Operations of a spaceflight experiment to investigate plant tropisms

Plants will be an important component in bioregenerative systems for long-term missions to the Moon and Mars. Since gravity is reduced both on the Moon and Mars, studies that identify the basic mechanisms of plant growth and development in altered gravity are required to ensure successful plant production on these space colonization missions. To address these issues, we have developed a project on the International Space Station (ISS) to study the interaction between gravitropism and phototropism in Arabidopsis thaliana. These experiments were termed TROPI (for tropisms) and were performed on the European Modular Cultivation System (EMCS) in 2006. In this paper, we provide an operational summary of TROPI and preliminary results on studies of tropistic curvature of seedlings grown in space. Seed germination in TROPI was lower compared to previous space experiments, and this was likely due to extended storage in hardware for up to 8 months. Video downlinks provided an important quality check on the automated experimental time line that also was monitored with telemetry. Good quality images of seedlings were obtained, but the use of analog video tapes resulted in delays in image processing and analysis procedures. Seedlings that germinated exhibited robust phototropic curvature. Frozen plant samples were returned on three space shuttle missions, and improvements in cold stowage and handing procedures in the second and third missions resulted in quality RNA extracted from the seedlings that was used in subsequent microarray analyses. While the TROPI experiment had technical and logistical difficulties, most of the procedures worked well due to refinement during the project.     

Proton lateral broadening distribution comparisons between GRNTRN,MCNPX, and laboratory beam measurements

Recent developments in NASA’s deterministic High charge (Z) and Energy TRaNsport (HZETRN) code have included lateral broadening of primary ion beams due to small-angle multiple Coulomb scattering, and coupling of the ion-nuclear scattering interactions with energy loss and straggling. This new version of HZETRN is based on Green function methods, called GRNTRN, and is suitable for modeling transport with both space environment and laboratory boundary conditions. Multiple scattering processes are a necessary extension to GRNTRN in order to accurately model ion beam experiments, to simulate the physical and biological-effective radiation dose, and to develop new methods and strategies for light-ion radiation therapy. In this paper we compare GRNTRN simulations of proton lateral broadening distributions with beam measurements taken at Loma Linda University Proton Therapy Facility. The simulated and measured lateral broadening distributions are compared for a 250 MeV proton beam on aluminum, polyethylene, polystyrene, bone substitute, iron, and lead target materials. The GRNTRN results are also compared to simulations from the Monte Carlo MCNPX code for the same projectile-target combinations described above.     

GPS data processing of networks with mixed single- and dual-frequency receivers for deformation monitoring

In order to obtain crustal deformations of higher spatial resolution, existing GPS networks must be densified. This densification can be carried out using single-frequency receivers at moderate costs. However, ionospheric delay handling is required in the data processing. We adapt the Satellite-specific Epoch-differenced Ionospheric Delay model (SEID) for GPS networks with mixed single- and dual-frequency receivers. The SEID model is modified to utilize the observations from the three nearest dual-frequency reference stations in order to avoid contaminations from more remote stations. As data of only three stations are used, an efficient missing data constructing approach with polynomial fitting is implemented to minimize data losses. Data from large scale reference networks extended with single-frequency receivers can now be processed, based on the adapted SEID model. A new data processing scheme is developed in order to make use of existing GPS data processing software packages without any modifications. This processing scheme is evaluated using a sub-network of the German SAPOS network. The results verify that the new scheme provides an efficient way to densify existing GPS networks with single-frequency receivers.     

ASTEX: An in situ exploration mission to two near-Earth asteroids

ASTEX (ASTeroid EXplorer) is a concept study of an in situ exploration mission to two Near-Earth-Asteroids (NEAs), which consists of an orbiting element and two individual lander units. The target candidates have different mineralogical compositions, i.e. one asteroid is chosen to be of “primitive’’ nature, the other to be a fragment of a differentiated asteroid. The main scientific goals of the ASTEX mission are the exploration of the physical, geological, and mineralogical nature of the NEAs. The higher level goal is the provision of information and constraints on the formation and evolution of our planetary system. The study identified realistic mission scenarios, defined the strawman payload as well as the requirements and options for the spacecraft bus including the propulsion system, the landers, the launcher, and assessed and defined the requirements for the mission’s operational ground segment.     

Development of a thin section device for space exploration: Overview and system performance estimates

In this paper we present a conceptual design of a spaceborne instrument for the in situ production of rock thin sections on planetary surfaces. The in situ Automated Rock Thin Section Instrument (IS-ARTS) conceptual design demonstrates that the in situ production of thin sections on a planetary body is a plausible new instrument capability for future planetary exploration. Thin section analysis would reduce much ambiguity in the geological history of a sampled site that is present with instruments currently flown. The technical challenge of producing a thin section device compatible with the spacecraft environment is formidable and has been thought too technically difficult to be practical. Terrestrial thin section preparation requires a skilled petrographist, several preparation instruments that individually exceed typical spacecraft mass and power limits, and consumable materials that are not easily compatible with spaceflight. In two companion papers we present research and development work used to constrain the capabilities of IS-ARTS in the technical space compatible with the spacecraft environment. For the design configuration shown we conclude that a device can be constructed that is capable of 50 sample preparations over a 2 year lifespan with mass, power, and volume constraints compatible with current landed Mars mission configurations. The technical requirements of IS-ARTS (mass, power and number of samples produced) depend strongly on the sample mechanical properties, sample processing rate, the sample size and number of samples to be produced.     

The hemispheric asynchrony of polar faculae during solar cycles 19–22

We investigate the north–south (N–S) asynchrony of the polar faculae and compare it with the hemispheric asynchrony of solar activity at low latitudes. We find that, (1) both the solar activity at high and low latitudes do not synchronously occur in the northern and southern hemispheres, there is phase shifts between the two hemispheres; (2) the N–S asynchrony of the polar faculae is a function of latitudes, implying that the asynchrony of the polar faculae between the two hemispheres is related to the hemispheric asymmetry and latitudinal distribution of the polar faculae.     

Prediction of Boundary Layer Transition Based on Modeling of Laminar Fluctuations Using RANS Approach

This article presents a linear eddy-viscosity turbulence model for predicting bypass and natural transition in boundary layers by using Reynolds-averaged Navier-Stokes (RANS) equations. The model includes three transport equations, separately, to compute laminar kinetic energy, turbulent kinetic energy, and dissipation rate in a flow field. It needs neither correlations of intermittency factors nor knowledge of the transition onset. Two transition tests are carried out: flat plate boundary layer under zero ...     

Aircraft with outboard horizontal stabilizers,history, current status,development potential

The potential of using outboard horizontal stabilizers (OHS) to reduce aircraft drag, and hence improve fuel economy, was investigated historically, experimentally and theoretically. The feasibility of OHS configurations on the basis of the structural stress levels expected was also studied. The findings of the work showed that from simple, low Reynolds number, wind-tunnel tests, at a wing-chord-based Reynolds number of approximately 6×10⁴ and also from theoretical analyses for a higher Reynolds number of 9×10⁶, lift/drag (L/D) value increases in the region of 40–50% for wing and tail surfaces can be expected relative to corresponding values for conventional aircraft. When account is taken of fuselage and tail-support boom drag, the expected overall L/D increase is in the region of 30–35%. The analytical stress-level work showed that contrary to what, on a first thought basis, might be expected, there were no major stress problems. Flight tests at the University of Calgary, and by others elsewhere, employing radio-controlled, powered, model aircraft (i.e. UAVs) showed that aircraft of the OHS type were easily controlled in flight and were stable. An examination was made of additional areas that may contribute yet further to the development of the OHS concept.     

Development of a thin section device for space exploration: Rock cutting mechanism

We have developed a rock cutting mechanism for in situ planetary exploration based on abrasive diamond impregnated wire. Performance characteristics of the rock cutter, including cutting rate on several rock types, cutting surface lifetime, and cut rock surface finish are presented. The rock cutter was developed as part of a broader effort to develop an in situ automated rock thin section (IS-ARTS) instrument. The objective of IS-ARTS was to develop an instrument capable of producing petrographic rock thin sections on a planetary science spacecraft. The rock cutting mechanism may also be useful to other planetary science missions with in situ instruments in which sub-sampling and rock surface preparation are necessary.