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Comparisons of tin depth profile analyses in float glass
(Elsevier BV, 1998-03-11) Townsend, P. D.; Can, N.; Chandler, P. J.; Farmery, B. W.; López Heredero, R.; Peto, A.; Salvin, L.; Underdown, D.; Yang, C.; 0000-0002-2197-8388
Data are presented showing the profile of tin diffusion during the production of float glass, by measuring non-destructively the refractive index profiles in the diffused layer. The optical waveguide modes give unequivocal evidence for an anomaly in the tin depth distribution. The results are compared with those from sectioning techniques, used in depth profiles determined by ion beam analyses and cathodoluminescence (CL). There is agreement between these methods which confirm the presence of a maximum in the tin concentration below the surface which had been in contact with the tin bath (this had been linked by Mössbauer data to a rise in the Sn4+ concentration). The ion beam analyses record different depth profiles for Si, Na and Ca. The Sn4+ feature increases the refractive index, as does the diffusion of Sn2+. The index becomes constant at large tin concentrations. We suggest that Sn4+ is linked to CL emission at 2.68 eV and Sn2+ to the 1.97 eV CL emission. Iron impurities give a 1.73 eV signal. Contrary to earlier suggestions, we propose that the luminescence associated with the presence of tin arises from intrinsic defects stabilised by the tin, not from tin acting directly as a luminescence site.
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Micromachined optical fiber current sensor
(OSA (The Optical Society) Publishing, 1999-09-01) López Heredero, R.; Fernández de Caleya, R. F.; Guerrero, H.; Los Santos, P.; Cruz Acero, M.; Esteve, J.; 0000-0002-2197-8388; 0000-0001-9440-7984; 0000-0003-2922-3489; 0000-0002-2131-1081
We describe a micromachined optical fiber current sensor. The sensing element consists of a squared silicon membrane (8 mm long and 20 µm thick) that has a cylindrical permanent magnet (NdFeB alloy, 3-mm diameter, 1.5 mm high) fixed on its central region. This structure allows the permanent magnet to vibrate in the presence of the magnetic field gradient generated by an ac. A linear relation between the electrical current and the magnet displacement was measured with white-light interferometry with an optical fiber low-finesse Fabry–Perot microcavity. A measurement range of 0–70 A and a minimum detectable intensity of 20 mA were obtained when distance D between the membrane and the electrical power line was 5 mm. The output signal directly shows a linear response with distance D.
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Adsorption of water on porous Vycor glass studied by ellipsometry
(OSA (The Optical Society) Publishing, 2001-02-01) Álvarez Herrero, A.; López Heredero, R.; Bernabeu, E.; Levy, D.; 0000-0002-8462-0156; 0000-0002-2197-8388; 0000-0002-8957-5745; 0000-0001-9228-3412
The variation of the optical properties of porous Vycor glass (Corning, Model 7930) under different relative-humidity conditions was studied. The adsorption of water into the glass pores was investigated with spectroscopic ellipsometry. The change of the refractive index was Δn ∼ 0.04 between 5% and 90% relative humidity. A linear relation between the ellipsometer parameter tan Ψ, the amount of water adsorbed in the glass pores, and information about the pore-size distributions was established. The results are in accord with the values obtained from N2 isotherms, transmission electron microscope micrographs, and the manufacturer’s specifications (radius of ∼20 Å). The possibility of using this material as a transducer for implementation in a fiber-optic sensor to measure humidity was evaluated.
Acceso Abierto
Arctic ozone loss in threshold conditions: Match observations in 1997/1998 and 1998/1999
(American Geophysical Union, 2001-04-01) Schulz, Astrid; Rex, Markus; Harris, Neil R. P.; Braathen, Geir O.; Reimer, E.; Alfier, R.; Kilbane Dawe, Iarla; Eckermann, Stephen; Allaart, Marc; Alpers, Matthias; Bojkov, B; Cisneros Sanchiz, Juan María; Claude, H.; Cuevas Agulló, Emilio; Davies, Jonathan; Backer, Hugo de; Dier, Horst; Dorokhov, Valery; Fast, Hans; Godin, Sophie; Johnson, B. J.; Kois, Bogumil; Kondo, Yutaka; Kosmidis, Evangelos; Kyrö, Esko; Litynska, Z.; Mikkelsen, I. S.; Molyneux, M. J.; Murphy, Gerry; Nagai, T.; Nakane, Hideaki; O'Connor, Fiona M.; Parrondo Sempere, María Concepción; Schmidlin, Frank J.; Skrivánková, Pavla; Varotsos, Costas; Vialle, C.; Viatte, P.; Yushkov, Vladimir; Zerefos, Christos S.; Gathen, Peter von der; European Commission (EC)
Chemical ozone loss rates inside the Arctic polar vortex were determined in early 1998 and early 1999 by using the Match technique based on coordinated ozonesonde measurements. These two winters provide the only opportunities in recent years to investigate chemical ozone loss in a warm Arctic vortex under threshold conditions, i.e., where the preconditions for chlorine activation, and hence ozone destruction, only occurred occasionally. In 1998, results were obtained in January and February between 410 and 520 K. The overall ozone loss was observed to be largely insignificant, with the exception of late February, when those air parcels exposed to temperatures below 195 K were affected by chemical ozone loss. In 1999, results are confined to the 475 K isentropic level, where no significant ozone loss was observed. Average temperatures were some 8°–10° higher than those in 1995, 1996, and 1997, when substantial chemical ozone loss occurred. The results underline the strong dependence of the chemical ozone loss on the stratospheric temperatures. This study shows that enhanced chlorine alone does not provide a sufficient condition for ozone loss. The evolution of stratospheric temperatures over the next decade will be the determining factor for the amount of wintertime chemical ozone loss in the Arctic stratosphere.
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A study of the optical properties of photopolymer Fabry-Perot microcavities by a dual-wavelength fibre optic architecture
(IOP Science Publishing, 2002-06-20) López Heredero, R.; Martín, S.; Fernández de Caleya, R. F.; Lobo Ribeiro, A. B.; Araújo, F. M.; Ferreira, L. A.; Santos, J. L.; Guerrero, H.; 0000-0002-7047-0273; 0000-0002-2988-1222; 0000-0003-2922-3489; 0000-0002-2197-8388; 0000-0002-0818-4268
We present a novel method to study the behaviour of the optical properties of photopolymer materials with temperature. The photopolymer is deposited on the tip of optical fibres by dip coating to fabricate low-finesse Fabry-Perot microcavities. The signal processing technique utilized to interrogate the cavity is based on the generation of two quadrature phase-shifted interferometric signals using two Bragg fibre gratings. This technique enables the determination of the values of the thermo-optical coefficient and the linear coefficient of thermal expansion of the photopolymer. The effectiveness of the processing technique is also exploited in the study of the dependence of the temperature sensitivity on the cavity thickness.
Acceso Abierto
Chemical depletion of Arctic ozone in winter 1999/2000
(American Geophysical Union, 2002-09-20) Rex, Markus; Salawitch, R. J.; Harris, Neil R. P.; Gathen, Peter von der; Braathen, Geir O.; Schulz, Astrid; Deckelmann, H.; Chipperfield, M.; Sinnhuber, B. M.; Reimer, E.; Alfier, R.; Bevilacqua, R.; Hoppel, K.; Fromm, M.; Lumpe, J.; Küllmann, H.; Kleinböhl, A.; Bremer, H.; Von König, M.; Künzi, K.; Toohey, D.; Vömel, H.; Richard, E.; Aikin, K.; Jost, H.; Greenblatt, J. B.; Loewenstein, M.; Podolske, J. R.; Webster, Christopher R.; Flesch, Gregory J.; Scott, D. C.; Herman, R. L.; Elkins, J. W.; Ray, E. A.; Moore, F. L.; Hurst, D. F.; Romashkin, P.; Toon, G. C.; Sen, B.; Margitan, J. J.; Wennberg, P.; Neuber, R.; Allart, M.; Bojkov, B. R.; Claude, H.; Davies, Jonathan; Davies, W.; De Backer, H.; Dier, Horst; Dorokhov, Valery; Fast, H.; Kondo, Yutaka; Kyrö, E.; Litynska, Z.; Mikkelsen, I. S.; Molyneux, M. J.; Moran, E.; Nagai, T.; H. Nakane; Parrondo Sempere, María Concepción; Ravegnani, Fabrizio; Skrivánková, Pavla; Viatte, P.; Yushkov, Vladimir; European Commission (EC); National Aeronautics and Space Administration (NASA)
[1] During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of polar stratospheric clouds (PSCs) lead to elevated abundances of chlorine monoxide (ClO) that, in the presence of sunlight, destroy ozone. Here we show that PSCs were more widespread during the 1999/2000 Arctic winter than for any other Arctic winter in the past two decades. We have used three fundamentally different approaches to derive the degree of chemical ozone loss from ozonesonde, balloon, aircraft, and satellite instruments. We show that the ozone losses derived from these different instruments and approaches agree very well, resulting in a high level of confidence in the results. Chemical processes led to a 70% reduction of ozone for a region ∼1 km thick of the lower stratosphere, the largest degree of local loss ever reported for the Arctic. The Match analysis of ozonesonde data shows that the accumulated chemical loss of ozone inside the Arctic vortex totaled 117 ± 14 Dobson units (DU) by the end of winter. This loss, combined with dynamical redistribution of air parcels, resulted in a 88 ± 13 DU reduction in total column ozone compared to the amount that would have been present in the absence of any chemical loss. The chemical loss of ozone throughout the winter was nearly balanced by dynamical resupply of ozone to the vortex, resulting in a relatively constant value of total ozone of 340 ± 50 DU between early January and late March. This observation of nearly constant total ozone in the Arctic vortex is in contrast to the increase of total column ozone between January and March that is observed during most years.
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Micromachined low-finesse Fabry-Perot interferometer for the measurement of DC and AC electrical currents
(Institute of Electrical and Electronics Engineers, 2003-04-22) López Heredero, R.; Santos, J. L.; Fernández de Caleya, R. F.; Guerrero, H.; López Heredero, R. [0000-0002-2197-8388]; Guerrero, H. [0000-0003-2922-3489]; Santos, J. L. [0000-0002-0818-4268]
A micromachined low finesse Fabry-Perot interferometer for measuring DC and AC electrical current is presented. Interrogation of the microcavity is achieved by a dual-wavelength fiber Bragg grating technique working in quadrature. A linear relation between the DC electrical current and the optical phase defined by the microcavity was detected. Large enhancement of the sensitivity of the microcavities is presented with the use of a planar coil instead of a power line. The sensitivity of the sensor with the planar coil configuration is 7.9 rad/A and resolution of ∼0.18 mA//spl radic/Hz is achieved when the distance between the planar coil and the transducer head is 2 mm. The response of the sensor for AC measurements is 0.14 V/A with a resolution of 6 mA//spl radic/Hz when the distance between the power line and the transducer head is 5.5 cm.
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The MIRI cold telescope simulator
(SPIE Astronomical Telescopes Instrumentation, 2004-10-12) Colina, L.; Díaz, E.; Aricha, A.; Alcacera Gil, María Ángeles; Balado, A.; Barandiarán, J.; Barrado, D.; Belenguer Dávila, T.; Blanco, J.; Figueroa, I.; García, G.; González, L.; López Heredero, R.; Herrada, F. J.; Laviada Hernández, C.; March, M.; Pastor, C.; Reina, M.; Sánchez, A.; Barrado, D. [0000-0002-5971-9242]; López Heredero, R. [0000-0002-2197-8388]; Balado, A. [0000-0003-4268-2516]; Colina, L. [0000-0002-9090-4227]; Pastor, C. [0000-0001-9631-9558]
The MIRI Telescope Simulator (MTS) is part of the Optical Ground Support System (OGSE) for the verification and calibration phase of the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI). The MTS will simulate the optical characteristics of the JWST output beam in an environment similar to the flight conditions. The different functionalities of the MTS are briefly described and its current design, including the illumination and imaging subsystems, is presented.
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The imaging magnetograph eXperiment for the SUNRISE balloon Antarctica project
(SPIE Astronomical Telescopes Instrumentation, 2004-10-12) Martínez Pillet, V.; Bonet Navarro, J. A.; Collados Vera, Manuel; Jochum, L.; Mathew, S.; Medina Trujillo, J. L.; Ruiz Cobo, B.; Del Toro Iniesta, J. C.; López Jiménez, A. C.; Castillo Lorenzo, J.; Herranz, M.; Jerónimo, J. M.; Mellado, P.; Morales, R.; Rodríguez, J.; Álvarez Herrero, A.; Belenguer Dávila, T.; López Heredero, R.; Menéndez, M.; Ramos, Gonzalo; Reina, M.; Pastor, C.; Sánchez, A.; Villanueva, J.; Domingo, V.; Gasent, J. L.; Rodríguez, P.; Rodríguez Huelves, Juan; López Heredero, R. [0000-0002-2197-8388]; López Jiménez, A. [0000-0002-6297-0681]; Reina, M. [0000-0003-0248-2771]; Del Toro Iniesta, J. C. [0000-0002-3387-026X]; Álvarez Herrero, A. [0000-0001-9228-3412]; De la Revilla, M. L. [0000-0003-4343-6632]; Callados, M. [0000-0002-6210-9648]; Morales Muñoz, R. [0000-0003-1661-0594]; Rodríguez Gómez, J. [0000-0002-6757-5912]; Ruiz Cobo, B. [0000-0001-9550-6749]; Gasent Blesa, J. L. [0000-0002-1225-4177]; Jerónimo, J. M. [0000-0002-4944-5823]; Pastor, C. [0000-0001-9631-9558]
The SUNRISE balloon project is a high-resolution mission to study solar magnetic fields able to resolve the critical scale of 100 km in the solar photosphere, or about one photon mean free path. The Imaging Magnetograph eXperiment (IMaX) is one of the three instruments that will fly in the balloon and will receive light from the 1m aperture telescope of the mission. IMaX should take advantage of the 15 days of uninterrupted solar observations and the exceptional resolution to help clarifying our understanding of the small-scale magnetic concentrations that pervade the solar surface. For this, IMaX should act as a diffraction limited imager able to carry out spectroscopic analysis with resolutions in the 50.000-100.000 range and capable to perform polarization measurements. The solutions adopted by the project to achieve all these three demanding goals are explained in this article. They include the use of Liquid Crystal Variable Retarders for the polarization modulation, one LiNbO3 etalon in double pass and two modern CCD detectors that allow for the application of phase diversity techniques by slightly changing the focus of one of the CCDs.
Acceso Abierto
The September 2002 Antarctic vortex major warming as observed by visible spectroscopy and ozone soundings
(Taylor & Francis Ltd, 2005-08) Yela González, M.; Parrondo Sempere, María Concepción; Gil Moulet, Manuel; Rodríguez, S.; Araujo, J.; Ochoa, H.; Deferrari, Guillermo Alejandro; Diaz, Susana Beatriz
The record of O3 total column and NO2 obtained by visible spectroscopy at Ushuaia (55° S), Marambio (64° S) and Belgrano (78° S) and vertical ozone profiles from the latter station provide insight into the unprecedented major warming observed above Antarctica in the last week of September 2002. From 18 September to 25 September the temperature increased 54°C at the isentropic level of 700 K. The temperature anomaly was observed down to the level of 300 K in which a well-defined tropopause was established. From comparison of the ozone profiles before and during the event, it can be seen that a fast increase in O3 took place basically above 500 K, but the layer where the ozone hole occurs was barely affected. Low potential vorticity values above Belgrano occurred only at levels above 500 K, confirming that the vortex split was confined to heights above the layer of the Antarctic spring depletion. The signature of poleward-transported air is clearly visible from the NO2 column departure from the envelope of the previous years in all three stations. NO2 columns larger than typical for ozone hole conditions by 400% were observed at Belgrano. Diurnal variations provide evidence of non-denitrified extra-vortex air.
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Lithium niobate Fabry-Perot etalons in double-pass configuration for spectral filtering in the visible imager magnetograph IMaX for the SUNRISE mission
(SPIE Astronomical Telescopes Instrumentation, 2006-06-14) Álvarez Herrero, A.; Belenguer Dávila, T.; Pastor, C.; López Heredero, R.; Ramos, G.; Martínez Pillet, V.; Bonet Navarro, J. A.; López Heredero, R. [0000-0002-2197-8388]; Álvarez Herrero, A. [0000-0001-9228-3412]; Martínez Pillet, V. [0000-0001-7764-6895]; Pastor, C. [0000-0001-9631-9558]
The Imaging MAgnetograph eXperiment, IMaX, is one of the three postfocal instruments of the Sunrise mission. The Sunrise project consists of a stratospheric balloon with a 1 m aperture telescope, which will fly from the Antarctica within the NASA Long Duration Balloon Program. IMaX should work as a diffraction limited imager and it should be capable to carry out polarization measurements and spectroscopic analysis with high resolution (50.000-100.000 range). The spectral resolution required will be achieved by using a LiNbO3 (z-cut) Fabry-Perot etalon in double pass configuration as spectral filter. Up to our knowledge, few works in the literature describe the associated problems of using these devices in an imager instrument (roughness, off-normal incidence, polarization sensitivity...). Because of that, an extensive and detailed analysis of etalon has been carried out. Special attention has been taken in order to determine the wavefront transmission error produced by the imperfections of a real etalon in double pass configuration working in collimated beam. Different theoretical models, numeric simulations and experimental data are analysed and compared obtaining a complete description of the etalon response.
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Detailed design of the imaging magnetograph experiment (IMaX): a visible imager magnetograph for the Sunrise mission
(SPIE Astronomical Telescopes Instrumentation, 2006-07-07) Álvarez Herrero, A.; Belenguer Dávila, T.; Pastor, C.; González, L.; López Heredero, R.; Ramos, G.; Reina, M.; Sánchez, A.; Villanueva, J.; Sabau, L.; Martínez Pillet, V.; Bonet Navarro, J. A.; Collados Vera, Manuel; Jochum, L.; Ballesteros, E.; Medina Trujillo, J. L.; Ruiz, C. B.; González, J. C.; Del Toro Iniesta, J. C.; López Jiménez, A. C.; Castillo Lorenzo, J.; Herranz, M.; Jerónimo, J. M.; Mellado, P.; Morales, R.; Rodríguez, J.; Domingo, V.; Gasent, J. L.; Rodríguez, P.; Rodríguez Huelves, Juan; 0000-0003-0248-2771; 0000-0001-9228-3412; 0000-0003-4343-6632; 0000-0002-6297-0681; 0000-0002-3387-026X; 0000-0002-2197-8388; 0000-0002-6210-9648; 0000-0002-4944-5823; 0000-0001-7764-6895; 0000-0003-1661-0594; 0000-0001-9631-9558; 0000-0002-1225-4177
In this work, it is described the Imaging Magnetograph eXperiment, IMaX, one of the three postfocal instruments of the Sunrise mission. The Sunrise project consists on a stratospheric balloon with a 1 m aperture telescope, which will fly from the Antarctica within the NASA Long Duration Balloon Program. IMaX will provide vector magnetograms of the solar surface with a spatial resolution of 70 m. This data is relevant for understanding how the magnetic fields emerge in the solar surface, how they couple the photospheric base with the million degrees of temperature of the solar corona and which are the processes that are responsible of the generation of such an immense temperatures. To meet this goal IMaX should work as a high sensitivity polarimeter, high resolution spectrometer and a near diffraction limited imager. Liquid Crystal Variable Retarders will be used as polarization modulators taking advantage of the optical retardation induced by application of low electric fields and avoiding mechanical mechanisms. Therefore, the interest of these devices for aerospace applications is envisaged. The spectral resolution required will be achieved by using a LiNbO3 Fabry-Perot etalon in double pass configuration as spectral filter before the two CCDs detectors. As well phase-diversity techniques will be implemented in order to improve the image quality. Nowadays, IMaX project is in the detailed design phase before fabrication, integration, assembly and verification. This paper briefly describes the current status of the instrument and the technical solutions developed to fulfil the scientific requirements.
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Data and Diagnostics in LISA PathFinder
(AIP Publishing, 2006-07-10) Lobo, A.; Nofrarias, M.; Ramos, J.; Sanjuan, J.; Conchillo, A.; Ortega, J. A.; Xirgu, X.; Araujo, H.; Boatella, C.; Chmeissani, M.; Grimani, C.; Puigdengoles, C.; Wass, P.; Anza, S.; Díaz Michelena, M.; García Berro, E.; Pérez del Real, R.
The Diagnostics measurement set is a subsystem of the LTP which is intended to monitor a number of spurious disturbances, even if the satellite complies with all cleanliness requirements. It monitors thermal and magnetic perturbations, and incorporates a charged particle counter. The purpose of this communication is to discuss the conceptual aspects of the mentioned subsystem, and to summarise its current status of development.
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OSIRIS – The Scientific Camera System Onboard Rosetta
(Springer Link, 2007-01-12) Keller, H. U.; Barbieri, C.; Lamy, Philippe; Rickman, H.; Rodrigo, Rafael; Wenzel, K. P.; Sierks, H.; A´Hearn, M. F.; Angrilli, F.; Angulo, M.; Bailey, M. E.; Barthol, P.; Barucci, M. A.; Bertaux, J. L.; Bianchini, G.; Boit, J. L.; Brown, V.; Burns, J. A.; Büttner, I.; Castro, J. M.; Cremonese, G.; Curdt, W.; Da Deppo, V.; Debei, S.; De Cecco, M.; Dohlen, K.; Fornasier, S.; Fulle, M.; Germerott, D.; Gliem, F.; Guizzo, G. P.; Hviid, S. F.; Ip, W. H.; Jorda, L.; Koschny, D.; kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Llebaria, A.; López, A.; López Jiménez, A. C.; López Moreno, J. J.; Meller, R.; Michalik, H.; Díaz Michelena, M.; Müller, R.; Naletto, G.; Origné, A.; Parzianello, G.; Pertile, M.; Quintana, C.; Ragazzoni, R.; Ramous, P.; Reiche, K. U.; Reina, M.; Rodríguez, J.; Rousset, G.; Sabau, L.; Sanz Andrés, Ángel; Sivan, J. P.; Stöckner, K.; Telljohann, U.; Thomas, N.; Timón, V.; Tomasch, G.; Wittrock, T.; Zaccariotto, M.; Rodríguez Huelves, Juan
The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS is the scientific camera system onboard the Rosetta spacecraft (Figure 1). The advanced high performance imaging system will be pivotal for the success of the Rosetta mission. OSIRIS will detect 67P/Churyumov-Gerasimenko from a distance of more than 106 km, characterise the comet shape and volume, its rotational state and find a suitable landing spot for Philae, the Rosetta lander. OSIRIS will observe the nucleus, its activity and surroundings down to a scale of ~2 cm px−1. The observations will begin well before the onset of cometary activity and will extend over months until the comet reaches perihelion. During the rendezvous episode of the Rosetta mission, OSIRIS will provide key information about the nature of cometary nuclei and reveal the physics of cometary activity that leads to the gas and dust coma. OSIRIS comprises a high resolution Narrow Angle Camera (NAC) unit and a Wide Angle Camera (WAC) unit accompanied by three electronics boxes. The NAC is designed to obtain high resolution images of the surface of comet 67P/Churyumov-Gerasimenko through 12 discrete filters over the wavelength range 250–1000 nm at an angular resolution of 18.6 μrad px−1. The WAC is optimised to provide images of the near-nucleus environment in 14 discrete filters at an angular resolution of 101 μrad px−1. The two units use identical shutter, filter wheel, front door, and detector systems. They are operated by a common Data Processing Unit. The OSIRIS instrument has a total mass of 35 kg and is provided by institutes from six European countries.
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Liquid-crystal variable retarders for aerospace polarimetry applications
(OSA (The Optical Society) Publishing, 2007-01-25) López Heredero, R.; Uribe Patarroyo, N.; Belenguer Dávila, T.; Ramos, G.; Sánchez, A.; Reina, M.; Martínez Pillet, V.; Álvarez Herrero, A.; Álvarez Herrero, A. [0000-0001-9228-3412]; López Heredero, R. [0000-0002-2197-8388]; Martínez Pillet, V. [0000-0001-7764-6895]
We present the optical effects of different tests that simulate the aerospace environment on the liquid-crystal variable retarders (LCVRs) used in the Imaging Magnetograph eXperiment postfocal instrument of the SUNRISE payload within the NASA Long Duration Balloon program. Analysis of the influence of vacuum, temperature, vibration, and gamma and ultraviolet radiation is performed by measuring the effects of these tests on the optical retardance, the response time, the wavefront distortion, and the transmittance, including some in situ measurements. Outgassing measurements of the different parts of the LCVRs are also shown. From the results obtained it can be concluded that these optical devices are suitable and seem to be excellent candidates for aerospace platforms.
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Magnetic Technologies for Space: COTS Sensors for Flight Applications and Magnetic Testing Facilities for Payloads
(Ingenta Connect, 2007-03-01) Díaz Michelena, M.; Del Real, R. P.; Guerrero, H.
The increasing trend of using Commercial of the Shelf components for Aerospace Applications makes Space Agencies open a brand new testing line devoted to the up-screening and characterization in extreme conditions of these "underqualified" components. The up-screening needs to deal with the tasks of degassing, temperature testing and thermal shock, vibration, ageing and stressing, and irradiation of the component under test. In this paper we report on the up-screening process, the previous magnetic characterization and the in-flight resulting data obtained with the magnetic sensors of NANOSAT-01 mission, one and a half years after the launch. The up-screening of the magnetic sensors used in this mission succeed. Their final in-flight qualification is on the road as the behavior of the sensors is nominal.
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Complex permittivity estimation by bio-inspired algorithms for target identification improvement
(Springer Link, 2007-05-14) Poyatos Martínez, D.; Escot Bocanegra, D.; Montiel, I.; Olmeda, I.; Instituto Nacional de Técnica Aeroespacial (INTA)
Identification of aircrafts by means of radar when no cooperation exists (Non-Cooperative Target Identification, NCTI) tends to be based on simulations. To improve them, and hence the probability of correct identification, right values of permittivity and permeability need to be used. This paper describes a method for the estimation of the electromagnetic properties of materials as a part of the NCTI problem. Different heuristic optimization algorithms such as Genetic Algorithms (GA) and Particle Swarm Optimization (PSO), as well as other approaches like Artificial Neural Networks (ANN), are applied to the reflection coefficient obtained via free-space measurements in an anechoic chamber. Prior to the comparison with real samples, artificial synthetic materials are generated to test the performance of these bio-inspired algorithms.
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Application of particle swarm optimization (PSO) to single-snapshot direction of arrival (DOA) estimation
(Institute of Electrical and Electronics Engineers, 2007-12-06) Escot Bocanegra, D.; Poyatos Martínez, D.; González, Iván; Sáez de Adana, F. M.; Cátedra, M. F.; Instituto Nacional de Técnica Aeroespacial (INTA)
This paper attempts to examine the feasibility of using an heuristic bio-inspired algorithm in DOA estimation. Specifically, particle swarm optimization (PSO) (Kennedy, et. al., 1995)
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Magnetic giant magnetoresistance commercial off the shelf for space applications
(AIP Publishing, 2008-02-13) Díaz Michelena, M.; Oelschlägel, W.; Arruego, I.; Del Real, R. P.; Mateos, J. A. D.; Merayo, J. M.
The increase of complexity and miniaturizing level of Aerospace platforms make use of commercial off the shelf (COTS) components constitute a plausible alternative to the use of military or rad-tolerant components. In this work, giant magnetoresistance commercial sensors are studied to be used as COTS, the next missions to be launched in the framework of the Spanish National Space Program: OPTOS and SEOSAT. This technology of magnetic sensors is interesting due to their high operating range up to 2mT and the high temperature dynamic range from −50 up to 150°C. However, in contrast, it presents high hysteresis and nonlinearity, temperature dependence, and poor repeatability. To improve the hysteretic, nonlinear and nonrepetitive behavior, a method consisting of a combination of reset and biasing has been designed and implemented for the ±75𝜇T linear region centered around 300–375𝜇T biasing field.
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IMaX: a polarimeter based on Liquid Crystal Variable Retarders for an aerospace mission
(Wiley Online Library, 2008-05-08) Uribe Patarroyo, N.; Álvarez Herrero, A.; López Heredero, R.; Del Toro Iniesta, J. C.; López Jiménez, A. C.; Domingo, V.; Gasent, J. L.; Jochum, L.; Martínez Pillet, V.; Del Toro Iniesta, J. C. [0000-0002-3387-026X]; López Jiménez, A. [0000-0002-6297-0681]; López Heredero, R. [0000-0002-2197-8388]; Álvarez Herrero, A. [0000-0001-9228-3412]; Gasenta Blesa, J. L. [0000-0002-1225-4177]; Martínez Pillet, V. [0000-0001-7764-6895]
IMaX is the Imaging Magnetograph eXperiment, an instrument part of the payload of SUNRISE, a stratospheric balloon mission in Antarctica. It is also the precursor of the Visible Imaging Magnetograph of the future ESA Solar Orbiter mission. It is essentially a diffraction-limited imager that carries out spectropolarimetric measurements of high resolution (bandwidth of < 100 mÅ at 525.02 nm), and relates the polarimetric properties of the incoming light through a telescope with magnetic fields in the Sun, via the Zeeman effect. At the core of the instrument there are the polarization modulation components, two Liquid Crystal Variable Retarders (LCVRs). A demodulation efficiency is defined and used as the figure of merit, and it serves to find the theoretical optimum states for the LCVRs as well as to judge the quality of the pre-flight calibration of the system. This calibration and the method used to optimize the actual efficiency is explained. Also, the space qualification of the LCVRs is presented, where ellipsometry played a major role in studying the effects of radiation, vacuum and temperature in the operation of the LCVRs. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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