Comparative analyses of ESA, NASA and JAXA signals of acceleration during the SODI IVIDIL experiment

10.1007/s12217-014-9376-yThe present work aims to complete the analysis of the vibrational impact generated by the Influence of VIbrations on DIffusion of Liquids, IVIDIL, experiment in a global way. To do so, we have analysed all the episodes which, along the active period between September 2009 and January 2010, accounts for simultaneous accelerometric signals coming from the Columbus (ESA) module, the Destiny (NASA) module and the Pressurized module of the Kibo complex, PM-Kibo, (JAXA) respectively. Signals have been downloaded thanks to the NASA Principal Investigator Microgravity Services, PIMS, website. Vibrational analysis involved the consideration of second and higher order statistical techniques. In addition, a comparative study of the RMS acceleration integrated over one-third octave frequency bands enabled to check if the ISS vibratory limit requirements are everywhere accomplished. In summary it can be concluded that, in the vibratory regime, the experiment in the Columbus module is isolated enough of the Destiny and PM-Kibo ones. In addition, concerning only the Columbus data, the study also concluded that the peculiar energy exchange detected between the nominal frequency of the movement and its third harmonic is due to nonlinearities probably originated by the shaker, the module of translational arrangement mounted on the SODI instrument. All these results introduce an interesting generic question: is it always correct to consider that the accelerometric data only coming from one module can offer to the Space Station customers a suitable global scenario of the ISS environment?, if not, what is the real extent of these data

Detecting accelerometric nonlinearities in the international space station

The present work aims to study mechanical nonlinearities detected in the accelerometric records during a thermodiffusion experiment performed at the International Space Station, ISS. In that experiment the test cell was subjected to harmonic vibrations of different frequencies and amplitudes. Accelerometric data associated to the runs were downloaded from NASA PIMS website. Second order spectral analysis shows that the shaker modifies the normality of the data and introduces nonlinearities in the distribution of energy. High Order Spectral Analysis, HOSA, based on the bispectrum, bicoherence, trispectrum and tricoherence functions enabled us to study the kind of these nonlinearities. Additionally, a new method using the biphase and triphase histograms helps us to assess if quadratic and/or cubic phase coupling mechanisms are responsible for the anomalous nonlinear energy transfer detected. Finally, the RMS acceleration values are investigated to check if the vibratory limit requirements of the ISS are exceeded. This methodology is important not only in generic research of aerospace engineering but also in space sciences in order to help space researchers to characterize more globally their experiments. It is mentioned finally that HOSA techniques are not new, but never have been used in the analysis of accelerometric data coming from the ISS. © 2014 IAA.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Ba3Yb(BO3)3 single crystals. Growth and spectroscopic characterization

We obtained Ba3Yb(BO3)3 single crystals by the flux method with solutions of the BaB2O4Na2OYb2O3 system. The evolution of the cell parameters with temperature shows a slope change at temperatures near 873 K, which may indicate a phase transition that is not observed by changes appearing in the x-ray powder patterns or by differential thermal analysis (DTA). The evolution of the diffraction patterns with the temperature shows incongruent melting at temperatures higher than 1473 K. DTA indicates that there is incongruent melting and this process is irreversible. Ba3Yb(BO3)3 has a wide transparency window from 247 to 3900 nm. We recorded optical absorption and emission spectra at room and low temperature, and we determined the splitting of Yb3+ ions. We used the reciprocity method to calculate the maximum emission cross section of 0.28 10-20 cm2 at 966 nm. The calculated lifetime of Yb3+ in Ba3Yb(BO3)3 is trad = 2.62 ms, while the measured lifetime is t = 3.80 ms

JALCOM-14961; No. of Pages 4

Abstract We observed ultraviolet and visible up-conversion signals with maximum intensity at 383 nm, 407 nm, 457 nm, 474 nm, 525 nm, 552 nm, 652 nm, 696 nm, 772 nm, 801 nm, 814 nm and 848 nm from the 4f states of erbium-doped KYb(WO 4 ) 2 single crystals after pumping at 981 nm (10 194 cm −1 ) at room temperature (RT) and low temperature (10 K). These emissions were generated after simultaneous excitation of erbium and ytterbium at 981 nm (Yb 3+ acts as a sensitizer of Er 3+ ). We discuss the up-conversion mechanism in which three and two photons were involved in the generation of the ultraviolet and visible emissions

Some considerations on the vibrational environment of the DSC-DCMIX1 experiment onboard ISS

The present work attempts to characterize the accelerometric environment of the DSC-DCMIX1 thermodiffusion experiment carried out in the International Space Station, from November 7th 2011 until January 16th 2012. Quasi-steady and vibrational/transient data coming from MAMS and SAMS2 sensors have been downloaded from the database of the PIMS NASA website. To be as exhaustive as possible, simultaneous digital signals coming from different SAMS2 sensors located in the Destiny and Columbus modules have also been considered. In order to detect orbital adjustments, dockings, undockings, as well as, quiescent periods, when the experiment runs were active, we have used the quasi-steady eight hours averaged (XA, YA and ZA) acceleration functions as well as the eight hours RMS ones. To determine the spectral contents of the different signals the Thomson multitaper and Welch methods have been used. On the other hand, to suppress the high levels of noise always existing in the raw SAMS2 signals, denoising techniques have been preferred for comparative reboostings considerations. Finally, the RMS values for specific 1/3 octave frequency bands showed that the International Space Station vibratory limit requirements have not been totally accomplished during both quiescent periods and strong disturbances, specially in the low frequency range.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Characterization of the Accelerometric Environment of DCMIX2/3 Experiments

A comparative analysis of the vibratory environment of the DCMIX2/3 thermodiffusion experiments is presented here by using acceleration signals coming from different sensors placed in the Destiny, Columbus and Kibo modules. The es03 sensor nearest to the experimental device and located inside the Glovebox (Destiny module) has been defined as reference. Data were downloaded from the NASA PIMS website paying special attention to the runs coinciding with disturbances such as dockings or extravehicular activities (EVAs) as they could particularly affect the International Space Station (ISS) microgravity levels. The analyses have been made minute by minute for the three acceleration components by using the Frequency Factor Index (FFI), Spectral Entropy (SEN) and Root Mean Square (RMS) values evaluated over one-third-octave frequency bands. Spearman’s rank correlation coefficient and the coherence function have been used to investigate the degree of linear correlation between the reference signal and the other ones. SEN evolution showed different patterns compared to the reference. Also, RMS values surpassing the ISS microgravity limits were detected in all sensors, mainly at low frequency bands (< 10 Hz) and prevailing on zA direction. However the sensors located in the Destiny module better accomplished the ISS vibratory limits requirements. Finally, some degree of linear correlation at structural frequencies (< 3 Hz) has also been detected. Overall, the sensors placed in the Destiny, Columbus and Kibo modules presented different vibratory characteristics and, despite they offer valuable information of the whole environment, may not be sufficient to properly characterize DCMIX2/3 experiments.SCOPUS: ar.jinfo:eu-repo/semantics/publishe