sometimes to theoretical conceptions. It is shown that correlates weakly with parameters A and describing the solar branch of the spectrum (J(E) = AE ^–). At the same time, a more significant correlation is observed between and the solar activity index, R _z, the counting rate of the Deep River neutron monitor, and the energy value in the minimum of the energy spectrum flux, E _min.     

Production of neutrons from interactions of GCR-like particles

In order to help assess the risk to astronauts due to the long-term exposure to the natural radiation environment in space, an understanding of how the primary radiation field is changed when passing through shielding and tissue materials must be obtained. One important aspect of the change in the primary radiation field after passing through shielding materials is the production of secondary particles from the breakup of the primary. Neutrons are an important component of the secondary particle field due to their relatively high biological weighting factors, and due to their relative abundance, especially behind thick shielding scenarios. Because of the complexity of the problem, the estimation of the risk from exposure to the secondary neutron field must be handled using calculational techniques. However, those calculations will need an extensive set of neutron cross section and thicktarget neutron yield data in order to make an accurate assessment of the risk. In this paper we briefly survey the existing neutron-production data sets that are applicable to the space radiation transport problem, and we point out how neutron production from protons is different than neutron production from heavy ions. We also make comparisons of one the heavy-ion data sets with Boltzmann-Uehling-Uhlenbeck (BUU) calculations.     

Radial velocity search for low mass companions of nearby stars

The detection of substellar companions of nearby stars is very difficult, because these objects are very faint and are located close to their bright parent stars. One way to attack this problem is to look for small periodic motion of the bright star, induced by the gravitational attraction exerted by the unseen small companion. Over the past decade stellar spectroscopy has been used by a few teams to monitor the radial velocities of several samples of stars, with a threshold for detection of companions well below the substellar limit of about 0.08 M. So far, only a few possible spectroscopic binaries have been identified where the unseen companions might be substellar.Recently, radio observers discovered that the millisecond pulsar PSR B1257+12 displays periodic variations in the pulse arrival times, indicating the existence of at least three unseen companions in circular orbits around the pulsar. This is the first convincing case for an extra-solar planetary system. This discovery suggests that planetary systems can form in very different situations, and therefore may prove to be common.