Development and testing of a pyro-driven launcher for harpoon-based comet sample acquisition

The CORSAIR (COmet Rendezvous, Sample Acquisition, Investigation, and Return) mission is a proposal for the fourth NASA New Frontiers program. It belongs to the Comet Surface Sample Return mission theme which focuses on acquiring and returning to Earth a macroscopic sample from the surface of a comet nucleus. CORSAIR uses a harpoon-based Sample Acquisition System (SAS) with the spacecraft hovering several meters above the comet surface. This stand-off strategy overcomes disadvantages of systems using drills or shovels. Since comets are low gravity objects, these techniques would require anchoring before sampling, which is not necessary here. Moreover, the harpoon-based system allows for acquiring several samples from different locations on the comet maximizing the scientifc output of the mission. Each SAS assembly consists of a pyro-driven launcher, a Sample Acquisition and Retrieval Projectile (SARP) and a retraction system using a deployable composite boom structure. In order to collect enough cometary material, the launcher has to provide the required kinetic energy to the SARP. Due to high energy densities, pyrotechnically actuated devices ultimately reduce the overall system mass and dimensions. Here, an overview of the development, design and testing of the launcher is given. Furthermore, the launcher theory is introduced explaining the entire reaction chain: initiation -> gas dynamics -> SARP motion

Morphological and electrical control of fullerene dimerization determines organic photovoltaic stability

Fullerene dimerization has been linked to short circuit current (Jsc) losses in organic solar cells comprised of certain polymer–fullerene systems. We investigate several polymer–fullerene systems, which present Jsc loss to varying degrees, in order to determine under which conditions dimerization occurs. By reintroducing dimers into fresh devices, we confirm that the photo-induced dimers are indeed the origin of the Jsc loss. We find that both film morphology and electrical bias affect the photodimerization process and thus the associated loss of Jsc. In plain fullerene films, a higher degree of crystallinity can inhibit the dimerization reaction, as observed by high performance liquid chromatography (HPLC) measurements. In blend films, the amount of dimerization depends on the degree of mixing between polymer and fullerene. For highly mixed systems with very amorphous polymers, no dimerization is observed. In solar cells with pure polymer and fullerene domains, we tune the fullerene morphology from amorphous to crystalline by thermal annealing. Similar to neat fullerene films, we observe improved light stability for devices with crystalline fullerene domains. Changing the operating conditions of the investigated solar cells from Voc to Jsc also significantly reduces the amount of dimerization-related Jsc loss; HPLC analysis of the active layer shows that more dimers are formed if the cell is held at Voc instead of Jsc. The effect of bias on dimerization, as well as a clear correlation between PL quenching and reduced dimerization upon addition of small amounts of an amorphous polymer into PC60BM films, suggests a reaction mechanism via excitons

Planetary Defense Ground Zero: MASCOT's View on the Rocks - an Update between First Images and Sample Return

At 01:57:20 UTC on October 3rd, 2018, after 3½ years of cruise aboard the JAXA spacecraft HAYABUSA2 and about 3 months in the vicinity of its target, the MASCOT lander was separated successfully by from an altitude of 41 m. After a free-fall of only ~5m51s MASCOT made first contact with C-type near-Earth and potentially hazardous asteroid (162173) Ryugu, by hitting a big boulder. MASCOT then bounced for ~11m3s, in the process already gathering valuable information on mechanical properties of the surface before it came to rest. It was able to perform science measurements at 3 different locations on the surface of Ryugu and took many images of its spectacular pitch-black landscape. MASCOT’s payload suite was designed to investigate the fine-scale structure, multispectral reflectance, thermal characteristics and magnetic properties of the surface. Somewhat unexpectedly, MASCOT encountered very rugged terrain littered with large surface boulders. Observing in-situ, it confirmed the absence of fine particles and dust as already implied by the remote sensing instruments aboard the HAYABUSA2 spacecraft. After some 17h of operations, MASCOT‘s mission ended with the last communication contact as it followed Ryugu’s rotation beyond the horizon as seen from HAYABUSA2. Soon after, its primary battery was depleted. We present a broad overview of the recent scientific results of the MASCOT mission from separation through descent, landing and in-situ investigations on Ryugu until the end of its operation and relate them to the needs of planetary defense interactions with asteroids. We also recall the agile, responsive and sometimes serendipitous creation of MASCOT, the two-year rush of building and delivering it to JAXA’s HAYABUSA2 spacecraft in time for launch, and the four years of in-flight operations and on-ground testing to make the most of the brief on-surface mission

Deep Learning for Ultrasound Speed-of-Sound Reconstruction: Impacts of Training Data Diversity on Stability and Robustness

Ultrasound b-mode imaging is a qualitative approach and diagnostic quality strongly depends on operators' training and experience. Quantitative approaches can provide information about tissue properties; therefore, can be used for identifying various tissue types, e.g., speed-of-sound in the tissue can be used as a biomarker for tissue malignancy, especially in breast imaging. Recent studies showed the possibility of speed-of-sound reconstruction using deep neural networks that are fully trained on simulated data. However, because of the ever present domain shift between simulated and measured data, the stability and performance of these models in real setups are still under debate. In this study, we investigated the impacts of training data diversity on the robustness of these networks by using multiple kinds of geometrical and natural simulated phantom structures. On the simulated data, we investigated the performance of the networks on out-of-domain echogenicity, geometries, and in the presence of noise. We further inspected the stability of employing such tissue modeling in a real data acquisition setup. We demonstrated that training the network with a joint set of datasets including both geometrical and natural tissue models improves the stability of the predicted speed-of-sound values both on simulated and measured data.Comment: 32 pages, 17 figures, submitted to the Journal of Machine Learning for Biomedical Imaging (MELBA

Monitoring fluorescent calcium signals in neural cells with organic photodetectors

International audienceWe demonstrate the use of organic photodetectors for monitoring fluorescent calcium signals as a measure of functional aspects of neural circuits, in vitro and ex vivo

Stress-enhanced opioid self-administration in healthy men: A randomized controlled experimental medicine study

Men are disproportionately likely to develop opioid use disorder, yet the mechanisms of addiction risk in men and women remain poorly understood. Preclinical, epidemiological and clinical studies converge upon stress as a key risk factor. To determine the mechanisms through which stress alters abuse liability, we measured opioid self-administration after acute stress induction in healthy men and women. Sixty-three healthy participants (31 men) completed four sessions in this repeated-measures, double-blind placebo-controlled randomized study. Social stress or a neutral control state was induced before injection of oxycodone (3.1mg/70kg) or saline. The primary outcome was amount of additional oxycodone obtained in an effortful self-administration task (0-125% of the sampling dose effect). The resulting dose was administered ~40 minutes later. Subjective, autonomic and endocrine responses were collected throughout sessions. Data were analyzed using Hierarchical Bayesian regressions. Pre-exposure to stress increased oxycodone self-administration by 5 percentage points (95% credible interval, 1 to 10, Posterior probability (Pr) > 0.99), but with a robust sex difference (16 percentage points; 95% credible interval, 7 to 24; Pr > 0.99). Stress induction only increased self-administration in men, although women showed higher stress responses. In both sexes, oxycodone induced drug high but did not improve mood or cause clear stress relief. We found no evidence that stress-enhanced drug wanting was related to stress relief or drug liking in men or women. By demonstrating a robust sex difference in stress-enhanced opioid self-administration, the study unveils a putative mechanism for men’s higher vulnerability to opioid addiction

Development and testing of a pyro-driven launcher for harpoon-based comet sample acquisition

The CORSAIR (COmet Rendezvous, Sample Acquisition, Investigation, and Return) mission was a proposal for the NASA New Frontiers program. It belongs to the Comet Surface Sample Return mission theme which focuses on acquiring and returning to Earth a macroscopic sample from the surface of a comet nucleus. CORSAIR uses a harpoon-based Sample Acquisition System (SAS) with the spacecraft hovering several meters above the comet surface. This stand-off strategy overcomes disadvantages of other systems such as drills. Since comets are low gravity objects, those techniques would require anchoring before sampling, which is not necessary here. Moreover, the harpoon-based system allows for acquiring several samples from different locations on the comet maximizing the scientific output of the mission. Each SAS assembly consists of a pyro-driven launcher, a Sample Acquisition and Retrieval Projectile (SARP) and a retraction system using a deployable composite boom structure. In order to collect enough cometary material, the launcher has to provide the required kinetic energy to the SARP. Due to high energy densities, pyrotechnically actuated devices ultimately reduce the overall system mass and dimensions. First, the scientific and technological background of the CORSAIR mission is explained. Then, an overview of the development, design and testing of the launcher is given. Finally, the launcher theory is introduced explaining the entire reaction chain: initiation -> gas -> dynamics -> SARP motion

The MMX Rover: Performing in-situ Surface Investigations on Phobos

Abstract The Japanese MMX sample return mission to Phobos by JAXA will carry a Rover developed by CNES and DLR that will be deployed on Phobos to perform in-situ analysis of the Martian moon's surface properties. Past images of the surface of Phobos show that it is covered by a layer of regolith. However, the mechanical and compositional properties of this regolith are poorly constrained. In particular nothing is known regarding the particle sizes, their chemical composition, the packing density of the regolith as well as other frictional parameters and surface dynamics from current remote images. Understanding the properties and dynamics of the regolith in the low-gravity environment of Phobos is important to trace back its history and surface evolution. Moreover, this information is also important to support the interpretation of data obtained by instruments onboard the main spacecraft and to minimize the risks involved in the sampling by the spacecraft. The instruments onboard the Rover are an infrared radiometer (miniRad), a Raman spectrometer (RAX), two cameras looking forwards for navigation and science purposes (NavCams), and two cameras observing the flow of regolith around the rover wheels (WheelCams). The Rover will be deployed before the sampling of Phobos' surface by MMX spacecraft and will be the first rover driving on a Martian moon and in a low-gravity environment

The MMX rover: performing in situ surface investigations on Phobos

The Japanese MMX sample return mission to Phobos by JAXA will carry a rover developed by CNES and DLR that will be deployed on Phobos to perform in situ analysis of the Martian moon's surface properties. Past images of the surface of Phobos show that it is covered by a layer of regolith. However, the mechanical and compositional properties of this regolith are poorly constrained. In particular, from current remote images, very little is known regarding the particle sizes, their chemical composition, the packing density of the regolith as well as other parameters such as friction and cohesion that influence surface dynamics. Understanding the properties and dynamics of the regolith in the low-gravity environment of Phobos is important to trace back its history and surface evolution. Moreover, this information is also important to support the interpretation of data obtained by instruments onboard the main MMX spacecraft, and to minimize the risks involved in the spacecraft sampling operations. The instruments onboard the Rover are a Raman spectrometer (RAX), an infrared radiometer (miniRad), two forward-looking cameras for navigation and science purposes (NavCams), and two cameras observing the interactions of regolith and the rover wheels (WheelCams). The Rover will be deployed before the MMX spacecraft samples Phobos' surface and will be the first rover to drive on the surface of a Martian moon and in a very low gravity environment