A Pre-Landing Assessment of Regolith Properties at the InSight Landing Site

This article discusses relevant physical properties of the regolith at the Mars InSight landing site as understood prior to landing of the spacecraft. InSight will land in the northern lowland plains of Mars, close to the equator, where the regolith is estimated to be ≥3--5 m thick. These investigations of physical properties have relied on data collected from Mars orbital measurements, previously collected lander and rover data, results of studies of data and samples from Apollo lunar missions, laboratory measurements on regolith simulants, and theoretical studies. The investigations include changes in properties with depth and temperature. Mechanical properties investigated include density, grain-size distribution, cohesion, and angle of internal friction. Thermophysical properties include thermal inertia, surface emissivity and albedo, thermal conductivity and diffusivity, and specific heat. Regolith elastic properties not only include parameters that control seismic wave velocities in the immediate vicinity of the Insight lander but also coupling of the lander and other potential noise sources to the InSight broadband seismometer. The related properties include Poisson’s ratio, P- and S-wave velocities, Young’s modulus, and seismic attenuation. Finally, mass diffusivity was investigated to estimate gas movements in the regolith driven by atmospheric pressure changes. Physical properties presented here are all to some degree speculative. However, they form a basis for interpretation of the early data to be returned from the InSight mission.Additional co-authors: Nick Teanby and Sharon Keda

Tightly-coupled model aided visual-inertial fusion for quadrotor micro air vehicles

© Springer International Publishing Switzerland 2015. The main contribution of this paper is a tightly-coupled visual-inertial fusion algorithm for simultaneous localisation and mapping (SLAM) for a quadrotor micro aerial vehicle (MAV). Proposed algorithm is based on an extended Kalman filter that uses a platform specific dynamic model to integrate information from an inertial measurement unit (IMU) and a monocular camera on board the MAV. MAV dynamic model exploits the unique characteristics of the quadrotor, making it possible to generate relatively accurate motion predictions. This, together with an undelayed feature initialisation strategy based on inverse depth parametrisation enables more effective feature tracking and reliable visual SLAM with a small number of features even during rapid manoeuvres. Experimental results are presented to demonstrate the effectiveness of the proposed algorithm

The metabolic activity of Mycobacterium tuberculosis, assessed by use of a novel inducible GFP expression system, correlates with its capacity to inhibit phagosomal maturation and acidification in human macrophages

M. tuberculosis generally reside in phagosomes within human macrophages that resist maturation and acidification, but exhibit significant heterogeneity. In this study we have constructed an IPTG inducible-GFP expression system in M. tuberculosis to assess the relationship between the metabolic status of M. tuberculosis and the degree of phagosomal maturation. Using these recombinant bacteria, we have found that, in human macrophages, M. tuberculosis that respond to IPTG with expression of GFP fluorescence, and hence are metabolically active, reside in non-acidified phagosomes that have not fused with Texas Red dextran prelabeled lysosomes. In contrast, M. tuberculosis that fail to express GFP in response to IPTG, and hence are metabolically inactive, reside within acidified phagosomes that have fused with Texas Red dextran labeled lysosomes. These studies demonstrate that metabolic activity of M. tuberculosis correlates strongly with phagosomal maturation and that the inducible GFP expression system is useful for assessing metabolic activity of intracellular M. tuberculosis

Thermal stability of Mo/Si multilayer soft-X-ray mirrors fabricated by electron-beam evaporation

Stock HJ, Kleineberg U, Heidemann B, et al. Thermal stability of Mo/Si multilayer soft-X-ray mirrors fabricated by electron-beam evaporation. Applied Physics A: Materials Science and Processing. 1994;58(4):371-376.Mo/Si multilayers are fabricated by electron-beam evaporation in UHV at different temperatures (30° C, 150° C, 200° C) during deposition. After completion their thermal stability is tested by baking them at temperatures (T bak) between 200° C and 800° C in steps of 50° C or 100° C. After each baking step the multilayers are characterized by small angle CuK[Alpha]-X-ray diffraction. Additionally, the normal incidence soft-X-ray reflectivity for wavelengths between 11 nm and 19 nm is determined after baking at 500° C. Furthermore, the layer structure of the multilayers is investigated by means of Rutherford Backscattering Spectroscopy (RBS) and sputter/Auger Electron Spectroscopy (AES) technique. While the reflectivity turns out to be highest for a deposition temperature of 150° C, the thermal stability of the multilayer increases with deposition temperature. The multilayer deposited at 200° C stands even a 20 min 500° C baking without considerable changes in the reflectivity behaviour