Serious games are an effective means to help children with ADHD improve their attention and impulse control. As prior works primarily focused on clinical benefits, the relationship among serious games, children, and their caregivers remains underexplored. To bridge this knowledge gap, we conducted a two-stage study: (1) with nine educators specialized in ADHD in clinical settings and (2) with seven dyads of children and their caregivers in home settings. To facilitate the study, we developed and deployed NeuroWorld DTx v1.0 , a suite of five games that train children to improve their attention capacity. Our analysis found that children demonstrated self-efficacy, engagement, and adherence despite NeuroWorld being less fun than entertainment games. Additionally, most caregivers emphasized the importance of educational aspects over entertainment aspects. Collectively, our findings provide novel insights into how serious games could be developed and deployed for at-home use among children with ADHD.

As the potential of the radar polarimetry on the parametric observation of the Earth’s environment gets wider awareness, the interest in low-frequency SAR is growing for the Earth observation. For the purpose of environment monitoring using SAR polarimetry, the requirement for the accurate and operational polarimetric calibrations is getting increased, especially under the Faraday rotation (FR). This manuscript proposes a novel method for the cross-talk calibration under FR applicable to L- and P-band spaceborne SAR missions including three generations of ALOS PALSAR series, SAOCOM, NISAR, ROSE-L, as well as BIOMASS. One of the earliest ideas of Klein’s eigenvector regulation and the widely assumed condition of reflection symmetry have been extended to the FR-condition. The channel imbalance is assumed to be calibrated in precedent in order to focus on the cross-talk calibration issue.

In this letter, we discuss the estimation of the location of ionospheric irregularities exploiting the appearance of intensity scintillations in ALOS-2 images, as they are semifocused at different heights. The intensity scintillations (stripes) are not always visible in the single-look complex (SLC) images. However, they start to be visible, as the image is semifocused at different heights with a peak of contrast where electron density irregularities are found (ionospheric height). The slant range between the satellite and the ionospheric plane can be estimated and converted directly into the ionospheric height by autofocusing the stripes. The observations show good agreement with the height of maximum ionization estimated by the International Reference Ionosphere (IRI). Furthermore, we perform an alternative geometric validation based on feature tracking by comparing the shifts between azimuth sublooks. With both methods for the presented dataset, the height of the ionospheric irregularities was estimated to be 330 km.

Model-based forest height inversion from single- and multi-baseline polarimetric synthetic aperture radar interferometry (Pol-InSAR) data is today well-established. One of the critical performance points is the parameterization of the vertical reflectivity profile. In this article, the parameterization of the vertical reflectivity profile using a tomographic reconstruction is proposed. To mitigate the limitations in the tomographic reconstruction induced by the limited vertical resolution especially for the ground-scattering component, the ground and volume contributions are separated using the sum of Kronecker products (SKPs) decomposition. For the forest height inversion, the Pol-InSAR line inclination angle is proposed, which, unlike the absolute coherence and the phase center, is invariant to the presence of a residual Dirac-like ground-scattering contribution. The inversion performance is addressed and compared for both single- and multi-baseline cases, in the absence and presence of temporal decorrelation. In all cases, the ground elevation is estimated from the tomographically reconstructed vertical reflectivity profiles and its accuracy directly influences the achieved inversion performance. The proposed methodology establishes a link between interferometric and tomographic measurements and is therefore relevant for missions that allow the implementation of both techniques. ESA’s BIOMASS is one such mission, and as such is being used as a test case to discuss different implementation scenarios. The different inversion strategies are applied to P-band campaign data acquired in the frame of the AFRISAR 2016 experiment and validated against reference measurements.

This paper presents our new SAR processing framework known as PRISM (Processor for Interferometric SAR Missions). This flexible approach allows the efficient and accurate processing of SAR data independent of the sensor and the acquisition mode. The two main PRISM components (the focusing and the interferometric chains) are described in this paper together with the philosophy of the software architecture. Experimental results are presented and discussed based on the impulse response function analysis of simulated data as well as the focusing and interferometric results using real TerraSAR-X data.

The estimation of the interferometric vertical wavenumber over sloped terrain is an integral step for many interferometric and tomographic synthetic aperture radar (SAR) applications. The state of the art for this estimation is to calculate the angle of incidence and the local terrain slope after geometric corregistration has been performed. In this letter, an alternative approach for estimating the vertical wavenumber is proposed that requires only the estimation of the range corregistration shifts. This considerably simplifies the calculation effort without compromising the estimation performance. The proposed approach is demonstrated on Advanced Land Observing Satellite (ALOS) phased array L-band synthetic aperture radar (PALSAR) data and compared against the conventional methodology.

Polarimetric SAR Interferometry (Pol-InSAR) is a SAR remote sensing discipline with unique and powerful applications related to the vertical structure of natural and man-made volume scatterers. The coherent combination of single- or multi -baseline interferograms acquired at different polarisations provides sensitivity to the vertical distribution of scattering processes and allows their characterisation by using the associated (volume) interferometric coherences.

At lower frequencies, synthetic aperture radar (SAR) images can be significantly affected by ionospheric scintillations. This letter proposes an approach to estimate ionospheric artifacts in single SAR images by combining Faraday rotation (FR) estimates and autofocus methods by using a Wiener filter. This novel approach achieves superior performance compared to using these techniques independently. This improvement is demonstrated by injecting randomly simulated ionospheric phase screens into simulated point targets and airborne data adjusted to the parameters of the Biomass system.

The realistic parameterization of the underlying (vertical) radar reflectivity profile is critical for a model-based inversion of forest height from polarimetric interferometric (Pol-InSAR) data. Indeed, an appropriate parameterization not only affects the final estimation performance, but also enables the inversion from a reduced observation space in terms of number of baselines and / or polarizations. Here, we investigate the possibility of using a full tomographic profile to parameterize the inversion. The proposed methodology is demonstrated and validated using Pol-InSAR and tomographic data acquired in the framework of relevant airborne campaigns.

Polarimetric SAR Interferometry (Pol-InSAR) is a SAR remote sensing discipline with unique and powerful applications related to the vertical structure of natural and man-made volume scatterers. The coherent combination of single- or multi -baseline interferograms acquired at different polarisations provides sensitivity to the vertical distribution of scattering processes and allows their characterisation by using the associated (volume) interferometric coherences [1]–[5].

A methodology that allows the separation of Faraday Rotation (FR) distortion from system induced distortion for the calibration of spaceborne polarimetric data is proposed and discussed. The separation is based on the azimuth variation of the FR and relies on the assumption that the antenna patterns are sufficiently well characterized.

We study small scale ionospheric effects on L-band SAR images in the equatorial region, known as equatorial stripes or streaks by using ALOS- 2/PALSAR-2 and ground air glow imager. Our experiment shows the existence of density depletion regions in the ionosphere within the radar geometry when SAR stripe phenomena occurred. This study experimentally demonstrates that the equatorial L-band SAR stripes are associated with plasma irregularities in density depletion regions, although further work is necessary to clarify the formation mechanism of irregularities.

Ionospheric parameters e.g., ionospheric height, TEC and the level of disturbances, are estimated using L-band SAR data acquired by ALOS-2 PALSAR-2 over Fairbanks, Alaska. These parameters are compared with coinciding ground-based monitoring data form the Poker Flat Incoherent Scatterer Radar (PFISR) and keograms measured by the University of Alaska, Fairbanks. The comparison results are discussed.

Interferograms at different polarisations form the basis of Polarimetric SAR Interferometry (Pol-InSAR), a radar remote sensing technique which uses the coherent combination of interferometric and polarimetric information to characterise and estimate structural parameters of natural and man-made (volume) scatterers. In the frame of the BIOMASS mission Pol-InSAR techniques are used to estimate yearly (top canopy) forest height on a global scale with a spatial resolution of 100 × 100 m2 and with an accuracy of 20-30%. The model based estimation is based on the Pol-InSAR data acquired by BIOMASS: three quad-polarimetric acquisitions (separated by 3 or 4 days from each other, with a constant progression on the order of 40% of the critical baseline) acquired in ascending and in descending geometry twice a year.

Polarimetric SAR Interferometry (Pol-InSAR) is a SAR remote sensing discipline with unique and powerful applications related to the vertical structure of natural and man-made volume scatterers. The coherent combination of single- or multi-baseline interferograms acquired at different polarisations provides sensitivity to the vertical distribution of scattering processes and allows their characterisation by using the associated (volume) interferometric coherences [1]-[5].

The BIOMASS mission gives completely new challenges in external calibration arising from the orbital pattern needed for the tomographic and Pol-InSAR phases of the mission, the strong effects of the ionosphere at P-band, and the lack of pre-existing P-band data except over very limited parts of the globe. Together these create problems that can only be solved by combining infrequent visits to instrumented calibration sites with systematic exploitation of the properties of distributed targets and targets of opportunity. Proposed approaches to performing radiometric and polarimetric calibration are described, together with meeting geolocation accuracy requirements.

A methodology that allows the separation of Faraday Rotation (FR) distortion from system induced distortion for the calibration of spaceborne polarimetric data is proposed. The separation is based on the frequency dependency of the FR across the system bandwidth and relies on the commonly used assumption that system distortions are frequency independent. A calibration schema appropriate for the calibration of polarimetric data in the presence of FR is proposed. The proposed methodology is applied and demonstrated on ALOS-2 data.

AfriSAR is an ESA-funded airborne P- and L-band SAR campaign over the African tropical forests of Gabon carried out by ONERA (July 2015) and DLR (February 2016). The different acquisitions were designed in order to collect multibaseline fully polarimetric data allowing the inversion of key forest vertical structure-based parameters, like e.g. forest height and high resolution reflectivity profiles. Results of processing and parameter inversion with the DLR's F-SAR data are shown in this paper at both P- and L-band.

The contribution focuses on the current status of the ESA study entitled “InSARAP Sentinel-1 Constellation Study”, which investigates the interferometric performance of the S1A/S1B units. General aspects like the interferometric compatibility in terms of common range and Doppler bandwidth and the burst synchronization are addressed. Besides the first interferometric results with both units, time series results over the pilot sites combining both satellites are also shown, as well as some investigations with fast moving (i.e., glaciers) scenarios.

In this work, we discuss the retrieval of information about the vertical structure of the ionospheric phase by means of Multi-Squint Interferometry (MSInSAR). A model of the MS phase is proposed that accounts for multiple ionospheric layers and residual topographical terms. This model is then generalized to the case of a continuous distribution, which can be retrieved from the MS phase via a 2D Fourier Transform. Moreover, we demonstrate the possibility to single out the phase screen at each layer, plus the residual topographic phase. The inversion procedure is demonstrated through numerical simulations, based on BIOMASS system parameters.

A significant amount of the data acquired by sun-synchronous space-borne low-frequency synthetic aperture radars (SARs) through the postsunset equatorial sector are distorted by the ionospheric scintillations due to the presence of plasma irregularities and their zonal and vertical drift. In the focused SAR images, the distortions due to the postsunset equatorial ionospheric scintillations appear in the form of amplitude and/or phase “stripe” patterns of high spatial frequency aligned to the projection of the geomagnetic field onto the SAR image plane. In this paper, a methodology to estimate the height and the drift velocity of the scintillations from the “stripe” patterns detected in the SAR images is proposed. The analysis is based on the fact that the zonal and vertical drift of the plasma irregularities are, at the equatorial zone, perpendicular to the geomagnetic field which is almost parallel aligned to the orbit. The methodology takes advantage of the time lapse and change of imaging geometry across azimuth subapertures. The obtained height estimates agree well with the reference measurements and independent estimates reported in the literature, while the drift velocities appear slightly overestimated. This can be attributed to a suboptimum geometry configuration but also to a decoupling of the ambient ionosphere and the plasma irregularities.

Recent studies indicate the potential of low frequency space-borne SAR sensors to monitor and quantify structure and dynamics of ionosphere [1-3]. At the post-sunset sector of the equatorial ionosphere, the instability of the electron density often induces plasma bubbles aligned to the geomagnetic field [4], whose effects are seen as distinctive stripe patterns on SAR data [5-6]. At the same time, the free-electrons in this sector of ionosphere drift eastward [7]. This paper explores this effect captured on ALOS and ALOS-2 SAR data to estimate the drift velocity and altitude of the bubbles [8]. Based on the azimuth sub-band of SAR data analysis the height and velocities are estimated, and compared to the measurements from ionosonde. The sensitivity of the estimates is analyzed, and finally a possible observation configuration for further ionospheric study is proposed.

In this paper the Pol-InSAR calibration - including coherence, phase and ionospheric calibration - of ALOS-2 is addressed based on repeat-pass fully polarimetric interferometric SAR data acquired over different sites during the CAL-VAL phase. ALOS-2, launched in May 2014, provides the possibility to demonstrate quantitative Pol-InSAR techniques from space over a wide range of test sites. Compared to ALOS-PalSAR, the increased bandwidth, reduced NESZ level and the shortened interferometric repeat-pass time promises a significantly increased potential of ALOS-2 for Pol-InSAR applications.

A correction methodology for distortions induced by ionospheric scintillation on fully polarimetric synthetic aperture radar (SAR) data is proposed. The correction is based on deriving the phase distortion induced by the ionosphere from Faraday rotation estimates. The estimated phase distortion is then used for correction. In order to compensate the phase and time-Doppler history distortions, the correction has to be performed at the slant range of the ionospheric layer, i.e., on partially focused single-look complex data. Accordingly, the performance of the proposed correction methodology depends, among other factors, on knowledge of the altitude of the effective ionospheric layer (assuming the thin ionospheric layer model). Its estimation from the SAR data itself is therefore also addressed. The methodology was applied and validated on simulated P-band data for various ionospheric conditions and on real L-band data acquired by the Advanced Land Observation Satellite Phased Array L-band SAR (PALSAR).

The European Space Agency is conducting studies for a low-earth orbiting polarimetric synthetic aperture radar called BIOMASS to provide global measurements of forest biomass and tree height. Phase scintillation across the synthetic aperture caused by ionospheric irregularities can degrade the impulse response function (IRF) and cause squinting, and its temporal variation can cause decorrelation in repeat-pass interferometry. These effects are simulated for a range of conditions for the baseline BIOMASS system configuration using the Wideband model of scintillation, which predicts that for a dawn–dusk orbit, impacts of scintillation over forest regions are negligible under all conditions except at high latitudes in the North American sector under high sunspot activity. In this sector, single-look IRFs have mean integrated sidelobe ratios (ISLRs) and peak sidelobe ratios (PSLRs) better than 0 and${-}{\rm 5}~{\rm dB}$, respectively, at 90% confidence interval under median solar activity up to the northern tree line (${\sim}{\rm 70}^{\circ}$geomagnetic). Degradation in the mean 3-dB resolution of up to 10% is predicted, with mean absolute azimuth shifts of the IRF peak of up to 2 m, which increases to 5 m at high sunspot number. Similar values are found for the dawn and dusk sides, and seasonal variations are negligible for latitudes below the tree line. Repeat-pass interferometric image pairs maintain coherence${>}{\rm 0.8}$up to 50$^{\circ}~{\rm N}$under median sunspot conditions. Four-look processing improves the ISLR and PSLR by several decibels, but causes significant degradation of the 3-dB resolution due to incoherent averaging of images with different random azimuth shifts.

A correction method for distortions induced by ionospheric scintillation effects on P-band quad-pol synthetic aperture radar (SAR) data acquired in polar and high latitude regions is presented. For this the estimation of the Faraday rotation (FR) is converted to ionospheric phase and used for the correction of the scintillation. The correction is performed on partially focused SLC data in order to compensate the ionosphere-induced phase and the distortion of the time-Doppler history. The degree of defocusing depends on the altitude of the ionosphere. The performance of the new correction method is tested on P-band simulated data for various ionospheric scenarios.

The theoretical framework necessary to facilitate the mitigation of ionospheric physical effects on amplitude and phase of low-frequency space-based synthetic aperture radars (SAR) is presented. By way of a unique research collaboration the authors have developed mathematical and stochastic descriptors of the spatio-temporal structure and its impact on SAR signals passing through the ionosphere during different levels of scintillation. The authors have developed a prototype integrated ionospheric processor that combines multiple existing and newly developed correction methods with the goal to maximize correction robustness and accuracy. For the first time, realistic stochastic models describing the amplitude and spatial structure the ionosphere were developed and validated; thereby, allowing the study and discovery of the origin of SAR image artifacts that are caused by ionosphere scintillation; i.e., a noise-like high frequency phase distortion.

In this paper we propose some ionospheric correction schemes for space-borne synthetic aperture radar (SAR) and polarimetric interferometric SAR (PolInSAR). The spatial and temporal variation of the free electron density in the uppermost atmosphere affects the propagation of the radar pulse resulting in image distortions. We estimate the total electron content (TEC) by applying the Appleton-Hartree equation to the distortions in the focusing, polarimetry, and interferometry. Then we propose a combined estimator that yields comprehensive differential TEC estimations. The effect of vertical structures of the ionosphere on interferometric phase is further discussed.