The SURPRISE demonstrator: a super-resolved compressive instrument in the visible and medium infrared for Earth Observation

While Earth Observation (EO) data has become ever more vital to understanding the planet and addressing societal challenges, applications are still limited by revisit time and spatial resolution. Though low Earth orbit missions can achieve resolutions better than 100 m, their revisit time typically stands at several days, limiting capacity to monitor dynamic events. Geostationary (GEO) missions instead typically provide data on an hour-basis but with spatial resolution limited to 1 km, which is insufficient to understand local phenomena. In this paper, we present the SURPRISE project - recently funded in the frame of the H2020 programme – that gathers the expertise from eight partners across Europe to implement a demonstrator of a super-spectral EO payload - working in the visible (VIS) - Near Infrared (NIR) and in the Medium InfraRed (MIR) and conceived to operate from GEO platform -with enhanced performance in terms of at-ground spatial resolution, and featuring innovative on-board data processing and encryption functionalities. This goal will be achieved by using Compressive Sensing (CS) technology implemented via Spatial Light Modulators (SLM). SLM-based CS technology will be used to devise a super-resolution configuration that will be exploited to increase the at-ground spatial resolution of the payload, without increasing the number of detector’s sensing elements at the image plane. The CS approach will offer further advantages for handling large amounts of data, as is the case of superspectral payloads with wide spectral and spatial coverage. It will enable fast on-board processing of acquired data for information extraction, as well as native data encryption on top of native compression. SURPRISE develops two disruptive technologies: Compressive Sensing (CS) and Spatial Light Modulator (SLM). CS optimises data acquisition (e.g. reduced storage and transmission bandwidth requirements) and enables novel onboard processing and encryption functionalities. SLM here implements the CS paradigm and achieves a super-resolution architecture. SLM technology, at the core of the CS architecture, is addressed by: reworking and testing off-the-shelf parts in relevant environment; developing roadmap for a European SLM, micromirror array-type, with electronics suitable for space qualification. By introducing for the first time the concept of a payload with medium spatial resolution (few hundreds of meters) and near continuous revisit (hourly), SURPRISE can lead to a EO major breakthrough and complement existing operational services. CS will address the challenge of large data collection, whilst onboard processing will improve timeliness, shortening time needed to extract information from images and possibly generate alarms. Impact is relevant to industrial competitiveness, with potential for market penetration of the demonstrator and its components

Does Perthionitrite (SSNO^–) Account for Sustained Bioactivity of NO? A (Bio)chemical Characterization

Hydrogen sulfide (H₂S) and nitric oxide (NO) are important signaling molecules that regulate several physiological functions. Understanding the chemistry behind their interplay is important for explaining these functions. The reaction of H₂S with <i>S</i>-nitrosothiols to form the smallest <i>S</i>-nitrosothiol, thionitrous acid (HSNO), is one example of physiologically relevant cross-talk between H₂S and nitrogen species. Perthionitrite (SSNO^–) has recently been considered as an important biological source of NO that is far more stable and longer living than HSNO. In order to experimentally address this issue here, we prepared SSNO^– by two different approaches, which lead to two distinct species: SSNO^– and dithionitric acid [HON­(S)­S/HSN­(O)­S]. (H)­S₂NO species and their reactivity were studied by ¹⁵N NMR, IR, electron paramagnetic resonance and high-resolution electrospray ionization time-of-flight mass spectrometry, as well as by X-ray structure analysis and cyclic voltammetry. The obtained results pointed toward the inherent instability of SSNO^– in water solutions. SSNO^– decomposed readily in the presence of light, water, or acid, with concomitant formation of elemental sulfur and HNO. Furthermore, SSNO⁻ reacted with H₂S to generate HSNO. Computational studies on (H)­SSNO provided additional explanations for its instability. Thus, on the basis of our data, it seems to be less probable that SSNO^– can serve as a signaling molecule and biological source of NO. SSNO^– salts could, however, be used as fast generators of HNO in water solutions

Reactions of Superoxide with Iron Porphyrins in the Bulk and the Near-Surface Region of Ionic Liquids

The redox reaction of superoxide (KO₂) with highly charged iron porphyrins (Fe­(P4+), Fe­(P8+), and Fe­(P8−)) has been investigated in the ionic liquids (IL) [EMIM]­[Tf₂N] (1-ethyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide) and [EMIM]­[B­(CN)₄] (1-ethyl-3-methylimidazolium tetracyanoborate) by using time-resolved UV/vis stopped-flow, electrochemistry, cryospray mass spectrometry, EPR, and XPS measurements. Stable KO₂ solutions in [EMIM]­[Tf₂N] can be prepared up to a 15 mM concentration and are characterized by a signal in EPR spectrum at <i>g</i> = 2.0039 and by the 1215 cm^–1 stretching vibration in the resonance Raman spectrum. While the negatively charged iron porphyrin Fe­(P8−) does not react with superoxide in IL, Fe­(P4+) and Fe­(P8+) do react in a two-step process (first a reduction of the Fe­(III) to the Fe­(II) form, followed by the binding of superoxide to Fe­(II)). In the reaction with KO₂, Fe­(P4+) and Fe­(P8+) show similar rate constants (e.g., in the case of Fe­(P4+): <i>k</i>₁ = 18.6 ± 0.5 M^–1 s^–1 for the first reaction step, and <i>k</i>₂ = 2.8 ± 0.1 M^–1 s^–1 for the second reaction step). Notably, these rate constants are four to five orders of magnitude lower in [EMIM]­[Tf₂N] than in conventional solvents such as DMSO. The influence of the ionic liquid is also apparent during electrochemical experiments, where the redox potentials for the corresponding Fe­(III)/Fe­(II) couples are much more negative in [EMIM]­[Tf₂N] than in DMSO. This modified redox and kinetic behavior of the positively charged iron porphyrins results from their interactions with the anions of the ionic liquid, while the nucleophilicity of the superoxide is reduced by its interactions with the cations of the ionic liquid. A negligible vapor pressure of [EMIM]­[B­(CN)₄] and a sufficient enrichment of Fe­(P8+) in a close proximity to the surface enabled XPS measurements as a case study for monitoring direct changes in the electronic structure of the metal centers during redox processes in solution and at liquid/solid interfaces

Compressive Sensing instrumental concepts for space applications

The need of high-resolution Earth Observation (EO) images for scientific and commercial exploitation has led to the generation of an increasing amount of data with a material impact on the resources needed to handle data on board of satellites. In this respect, Compressive Sensing (CS) can offer interesting features in terms of native compression, onboard processing and instrumental architecture. In CS instruments the data are acquired natively compressed by leveraging on the concept of sparsity, while on-board processing is offered at low computational cost by information extraction directly from CS data. In addition, instrument’s architecture can enjoy super-resolution capabilities that ensure a higher number of pixels in the reconstructed image with respect to that natively provided by the detector. In this paper, we present the working principle and main features of a CS demonstrator of a super-resolved instrument for EO applications with ten channels in the visible and two channels in the medium infrared. Besides the feature of merging in a single step the acquisition and compression phases of the image generation, its architecture allows to reach a superresolution factor of at least 4x4 in the images reconstructed at the end of process. The outcome of the research can open the way to the development of a novel class of EO instruments with improved Ground Sampling Distance (GSD) - with respect to that one provided natively by the number of sensing elements of the detector - and impact EO applications thanks to native compression, on-board processing capabilities and increased GSD

Dynamic Structural Response and Deformations of Monolayer MoS₂ Visualized by Femtosecond Electron Diffraction

Two-dimensional materials are subject to intrinsic and dynamic rippling that modulates their optoelectronic and electromechanical properties. Here, we directly visualize the dynamics of these processes within monolayer transition metal dichalcogenide MoS₂ using femtosecond electron scattering techniques as a real-time probe with atomic-scale resolution. We show that optical excitation induces large-amplitude in-plane displacements and ultrafast wrinkling of the monolayer on nanometer length-scales, developing on picosecond time-scales. These deformations are associated with several percent peak strains that are fully reversible over tens of millions of cycles. Direct measurements of electron–phonon coupling times and the subsequent interfacial thermal heat flow between the monolayer and substrate are also obtained. These measurements, coupled with first-principles modeling, provide a new understanding of the dynamic structural processes that underlie the functionality of two-dimensional materials and open up new opportunities for ultrafast strain engineering using all-optical methods