Optimization of project-ballistic parameters for low earth orbit spacecraft with propulsion systems with energy storage

Optimization of project-ballistic parameters of the spacecraft with propulsion systems with energy accumulation during the orbital transfer between low Earth orbits in the non-central gravitational field of the Earth is considered. The mass model of the spacecraft with an uncontrollable power-limited engine with the energy accumulator is used. The method of the project-ballistic optimization is obtained as an iterative procedure. Energy storage usage efficiency during the orbital transfer between low Earth orbits is estimated.     

Study of the mesosphere using wide-field twilight polarization measurements: Early results beyond the polar circle

This paper discusses the results of early measurements of temperature and dust in the mesosphere on the basis of wide-field twilight sky polarimetry, which began in 2015 in Apatity (North of Russia, 67.6° N, 33.4° E) using the original entire-sky camera. These measurements have been performed for the first time beyond the Polar Circle in the winter and early spring period. The general polarization properties of the twilight sky and the procedure for identifying single scattering are described. The key results of the study include the Boltzmann temperature values at altitudes higher than 70 km and the conclusion on a weak effect of dust on scattering properties of the mesosphere during this period.     

Optimization of measurements of the Earth’s radiation belt particle fluxes

The Earth’s radiation belts discovered at the end of the 1950s have great scientific and practical interest. Their main characteristics in magnetically quiet periods are well known. However, the dynamics of the Earth’s radiation belts during magnetic storms and substorms, particularly the dynamics of relativistic electrons of the outer belt, when Earth’s radiation belt particle fluxes undergo significant time variations, is studied insufficiently. At present, principally new experiments have been performed and planned with the intention to better study the dynamics of the Earth’s radiation belts and to operationally control the space-energy distributions of the Earth’s radiation belt particle fluxes. In this paper, for spacecraft designed to measure the fluxes of electrons and protons of the Earth’s radiation belts at altitudes of 0.5–10000 km, the optimal versions for detector orientation and orbital parameters have been considered and selected.     

Study of the Microphonics for Prospective Space-Based Neutron and Gamma-Ray Detectors and Methods for its Suppression

The results of testing a number of space-based detectors that contain PMTs or high-voltage electrodes for the noise from the microphonics that occurs in the signal path due to external mechanical action have been presented. A method for the vibration isolation of instruments aboard a spacecraft has been proposed to reduce their responsivity to vibrations.     

A Methodology for Computing Link Availability

An efficient and systematic numerical technique is presented for predicting availability of an RF link between a ground station and a communication satellite. This new methodology takes into account the effects of weather and time-varying link geometry caused by satellite motion as well as the customary ground/satellite link parameters. The availability computed under the worst link geometry (5 deg elevation) has been compared with the average availability computed with the new methodology. The results indicate that the traditional worst-case design approach is too pessimistic to provide a realistic design criterion where links operate at K band or above.     

Fate of prebiotic adenine

Equilibrium adsorption isotherm data for the purine base adenine has been obtained on several prebiotically relevant minerals by frontal analysis using water as a mobile phase. Adenine is far displaced toward adsorption on pyrite (FeS2), quartz (SiO2), and pyrrhotite (FeS), but somewhat less for magnetite (Fe3O4) and forsterite (Mg2SiO4). The prebiotic prevalence of these minerals would have allowed them to act as a sink for adenine; removal from the aqueous phase would confer protection from hydrolysis as well, establishing a nonequilibrium thermodynamic framework for increased adenine synthesis. Our results provide evidence that adsorption phenomena may have been critical for the primordial genetic architecture.     

Decentralized reduced-order filters

Continuous and discrete methods of designing simple reduced-order local filters within a large-scale network are suggested. The filters are designed to estimate only the local variables of interest and not the entire state vector. The method has the advantage that one need not know the mathematical models of the subsystems generating the interconnection variables. The order of the filter can be small enough so that there is no computational burden associated with the filter. The disadvantage of the method is that performance is lost by using a reduced-order filter instead of a full-order filter. An example that demonstrates one application in the aerospace industry is presented     

Recent advances in analog signal processing

Analog signal processors which perform convolution, correlation, matched filtering, and Fourier transformation are considered. Specifically, the authors focus on one- and two-dimensional signal processors using charge-coupled-device, surface-acoustic-wave, acoustooptic, and superconductive components. The device performances are compared in terms of parameters such as signal bandwidth, time-bandwidth product, and dynamic range. These analog components are compared with existing and planned digital processor designs. Potential applications are highlighted in wideband spread-spectrum packet-radio communication, radar range-Doppler imaging, wideband compressive receivers, and low-bit-rate image-coding systems