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

Monte Carlo analysis of the influence of dc conditions on the upconversion of generation-recombination noise in semiconductors

Se analiza el método de Monte Carl

Design of a X-band GaN oscillator: from the low frequency noise device characterization and large signal modeling to circuit design

International audienceAlthough GaN technologies were initially developed for solid state source amplifiers, it was recently demonstrated that AlGaN/GaN HEMT transistors were also suitable for low noise applications such as LNA. The frequency synthesis is not yet widely explored for these technologies. In this paper the design of a low phase noise X-Band oscillator is proposed. The low frequency noise performance and the residual phase noise, as well as dynamic S-parameters were carried out on AlGaN/GaN HEMT grown on SiC. A large-signal modeling technique is also presented. The reduced complexity and the good accuracy of our large signal model permits an efficient circuit design, without intensive knowledge of the technological device parameters. These characterization and modeling tools are used for the design of an 1-stage oscillator working at 10 GHz delivering 20dBm

Performances of AlInN/GaN HEMTs for Power Applications at Microwave Frequencies

International audienceWe report a comparative study on AlInN/GaN HEMTs on SiC substrates having four different processes and epitaxies. The outstanding performances of such devices will be explained thanks to intensive characterizations: pulsed-IV, [S]-parameters and load-pull at several frequencies from S to Ku bands. The measured transistors with 250nm gate lengths from different wafers delivered in cw: 10.8 W/mm with 60 % associated PAE at 3,5 GHz, 6.6 W/mm with 39% associated PAE at 10,24 GHz, and 4.2 W/mm with 43 % associated PAE at 18 GHz