The Dynamic Albedo of Neutrons (DAN) experiment for NASA's 2009 Mars Science Laboratory

We present a summary of the physical principles and design of the Dynamic Albedo of Neutrons (DAN) instrument onboard NASA's 2009 Mars Science Laboratory (MSL) mission. The DAN instrument will use the method of neutron-neutron activation analysis in a space application to study the abundance and depth distribution of water in the martian subsurface along the path of the MSL rover.     

The Scanning Sky Monitor (SSM) on ASTROSAT

The Scanning Sky Monitor is one of the experiments onboard the ASTROSAT, an Indian multiwavelength astronomy satellite mission. This experiment will detect and monitor X-ray transients in the energy band 2–10 keV. It is similar in design to the ASM on RXTE. It consists of position-sensitive proportional counters with one-dimensional mask. We describe the configuration of the experiment. We also discuss some of the results obtained using a detector which has already been fabricated and tested in our laboratory.     

Sodium and potassium uptake of Ulva – Application of marine macro-algae for space agriculture

The treatment of sodium, Na, and potassium, K, presents a challenge in space agriculture material recycling, as humans require Na and plants cannot grow at high Na concentrations. Hence, we are proposing the use of marine macro-algae to harvest K and other minerals from composted human waste. Ulva was selected for this feasibility study, since it tolerates a wide range of salinity levels. Growth capability of Ulva was examined under various total salinity levels and proportions of Na and K in the incubation medium. A homeostatic feature of Ulva was found in its intra-cellular concentration of Na and K, and in the intra-cellular ratio between Na and K (at 0.58 ± 0.30, lower than that of human metabolic waste). Intracellular concentration of K in Ulva is 20 times higher than seawater. Because of these characteristics, Ulva is a good candidate species for space agriculture.     

Ionospheric wave processes during HF heating experiments

Effects of ionospheric modification produced by powerful high frequency radio waves are studied using the method of field-aligned scattering of diagnostic HF radio signals. Observations of scattered HF signals have been made by the Doppler spectrum method. Analysis of the experimental data shows the appearance of quasiperiodic variations in Doppler frequency shift f_d, with periods 30–60 s during the heating cycles. Powerful HF waves are assumed to excite the Alfvén resonator generating oscillations of the magnetic field lines in the heated region and giving rise to f_d artificial variations and magnetic pulsations. In the case of continuous action of the powerful HF transmitter ionospheric waves are sometimes observed with periods 12–25 min, typical of medium-scale travelling ionospheric disturbances.     

Occurrence rate of SAR arcs during the 23rd solar activity cycle

The occurrence rate of SAR arcs during 1997–2007 has been analyzed based on the photometric observations at the Yakutsk meridian (Maimaga station, corrected geomagnetic coordinates: 57°N, 200°E). SAR arcs appeared in 114 cases (∼500 h) during ∼370 nights of observations (∼3170 h). The occurrence frequency of SAR arcs increases to 27% during the growth phase of solar activity and has a clearly defined maximum at a decline of cycle 23. The SAR arc registration probability corresponds to the variations in geomagnetic activity in this solar cycle. The dates, intervals of UT, and geomagnetic latitudes of SAR arc observations at the Yakutsk meridian are presented.     

DORIS geodesy: A dynamic determination of geocentre location

Geoscience Australia contributed a multi-satellite, multi-year weekly time series to the International DORIS Service combined submission for the construction of International Terrestrial Reference Frame 2008 (ITRF2008). This contributing solution was extended to a study of the capability of DORIS to dynamically estimate the variation in the geocentre location. Two solutions, comprising different constraint configurations of the tracking network, were undertaken. The respective DORIS satellite orbit solutions (SPOT-2, SPOT-4, SPOT-5 and Envisat) were verified and validated by comparison with those produced at the Goddard Space Flight Center (GSFC), DORIS Analysis Centre, for computational consistency and standards. In addition, in the case of Envisat, the trajectories from the GA determined SLR and DORIS orbits were compared. The results for weekly dynamic geocentre estimates from the two constraint configurations were benchmarked against the geometric geocentre estimates from the IDS-2 combined solution. This established that DORIS is capable of determining the dynamic geocentre variation by estimating the degree one spherical harmonic coefficients of the Earth’s gravity potential. It was established that constrained configurations produced similar results for the geocentre location and consequently similar annual amplitudes. For the minimally constrained configuration Greenbelt–Kitab, the mean of the uncertainties of the geocentre location were 2.3, 2.3 and 7.6 mm and RMS of the mean uncertainties were 1.9, 1.2 and 3.5 mm for the X, Y and Z components, respectively. For GA_IDS-2_Datum constrained configuration, the mean of the uncertainties of the geocentre location were 1.7, 1.7 and 6.2 mm and RMS of the mean uncertainties were 0.9, 0.7 and 2.9 mm for the X, Y and Z components, respectively. The mean of the differences of the two DORIS dynamic geocentre solutions with respect to the IDS-2 combination were 1.6, 4.0 and 5.1 mm with an RMS of the mean 21.2, 14.0 and 31.5 mm for the Greenbelt–Kitab configuration and 4.1, 3.9 and 4.3 mm with an RMS 8.1, 9.0 and 28.6 mm for the GA_IDS-2_Datum constraint configuration. The annual amplitudes for each component were estimated to be 5.3, 10.8 and 11.0 mm for the Greenbelt–Kitab configuration and 5.3, 9.3 and 9.4 mm for the GA_IDS-2_Datum constraint configuration. The two DORIS determined dynamic geocentre solutions were compared to the SLR determined dynamic solution (which was determined from the same process of the GA contribution to the ITRF2008 ILRS combination) gave mean differences of 3.3, −4.7 and 2.5 mm with an RMS of 20.7, 17.5 and 28.0 mm for the X, Y and Z components, respectively for the Greenbelt–Kitab configuration and 1.1, −5.4 and 4.4 mm with an RMS of 9.7, 13.3 and 24.9 mm for the GA_IDS-2_Datum configuration. The larger variability is reflected in the respective amplitudes. As a comparison, the annual amplitudes of the SLR determined dynamic geocentre are 0.9, 1.0 and 6.8 mm in the X, Y and Z components. The results from this study indicate that there is potential to achieve precise dynamically determined geocentre from DORIS.     

Relative amplitude of the total electron content variations depending on geomagnetic activity

We developed a method of estimation of a relative amplitude dI/I of the total electron content (TEC) variations in the ionosphere as deduced from the data of the global GPS receivers network. To obtain statistically significant results we picked out three latitudinal belts provided in the Internet by the maximum number of GPS sites. They are high-latitudinal belt (50–80°N, 200–300°E; 59 sites), mid latitude belt (20–50°N, 200–300°E; 817 sites), and equatorial belt (±20°N, 0–360°E; 76 sites). The results of the analysis of the diurnal and latitudinal dependencies of dI/I and dI/I distribution probability for 52 days with different levels of geomagnetic activity are presented. It was found that on average the relative amplitude of the TEC variations varies within the range 0–10% proportionally to the value of the K_p geomagnetic index. In quiet conditions the relative amplitude dI/I of the TEC variations at night significantly exceeds the daytime relative amplitude. At high levels of magnetic field disturbances, the geomagnetic control of the amplitude of TEC variations at high and middle latitudes is much more significant than the regular diurnal variations. At the equatorial belt, on average, the amplitude of TEC variations in quiet and disturbed periods almost does not differ. The obtained results may be useful for development of the theory of ionospheric irregularities.     

Investigation into impact of tropical cyclones on the ionosphere using GPS sounding and NCEP/NCAR Reanalysis data

Ionospheric response to tropical cyclones (TCs) was estimated experimentally on the example of three powerful cyclones – KATRINA (23–31 August 2005), RITA (18–26 September 2005), and WILMA (15–25 October 2005). These TCs were active near the USA Atlantic coast. Investigation was based on Total Electron Content (TEC) data from the international network of two-frequency ground-based GPS receivers and the NCEP/NCAR Reanalysis data. We studied the spatial–temporal dynamics of wave TEC disturbances over two periods of ranges (02–20 min and 20–60 min). To select the ionospheric disturbances which were most likely to be associated with the cyclones, maps of TEC disturbances were compared with those of meteorological parameters.     

Modelling of genetically engineered microorganisms introduction in closed artificial microcosms.

The possibility of introducing genetically engineered microorganisms (GEM) into simple biotic cycles of laboratory water microcosms was investigated. The survival of the recombinant strain Escherichia coli Z905 (Apr, Lux+) in microcosms depends on the type of model ecosystems. During the absence of algae blooming in the model ecosystem, the part of plasmid-containing cells E. coli decreased fast, and the structure of the plasmid was also modified. In conditions of algae blooming (Ankistrodesmus sp.) an almost total maintenance of plasmid-containing cells was observed in E. coli population. A mathematics model of GEM's behavior in water ecosystems with different level of complexity has been formulated. Mechanisms causing the difference in luminescent exhibition of different species are discussed, and attempts are made to forecast the GEM's behavior in water ecosystems.     

Charge exchange lifetimes for ring current ions

In applying the charge exchange mechanism to ion phenomena within the Earth's magnetosphere it is critical to the proper interpretation of observations that the charge exchange lifetimes for the ions be known as accurately as possible. Various new results have been published which significantly modify the charge exchange lifetimes which have been used in space physics research during the past decade and a half. Some of the newer results have been used in the application of the charge exchange decay mechanism but the use has been limited and for the most part incomplete. The neutral hydrogen density distribution now yields lifetimes which are shorter than previously calculated, while the functional dependence of the lifetimes on pitch angle provides for slower decay for ions mirroring off the geomagnetic equator. This review coalesces and summarizes the latest and best measurements of the physical quantities involved in the complete calculation of the charge exchange lifetime of the mirroring magnetospheric ions.