Compact Laser Communication Terminal for Small Satellites

The New Space Economy is booming, as more than 7000 small satellites will be launched in the next decade. Dominant applications such as telecommunication & Earth imaging will generate data volumes that are simply not manageable with classic RF telecom payloads. Optical communication is a crucial technology of the future commercial space assets, granting stand-alone satellites and constellations the ability to route in space and transmit to ground unprecedented amounts of data, with limited spacecraft’s complexity and cost

Studio ed implementazione di algoritmi di stereo vision in ambito mobile: l'applicazione "SuperStereo"

L'analisi di un'immagine con strumenti automatici si è sviluppata in quella che oggi viene chiamata "computer vision", la materia di studio proveniente dal mondo informatico che si occupa, letteralmente, di "vedere oltre", di estrarre da una figura una serie di aspetti strutturali, sotto forma di dati numerici. Tra le tante aree di ricerca che ne derivano, una in particolare è dedicata alla comprensione di un dettaglio estremamente interessante, che si presta ad applicazioni di molteplici tipologie: la profondità. L'idea di poter recuperare ciò che, apparentemente, si era perso fermando una scena ed imprimendone l'istante in un piano a due dimensioni poteva sembrare, fino a non troppi anni fa, qualcosa di impossibile. Grazie alla cosiddetta "visione stereo", invece, oggi possiamo godere della "terza dimensione" in diversi ambiti, legati ad attività professionali piuttosto che di svago. Inoltre, si presta ad utilizzi ancora più interessanti quando gli strumenti possono vantare caratteristiche tecniche accessibili, come dimensioni ridotte e facilità d'uso. Proprio quest'ultimo aspetto ha catturato l'attenzione di un gruppo di lavoro, dal quale è nata l'idea di sviluppare una soluzione, chiamata "SuperStereo", capace di permettere la stereo vision usando uno strumento estremamente diffuso nel mercato tecnologico globale: uno smartphone e, più in generale, qualsiasi dispositivo mobile appartenente a questa categoria

Effect of honeycomb core under hypervelocity impact: numerical simulation and engineering model

Abstract Honeycomb sandwich panels (HC/SP) are the most common used structures for space vehicle. Under the threat of meteoroid and space debris, the distribution of the fragments produced in a hypervelocity impact event on HC/SP is critical to the vulnerability assessment of space vehicle. CISAS developed an engineering model to describe fragments clouds propagating inside spacecraft in consequence of space debris impact on HC/SP. In this model, the effect of the honeycomb core was modeled by an empirical corrective factor, which was not related to the physical of the impact. To improve this model, a new model to describe the effect of the honeycomb core was developed. In the new model, the honeycomb core was equaled to multi-parallel thin plates, which can represent the discontinuity of honeycomb core without complex boundary. Based on the knowledge of hypervelocity impact on a simple thin plate and approximation supported by numerical simulation results, the model was deduced. The coefficient of the model was fitted by the numerical simulation results

High Precision Dual-Stage Pointing Mechanism for Miniature Satellite Laser Communication Terminals

This paper presents an innovative mechatronic design of a high-accuracy pointing mechanism for orbital laser communication terminals. The system is based on a dual-stage architecture and is miniaturized to fit nanosatellite-class spacecraft, aiming to enable optical communication on small-size space platforms. The focus is on control design aspects and on the performance assessment of an experimental prototype under emulated external environmental disturbances

Computational analysis of a vortex ingesting bioreactor for hydrogen production

In this work, the fluid dynamics behaviour of a bioreactor specifically designed for a fermentative hydrogen production process is investigated by Computational Fluid Dynamics (CFD) simulations. The geometrical features of the bioreactor, which is a dual impellers baffled stirred tank provided with a draft tube, and the gas-liquid characteristics of the vortex ingesting operating mode make the modelling and the numerical solution tasks particularly challenging. The computational strategy is based on the two-phase formulation of the Reynolds Averaged Navier-Stokes equations in an Eulerian framework for both the continuous and the dispersed phase. The results of the simulations are compared with available experimental data collected in a parallel investigation under the same operating conditions and a identical bioreactor geometry. The reliability of the predicted overall hydrodynamics behaviour and the accuracy of the turbulent two-phase mean velocity field are evaluated and critically discussed. The results confirm that the proposed CFD approach is a suitable tool for the design and optimization of stirred bioreactors.Fil: Montante, Giuseppina. Universita Di Bologna; ItaliaFil: Coroneo, Mirella. Universita Di Bologna; ItaliaFil: Francesconi, Javier Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo y Diseño (i); ArgentinaFil: Paglianti, Alessandro. Universita Di Bologna; ItaliaFil: Magelli, Franco. Universita Di Bologna; Itali

Development of a multi-payload 2U CubeSat: the Alba project

Alba CubeSat UniPD is a student team of University of Padova with the aim to participate to the ESA Fly Your Satellite! (FYS!) programme and to launch for the first time at University of Padova a CubeSat made by students. The proposed mission has three independent objectives: (1) to collect in-situ measurements of the sub-mm space debris environment in LEO, (2) to study the micro-vibration environment on the satellite throughout different mission phases, (3) to do precise orbit determination through laser ranging and evaluate procedures for fast satellite Pointing, Acquisition and Tracking (PAT) from ground. The proposed technological experiments aim to obtain data that will enrich the current knowledge of the space environment and will provide precious information useful for the further development of some research projects currently performed at University of Padova. In order to reach the objectives, in these years the activities of the teams aimed to develop a 2U CubeSat equipped with three payloads. The first payload is an impact sensor that will be placed on one of the outer faces of the satellite and will be able to count the number of debris impacting the spacecraft thus being able to measure the energy/momentum transferred to the satellite. The second one is a Commercial Off The Shelf (COTS) sensor that measures the micro-vibrations experienced by payloads in a CubeSat in different mission phases. The third one consists in a number of COTS Corner Cube Retroreflectors that will be placed onboard the satellite. Thanks to this, Satellite Laser Ranging (SLR) will be done to collect data on the satellite range and range rate using a facility currently under development at University. This paper presents the mission objectives and motivations. In addition, the mission phases and the preliminary design of the CubeSat reached during the activities of the project are shown. Particular attention is given to the payloads which are the most challenging aspect of this project

A Variational Method for the Propagation of Spacecraft Relative Motion.

A new formulation of the spacecraft relative motion for a generic orbit is presented based on the orbital propagation method proposed by Peláez et al. in 2006 [1]. Two models have been developed. In the first model the method is applied to each spacecraft using a time synchronization of the system dynamical states. In the second model we employ a local orbital reference frame with a linearization of gravitational terms, apply the method to the formation center of mass and propagate the relative dynamics with respect to the center of mass reference orbit. The models are compared in terms of computational speed for the case of a bounded triangular formatio

Excretion of Aflatoxin M1 in milk of goats fed diet contaminated by Aflatoxin B1

An experiment was carried out to study the excretion of aflatoxin M1(AFM1) in milk of three goats fed a single dose (0.8mg/head) of pure aflatoxin B1 (AFB1). The values of AFM1 concentration excreted in milk was highly variable among goats, even if the pattern of excretion over time was very similar among the three animals. AFM1 was first detected at the milking performed 1h after the AFB1 administration. The highest values of AFM1 concentration in milk were reached 3 and 6h after the AFB1 intake. The trend of clearance of AFM1 in milk over time was expressed by a decreasing exponential equation. AFM1 concentration was below the EU maximum allowed level (50 ng/L) in milk collected 36 h after the AFB1 administration

LaserCube optical communication terminal for nano and micro satellites

This paper presents the design and testing of LaserCube, a miniature optical communication terminal conceived for nano and microsatellites. The system architecture has been designed for both the downlink and intersatellite link version of the system. Then, a complete engineering model of LaserCube in its intersatellite link configuration has been developed and tested. It features (1) a dual stage pointing and tracking system based on a coarse pointing mechanism patented by Stellar Project, (2) an optical head with a full-duplex telecom channel with transmission and reception on the same wavelength for two-way links, (3) a transceiver section with telecom laser source and optical receiver and (4) the terminal control unit with onboard computer, actuator drivers and data interface. Experimental validation of the system is achieved through a laboratory simulation of an intersatellite link scenario with realistic dynamic disturbance coming from the host satellite attitude jitter

Shearing influences the milk fatty acid profile of dairy ewes

In Mediterranean areas shearing is commonly performed during late spring and, therefore, ewes may be exposed to cold stress especially during the night. Short-term periods of cold exposure can increase hepatic glucose production, decrease insulin secretion and increase fat catabolism and plasma non-esterified free fatty acids (NEFA) concentration. These metabolic adaptations to cold exposure can increase the mammary uptake of long-chain fatty acid from plasma. The present study aimed to investigate the metabolic response of dairy ewes to shearing by monitoring their milk fatty acid (FA) profile. Twelve 2-4-year-old Sarda ewes, in mid-late lactation, were used. The trial lasted from 30th May to 9th June 2006. The pre-experimental period (pre-shearing, PrS) was from 30th May to 5th June (shearing day), being followed by the experimental period (post-shearing, PoS) until 9th June. On shearing day, the flock was divided in two groups (6 ewes each) which were then managed differently: non-confined group (NCG) and confined group (CG) which was kept in a sheepfold during the night. Four samplings during PrS and other four during PoS periods were performed. During the trial, ewes were fed concentrate at 1000g/d per head, during the two daily milking, and hay ad libitum, and grazed on green clover (3h/day). Daily milk production was recorded and daily milk samples were collected for analysis of fat content and FA profile. Shearing did not influence milk yield but increased significantly milk fat content (6.37 vs. 6.94% for PrS and PoS, respectively; P<0.01). Ewes confinement during the night did not affect milk yield and its fat content. Shearing modified significantly the FA profile of milk. The concentration of C8, C10, C12 and C16 increased significantly from PrS to PoS. On the other hand, the content of long-chain FA (>C18:0) did not change between PrS and PoS (46.26 vs. 46.40mg/100g of FAME, respectively). These results suggest that the increase of milk fat after shearing was related to the increase of the main FA synthesized by the mammary gland. However, the unexpected increase in the synthesis of short- and medium-chain FA after shearing suggests that these animals were not subjected to cold stress. Therefore, the mechanism involved in the modification of the FA profile caused by shearing in dairy ewes should be elucidated