Pluto's lower atmosphere and pressure evolution from ground-based stellar occultations, 1988-2016

Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015. Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ~5 and ~380 km (i.e. pressures from ~ 10 μbar to 10 nbar). Results. (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ~0.3 are present at 4–7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ~20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere

Towards a smart camera for monocular SLAM

International audienceIn recent years the interest on monocular-SLAM (Simultaneous Localization and Mapping) has increased, this because nowadays it is possible to find inexpensive, small and light commercial cameras and they provide visual environmental information that can be exploited to create 3D maps and camera pose in an unknown environment. A smart camera that could deliver monocular-SLAM is highly desirable, since it can be the basis of several robotics/drone applications. In this article, we present a new SLAM framework that is robust enough for indoor/outdoor SLAM applications, and at the same time is parallelizable in the context of FPGA architecture design. We introduce new feature-extraction/feature-matching algorithms, suitable for FPGA implementation. We propose an FPGA based sensor-processor architecture where most of the visual processing is carried out in a parallel architecture, and the 3D map construction and camera pose estimation in the processor of a SoC FPGA. An FPGA architecture is lay down and hardware/software partition is discussed. We show that the proposed sensor-processor can deliver high performance under several indoor/outdoor scenarios. CCS Concepts • Computer systems organization ➝ System on a chip

Fission studies by prompt gamma-ray spectrometry

The feasibility of retrieving accurate fission observables with a Ge-detector array around a fissile target placed in a cold neutron beam was tested. In three measurement campaigns performed at ILL with the EXILL setup, 235U and 241Pu targets were placed in the high flux cold neutron beam available at the PF1B neutron guide. Gamma-rays following fission were detected by an array of 16 Ge detectors. In the following study, part of data was analyzed as a proof of principle. A set of yields belonging to the Kr-Ba pair were extracted using a gamma-gamma coincidence technique. Preliminary results were compared to the predictions of two phenomenological models: GEF and FIFRELIN

Fission study by prompt gamma-ray spectrometry

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence 4.0International audienceThe feasibility of retrieving accurate fission observables with a Ge-detector array around a fissile target placed in a cold neutron beam was tested. In three measurement campaigns performed at ILL with the EXILL setup, 235U and 241Pu targets were placed in the high flux cold neutron beam available at the PF1B neutron guide. Gamma-rays following fission were detected by an array of 16 Ge detectors. In the following study, part of data was analyzed as a proof of principle. A set of yields belonging to the Kr-Ba pair were extracted using a gamma-gamma coincidence technique. Preliminary results were compared to the predictions of two phenomenological models: GEF and FIFRELIN