The O/OREOS mission: first science data from the Space Environment Survivability of Living Organisms (SESLO) payload

We report the first telemetered spaceflight science results from the orbiting Space Environment Survivability of Living Organisms (SESLO) experiment, executed by one of the two 10?cm cube-format payloads aboard the 5.5?kg Organism/Organic Exposure to Orbital Stresses (O/OREOS) free-flying nanosatellite. The O/OREOS spacecraft was launched successfully to a 72° inclination, 650?km Earth orbit on 19 November 2010. This satellite provides access to the radiation environment of space in relatively weak regions of Earth's protective magnetosphere as it passes close to the north and south magnetic poles; the total dose rate is about 15 times that in the orbit of the International Space Station. The SESLO experiment measures the long-term survival, germination, and growth responses, including metabolic activity, of Bacillus subtilis spores exposed to the microgravity, ionizing radiation, and heavy-ion bombardment of its high-inclination orbit. Six microwells containing wild-type (168) and six more containing radiation-sensitive mutant (WN1087) strains of dried B. subtilis spores were rehydrated with nutrient medium after 14 days in space to allow the spores to germinate and grow. Similarly, the same distribution of organisms in a different set of microwells was rehydrated with nutrient medium after 97 days in space. The nutrient medium included the redox dye Alamar blue, which changes color in response to cellular metabolic activity. Three-color transmitted intensity measurements of all microwells were telemetered to Earth within days of each of the 48?h growth experiments. We report here on the evaluation and interpretation of these spaceflight data in comparison to delayed-synchronous laboratory ground control experiments.     

Interplanetary Origin of Intense,Superintense and Extreme Geomagnetic Storms

We present a review on the interplanetary causes of intense geomagnetic storms (Dst≤−100 nT), that occurred during solar cycle 23 (1997–2005). It was reported that the most common interplanetary structures leading to the development of intense storms were: magnetic clouds, sheath fields, sheath fields followed by a magnetic cloud and corotating interaction regions at the leading fronts of high speed streams. However, the relative importance of each of those driving structures has been shown to vary with the solar cycle phase. Superintense storms (Dst≤−250 nT) have been also studied in more detail for solar cycle 23, confirming initial studies done about their main interplanetary causes. The storms are associated with magnetic clouds and sheath fields following interplanetary shocks, although they frequently involve consecutive and complex ICME structures. Concerning extreme storms (Dst≤−400 nT), due to the poor statistics of their occurrence during the space era, only some indications about their main interplanetary causes are known. For the most extreme events, we review the Carrington event and also discuss the distribution of historical and space era extreme events in the context of the sunspot and Gleissberg solar activity cycles, highlighting a discussion about the eventual occurrence of more Carrington-type storms.     

Optimum Power Division for Phase-Modulated Deep-Space Communications Links

Optimum power division is required in deep-space communications links to maximize transmission range or data rate and to permit efficient performance of both carrier tracking and data reception functions. A simple, graphical technique has been developed for phase-modulated links to determine the particular set of peak phase deviations, or modulation indexes, which results in an optimum power division between the carrier and any combination of sine-wave and square-wave subcarriers. Whereas previous methods for the selection of modulation indexes generally necessitated either lengthy solutions of simultaneous equations or complex computer programs, the methods developed in this paper involve simplified graphical procedures, using the trigonometric and Bessel function expressions which describe the power balance between carrier and subcarriers. The optimization procedure is a valuable tool for preliminary design analysis and should be of interest to communications-system engineers, The techniques developed here are particularly applicable when subcarriers have wide differences in data rates, since under these conditions, it becomes increasingly difficult to select arbitrarily the proper modulation indexes. Channel optimization is developed for both nominal and worst-case link conditions and examples are presented to demonstrate the techniques involved.     

Hybrid Simulations of Wave Propagation and Ion Cyclotron Heating in the Expanding Solar Wind

We present results from hybrid (particle ions, fluid electrons) simulations of the evolution of Alfvén waves close to the ion cyclotron frequency in the solar wind, which take into account the basic properties of the background solar wind flow, i.e., the spherical expansion and the consequent decrease in magnetic field and cyclotron frequency with increasing distance from the Sun. We follow the evolution of a plasma parcel in a frame of reference moving with the solar wind using a 1D expanding box hybrid model; use of the hybrid model yields a fully self-consistent treatment of the resonant cyclotron wave-particle interaction. This model is related to a previous MHD model (Velli et al. 1992), which allows the use of a simple Cartesian geometry with periodic boundary conditions. The use of stretched expanding coordinates in directions transverse to the mean radial solar wind flow naturally introduces an anisotropic damping effect on velocity and magnetic field. We present results for the case of a single circularly polarized Alfvén wave propagating radially outward. Initially, the wave is below the cyclotron frequency for both the alpha partcles and protons. As the wind expands, the wave frequency (as seen in the solar wind frame) decreases more slowly than the cyclotron frequencies and the wave comes into resonance. With only protons, heating occurs as the wave frequency approaches the proton cyclotron frequency. With both alphas and protons, the alphas, which come into resonance first, are observed to be preferentially heated and accelerated. This revised version was published online in June 2006 with corrections to the Cover Date.     

Forecasting the next major thrust into space

Patterns in societal energy use enable forecasts of the times of future events associated with important human exploration and technology programs. Discovered in 1989, the 56 year energy cycle has previously been linked with many technological, economic, and social parameters. A review of the last 200 years reveals that major human explorations (e.g. polar expeditions), macro-engineering projects (e.g. Panama Canal), and large wars (e.g. World War I) cluster together in time near energy cycle peaks approximately every 56 years. The energy cycle and several other indicators suggest that large-scale human operations in space will begin to appear around 2015. They should culminate in a space spectacular near 2025. Another window of opportunity for space exploration will not open until late in the twenty-first century.     

Implicit plasma simulation

Implicit time integration methods have been used extensively in numerical modelling of slowly varying phenomena in systems that also support rapid variation. Examples include diffusion, hydrodynamics and reaction kinetics. This article discusses implementation of implicit time integration in plasma codes of the “particle-in-cell” family, and the benefits to be gained.     

Petrographic criteria for recognizing certain types of impact spherules in well-preserved precambrian successions

Impact spherule layers in sedimentary successions can open a new window on large impacts to complement the better-known record of terrestrial craters. At least six spherule layers have been found in well-preserved late Archean to Paleoproterozoic strata, and a growing body of geochemical evidence indicates they are impact ejecta. The most distinctive characteristics of these impact spherules are: (1) a predominance of highly spherical grains; (2) the presence of grains with unusual shapes such as teardrops and dumbbells; (3) fibroradial aggregates of K-feldspar crystals nucleated on the edges of spherules; and (4) clear internal spots representing both cement-filled vesicles and replaced glass cores, which, in contrast to the nuclei of ooids and armored lapilli, are not always located in the centers of the spherules. These characteristics permit the reliable differentiation of these impact spherules from spheroidal particles of other origins, such as sedimentary ooids or volcanic accretionary lapilli, often with just a hand lens. However, petrographic identification becomes progressively more difficult as the spherules become smaller or more altered. Moreover, impact spherules in other layers of other ages sometimes have different textures, so the ones described here are not representative of all types of impact spherules. They are provided as a starting point for researchers interested in identifying impact spherule layers. Given the visible record of impacts on the Moon and the much greater mass of the Earth, there should be many more impact spherule layers on Earth than have been discovered to date.