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Fabra F.,Institute Of Ciencies Of Lespai Ice Ieec Csic | Cardellach E.,Institute Of Ciencies Of Lespai Ice Ieec Csic | Nogues-Correig O.,Institute Of Ciencies Of Lespai Ice Ieec Csic | Oliveras S.,Institute Of Ciencies Of Lespai Ice Ieec Csic | And 8 more authors.
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2010

GPS reflected signals have become a source of opportunity for remote sensing of the Earth's suface. In this work, we present several capabilities of this technique in two different polar environments: Greenland and Antarctica. The first part is dedicated to the retrieval of sea-ice properties, giving emphasis to the study of the coherent phase for altimetric and roughness estimations, and polarimetric measurements for the determination of the ice salinity variation. The results show good agreement with a tide model and daily ice charts. On the second part, some preliminary results and analysis strategies to retrieve dry snow signatures are presented. © 2010 IEEE.


Eriksen M.B.,Leiden University | Gaztanaga E.,Institute Of Ciencies Of Lespai Ice Ieec Csic
Proceedings of the International Astronomical Union | Year: 2015

Does photometric and spectroscopic survey benefit from overlapping areas? The photometric survey measures 2D Weak Lensing (WL) information from galaxy shape distortions. On the other hand, the higher redshift precision of an spectroscopic survey allows measurements of redshift space distortions (RSD) and baryonic accustic oscillations (BAO) from 3D galaxy counts. The two surveys are combined using 2D-correlations, using sufficiently narrow bins to capture the radial information. This poster present effects of RSD and intrinsic correlations between narrow redshift bins. In understanding how the effects affects cosmological constrains, we first define two stage-IV and then present forecast for various configurations. When surveys overlap, they benefit from additional cross-correlations and sample variance cancellations from overlapping volumes. For a combined dark energy and growth history figure of merit, the result increase 50% for overlapping surveys, corresponding to 30% larger area. © International Astronomical Union 2015.


Pujol A.,Institute Of Ciencies Of Lespai Ice Ieec Csic | Chang C.,ETH Zurich | Gaztanaga E.,Institute Of Ciencies Of Lespai Ice Ieec Csic | Amara A.,ETH Zurich | And 10 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2016

We present a newmethod to measure redshift-dependent galaxy bias by combining information from the galaxy density field and the weak lensing field. This method is based on the work of Amara et al., who use the galaxy density field to construct a bias-weighted convergence field κg. The main difference between Amara et al.'s work and our new implementation is that here we present another way to measure galaxy bias, using tomography instead of bias parametrizations. The correlation between κg and the true lensing field κ allows us to measure galaxy bias using different zero-lag correlations, such as 〈κgκ〉/〈κ κ〉 or 〈κgκg〉/〈κgκ〉. Our method measures the linear bias factor on linear scales, under the assumption of no stochasticity between galaxies and matter. We use the Marenostrum Institut de Ciéncies de l'Espai (MICE) simulation tomeasure the linear galaxy bias for a flux-limited sample (i < 22.5) in tomographic redshift bins using this method. This article is the first that studies the accuracy and systematic uncertainties associated with the implementation of the method and the regime in which it is consistent with the linear galaxy bias defined by projected two-point correlation functions (2PCF). We find that our method is consistent with a linear bias at the per cent level for scales larger than 30 arcmin, while non-linearities appear at smaller scales. This measurement is a good complement to other measurements of bias, since it does not depend strongly on s8 as do the 2PCF measurements. We will apply this method to the Dark Energy Survey Science Verification data in a follow-up article. © 2016 The Authors.


Fabra F.,Institute Of Ciencies Of Lespai Ice Ieec Csic | Cardellach E.,Institute Of Ciencies Of Lespai Ice Ieec Csic | Nogues-Correig O.,Institute Of Ciencies Of Lespai Ice Ieec Csic | Oliveras S.,Institute Of Ciencies Of Lespai Ice Ieec Csic | And 5 more authors.
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2011

We present in this paper an empirical approach for the characterization of the internal layering of dry snow masses by means of GNSS-R. A forward model has been designed for reconstructing reflected waveforms given a dry snow profile and geometry (elevation and elevation-rate), as a sum of multiple responses from different layers. To extract the internal information, Fourier transforms of time series of waveforms are computed to generate lag-holograms. The frequency stripes that appear are related to the depths of the contributing snow layers. The same analysis has been done with real data, showing with agreement with the models. © 2011 IEEE.

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