Three scenarios fro valuable planetary science missions on Mars: next generation of CubeSats to support space exploration

Planetary science originally tended to make use of “flagship” missions characterized by big satellites and expensive resources. In the near future this traditional satellite paradigm could dramatically change with the introduction of very small satellites. This shift towards smaller, less expensive devices mirrors the paradigm shift that happened in the computer industry with the miniaturization of electronics, as focus has moved from massive machines to personal computer up to smart phones. The ultimate expression of spacecraft miniaturization is today represented by CubeSats, but while over a hundred CubeSats have been launched into Earth orbit, space-based research beyond LEO struggles to find practical application. CubeSat small size poses hard challenges for independent planetary exploration, nevertheless they remain highly attractive due to the reduced development time and cost coming from platform modularity and standardization, availability of COTS parts, reduced launch cost. Constellations of CubeSats, collaborative networks, fractionated or federated systems are becoming popular concepts as they can offer spatially distributed measurements and the opportunity to be used as disposable sensors with a flexibility not achievable by single-satellite platforms. We have worked towards advancing the state of the art in CubeSat missions design and implementation by defining the range of science capabilities for CubeSats beyond LEO, and by enhancing the top technological challenges to support science objectives (e.g. propulsion, communications, radiation environment protection). Planet Mars was chosen as target destination to the purpose of this work, by selecting a set of scientific objectives for CubeSats to serve astrobiology goals and future human exploration. Missions to accomplish orbital and atmospheric measurement, in situ analyses related to biosignatures detection and environmental characterization have been explored. The opportunity to rely on already existing space assets in the proximity of Mars, or on a “mothership” for data relay or orbit insertion, has been considered in this context. A tradespace exploration led to the definition of three classes of mission architectures, respectively based on surface penetrators, atmosphere scouts and orbiting fleet. Each architecture has been assessed in the perspective of science return against a set of leading indicators that draw out cost, utility, complexity, technology readiness among others. For each class a mission concept has been created, providing a basis to elicit the definition of top-level requirements and to assess the value of science return in the context of complex mission scenarios

Superconducting, Insulating, and Anomalous Metallic Regimes in a Gated Two-Dimensional Semiconductor-Superconductor Array

The superconductor-insulator transition in two dimensions has been widely investigated as a paradigmatic quantum phase transition. The topic remains controversial, however, because many experiments exhibit a metallic regime with saturating low-temperature resistance, at odds with conventional theory. Here, we explore this transition in a novel, highly controllable system, a semiconductor heterostructure with epitaxial Al, patterned to form a regular array of superconducting islands connected by a gateable quantum well. Spanning nine orders of magnitude in resistance, the system exhibits regimes of superconducting, metallic, and insulating behavior, along with signatures of flux commensurability and vortex penetration. An in-plane magnetic field eliminates the metallic regime, restoring the direct superconductor-insulator transition, and improves scaling, while strongly altering the scaling exponent

Quantized conductance doubling and hard gap in a two-dimensional semiconductor-superconductor heterostructure

The prospect of coupling a two-dimensional (2D) semiconductor heterostructure to a superconductor opens new research and technology opportunities, including fundamental problems in mesoscopic superconductivity, scalable superconducting electronics, and new topological states of matter. For instance, one route toward realizing topological matter is by coupling a 2D electron gas (2DEG) with strong spin-orbit interaction to an s-wave superconductor. Previous efforts along these lines have been hindered by interface disorder and unstable gating. Here, we report measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al, yielding multilayer devices with atomically pristine interfaces between semiconductor and superconductor. Using surface gates to form a quantum point contact (QPC), we find a hard superconducting gap in the tunneling regime, overcoming the soft-gap problem in 2D superconductor-semiconductor hybrid systems. With the QPC in the open regime, we observe a first conductance plateau at 4e^2/h, as expected theoretically for a normal-QPC-superconductor structure. The realization of a hard-gap semiconductor-superconductor system that is amenable to top-down processing provides a means of fabricating scalable multicomponent hybrid systems for applications in low-dissipation electronics and topological quantum information.Comment: includes main text, supplementary information and code for simulations. Published versio

Out-of-equilibrium phonons in gated superconducting switches

Recent experiments have suggested that superconductivity in metallic nanowires can be suppressed by the application of modest gate voltages. The source of this gate action has been debated and either attributed to an electric-field effect or to small leakage currents. Here we show that the suppression of superconductivity in titanium nitride nanowires on silicon substrates does not depend on the presence or absence of an electric field at the nanowire, but requires a current of high-energy electrons. The suppression is most efficient when electrons are injected into the nanowire, but similar results are obtained when electrons are passed between two remote electrodes. This is explained by the decay of high-energy electrons into phonons, which propagate through the substrate and affect superconductivity in the nanowire by generating quasiparticles. By studying the switching probability distribution of the nanowire, we also show that high-energy electron emission leads to a much broader phonon energy distribution compared with the case where superconductivity is suppressed by Joule heating near the nanowire

Manual de biossegurança em laboratórios da Embrapa Florestas.

bitstream/item/24481/1/Doc201.pd