Geoscience for Understanding Habitability in the Solar System and Beyond

Space Science Reviews - This paper reviews habitability conditions for a terrestrial planet from the point of view of geosciences. It addresses how interactions between the interior of a planet or...     

Initial experimental results from the Laboratory Biosphere closed ecological system facility.

An initial experiment in the Laboratory Biosphere facility, Santa Fe, New Mexico, was conducted May-August 2002 using a soil-based system with light levels (at 12 h per day) of 58-mol m-2 d-1. The crop tested was soybean, cultivar Hoyt, which produced an aboveground biomass of 2510 grams. Dynamics of a number of trace gases showed that methane, nitrous oxide, carbon monoxide, and hydrogen gas had initial increases that were substantially reduced in concentration by the end of the experiment. Methane was reduced from 209 ppm to 11 ppm, and nitrous oxide from 5 ppm to 1.4 ppm in the last 40 days of the closure experiment. Ethylene was at elevated levels compared to ambient during the flowering/fruiting phase of the crop. Soil respiration from the 5.37 m2 (1.46 m3) soil component was estimated at 23.4 ppm h-1 or 1.28 g CO2 h-1 or 5.7 g CO2 m-2 d-1. Phytorespiration peaked near the time of fruiting at about 160 ppm h-1. At the height of plant growth, photosynthesis CO2 draw down was as high as 3950 ppm d-1, and averaged 265 ppm h-1 (whole day averages) during lighted hours with a range of 156-390 ppm h-1. During this period, the chamber required injections of CO2 to continue plant growth. Oxygen levels rose along with the injections of carbon dioxide. Upon several occasions, CO2 was allowed to be drawn down to severely limiting levels, bottoming at around 150 ppm. A strong positive correlation (about 0.05 ppm h-1 ppm-1 with r2 about 0.9 for the range 1000-5000 ppm) was observed between atmospheric CO2 concentration and the rate of fixation up to concentrations of around 8800 ppm CO2.     

Selection and hydroponic growth of potato cultivars for bioregenerative life support systems

As part of the ESA-funded MELiSSA program, Ghent University and the Université catholique de Louvain investigated the suitability, growth and development of four potato cultivars in hydroponic culture under controlled conditions with the aim to incorporate such cultivation system in an Environmental Control and Life Support System (ECLSS). Potato plants can fulfill three major functions in an ECLSS in space missions: (a) fixation of CO₂ and production of O₂, (b) production of tubers for human nutrition and (c) production of clean water after condensation of the water vapor released from the plants by transpiration. Four cultivars (Annabelle, Bintje, Desiree and Innovator) were selected and grown hydroponically in nutrient film technique (NFT) gullies in a growth chamber under controlled conditions. The plant growth parameters, tuber harvest parameters and results of tuber nutritional analysis of the four cultivars were compared. The four potato cultivars grew well and all produced tubers. The growth period lasted 127 days for all cultivars except for Desiree which needed 145 days. Annabelle (1.45 kg/m²) and Bintje (1.355 kg/m²) were the best performing of the four cultivars. They also produced two times more tubers than Desiree and Innovator. Innovator produced the biggest tubers (20.95 g/tuber) and Desiree the smallest (7.67 g/tuber). The size of Annabelle and Bintje potatoes were intermediate. Bintje plants produced the highest total biomass in term of DW. The highest non-edible biomass was produced by Desiree, which showed both the highest shoot and root DW. The manual length and width measurements were also used to predict the total tuber mass. The energy values of the tubers remained in the range of the 2010 USDA and Souci-Fachmann-Kraut food composition databases. The amount of Ca determined was slightly reduced compared to the USDA value, but close to the Souci-Fachmann-Kraut value. The concentration of Cu, Zn and P were high compared to both databases.     

Design and application of quadratic correlation filters for target detection

We introduce a method for designing and implementing quadratic correlation filters (QCFs) for shift-invariant target detection in imagery. The QCFs are a quadratic classifier that operates directly on the image data without feature extraction or segmentation. In this sense, the QCFs retain the main advantages of conventional linear correlation filters while offering significant improvements in other respects. Not only is more processing required to detect peaks in the outputs of multiple linear filters, but choosing a winner among them is an error prone task. On the other hand, all channels in a QCF work together to optimize the same performance metric and produce a combined output that leads to considerable simplification of the postprocessing scheme. In addition, QCFs also yield better performance than their linear counterparts for comparable throughput requirements. Two different methods for designing basis functions that optimize the QCF performance criterion are presented. An efficient architecture for implementing QCFs is discussed along with a case study of the proposed approach for detecting targets in LADAR imagery.     

The Effect of Loop Curvature on Coronal Loop Kink Oscillations

We will review analytical and numerical efforts in modelling the influence of curvature on coronal loop oscillations. We will mainly focus our attention on fast kink mode oscillations. A curved slab model will be presented, where it becomes clear that curvature introduces wave leakage into the system, because of changes in the equilibrium. The importance of leakage will be assessed through the use of a slab and cylindrical model where lateral leakage is allowed. A full analytical model for a semi-toroidal loop will be constructed for a system with no leaking waves but with an inhomogeneous layer that introduces damping due to the process of resonant absorption. The model for a semi-toroidal loop will be extended to also include leakage, and will be studied numerically. The numerical results will be compared to the analytical model.     

Modeling Nonstationary Random Processes with an Application to Gyro Drift Rate

The problem of estimating the a priori statistics of a nonstationary process is considered using finite-time averages of experimental data. A model of the form of a linear time-invariant difference equation with a stationary independent random sequence driving function is proposed and investigated. Finite-time averages are calculated and then used in a steepest descent method to determine the coefficients of the difference nce equation. Methods are presented for transforming this model to the statespace pace format necessary for Kalman filtering, and an example is given using actual gyro drift-rate data.     

Optimal observer maneuver for bearings-only tracking

In bearings-only tracking, observer maneuver is critical to ensure observability and to obtain an accurate target localization. Here, optimal control theory is applied to the determination of the course of a constant speed observer that minimizes an accuracy criterion deduced from the Fisher information matrix (FIM). Necessary conditions for optimal maneuver (Euler equations) are established and resolved, partly by analytical means and partly by an iterative numerical procedure. Examples of optimal observer maneuvers are presented and discussed     

Coronal Seismology by Means of Kink Oscillation Overtones

The detection of overtones of coronal loop kink oscillations has been an important advance in the development of coronal seismology. It has significantly increased the potential of coronal seismology and has thus initiated important theoretical and observational improvements. New detections of overtones have been made and a reduction of the error bars has been obtained. The efforts of theoreticians to extend eigenmode studies to more general coronal loop models is no longer a matter of checking the robustness of the model but now also allows for the estimation of certain equilibrium parameters. The frequencies of the detected (longitudinal) overtones are in particular sensitive to changes in the equilibrium properties along the loop, especially the density and the magnetic field expansion. Also, attempts have been made to use the limited longitudinal resolution in combination with the theoretical eigenmodes as an additional seismological tool.     

Atmospheric Science with InSight

In November 2018, for the first time a dedicated geophysical station, the InSight lander, will be deployed on the surface of Mars. Along with the two main geophysical packages, the Seismic Experiment for Interior Structure (SEIS) and the Heat-Flow and Physical Properties Package (HP³), the InSight lander holds a highly sensitive pressure sensor (PS) and the Temperature and Winds for InSight (TWINS) instrument, both of which (along with the InSight FluxGate (IFG) Magnetometer) form the Auxiliary Sensor Payload Suite (APSS). Associated with the RADiometer (RAD) instrument which will measure the surface brightness temperature, and the Instrument Deployment Camera (IDC) which will be used to quantify atmospheric opacity, this will make InSight capable to act as a meteorological station at the surface of Mars. While probing the internal structure of Mars is the primary scientific goal of the mission, atmospheric science remains a key science objective for InSight. InSight has the potential to provide a more continuous and higher-frequency record of pressure, air temperature and winds at the surface of Mars than previous in situ missions. In the paper, key results from multiscale meteorological modeling, from Global Climate Models to Large-Eddy Simulations, are described as a reference for future studies based on the InSight measurements during operations. We summarize the capabilities of InSight for atmospheric observations, from profiling during Entry, Descent and Landing to surface measurements (pressure, temperature, winds, angular momentum), and the plans for how InSight’s sensors will be used during operations, as well as possible synergies with orbital observations. In a dedicated section, we describe the seismic impact of atmospheric phenomena (from the point of view of both “noise” to be decorrelated from the seismic signal and “signal” to provide information on atmospheric processes). We discuss in this framework Planetary Boundary Layer turbulence, with a focus on convective vortices and dust devils, gravity waves (with idealized modeling), and large-scale circulations. Our paper also presents possible new, exploratory, studies with the InSight instrumentation: surface layer scaling and exploration of the Monin-Obukhov model, aeolian surface changes and saltation / lifing studies, and monitoring of secular pressure changes. The InSight mission will be instrumental in broadening the knowledge of the Martian atmosphere, with a unique set of measurements from the surface of Mars.     

High-performance EHA controls using an interior permanent magnetmotor

A controller for a high-performance electrohydrostatic actuator (EHA) using an interior permanent magnet (IPM) synchronous motor to produce servo motion is described. The buried-magnet design of the IPM motor yields desired characteristics such as high efficiency, robust rotor construction, and wide operating speed range. Power converter size is minimized by using insulated-gate bipolar transistor (IGBT) power switches combined with high-voltage integrated circuit (HVIC) gate drivers in phase-leg power modules. Experimental results for the demonstrator motor-controller hardware rated at 12 hp (continuous) are presented confirming the IPM motor drive's performance