Brightness temperature (BT) images acquired via satellite platforms are at the core of Earth Observation applications, aiding activities such as agriculture, forestry, and urbanization management. ...However, said applications may suffer from limitations on the spatial resolution and/or acquisition rate of image sequences. Indeed, due to physical constraints on the sensing devices and on the orbiting platforms, the information is typically sparse in either space or time. This problem can be faced through data fusion techniques that yield improved synthetic images by taking advantage of multisensor data. In this work, we address the specific issue of enhancing image sequences through deterministic interpolation and combination procedures. We assume that an high temporal resolution/low spatial resolution (htr/LSR) sequence is available along with a low temporal resolution/high spatial resolution (ltr/HSR) and propose an approach to obtain an htr/HSR sequence consisting in three steps: (i) spatially interpolating the htr/LSR sequence; (ii) temporally interpolating the ltr/HSR sequence; and (iii) combining the two intermediate sequences. We consider and assess comparatively several options to carry out the three steps on thermal infrared images acquired by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) and Moderate Resolution Imaging Spectroradiometer (MODIS) sensors acting as the htr/LSR and the ltr/HSR sequence, respectively.
A wireless sensor network designed according to the sensor network with mobile agents (SENMA) architecture is engaged in a detection task, with a mobile agent (MA) that sequentially queries the ...networks nodes. The focus is on the effect of censoring: sensors respond to the query from the MA only if the local observations are deemed sufficiently informative; otherwise, they stay silent. Delivered data, if any, can be either unquantized or quantized to a single bit. The study is limited to shift-in-mean problems, involving two simple statistical hypotheses, where the noise distribution must be an even function but is otherwise arbitrary. Simple analytical relationships characterizing the tradeoff between the detection delay and the energy consumption of the network are derived, and examples of their applications are provided.
Inpainting in hyperspectral imagery is a challenging research area and several methods have been recently developed to deal with this kind of data. In this paper we address missing data restoration ...via a convex optimization technique with regularization term based on Collaborative Total Variation (CTV). In particular we evaluate the effectiveness of several instances of CTV in conjunction with different dimensionality reduction algorithms.
A successful mathematical description of natural landscapes relies upon a class of random processes known as fractional Brownian motions (fBms), which may exhibit correlation with long-range ...dependence (LRD). In remote sensing applications, the sensor observes a certain real scene B and records data I for successive signal processing tasks. Assuming that B is modeled as an fBm, does the recorded signal I preserve the LRD character of B ? More in general, can we relate the Hurst coefficient (an index of LRD) of the real scene to that of the recorded data? We address the problem in a simplified setup in which the data are related to (the slope of) the original scene through a zero-memory mapping. A mathematical framework is presented in which the above questions can be answered in the asymptotic regime of infinite data size. The effect of the finite sample size is also investigated. The mathematical model is also validated by real data, which are collected by a synthetic aperture radar that is mounted onboard of ERS-1/2 satellites.
A fully decentralized sensor network, without fusion center, is deployed to estimate the position of a target. Taking advantage of the limited communication range of the nodes, and exploiting their ...(unknown) location inside the surveyed area, the likelihood profile is approximately reconstructed. A distributed ML-like estimator is, therefore, proposed and its asymptotic performance is investigated analytically, while computer experiments assess the behavior of the estimator in nonasymptotic regimes. The differences between one- and two-dimensional scenarios are also discussed.
This Supplement provides supporting material for Abbott et al. (2016a). We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM ...follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands.
We describe directed searches for continuous gravitational waves in data from the sixth LIGO science data run. The targets were nine young supernova remnants not associated with pulsars; eight of the ...remnants are associated with non-pulsing suspected neutron stars. One target's parameters are uncertain enough to warrant two searches, for a total of ten. Each search covered a broad band of frequencies and first and second frequency derivatives for a fixed sky direction. The searches coherently integrated data from the two LIGO interferometers over time spans from 5.3-25.3 days using the matched-filtering F-statistic. We found no credible gravitational-wave signals. We set 95% confidence upper limits as strong (low) as 4×10−25 on intrinsic strain, 2×10−7 on fiducial ellipticity, and 4×10−5 on r-mode amplitude. These beat the indirect limits from energy conservation and are within the range of theoretical predictions for neutron-star ellipticities and r-mode amplitudes.
A gravitational-wave (GW) transient was identified in data recorded by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) detectors on 2015 September 14. The event, initially ...designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the GW data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network circulars, giving an overview of the participating facilities, the GW sky localization coverage, the timeline, and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic (EM) signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the EM data and results of the EM follow-up campaign are being disseminated in papers by the individual teams.
We examine the potential of sparse time-frequency representations for gravitational wave data analysis, as regards: i) characterizing the fine structure of the nonstationary disturbances (glitches) ...of instrumental/environmental origin affecting the interferometric detectors, and ii) improving the network detection of unmodeled and nonstationary gravitational wave signals coexisting with glitches. These goals are achieved by elaborating on classical and new results about time-frequency and sparse representations. We propose to use a compressed sensing technique (which enables exploiting time-frequency sparsity), in conjunction with an adaptive smoothing of the Wigner-Ville distribution (which enables exploiting the different coherency properties of the different signals of interest).
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