The need of a mission ensuring the continuation of L-band measurements from space with increased spatial resolution with respect to the current generation of sensors is discussed. The status of the SMOS-High Resolution (HR) mission project, currently under a Phase A study at CNES, is presented. 

The SMOS-HR Mission: Science Case and Project Status

The need of a mission ensuring the continuation of L-band measurements from space with increased spatial resolution with respect to the current generation of sensors is discussed. The status of the SMOS-High Resolution (HR) mission project, currently under a Phase A study at CNES, is presented.

Array configuration design is a critical issue for a high quality of the snapshot point spread function (PSF) and restored image in Michelson imaging interferometer. In classic design, the optimized configurations usually address the few specifications and single objective, which is unable to balance the requirements of both non-redundancy and sampling distribution. In this paper, we formalize mathematically the composite metric to trade-off the multiple demands of observation, and propose the hybrid-index-based array layout optimization strategy. The simulation results demonstrate that, in comparison with the typical distribution, the optimized array using the proposed optimization framework enables the acquisition of more comprehensive spectrum information while utilizing an equal number of apertures, providing superior imaging quality in different observation situations. Furthermore, the designed optimized array masks and the compared conventional array masks were fabricated and used for our experimental validation, further verifying the feasibility of this strategy. This array configuration optimization framework may not only find applications to Michelson interferometric imaging, but also provide a positive impact on all u-v sampling-based imaging modes, including radio interferometry, magnetic resonance imaging, and photonic integrated interferometric imaging.

Hybrid-index-based array configuration optimization for Michelson interferometric imaging

: Research is underway on the use of sensor simulation in generating sensor data to design a real-world human gesture recognition system. The overall development process suffers from poor interactive performance, because developers lack an efficient tool to support the sensor configuration, result checking, and trial-and-error that arise when designing a machine learning system. Hence, we have developed VirSen 1.0, a virtual environment with a user interface to support the process of designing a sensor-based human gesture recognition system. In this environment, a simulator produces lightness data and combines it with an avatar’s motion to train a classifier. Then, the interface visualises the importance of the features used for the model, via the permutation feature importance, and it provides feedback on the effect of each sensor to the classifier. This paper proposes a complete development process, from acquisition of learning data to creation of a learning model, using a single software tool. Additionally, a user study confirmed that by visualising the importance of the features used in the model, users can create learning models that achieve a certain level of accuracy.

VirSen1.0: toward sensor configuration recommendation in an interactive optical sensor simulator for human gesture recognition

The Soil Moisture and Ocean Salinity (SMOS) satellite [3] produces images of L-band brightness temperature using interferometry. The brightness temperatures that gave rise to a set of observed visibilities are inferred by solving an inverse problem based on the Van Cittert-Zernike theorem. The images are generated from visibilities one correlation period at a time, even though a given patch of Earth’s surface may be visible to the satellite for 100 consecutive periods. The recovered brightness temperature images are noisy and, due to the antenna array’s undersampling of the u-v frequency plane, aliased. A simultaneous inversion of multiple snapshots (call it "satellite-rotation synthesis" or a "global inversion") could take advantage of these multiple looks to improve resolution, field of view, and noise level, but appeared prohibitively expensive computationally and ill-posed: due to directional emissivity, many brightness temperatures must be recovered for each pixel. However, this directional emissivity can be sparsely modeled; accordingly, for satellites like SMOS, the observation model becomes shift-invariant across an orbital segment when expressed in geodetic coordinates relative to the trace. The observation model performs a convolution on the image of parameters (uniform in geodetic coordinates) governing observed brightness as a function of satellite position, and we can use the "Fourier transform trick" introduced in [6], to enable a global inversion.For the proposed L-Band Interferometer for Fluxes and Interfaces in the Environment (LIIFE) [7], [11], we present a realistic global inversion of the observation model across the orbital trace, which simultaneously unfolds and denoises the aliased snapshots. By using sparse spline models of the brightness temperature parameters, we can ensure this inversion is accurate and stable, even with a realistic simulation that accounts for the difficulty of modeling the Van Cittert-Zernike theorem (expressed in satellite-centered direction-cosine coordinates) using geodetic coordinates.

Multisnapshot imaging for LIIFE: Along-the-track inversion of the Van Cittert-Zernike theorem for unfolding and denoising

We address the optimization problem of antenna placement on satellite-mounted interferometric synthetic-aperture instruments. In classic designs, the antennas on satellites are aligned regularly on the satellite’s frame. Inspired by methods proposed for the placement of antennas in astronomical interferometers, such as ALMA or SKA, we explore irregular layouts and show that they are a valid alternative in terms of spatial resolution and reconstruction error. We formalize mathematically the optimization problem of irregularly placed antennas and we show that this kind of arrays can still be calibrated with the same methods used for regular arrays. Finally, this strategy is evaluated in the context of soil moisture and ocean salinity (SMOS) follow-up concepts, such as SMOS-HR (high resolution), for which the new optimized irregular configurations are compared to the regular ones.

/pdf/irregular-layout-for-a-satellite-s-interferometric-array-4rwbi6cw9h.pdf

Irregular Layout for a Satellite’s Interferometric Array

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Irregular Layout for a Satellite’s Interferometric Array