Spherical near field acoustic holography with microphones mounted on a rigid spherical surface is used to reconstruct the incident sound field. However, reconstruction outside the sphere is an ill-posed inverse problem, and since this is very sensitive to the measurement noise, straightforward implementation might lead to disastrous reconstructions. A large number of regularisation tools based on singular value decomposition are available, and it has been found that the acoustic holography problem for certain geometries can be formulated in such a way that similarities to singular value decomposition become apparent. Hence, a number of regularisation methods, including truncated singular value decomposition, standard Tikhonov, constrained Tikhonov, iterative Tikhonov, Landweber and Rutishauser, have been adapted for spherical near field acoustic holography. The accuracy of the methods is examined by means of simulations and measurements, which leads to practical recommendations on the use of regularisation techniques regarding space and frequency.

This paper provides an overview of the Dragon 4 project dealing with operational monitoring of sea ice and sea surface salinity (SSS) and new product developments for altimetry data. To improve sea ice thickness retrieval, a new method was developed to match the Cryosat-2 radar waveform. Additionally, an automated sea ice drift detection scheme was developed and tested on Sentinel-1 data, and the sea ice drifty capability of Gaofen-4 geostationary optical data was evaluated. A second topic included implementation and validation of a prototype of a Fully-Focussed SAR processor adapted for Sentinel-3 and Sentinel-6 altimeters and evaluation of its performance with Sentinel-3 data over the Yellow Sea; the assessment of sea surface height (SSH), significant wave height (SWH), and wind speed measurements using different altimeters and CFOSAT SWIM; and the fusion of SSH measurements in mapping sea level anomaly (SLA) data to detect mesoscale eddies. Thirdly, the investigations on the retrieval of SSS include simulations to analyse the performances of the Chinese payload configurations of the Interferometric Microwave Radiometer and the Microwave Imager Combined Active and Passive, SSS retrieval under rain conditions, and the combination of active and passive microwave to study extreme winds.

High-speed movies of the vocal fold vibration are valuable data to reveal vocal fold features for voice pathology diagnosis. This work presents a suitable Bayesian model and a purely theoretical discussion for further development of a framework for continuum biomechanical features estimation. A linear and Gaussian nonstationary state-space model is proposed and thoroughly discussed. The evolution model is based on a self-sustained three-dimensional finite element model of the vocal folds, and the observation model involves a dense optical flow algorithm. The results show that the method is able to capture different deformation patterns between the computed optical flow and the finite element deformation, controlled by the choice of the model tissue parameters.

Radar scatterometers are active, microwave sensors that provide well-calibrated estimates of radar backscatter with a wide range of incidence angles. For Earth observation purposes, they are often used to monitor wind speed and direction over ocean, as well as to estimate root-zone soil moisture and to study sea ice properties, amongst others. For spaceborne, fan-beam scatterometers such as ASCAT, the nature of their measuring process, defined by the spatial response function, produces the effect of blurring point targets in their full-resolution backscatter images. To address this problem, in this study we provide a comprehensive analysis of the performance of three different image reconstruction methods: MAP-TSVD, MAP-Tikhonov and SIR. The level of noise reduction achieved by these deblurring methods is controlled by the selection of the optimal regularisation parameter based on the L-curve criterion. These methods are applied to ASCAT full-resolution data of island/coastal scenes in single-pass single-beam scenarios. We assess their effectiveness and suitability in terms of coastline retrieval and backscatter stability over ocean. The results obtained point to a general improvement with respect to coastline retrieval for all three methods under optimal regularisation conditions; the SIR algorithm achieves the most consistent performance, with a mean distance to reference coastline improvement of 42 %, while MAP options are computationally faster by a factor of 1.5. We conclude that with the right regularisation level, MAP-Tikhonov and SIR are generally successful in deblurring targets in ASCAT full-resolution backscatter images, generating reconstructed, high-resolution images of 3.125 km pixel size with minimal noise amplification and artefacts. These reconstruction algorithms could potentially become an improvement strategy of the current low-resolution ’gridded’ L1B ASCAT products of 12.5 and 25 km pixel size.

In voice-loading occupations employees are required to use their voice for continuous and large periods of time, which might lead to voice problems. In this work anomalous vocal-fold vibrations due to long-time high voice-load are investigated. Laryngeal endoscopic high-speed images within the vocal-fold plane are available. This data is used to improve existing continuum biomechanical models of the vocal-folds by analyzing the injury processes. The project is expected to result in methods that objectively demonstrate the impact of high voice-load on voice. A detailed description of the currently developing work will be presented, including a rigorous analysis of the hypothesized injury processes of the vocal folds.