A Model of Jupiter’s Current Disk Optimized for Juno and Galileo Magnetic Field Data

Cosmic Research - A distinctive feature of the Jovian magnetosphere is a powerful disklike current system—the current disk. There are several models of the magnetic field of this current...     

Earth-Based Visible and Near-IR Imaging of Mercury

New planned orbiter missions to Mercury have prompted renewed efforts to investigate the surface of Mercury via ground-based remote sensing. While the highest resolution instrumentation optical telescopes (e.g., HST) cannot be used at angular distances close to the Sun, advanced ground-based astronomical techniques and modern analytical and software can be used to obtain the resolved images of the poorly known or unknown part of Mercury. Our observations of the planet presented here were carried out in many observatories at morning and evening elongation of the planet. Stacking the acquired images of the hemisphere of Mercury, which was not observed by the Mariner 10 mission (1974–1975), is presented. Huge features found there change radically the existing hypothesis that the “continental” character of a surface may be attributed to the whole planet. We present the observational method, the data analysis approach, the resulting images and obtained properties of the Mercury’s surface.     

Influence of altered gravity on the cytochemical localization of cytochrome oxidase activity in central and peripheral gravisensory systems in developing cichlid fish.

Cichlid fish larvae were reared from hatching to active free swimming under different gravity conditions: natural environment, increased acceleration in a centrifuge, simulated weightlessness in a clinostat and near weightlessness during space flight. Cytochrome oxidase activity was analyzed semiquantitatively on the ultrastructural level as a marker of regional neuronal activity in a primary, vestibular brainstem nucleus and in gravity receptive epithelia in the inner ear. Our results show, that gravity seems to be positively correlated with cytochrome oxidase activity in the magnocellular nucleus of developing fish brain. In the inner ear the energy metabolism is decreased under microgravity concerning utricle but not saccule. Hypergravity has no effect on cytochrome oxidase activity in sensory inner ear epithelia.     

Heavy ion induced double strand breaks in bacteria and bacteriophages.

DNA damage induced by heavy ions in bacterial cells and bacteriophages such as Bacillus subtilis, E. coli and Bacteriophage T1 were investigated by analyzing the double strand breaks in the chromosomal DNA. This kind of lesion is considered as one of the main reasons for lethal events. To analyze double strand breaks in long molecules of DNA--up to some Mbp in length--the technique of pulse field agarose gel electrophoresis has been used. This allows the detection of one double strand break per genome. Cell lysis and DNA isolation were performed in small agarose blocks directly. This procedure secured minimum DNA destruction by shearing forces. After running a gel, the DNA was stained with ethidium bromide. The light intensity of ethidium bromide fluorescence for both the outcoming (running) DNA and the remaining intact DNA were measured by scanning. The mean number of double strand breaks was calculated by determining the quotient of these intensities. Strand break induction after heavy ion and X-ray irradiation was compared.     

Generation mechanisms of the ELF-ULF waves related to the flux transfer events

Satellite observations near the magnetopause and within the magnetosheath revealed the existence of some structures characterised by specific magnetic field and plasma signatures. They have been called “Flux Transfer Events”. One of the models of FTEs is a reconnected fluxtube, extending from the inner magnetosphere into the magnetosheath. ELF-ULF waves are often observed in together with other FTE's signatures. Wideband emissions are associated with the boundaries of FTEs with characteristic maxima at lower hybrid and ion-cyclotron frequencies. They provide a tool for better timing of the events. These emissions might also be related to the reconnection process. Observations of FTE's by Prognoz-8 satellite are presented in our paper. Wave signatures of the FTEs are described. Various mechanisms of generation of the emissions by instabilities depending on local plasma conditions are discussed along with non-local aspects of such waves. Numerical solutions of the dispersion equation for the typical conditions in FTEs are presented. Possible relation of these waves to the reconnection process are discussed.     

Extrasolar space exploration by a solar sail accelerated via thermal desorption of coating

For extrasolar space exploration it might be very convenient to take advantage of space environmental effects such as solar radiation heating to accelerate a solar sail coated by materials that undergo thermal desorption at a particular temperature. Thermal desorption can provide additional thrust as heating liberates atoms, embedded on the surface of the solar sail. We are considering orbital dynamics of a solar sail coated with materials that undergo thermal desorption at a specific temperature, as a result of heating by solar radiation at a particular heliocentric distance, and focus on two scenarios that only differ in the way the sail approaches the Sun. For each scenario once the perihelion is reached, the sail coat undergoes thermal desorption. When the desorption process ends, the sail then escapes the Solar System having the conventional acceleration due to solar radiation pressure. We study the dependence of a cruise speed of a solar sail on perihelion of the orbit where the solar sail is deployed. The following scenarios are considered and analyzed: (1) Hohmann transfer plus thermal desorption. In this scenario the sail would be carried as a payload to the perihelion with a conventional propulsion system by a Hohmann transfer from Earth’s orbit to an orbit very close to the Sun and then be deployed. Our calculations show that the cruise speed of the solar sail varies from 173?km/s to 325?km/s that corresponds to perihelion 0.3?AU and 0.1 AU, respectively. (2) Elliptical transfer plus Slingshot plus thermal desorption. In this scenario the transfer occurs from Earth’s orbit to Jupiter’s orbit; then a Jupiter’s fly-by leads to the orbit close to the Sun, where the sail is deployed and thermal desorption comes active. In this case the cruise speed of the solar sail varies from 187?km/s to 331?km/s depending on the perihelion of the orbit. Our study analyses and compares the different scenarios in which thermal desorption comes beside traditional propulsion systems for extrasolar space exploration.     

Partially Ionized Plasmas in Astrophysics

Partially ionized plasmas are found across the Universe in many different astrophysical environments. They constitute an essential ingredient of the solar atmosphere, molecular clouds, planetary ionospheres and protoplanetary disks, among other environments, and display a richness of physical effects which are not present in fully ionized plasmas. This review provides an overview of the physics of partially ionized plasmas, including recent advances in different astrophysical areas in which partial ionization plays a fundamental role. We outline outstanding observational and theoretical questions and discuss possible directions for future progress.     

System Design for the Event Horizon Imaging Experiment Using the PECMEO Concept

The concept for space interferometry from Polar or Equatorial Circular Medium Earth Orbits (the PECMEO concept) is a promising way to acquire the image of the “shadow” of the event horizon of Sagittarius A* with an angular resolution of circa 5 microarcseconds. The concept is intended to decrease the size of the main reflector of the instrument to about 3 m using a precise orbit reconstruction based on Global Navigation Satellite System (GNSS) navigation, inter-satellite range and range-rate measurements, and data from the Attitude and Orbit Determination System (AODS). The paper provides the current progress on the definition of the subsystems required for the concept on the basis of simulations, radio regulations, and available technology. The paper proposes the requirement for the localization of the phase centre of the main reflector. The paper provides information about the visibility of GNSS satellites and the needed accuracies of the AODS. The paper proposes the frequency plan for the instrument and its Inter-Satellite Links (ISLs). The concepts for measurement of range and range rate using ISLs (as well as for the data exchange at these ISLs) are presented. The block diagram of the interferometer is described and its sensitivity is estimated. The link budget for both ISLs is given as well as their critical components. The calculated measurement quality factors are given. The paper shows the expected performance of the sub-systems of the interferometer. The requirements for the localization of the main reflectors and the information about the availability of the GNSS satellites are based on the simulations results. The frequency plan is obtained according to the PECMEO concept and taking into account the radio regulations. The existing technology defines the accuracies of the AODS as well as the link budgets and the measurement accuracies for both ISLs and the sensitivity of the instrument. The paper provides input information for the development of the orbit reconstruction filter and the whole PECMEO system.      

Strategies for detection of putative life on Europa

Planned future exploration missions to the Jovian satellite Europa have a strong astrobiological motivation. Characterization of the potential habitability of the liquid water environments, and searching for life signals are the main astrobiological objectives of these missions. To meet these objectives specific strategies and instrumentation are required. Here we discuss some scenarios for the development of Europa potential biospheres. These scenarios are based on assumptions of the life similarity concept and knowledge about terrestrial life in extreme environments. Since the potential habitable environments on Europa are in the interior of the satellite it is not possibly to directly detect life. However, there are processes that link aqueous sub-surface environments with the near-surface environment, such as tectonism or magmatism. Therefore, by analysing endogenous materials that arise from the interior it is possible to make predictions about what is in the sub-surface. We propose some measurements and instrumentation for future missions to detect biosignatures on the upper layers of Europa, including the simple physico-chemical traces of metabolism to complex biomolecules or biostructures. Raman spectroscopy or biosensor technologies are the future for in situ exploration of the Solar System.     

Optimization of the trajectory of the spacecraft insertion into the system of heliocentric orbits

The possibility of the spacecraft insertion into the system of operational heliocentric orbits has been analyzed. It has been proposed to use a system of several operational heliocentric orbits. On each orbit, the spacecraft makes one or more revolutions around the Sun. These orbits are characterized by a relatively small perihelion radius and relatively high inclination, which allows one to investigate the polar regions of the Sun. The transition of the spacecraft from one orbit to another has been performed using an unpowered gravity assist maneuver near Venus and does not require the cruise propulsion operation. Each maneuver transfers the spacecraft into the sequence of operational heliocentric orbits. We have analyzed several systems of operational heliocentric orbits into which the spacecraft can be inserted by means of the considered transportation system with electric propulsion (EP). The mass of the spacecraft delivered to these systems of operational orbits has been estimated.