This PDF file contains the front matter associated with SPIE Proceedings Volume 13144, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

The Department for Planetary Laboratories (PLL) of DLR provides a wide and diverse range of laboratory setups and environmental chambers, covering the study of a variety of planetary bodies in our solar system and beyond. This planetary science infrastructure has an extensive set of instruments and specialized tools, including a Planetary Spectroscopy Laboratory (PSL), a Planetary Simulation Laboratory (PASLAB), a Raman-Mineral-Biosignature Laboratory, a Sample Analysis Laboratory (SAL) and a Sample Preparation laboratory. PLL’s primary focus is based on understanding the formation and evolution of planetary surfaces and assessing their potential for past or present habitability. While remote sensing data from planetary objects of our solar system such as Mars, the Moon, asteroids, Mercury, and Venus have provided valuable insights into planetary evolution, they also pose unresolved questions. To address these, PLL integrates analysis of data from space missions, laboratory and on the field analog studies simulating planetary conditions, and analysis of returned samples. Simulating planetary environments in our laboratory facility helps interpreting remote sensing data and surface alteration processes. The in-situ analysis of returned samples offers the most reliable ground truth. PLL’s capabilities enable us to connect this ground truth to both local and global contexts, advancing our understanding of planetary formation, evolution, and habitability potential.
PLL currently supports a wide range of planetary missions including the ESA EnVision, BepiColombo, ExoMars rover and JUICE missions as well as the NASA VERITAS and DAVINCI missions and the JAXA Hayabusa 2 and MMX missions. PLL also performs measurements for industry on optical components (entrance windows, filters, radiators, reference surfaces), and materials for industrial uses (3D-printing, ceramics).

A new setup for detector characterization consisting of a cryostat, tunable collimated light source, and versatile data acquisition system is currently being commissioned. The setup enables testing optical and infrared sensors in the 400 to 14000 nm wavelength range and the devices under test can be cooled to cryogenic temperatures of down to 50 K under vacuum condition. 32 spectral band passes with bandwidths of λ{ΔΛ ≥ 50 are available for spectral characterization, covering the full range from 400 to 14000 nm. The setup can be used to characterize responsivity, detectivity, noise equivalent temperature difference, dark current, linearity, dynamic range, well depth, and pixel response non-uniformity. We report on first results for the characterization of imaging sensors using Teledyne’s CCD47-20 as the device under test for which camera gain, linearity error, full well capacity, read noise, dark noise, and quantum efficiency have been determined. Furthermore, the performance of the light source and cryostat system will be discussed.

The Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is part of the ESA-JAXA BepiColombo science payload en-route to Mercury. On April 10th 2020, BepiColombo flyby the Earth and obtained data from the Moon surface at a distance of around 700,000 km. The MERTIS thermal-infrared spectrometer (TIS) operating between 7 μm and 14 μm recorded more than 9,600 single hyperspectral observations of the Moon through its space baffle built for deep-space calibration. MERTIS has been designed to observe the surface of Mercury at a spatial resolution more than 1000 times better and at temperatures up to 2 times greater than that of the Moon. Therefore, lunar observations present a significant challenge for the instrument and the team. The standard acquisition procedure and the operations software were adapted to obtain data during the BepiColombo cruise phase. A specific calibration procedure and spatial binning have been developed to obtain the best radiometric data from the lunar surface. The calibrated data demonstrate the exceptional performance of the instrument, developed for a very different planetary object, comparable with ground-based measurements. The observations made during the cruise phase are very promising for future observations of Mercury with the space baffle during the fifth Mercury flyby scheduled for December 2024 and the nominal nadir viewing port (planet baffle) in orbit around Mercury.

The Earth-observing Photonic Integrated Circuit (EPIC) Multispectral Aerosol Polarimeter (MAP) mission concept has been developed to investigate the properties of aerosol from a constellation of orbiting photonic sensors. Each sensor in the EPIC MAP constellation is an imaging spectropolarimeter that is sensitive to multiple wavelength bands from the visible through the infrared. The photonic sensor is a novel, compact, interferometric imager. Light is collected by millimeter-sized lenslets, which couple to waveguides in the photonic circuit, where signal phases and amplitudes are measured. Coupling into the device with waveguide-grating couplers is polarization selective. Pairs of lenslets form interferometer baselines that sample spatial frequencies in two dimensions for reconstructing images of the intensity distribution in the field of regard. Silicon nitride and lithium niobate structures are hybridized for a photonic device design that is compact, low-noise, and stable. Here we demonstrate the viability of the photonic sensor design by fabricating and characterizing the irreducible component of the photonic imager; that is, the set of photonic structures that are required to measure the amplitude, phase, and polarization state along an interferometer baseline. Imaging performance models are developed to demonstrate the spatial resolution of the device for a given lenslet distribution, with noise properties of the images determined by propagation of the uncertainties in the phase and amplitude measurements. These performance models can be used to detail the technical requirements of an imager that addresses the specific science objectives of the EPIC MAP mission concept.

Given the ever-expanding usage of hyperspectral imagery in earth imaging applications and the proliferation of various types and capabilities of new and planned hyperspectral sensors, the need for rigorous calibration and characterization has become essential; especially when there is a requirement and need for using different sensors in performing change detection and other applications using temporal spatial/spectral signatures. This manuscript will cover an overview of the methodologies utilized and show results of spectral and radiometric calibration performed on the GHOSt payloads as well as the optical characterization specified by the empirically-derived system point spread function. An exemplar of this review would step through a radiometric calibration in acquiring near-nadir imagery of a RadCalNet site such as Railroad Valley, Nevada, obtaining near-coincident atmospheric characterization data from RadCalNet, transforming these data for use in a forward model, propagating to Top-of-the-Atmosphere (TOA) spectral radiance, deriving calibration coefficients, and presenting examples of before and after calibration imagery. Discussion includes challenges acquiring imagery and sufficient data to perform a calibration and various alternative community-accepted methods available. Spectral calibration of the GHOSt hyperspectral sensor will also be covered, from initial pre-launch calibration in the lab to methodology and results computed from gathered imagery over homogeneous areas in USGS pseudo-invariant sites. Optical characterization includes PSF/MTF information derived in the pre-launch in the lab and empirically derived PSFs from selected in-scene targets such as bridges, buildings, and other man-made target sets. The presentation of the calibration and characterization of this sensor payload, which has no onboard calibration or characterization additions, is expected to contribute to the continuing community discussion toward future accomplishment in hyperspectral and other types of satellite imagery standardization, quality assessment, and the expanding complementary use of imagery products.

Wildfires increasingly endanger people and property due to the growing population in the wildland urban interface, drought, and climate change. In the United States in 2023 over 1,000,000 acres burned in the western CONUS with no fire encompassing over 100,000 acres. Also, tragically the Lahaina Fire in Hawaii caused the deaths of over 100 people. In Canada, the extreme 2023 fire season resulted in almost 18,500,000 hectares burned, which was a factor of 2.6 larger than the previous high in 1995. The economic losses are enormous with resource expenditures running into the billions and insured losses running into the tens of billions of dollars in the United States. We propose the application of an imaging spectrometer for pre- and post-fire assessments and fire detection. MIT Lincoln Laboratory has developed three critical technologies that are applicable to the wildfire problem. The first is a compact spectrometer, the Chrisp Compact VNIR/SWIR Imaging Spectrometer (CCVIS), that can be modularly implemented for a wide-field imaging spectrometer. The second is the digital focal plane array (DFPA) technology with different detector materials, such as InGaAs or Mercury Cadmium Telluride (MCT), and extremely large well depths exceeding 108 electrons. The DFPA is critical for this application since traditional FPAs will saturate even for relatively cool fires with small spatial sample fill fractions. The DFPA also has sufficient signal to noise performance for pre- and post-fire products such as canopy cover, fuel quantification, and burnt area quantification and monitoring. The third is the TeraByte InfraRed Delivery (TBIRD) space-to-ground optical link that has a maximum data rate of 800 Gbps, which will not be addressed here. A small satellite implementation in a low Earth orbit (∼450 km) will have an entrance pupil on the order of 10 cm for a 50 m ground sample distance (GSD).

Technological progress in uncooled infrared focal plane array sensors have contributed significantly to the broadening of the application of this sensing technique in many fields: Leisure, Manufacturing, Process Control, Building insulation diagnostic, Civil Engineering, Road works, etc. A review of in-situ experiments studied on transport infrastructures over the past decade, advances in measurement system architectures and processing approaches are presented and discussed. Challenges with current uncooled infrared sensor performance and computational requirements are presented and discussed in the context of few selected use cases. Finally, conclusions and perspectives are proposed.

A new era in the study of Earth-like planets in exosolar systems has provided a fundamental and new impetus for understanding the evolution of planetary systems, placing traditional comparative planetology focused on our own system in a much broader context and a wide range of possible variability. Against this background, the study of our sister planet Venus in comparison to Earth is becoming increasingly important. Venus provides a laboratory for comparative planetology, with important insights into the sensitive effects of stellar environmental conditions on the evolution of habitable planets. A number of space missions to Venus, planned and under development, reflect this approach to comparative planetology in the Solar System and its application to understanding global stellar planetary systems. This article evaluates and classifies the planned Venus investigations using infrared and ultraviolet spectroscopy in terms of their ability to answer these questions. The article is based on known data from missions such as Venera 15/PMV (RU), VIRTIS, SPICAV and SPICAV-SOIR/VEX (ESA), and MERTIS (ESA), as well as many others in which the authors have been involved. We report on the key questions concerning the evolution of Venus, and the contribution of infrared and ultraviolet spectroscopy, and reflect on them in the light of planned space missions.

VenSpec is an instrument-suite composed of three spectrometers sharing a central control unit. Tied together by the common goal of exploring the different layers of Venus from the surface to the upper atmosphere in a holistic manner, three instrument lead scientists from Germany (DLR), France (LATMOS) and Belgium (BIRA-IASB) have joined forces. From the outset of the phase A study a collaborative work environment has been put in place to enable synergistic scientific planning and development work from the initial conceptual design throughout the actual instrument development and leading up to the operations and analysis of scientific returns. This paper addresses the challenges the consortium has faced in the process of guiding geographically, financially and institutionally separated projects towards a common goal with as little organizational overhead to the teams as possible. In the case of VenSpec, the scientific aspiration of working together via a common science team was set down at the beginning of the project: the consortium was consolidated by assuring each party full access to all scientific data produced by any instrument and also by connecting them physically to a common central control unit. This enables the consortium to act as a single entity towards the European Space Agency as well as the prime industrial contractor when beneficial while giving each party the freedom to act independently of each other for those aspects of scientific planning or technical development in which harmonization is not required. This paper lays out how the VenSpec consortium is organized and explains how close collaboration and the leveraging of synergies can be balanced with independent activities and individual and tailored strategies.

For ESA’s EnVision Mission to Venus, a consortium of three spectrometers from across Europe has been formed to collaborate not only on the management and science aspects, but also on the technical implementation. One important technical goal of the VenSpec suite is to implement a clean, simple and robust interface to the spacecraft and to provide an abstraction layer between the channels and the spacecraft. This is achieved by implementing the Central Control Unit (CCU), which provides a harmonized power and data interface to the spacecraft and allows the channels to design for a simple tailored internal interface to the CCU. The CCU consists of two electrical subsystems, the Data Handling Unit (CCU DHU), developed by the Max Planck Institute for Solar System Research (MPS) in Göttingen and the Institute of Computer and Network Engineering (IDA) in Braunschweig and the Power Supply Unit (CCU PSU), developed by the Instituto de Astrofísica de Andalucía (IAA-CSIC) in Granada, the system responsibility being at the DLR Institute of Planetary Research (DLR-PF) in Berlin. Within this framework, an extended electrical architecture trade-off was performed in 2023 to optimize the system, guaranteeing the requested functionality and complying to requirements from all sides. As a result of the trade-off. a single power and data interface were found to be the most suitable and robust solution considering performance, reliability, Fault Detection Isolation and Recovery (FDIR) and Electromagnetic Compatibility (EMC) considerations as well as the complexity of the associated verification campaign. This paper demonstrates the options that were suggested by the different parties and justifies the final architecture, which has been chosen to achieve the best solution for the VenSpec suite.

EnVision is ESA’s upcoming mission to Venus with a launch scheduled in 2031. One of the payloads on board is the VenSpec suite,1 containing three spectrometer channels, one of which is VenSpec-H. VenSpec-H (Venus Spectrometer with High resolution) performs absorption measurements in the atmosphere of Venus in four near-infrared spectral bands. VenSpec-H is developed under Belgian management and builds on heritage from instruments on Venus-Express and TGO. Techniques used in these precursor instruments are improved and complemented with new technologies to comply with the scientific goals of the EnVision mission. The operating wavelength range (1.15 - 2.5 μm) imposes stringent temperature requirements on the instrument to make nightside measurements below the Venus clouds possible. Most importantly, the spectrometer’s optical components are held in a separate cold section inside the instrument, cooled down to −45°C, to remove thermal background from the signal. To avoid heat dissipation close to the spectrometer optics, the electronic boards are kept in a separate box. Besides that, some mechanisms, placed in the warmer part of the instrument at the entrance or exit of the cold section, had to be developed: a turn window unit to protect the interior of the instrument during the aerobraking phase of the mission, a filter wheel mechanism to select the spectral bands of interest, and an integrated detector-cooler-assembly to register the spectra. Some passive optical elements in the spectrometer had low technological readiness at the start of the project. One of them is a freeform corrector plate, used to compensate for aberrations introduced in the system by a parabolic mirror. This device is developed by the Brussels Photonics lab of VUB (Brussels) using a supply chain with shape adaptive corrective polishing and dedicated metrology. Another is the echelle grating, used to disperse the incoming light into its spectral components, which is built by AMOS. Both devices are highlighted in this article.

EnVision, ESA's upcoming Venus orbiter, seeks to comprehensively understand the planet's evolution, building on the success of Venus Express. It will map Venus's interior, surface, and atmosphere with unprecedented detail, enhancing insights into its geological evolution [1]. VenSpec-H – one of the instruments within the VenSpec Suite – is focusing on the atmosphere both below and above the clouds as it will analyze volcanic plumes, as well as complementing surface and subsurface observations [2]. The results are foreseen to support the research teams of BIRA-IASB under Instrument Lead (IL) Dr. Séverine Robert and ETH Zürich under Profs. Paul Tackley and Taras Gerya – Co-ILs of the VenSpec-H Instrument – in understanding commonalities and differences between the planetary evolutions of Venus and Earth [3][4]. VenSpec-H is an optical spectrometer using an echelle grating to diffract uniform light for detailed compositional analysis. A cooled spectrometer section is preceded by a band selection section based on a combination of a filter wheel and a fixed horizontal double stripe filter.
This paper focusses on the development approach of the Filter Wheel Mechanism (FWM) lead by the Swiss Team of VenSpec-H (HSLU, ETH, FHNW, KOEGL Space) and its drive electronics lead by BIRA. It also gives insights in the tests that were performed with a detailed breadboard built within phase B1 of the project.

We report on the current Venus Emissivity Mapper (VEM) instrument design and development status onboard NASAs Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy (VERITAS) and ESAs EnVision orbiters. The VEM instrument is a push broom multispectral imager that comprises an optical system based on a sophisticated filter assembly with 14 spectral bands and an InGaAs detector with integrated thermoelectric cooler. A turn window mechanism and a two-staged baffle in front of the optics protect the instrument against contamination and straylight. The instruments nominal mass is approximately 6 kg. VEM opens the path for mapping Venus surface emission with a global coverage of >70%.

The first NASA spacecraft to visit and explore planet Venus since the 1990s will be the Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy mission (VERITAS) orbiter. The Venus Emissivity Mapper (VEM) onboard the spacecraft is designed for surface mapping of Venus within dedicated atmospheric spectral windows. The instrument will provide global coverage for the detection of thermal emissions like volcanic activity, surface rock composition, water abundance, cloud formation and their dynamics by observing 14 narrow filter bands in the near-infrared to short-wave infrared (NIR, SWIR) range of 790 nm to 1510 nm. An almost identical instrument will be part of ESA’s recently announced EnVision mission to Venus, the VenSpec-M in the Venus Spectroscopy Suite (VenSpec). The utilized photodetector for both missions will be an InGaAs type imaging sensor with integrated thermoelectric (TE) cooling, comprising a 640x512 pixel array with 20 μm pixel pitch.
In general, a space environmental qualification of electronic devices combines its susceptibility to radiation induced single event effects (SEE) and the evaluation of permanent degradation effects due to total ionizing dose (TID) and displacement damage dose (DDD). Following a successful qualification test with heavy-ions focusing on SEE, our imaging sensor was subject to a proton irradiation test campaign at Helmholtz-Zentrum Berlin (HZB) for combined TID and DDD testing. To track the sensor evolution, we subdivided the proton fluence into 10 irradiation steps with intermediate measurements. The collected data provide information on the evolution of dark current, light sensitivity and pixels showing randomtelegraph- noise (RTN) on the sensor during a 5-year mission.

Both NASA’s VERITAS and ESA’s EnVision missions to Venus incorporate a Venus Emissivity Mapper (VEM) to characterize the surface and distinguish basalt from more felsic rock types. Though Venus’ optically dense atmosphere makes direct observations of the surface challenging, five windows in the CO₂ spectrum near 1 μm will be exploited by the VEM instrument. In preparation for these missions, an analog of the VEM instrument (VEMulator2.0) was constructed for field measurements. It was used in a two-week field campaign at Venus-analog sites in Iceland in August 2023 as part of a VERITAS field campaign to collect multi-frequency reflectance measurements of volcanic rocks of varying age and surface conditions, as well as to measure emission from recently erupted lava with hot spots up to ~400°C. The goal of the work was to train scientists and to help assess the capability of the VEM instrument to detect differences in surface composition in a wide variety of volcanic rocks in the field with the limited spectral information provided by six bands. In addition, samples of the imaged regions were collected to be analyzed in detail at the Planetary Spectroscopy Laboratory at DLR in Berlin. Comparing field and laboratory spectra gives insights into the efficacy and limitations of the analog instrument. This paper describes the emulator design and calibration procedure as well as first results from field and laboratory measurements.

The Planetary Spectroscopy Laboratory (PSL) in the Department of Planetary Laboratories (PLL), German Aerospace Center (DLR) in Berlin is working on a database that will encompass a wide range of spectral measurements, studying different effects such as grain sizes, temperature, mixing and weathering. Our goal is to create a database large enough to address the diverse range of spectral characteristics that might be observed on planetary surfaces, thereby enhancing our capabilities to interpret orbital data coming from their surfaces. A part of this database is an extensive spectral library to interpret and validate data from the Venus Emissivity Mapper (VenSpec-M/VEM) of the ESA EnVision and NASA VERITAS missions. VenSpec-M/VEM will remotely collect data about the surface of Venus in the Near-InfraRed (NIR) spectral range, covering five spectral windows in the Venus atmosphere between 0.85 and 1.18 μm, to map rock types and study Venus surface composition and activity, by comparing orbital data with laboratory spectra. Here we present the first results of a study aimed at understanding the NIR spectral behavior of particulate mixtures in emissivity at Venus surface temperature varying the grain size of the components and the actual physical distribution of particles in the mixture. Spectra are acquired using a high-temperature emissivity setup coupled with a Bruker FTIR 80V spectrometer to measure NIR emissivity spectra of Venus analogs at relevant Venus surface temperatures in a vacuum environment. Detailed image analyses are performed using a Digital Microscope Keyence VHX-7000 to ensure precise mixing ratios and quantify modal mineralogy. Results show that linear mixing does not reproduce laboratory emissivity spectral behavior accurately in this wavelength range, leading to the future exploration of non-linear mixing approaches. This data provides important insight on the need for Machine Learning models as they are planned for the VEM and VenSpec-M data analysis and will be invaluable to train those algorithms. Furthermore, the datasets can help in the planning of instrumentation for future aerial and lander missions exploring the surface of Venus.

VenSpec-U is one of the three channels of the VenSpec suite onboard the ESA’s mission Envision to Venus, whose launch is foreseen in 2031. It is a UV spectrometer operating in the 190-380 nm range aiming at analyzing the sulfured gases in the high atmosphere of Venus by absorption spectroscopy and investigating the unknown “UV absorber”, thus contributing to answer one of the key questions the Envision mission will address: “How has Venus’ climate become so hostile”. VenSpec-U, developed under LATMOS (Guyancourt, France) PI-ship, is part of the spectrometer suite named ”VenSpec” led by DLR (Berlin, Germany). This manuscript provides an overview of the current instrument design, at the time of the end of phase B1/early phase B2.

The dual-channel UV spectrometer VenSpec-U onboard ESA’s next mission to Venus, EnVision, will study the upper layer of the atmosphere located above the clouds. It aims to characterise the chemical composition, with a focus on the sulphured gases (SO₂ and SO) and the identification of the unknown UV absorber, and will also monitor the dynamical processes such as gravity waves and convection cells. In this article, we are interested in knowing how the instrumental design allows to comply with requirements arising from these scientific objectives. This study is based on the radiative transfer model (RTM) developed for SPICAV/Venus-Express data analysis, that is used to retrieve of atmospheric features from radiance factor spectra, which will be derived from VenSpec- U’s measurements of Venus’ radiance. We will then study the sensitivity of the model to various error sources: random errors or biases. For the first ones, we assess the impacts of the Signal-to-Noise Ratio on the uncertainties of the inverse RTM outputs, in order to check that the required uncertainties are achieved for the main science goals. Limits in terms of SNR can also be defined in order to ensure the compliance with the specifications. We then present the approach implemented for the characterisation of systematic errors: the Effective Spectral Radiometric Accuracy (ESRA) requirement is used to estimate the impact of a bias on the accuracy of the retrieved science products based on the spectral characteristics of the biased spectra. After identifying some bias sources that could occur in VenSpec-U’ case, combinations are considered in order to study potential compensations and estimate allowable envelopes of residual error levels for each kind.

Some paints can create surprisingly good blackbody sources. Anodized aluminum is another coating that has a surprisingly high emissivity. We review the structure of these inhomogeneous materials and explore the theory explaining their emission properties. Using a model for volumetric emission from non-isothermal inhomogeneous media, we present a quantitative discussion of the conditions under which Kirchhoff’s law is valid. Using this model, we show how it is possible for many blackbody simulators and infrared camera shutters to produce such high emissivity, despite being constructed of only a thin layer of paint over a metal surface.

GÉANT Association aims to establish a fibre infrastructure for the distribution of time and frequency throughout Europe, with the implementation planned within the Horizon Europe GN5-2 funding cycle. These new fibre links will complement existing connections performing predominantly coherent optical frequency transfers, forming a basis of comprehensive Europe-wide infrastructure. This presentation will explore how this emerging fibre network will facilitate novel scientific research initiatives in Europe.

Moreover, the development of a pan-European fibre infrastructure will unlock opportunities for pioneering research in applied and fundamental science. This encompasses studies such as geodesy e.g. for underground water monitoring or unification of height systems across Europe, earthquake monitoring, the search for dark matter, and urban activity surveillance.

In the mid-18th century, Isaac Newton regarded light as some extremely small particles. Based on this, Newton established the particle theory of light. In the mid-19th century, Huygens and Augustine Jean Fresnel conducted extensive research on light and concluded that light is a wave. Afterwards, Maxwell proposed the theory of electromagnetism. Maxwell believed that light is a wave with a wavelength within a limited range.

With the establishment of Maxwell's equation electromagnetic wave theory, the wave nature of light began to dominate the mainstream consciousness; However, in the late 19th century, a series of experimental phenomena represented by the photoelectric effect could not be accurately explained by the wave theory of light. In 1905, Einstein proposed the concept of light quanta and successfully explained the photoelectric effect. While perfectly explaining these issues, a new question arises: what is the essence of light, given that both particle and wave properties can accurately reflect certain properties of light? It has always been the most fiercely debated issue in the history of optics. Einstein said that we are not yet clear about what light quanta are, and wave particle duality cannot fully explain optical phenomena.

Based on the study of Albert Einstein's concept of quanta light, wave particle duality of light, string theory, and optical frequency combs, the author proposes the concept of lightstring, attempting to propose new ideas for studying the essence of light and its generation mechanism.

Siwen Bi has been researching quantum remote sensing since March 2000 and quantum spectral imaging since June 2003, but has encountered some difficulties and problems. What is the basic theory of passive imaging in quantum remote sensing? How is technology implemented? What is the fundamental theory of quantum spectroscopy? The Implementation Technology of Quantum Optical Field Entangled States in Long Distance Quantum Detection Process? These difficulties and questions prompt the author of this article to contemplate and study the essence of light? What is the fundamental theory of the future technology of quantum optics?

Siwen Bi conducted exploratory research on the nature of light in 2006. This article first provides an overview of the development history and research status of optics and describes the difficulties and shortcomings in fully explaining optical phenomena due to the wave particle duality of light quantum and light; Then, two inspiring viewpoints on optical frequency comb and chord theory were introduced. On this basis, the basic concept of optical string (optical frequency string), the prototype description of optical string, the mechanism of optical string generation, and the discussion of Lightstring, generation process are proposed and emphasized; Proposed the mechanism of string light effect. Published On Two Heuristic Viewpoints Concerning the Study of Light (October 13-15, 2014), New Viewpoints In Light Quantum Research: Lightstring (2016), Discuss wave-particle duality of light, (February 28, 2017), and an Exploratory research on the light quantum future technical basis (February 1, 2019). Over the past 17 years, achieved some original and innovative research results. some original innovative research achievements have been achieved. Received high praise from international scholars and professors, such as the American Journal of Physics and Applications, which sent me a congratulatory letter saying, "Dear Bi Siwen, Warmest greeting from the Editorial Department! It is reported that at the International conference on photo and optical Engineering (ICPOE 2014), a paper entitled" Two Enlightening Views on Optical Research "was published, and the theme of the paper impressed us deeply. It has attracted the attention of Photon researchers and Scholars ...Your research is highly appreciated by us … " And invite Professor Bi Siwen as a paper reviewer for the American Journal of Physics and Applications. I have received the paper review certificate, dated May 25th, 2018.

Based on the above research, Siwen Bi elaborated on the geometric and kinematic characteristics of Lightstring, and proposed the essence of light based on the concept of Lightstring, in order to concretize the concept of light quanta. On this basis, the mechanism of string light effect based on the concept of optical string is proposed. An attempt has been made to further study the quantum and wave particle duality of light, gain a profound understanding of the nature of light, and answer the question "What is light?" by proposing a new approach and method for studying the nature of light and its generation mechanism. Proposed a study on optical quantum; The wave particle duality of light; New ideas, methods, and perspectives on the mechanism of light generation.

The present paper builds upon the novel, graphical method that we have introduced [V.-F. Duma, A. Schitea, Proc. of the Romanian Acad. Series A 19, 53-60, 2018] and developed [V.-F. Duma, A-L. Dimb, Applied Sciences 11, 8451, 2021] in order to study laser scanning with Risley prisms. An advantage of these scanning systems (and modality) is speed, while its main issue concerns the non-linearity of the generated scan patterns. The advantages of the proposed graphical method are that it provides (simulated) exact scan patterns (in contrast to the most utilized approximate methods) and that it is fast and easy to use (in contrast to rather complicated analytical methods). An essential aspect is highlighted in the present work regarding the functioning of the most common scanner with such components, i.e. with a pair of rotational Risley prisms. Thus, we approach the symmetries of generated scan patterns, presenting results that we recently obtained in [AL. Dimb, V.-F. Duma, Symmetry 15, 336, 2023]. Several aspects have been determined, starting with the number of symmetry axes. A novel notion, of structures of symmetry was proposed and developed. We showed how it is possible to generate (with high resolution) only a (small) part of the scan pattern, and further on to reproduce the entire pattern by using symmetries, including by (simply) rotating one of the proposed structures of symmetry. These were optimally defined and utilized in order to simplify the process of generating scan patterns for an increase in their resolution and/or a decrease in the simulation time. Characteristic geometrical aspects of the scan patterns have been determined, as well. Future directions of work to advance the domain are discussed.

NASA’s Atmospheric Waves Experiment (AWE) mission is a Heliophysics Small Explorers Mission of Opportunity designed to investigate how terrestrial weather affects space weather, via small-scale atmospheric gravity waves (GWs) produced in Earth’s atmosphere. Following its launch to the International Space Station (ISS) in November 2023, AWE began a 2-year mission to explore the global distribution of AGWs, study the processes controlling their propagation throughout the upper atmosphere, and quantify their impacts on the ionosphere–thermosphere–mesosphere (ITM) system. The AWE science instrument is an ISS–compatible version of the Advanced Mesospheric Temperature Mapper (AMTM)—a wide field-of-view Shortwave Infrared (SWIR) imager that quantifies gravity wave-induced temperature disturbances in the hydroxyl (OH) airglow layer, which lies near the mesopause at ~87 km altitude. The AMTM’s four identical telescopes make continuous nighttime observations of the P₁(2) and P₁(4) emission lines of the OH (3,1) band, as well as the atmospheric background simultaneously, from which the OH layer temperature is derived. AWE images are collected once per second, co-added, and processed into temperature swaths using correction algorithms derived from ground calibration test results. Global coverage of the GWs in the OH layer is achieved about every four days, which will enable regional and seasonal studies, as well as characterization of AGW ‘hot spots.’ This paper will present an overview of the AWE mission, including science objectives, measurement technique, instrument design and development, prelaunch performance and environmental testing, data processing, and a brief look at on-orbit science results.

The AWE AMTM is a widefield of view (WFOV) infrared imaging radiometer designed for use in measuring the P₁(2) and P₁(4) emission lines of the earth’s OH layer to determine temperature and produce images of gravity waves. The sensor was designed, built, and characterized by Utah State University (USU) Space Dynamics Laboratory (SDL) and has been externally mounted to the International Space Station (ISS) looking nadir to collect images for analysis for a minimum of two years. The Opto-Mechanical Assembly (OMA) consists of four identical imaging telescopes, each comprised of a fisheye lens, a field lens, and a re-imager lens and share a common filter wheel with four narrow band filters. The sixteen lenses in each telescope are coaligned and bonded into five stress stabilized aluminum lens barrels. Precision machining allowed the barrels to be mated together via mechanical tolerances (i.e., snap-to-fit) to form the fore and aft assemblies of each telescope that mount to the front and rear of a common, central tombstone assembly which houses the filter wheel mechanism. The detectors were aligned, supported, and thermally compensated via a titanium thermal compensator and custom focus shim attached to the aft end of each telescope. Following assembly, the OMA was environmentally tested including EMI/EMC, vibration, and thermal cycling. Prior to and following each environmental test, the point response function of each telescope was measured and compared to verify performance.

This paper will present an overview of the design, fabrication, assembly, integration, and environmental testing of the OMA.

Exploring the outer solar system is a priority, with upcoming missions including ESA JUICE and NASA Europa Clipper and Lucy missions. Spectroscopic analyses under extraterrestrial conditions are highly relevant in space science business. To meet this demand, PSL has added a compact low-temperature vacuum chamber for bi-directional reflectance measurements that attaches directly to an existing spectrometer. In this chamber, rock samples are examined in a high vacuum at temperatures of down to -200°C. In this cryo-chamber, solar radiation on asteroids and moons will be simulated in order to gain insights into their spectral properties. Initial functional tests showed that the heat transfer between the cooling system and the sample cylinder did not produce satisfactory results, since temperatures below -150°C could not be reliably achieved and cooling times were long. Subsequent work was dedicated to optimizing the heat transfer in the cooling system, consisting of a Stirling cooler, cooling block and sample cylinder. As a result of these improvements temperatures of down to -200°C and significantly shorter cooling and warming times can be achieved. The updated system allows for measurements from UV to far infrared and includes a two-stage turbo vacuum pump, a glove box for preparing icy samples, and an airlock for loading samples while maintaining high vacuum.

The estimation of caloric content of vegetation is relevant in areas such as biofuels and forest fire prevention. In this work we explore the transmission mechanism of infrared radiation through a leaf by finite element analysis to determine the energy transmission and reflection. We quantify the absorption inside the leaf using a wavelength at 1064 nm. The results obtained are determined experimentally at incidence normal to the leaf surface. We use an infrared laser source, controlling its power settings and a neutral density filter for step-wise power increments. We assumed a non-porous, uniform material, a constant refractive index. We select a specific absorption coefficient according to the senescent state of the leaf. The results describe the relationship between the absorption measured experimentally and computed by finite element analysis (FEA).

The 2011 off the Pacific coast of Tohoku Earthquake occurred, and coastal forests were severely damaged by a huge tsunami. Since the disaster, coastal forest restoration projects have been underway by the Forestry Agency and local governments. Detailed time-series monitoring of the regeneration process of coastal forests is important in order to proceed with regeneration appropriately. The Normalized Difference Vegetation Index (NDVI), which uses near-infrared and visible red images obtained from optical satellite observations, has been widely used to survey trees and vegetation. However, it has been reported that NDVI tends to be saturated depending on the observation period and vegetation type. In addition, there is a tendency for index values to be overestimated on the soil surface. In particular, in the case of coastal forest regeneration, the influence of the soil surface is even greater because the complex mixture of soil surface and afforestation is assessed from observation images. To date, many improvement vegetation indices have been proposed to reduce soil surface effects and more appropriately evaluate vegetation activity. However, the applicability of improvement indexes using higher-resolution satellite images for evaluating the regeneration of tsunami-affected coastal forests has not yet been sufficiently investigated.

Hooray! The ESA EnVision mission is adopted.
Onboard the spacecraft, there will be a suite of three spectrometers, VenSpec. One of these is called VenSpec-H where the H stands for high spectral resolution. Its scientific objectives consist in measuring variations of minor species’ abundances in the atmosphere of Venus. H₂O, SO₂, CO and OCS will be measured to characterize the potentially ongoing volcanic activity. These observations will allow us to understand both the importance of volatiles in volcanic activity on Venus and their effect on cloud maintenance and dynamics. VenSpec-H will measure these molecules in nadir viewing geometry, in infrared transparency windows of Venus’ nightside to probe the troposphere and in infrared spectral ranges on the dayside to measure the mesosphere. In this paper, the scientific requirements enabling our scientific objectives will be demonstrated. An intercomparison exercise was first led to reproduce modelled and observational reference spectra. The molecular vertical profiles, the aerosols’ model and the CO₂ continuum contribution were validated for the different spectral windows. This enabled us to determine the spectral bands, their bandwidth and the resolving power necessary for our purposes. Along the way, we identified possible improvements and science avenues. Some of them impact the instrument design, such as the need for polarimetric measurements. Others are related to remaining uncertainties in the model and laboratory measurements that will complement the investigation.

3D printing technologies have allowed the development of prototypes in several fields, such as clinical, aerospace, and infrastructure, to name a few. Another use is to adapt the laboratory instruments to customized applications to improve experiments and measurements in the data acquisition process. Some equipment is modified to include low-cost cameras, optical components, sensors, and mechanical artifacts using printed accessories employing PLA or PETG filaments, such as telescopes, microscopes, and spectrometers. These accessories allow us to maximize the features of the instruments and reduce the research cost. We describe a semi-automatic method for microalgae counting based on a digital microscope adapted to a 3D printing mechanical support and image processing in Matlab. Calibration will be carried out using a Neubauer chamber but will not be required for measurements, which makes a difference compared to similar methods. The results obtained for micro-algae counting show an average error of less than 5% compared to visual counting conducted by a biochemical specialist. We are describe a simple and low-cost method of counting microalgae using 3D printing technologies.

This study explores the generation of complex scanning patterns using Risley prisms for advanced optical applications. Risley prisms, composed of two independently rotating wedge prisms, allow precise control of light beam deviation. We investigate the generation of spirals, polar roses, epitrochoids, and hypotrochoids, highlighting their distinct fill factors, probability densities, and scanning velocities. These patterns are optimized for scanning different regions with high precision. The implementation of these methods in sequential and parallel systems is discussed, emphasizing the trade-offs between data processing complexity and scanning efficiency. This research provides valuable insight into optimizing scanning patterns and integrating real-time data analysis to improve efficiency in optical systems.

Achieving optimal synchronization accuracy between two White Rabbit devices hinges on the proper selection of transceivers, which act as electro-optical converters connecting WR devices to the optical network infrastructure. The correct choice of transceivers can significantly improve resilience to changes in the time offset between WR devices due to temperature fluctuations in the connecting optical fiber. To compare the performance of BiDi WDM and DWDM transceivers, an experimental setup was established under laboratory conditions to simulate a real optical network used for distributing precise time and frequency between two remote locations. The optical connection was emulated by integrating a 20 km G.652.D optical fiber into a climatic chamber, which provided variable environmental conditions similar to those experienced in real applications. The study compared BiDi WDM 1310/1550 nm transceivers with DWDM Ch33/Ch34 transceivers. Results showed that DWDM transceivers exhibited nearly thirteen times less sensitivity to temperature-induced changes in the optical connection, leading to a smaller time offset. Therefore, for achieving the highest accuracy in synchronizing WR devices in practical applications, DWDM transceiver technology is essential.

In recent years, terahertz frequency bands have attracted more and more attention due to their unique advantages, and terahertz imaging technology is developing into a new supplementary means of non-destructive testing. We have conducted in-depth research on terahertz non-destructive testing technology and developed a terahertz detector that can be used for non-destructive testing of wood. The detector mainly includes terahermet transceiver, signal processing system and data acquisition system. In order to achieve three-dimensional imaging, fast frequency sweep and the best anti-interference ability when detecting targets, wideband chirp continuous wave was selected as the radiation waveform of the system. In order to improve the ranging accuracy and three-dimensional imaging performance, a fully coherent form suitable for the terahertz band was selected. Based on the superheterodyne detection structure, the three-dimensional reconstruction of the sample is realized by the data acquisition system. On this basis, we use the self-developed quantum image data processing system to perform quantum image enhancement processing on the acquired three-dimensional reconstructed images, which further improves the contrast and clarity of the images, and is especially prominent in the noise environment, and has made significant progress in presenting details and information extraction. The center frequency of the terahertz detector is about 200GHz, the dynamic range is large, the operating distance can reach about 1m, and the distance resolution and direction resolution can reach the millimeter level. It lays the foundation for high-quality three-dimensional imaging and provides an effective way for non-destructive testing of non-metallic materials. Also,it can be applied to non-destructive testing of remote sensing target information.

Flood-induced changes over a wide area can be detected and assessed using bitemporal high-resolution satellite images in a timely and cost-effective manner [1]. Multivariate alteration detection-based method [2] is designed to use twice of the standard deviation of a variate as a threshold to separate change from no-change pixels in the variate and the final detection result is the union of individual variates results. However, the threshold in this method is significantly affected by the number of pixels of no-change to the number of pixels with change which leads to high omission error. Moreover, using all the whole set of variates increases the commission error due to including the variates with high correlation. In this paper, we introduced a novel method to decide between change and no-change, by using Otsu technique which is an optimal technique to separate between classes in gray level images [3]. Also, we proposed using the variate of least correlation instead of using the whole set of variates in detecting the induced change. Using this variate is justified since a variate with least correlation includes the induced change between bitemporal input images. The proposed algorithm is summarized as follows: Firstly, we have adjusted radiometric reflectance of the images that acquired at different times by using normalization which is a critical step in the application of flood-induced change detection. Multivariate alteration detection [2,4] is implemented as an approach for normalization. Secondly, we employed the variate with least correlation for induced flood detection by using Otsu method. To evaluate the proposed algorithm, real bitemporal-images of flood events are employed in this study. The experimental results on these images show that the proposed method quantitatively and qualitatively has outperformed the traditional MAD-based method for flood induced-detection and simultaneously reduced omission and commission errors.

In this work, we present a procedure to obtain optimized designs of the antireflection coatings of TARSIS optics. TARSIS, acronym for Tetra-Arm Super-Ifu Spectrograph, is a new Integral Field Spectrograph that incorporate image slicers. It will explore the sky in the near ultraviolet with an unprecedented field of view, and will be installed on the 3.5m telescope of the Calar Alto Observatory. In astronomical observations, we aim to maximize the amount of light of a telescope that reach the final stage of the instrument. However, the blue-UV range is particularly challenging because the optical materials available, for both the lenses and the coatings, are limited due to light absorption. Times increase dramatically, and the design and manufacturing processes are more complex. Particularly for coatings, we find the best design that maximize optical throughput combined with high robustness to manufacturing tolerances. TARSIS requires 40 different coatings designs. We achieve multi-layer coatings with: 1) very high transmittance, 2) at the mean angle on convex and concave surfaces, 3) minimum sensitivity to thin film deposition tolerances, and 4) minimum number of layers. To reflect the performance of the multi-layer coatings, we defined a merit function. We conducted a global search to find the best high-transmittance solutions with the fewest layers. We introduced random thickness variations into each solution in order to evaluate the effect on the merit function. We have developed a pseudo-color evaluation tool that shows design reliability over wavelength. This visualization allowed us to directly compare the performance of equivalent solutions. Finally, we evaluated that the optimized solutions did in fact provide a high level of transmission over a range of incidence angles. In summary, our designs have a high average transmittance > 99%, just four layers and are highly insensitive to thickness variations which speed-up the manufacturing process.