Aspectos prácticos del control de actitud del satélite INTA-Nanosat-1B

[Resumen] Los Subsistemas de Determinación y Control de Actitud (ADCS) de las misiones satelitales ambiciosas utilizan habitualmente sensores y actuadores de muy altas prestaciones, como sensores estelares, girómetros laser y ruedas de reacción. En misiones de bajo coste no es posible utilizar estos sensores y actuadores por limitaciones presupuestarias. En estos casos es típico resolver el problema de la determinación con sensores magnéticos y solares, como es el caso del satélite INTA-Nanosat-1B (NS-1B). En muchas situaciones estos sensores no proporcionan suficiente información o precisión para determinar la actitud del satélite, por lo que es necesario subsanar estas deficiencias con una algoritmia más complicada. En NS-1B es necesario propagar matemáticamente la actitud del satélite durante el eclipse. Para ello es necesario caracterizar la principal perturbación que éste sufre, que es el Momento generado por el Dipolo Magnético (MDM). El artículo presenta diferentes aspectos práctico del ADCS de NS-1B, como los diferentes modos de determinación de actitud, la calibración en vuelo del magnetómetro y la estimación también en vuelo del MDM. Se muestra que estas aportaciones mejoran significativamente la precisión del ADCS en la zona de eclipse. Trasladar estas calibraciones y estimaciones a etapas de vuelo supone un ahorro significativo en costes y tiempo que puede ser interesante para misiones de bajo coste, como los CubeSats.Los autores quieren agradecer al Programa de Nanosatélites del INTA por apostar por el desarrollo del conocimiento, en lugar de limitarse a comprar soluciones. También es de agradecer la financiación obtenida por el CICYT a través del proyecto DPI2013-46665-C1https://doi.org/10.17979/spudc.978849749808

Implementation of a Time-Sensitive Networking (TSN) Ethernet Bus for Microlaunchers

The design of the aerospace systems for future aircraft requires the identification of new suitable communication infrastructures that can overcome the limitations that often come with the use of the legacy, albeit well-proven, protocols that are routinely integrated into aerospace. This allows us to overcome the bandwidth constraints, large deployment costs, or the lack of flexibility of other alternatives, such as SpaceWire, or legacy systems, such as the MIL-STD-1553B bus. These protocols can be replaced with new technologies that can fulfill the greater real-time and interconnectivity demands of advanced scientific probes or manned spacecraft. The advent of the new microlauncher systems has all but confirmed this trend. In this context, we describe the design and implementation of a time-sensitive networking (TSN) bus for the avionics of the Miura 1 suborbital microlauncher. TSN represents an appropriate interface for this type of platform given its ability to provide the determinism and reliability expected in space-grade systems in combination with the higher data rates (gigabit Ethernet) and greater flexibility of standard Ethernet. This has resulted in a TSN platform developed by Seven Solutions S.L. based on the commercially available Zynq-7000 devices from Xilinx. Thus, our design features a light-footprint field-programmable gate array (FPGA) architecture powered by a real-time executive for multiprocessor systems (RTEMS) operating system, which is currently pending its certification from the European space agency (ESA) for space applications. All these elements have been successfully integrated and validated for the avionics of the Miura 1 sounding rocket, which represents an illustrative case that verifies their applicability to similar scenarios. © 1965-2011 IEEE.This work was supported in part by the Amiga-7 under Grant RTI2018-096 228-B-C3 and it was conducted in the context of the Gigabit Ethernet TSN Deterministic Network (GETDEN) Project of the European Space Agency.With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.Peer reviewe

Legume nodule senescence: roles for redox and hormone signalling in the orchestration of the natural aging process

23 pages, and figuresResearch on legume nodule development has contributed greatly to our current understanding of plant–microbe interactions. However, the factors that orchestrate root nodule senescence have received relatively little attention. Accumulating evidence suggests that redox signals contribute to the establishment of symbiosis and senescence. Although degenerative in nature, nodule senescence is an active process programmed in development in which reactive oxygen species (ROS), antioxidants, hormones and proteinases have key roles. Nodules have high levels of the redox buffers, ascorbate and glutathione, which are important in the nodulation process and in senescence. These metabolites decline with N-fixation as the nodule ages but the resultant decrease in redox buffering capacity does not necessarily lead to enhanced ROS or oxidative stress. We propose models by which ROS and antioxidants interact with hormones such as abscisic acid in the orchestration of nodule senescencePeer reviewe