CREAM: 70 days of flight from 2 launches in Antarctica

The Cosmic-Ray Energetics And Mass balloon-borne experiment has been launched twice in Antarctica, first in December 2004 and again in December 2005. It circumnavigated the South Pole three times during the first flight, which set a flight duration record of 42 days. A cumulative duration of 70 days within 13 months was achieved when the second flight completed 28 days during two circumnavigations of the Pole on 13 January 2006. Both the science instrument and support systems functioned extremely well, and a total 117 GB of data including 67 million science events were collected during these two flights. Preliminary analysis indicates that the data extend well above 100 TeV and follow reasonable power laws. The payload recovered from the first flight has been refurbished for the third flight in 2007, whereas the payload from the second flight is being refurbished to be ready for the fourth flight in 2008. Each flight will extend the reach of precise cosmic-ray composition measurements to energies not previously possible.     

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.     

Shock interactions in the outer heliosphere

Observations of plasma and magnetic fields by Pioneer 10 and 11 and Voyager 1 and 2 reveal that MHD shocks are an important component of the large-scale solar wind structures in the outer heliosphere. This review discusses recent progress in simulation studies of the nonlinear evolution of the solar wind structures, and in particular concentrates on the theoretical development and applications of the shock interactions model. Various stream propagation models, which do not use the Rankine-Hugoniot relations to calculate the jump conditions at shock crossings, have been used to simulate the essential evolution process of isolated streams and the formation and propagation of corotating and transient shocks. They produce fairly good results in the region up to a few AU. In 1984, the shock interactions model was introduced to study the evolution of large-scale solar wind structures in the region outside 1 AU up to several tens of AU. The model uses the exact Rankine-Hugoniot relations to calculate the shock speed and shock strength at all shock crossings. So that the model can more accurately calculate the shock speeds and the accumulated irreversible shock heating of plasma at several tens of AU. The applications of the shock interactions model are presented in three groups. (a) The first group covers the basic interaction of a shock with the ambient solar wind, the formation and propagation of shock pairs, and the collision and merging of shocks. (b) The second group covers the use of the shock interactions model to simulate the nonlinear evolution of large-scale solar wind structures in the outer heliosphere. These simulation results can provide the detailed evolution process for large-scale solar wind structures in the vast region not directly observed. Two selected studies are reported. (c) Finally, the shock interactions model is applied to studying the heating of the solar wind in the outer heliosphere. The model calculations support shocks being chiefly responsible for the heating of the solar wind plasma in the outer heliosphere at least up to 30 AU.     

Structure and UV absorption of QCCs: carbonaceous dust analogues.

"Quenched Carbonaceous Composites (QCCs)" are carbonaceous interstellar dust analogues synthesized in the laboratory from a hydrocarbon plasma. We produced new types of carbonaceous condensates from the ejecta of plasma with mixtures of methane and hydrogen as source gases. We find that QCC with an absorbance peak at 220 nm is composed of onion-like spherules, and QCCs with an absorbance peak at 230-240 nm are composed of polyhedral particles. The onion-like QCC contains aromatic hydrogen bonds, and it shows the 3.3 and 11.4 micrometers absorption bands. The QCC with an absorbance peak at 230-240 nm is composed of ribbons with bent graphitic layers. This suggests that the carrier of the interstellar 220 nm extinction band might also be an emitter of the interstellar diffuse emission bands.     

Model for induced ionization by galactic cosmic rays in the Earth atmosphere and ionosphere

The ionization profiles produced by galactic cosmic rays in the Earth atmosphere and ionosphere are obtained on the basis of Monte Carlo simulations. Cascade processes in the atmosphere are simulated using CORSIKA 6.52 code with FLUKA 2006 and QGSJET II hadronic interaction subroutines. Proton induced showers are considered using a realistic atmospheric model (US Standard Atmosphere). The energy deposit from different components is taken into account, namely electromagnetic, hadron and muon components. The curvature of the atmosphere is considered in the computer code. On the basis of the computed ionization yield function the ion pair production rate in the atmosphere is obtained for different conditions and locations. The model is applicable to the entire atmosphere, from ground level to upper atmosphere. Several applications of the obtained results are discussed. The Monte Carlo simulation model considers nuclear interactions below the altitude of 35 km. It is compared with analytical–numerical electron production rate model. The latter model which takes into account the electromagnetic interactions above altitudes of 35 km has two main regions of application: above 50 km (thin target model) and between 35 and 50 km (intermediate target model). A good agreement between the CORSIKA results and analytical–numerical model results is found above altitude of 35 km.     

IMF Direction Derived from Cycloid-Like Ion Distributions Observed by Mars Express

Although the Mars Express (MEX) does not carry a magnetometer, it is in principle possible to derive the interplanetary magnetic field (IMF) orientation from the three dimensional velocity distribution of pick-up ions measured by the Ion Mass Analyser (IMA) on board MEX because pick-up ions' orbits, in velocity phase space, are expected to gyrate around the IMF when the IMF is relatively uniform on a scale larger than the proton gyroradius. During bow shock outbound crossings, MEX often observed cycloid distributions (two dimensional partial ring distributions in velocity phase space) of protons in a narrow channel of the IMA detector (only one azimuth for many polar angles). We show two such examples. Three different methods are used to derive the IMF orientation from the observed cycloid distributions. One method is intuitive (intuitive method), while the others derive the minimum variance direction of the velocity vectors for the observed ring ions. These velocity vectors are selected either manually (manual method) or automatically using simple filters (automatic method). While the intuitive method and the manual method provide similar IMF orientations by which the observed cycloid distribution is well arranged into a partial circle (representing gyration) and constant parallel velocity, the automatic method failed to arrange the data to the degree of the manual method, yielding about a 30° offset in the estimated IMF direction. The uncertainty of the derived IMF orientation is strongly affected by the instrument resolution. The source population for these ring distributions is most likely newly ionized hydrogen atoms, which are picked up by the solar wind.     

Structure and NIR feature of QCC: a laboratory analog of carbon dust.

We have produced thin films of quenched carbonaceous composite (QCC) by hydrocarbon plasma deposition. The effect of thermal annealing on QCC has been investigated to understand how QCC, as a laboratory analog of carbon dust, is transformed in the warm environment around evolved stars. Spectroscopic measurements have indicated that, by heating, the proportion of aromatic sp2 CH bonds increases relative to sp3 CH bonds. Carbon onion-like spherules of approximately 10 nm in diameter are found with electron microscopic images after "graphitization" of thermal annealing.     

Novel quaternion Kalman filter

This paper presents a novel Kalman filter (KF) for estimating the attitude-quaternion as well as gyro random drifts from vector measurements. Employing a special manipulation on the measurement equation results in a linear pseudo-measurement equation whose error is state-dependent. Because the quaternion kinematics equation is linear, the combination of the two yields a linear KF that eliminates the usual linearization procedure and is less sensitive to initial estimation errors. General accurate expressions for the covariance matrices of the system state-dependent noises are developed. In addition, an analysis shows how to compute these covariance matrices efficiently. An adaptive version of the filter is also developed to handle modeling errors of the dynamic system noise statistics. Monte-Carlo simulations are carried out that demonstrate the efficiency of both versions of the filter. In the particular case of high initial estimation errors, a typical extended Kalman filter (EKF) fails to converge whereas the proposed filter succeeds.     

Verification of shielding effect by the water-filled materials for space radiation in the International Space Station using passive dosimeters

The dose reduction effects for space radiation by installation of water shielding material (“protective curtain”) of a stack board consisting of the hygienic wipes and towels have been experimentally evaluated in the International Space Station by using passive dosimeters. The averaged water thickness of the protective curtain was 6.3 g/cm². The passive dosimeters consisted of a combination of thermoluminescent detectors (TLDs) and plastic nuclear track detectors (PNTDs). Totally 12 passive dosimeter packages were installed in the Russian Service Module during late 2010. Half of the packages were located at the protective curtain surface and the other half were at the crew cabin wall behind or aside the protective curtain. The mean absorbed dose and dose equivalent rates are measured to be 327 μGy/day and 821 μSv/day for the unprotected packages and 224 μGy/day and 575 μSv/day for the protected packages, respectively. The observed dose reduction rate with protective curtain was found to be 37 ± 7% in dose equivalent, which was consistent with the calculation in the spherical water phantom by PHITS. The contributions due to low and high LET particles were found to be comparable in observed dose reduction rate. The protective curtain would be effective shielding material for not only trapped particles (several 10 MeV) but also for low energy galactic cosmic rays (several 100 MeV/n). The properly utilized protective curtain will effectively reduce the radiation dose for crew living in space station and prolong long-term mission in the future.     

Renal excretion of water in men under hypokinesia and physical exercise with fluid and salt supplementation

It has been suggested that under hypokinesia (reduced number of steps/day) and intensive physical exercise, the intensification of fluid excretion in men is apparently caused as a result of the inability of the body to retain optimum amounts of water. Thus, to evaluate this hypothesis, studies were performed with the use of fluid and sodium chloride (NaCl) supplements on 12 highly trained physically healthy male volunteers aged 19-24 years under 364 days of hypokinesis (HK) and a set of intensive physical exercises (PE). They were divided into two groups with 6 volunteers per group. The first group of subjects were submitted to HK and took daily fluid and salt supplements in very small doses and the second group of volunteers were subjected to intensive PE and fluid-salt supplements. For the simulation of the hypokinetic effect, both groups of subjects were kept under an average of 4000 steps/day. During the prehypokinetic period of 60 days and under the hypokinetic period of 364 days water consumed and eliminated in urine by the men, water content in blood, plasma volume, rate of glomerular filtration, renal blood flow, osmotic concentration of urine and blood were measured. Under HK, the rate of renal excretion of water increased considerably in both groups. The additional fluid and salt intake failed to normalize water balance adequately under HK and PE. It was concluded that negative water balance evidently resulted not from shortage of water in the diet but from the inability of the body to retain optimum amounts of fluid under HK and a set of intensive PEs.