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The VIRUS2 instrument is a new fiber-fed multiplexed integral field spectrograph consisting of 6 units, each with 4 spectral channels, to provide large on-sky area coverage coupled with broad spectral coverage. VIRUS2 will be a new facility instrument on the McDonald Observatory 2.7 m Harlan J Smith Telescope. The instrument employs a novel beam-switch module within the fiber feed to split the light into the 4 spectral channels covering 370-930 nm at R~2000, while achieving a very compact and highly stable instrument. The design of VIRUS2 emphasizes stability and careful calibration, with scrambling in the beam-switch module, compact spectrograph format, and tight thermal control. This is the first time such measures have been employed at moderate spectral resolution. In this paper, we provide an overview of the instrument and the build status of the 24 spectrographs, dete ield units. VIRUS2 is funded by NSF and deployment is planned in the second half of 2021.

THz Atmospheric Limb Sounder (TALIS) is a microwave radiometer designed by the National Space Science Center (NSSC) of the Chinese Academy of Sciences (CAS) for sounding the vertical distribution of the atmosphere, focusing on measuring the temperature and the chemical composition of the middle and upper atmosphere. Fast Fourier transform spectrometer (FFTS) is the core component of TALIS back-end, which mainly undertakes the function of spectral analysis. In this paper, a new wideband, real-time FFTS design and implementation scheme is proposed to obtain the power spectrum of the signal through the core radix 16 real-time complex FFT algorithm. The analysis bandwidth and the number of channels of FFTS are 2 GHz and 1 k, respectively. The simulations and tests are performed using sinusoidal signals, and the results show that the effective number of bits (ENOB) is better than 3-bit, the signal-to-noise ratio (SNR) is better than 20 dB, and the spectral resolution is constant at 2.3 MHz. Moreover, the peak frequencies of the simulation and test are consistent, which can meet the requirements of the spectral line detection in TALIS.

The liquid crystal modulator devices (LCMD) have become an important technique in the field of hyperspectral imaging. However, the spectral resolution and accuracy of LCMD-based imaging spectrometers are limited due to their principle. To break this limitation and promote the application of LCMD, we propose a spectral reconstruction method using model-based neural networks. The calibrated spectral transmittance of LCMD and a carefully designed loss function are used to constraint the calculation. Experiments on reconstructing both substance spectra and spectral image cubes have validated the effectiveness and superiority of the proposed method.

For the requirement of the great breadth and high spectral resolution of hyperspectral sensor, Offner spectral imaging system, which can be divided into two types: prisms and gratings, is designed, and methods to filter secondary spectrum are also discussed. Basic the design, an Offner spectral imaging system with gratings is developed and tested. The research shows that, compared to prisms, Offner spectral imaging system with gratings not only have high spectral resolution, large flat field, little spectral smile and keystone, but also can satisfy the requirement of hyperspectral sensor that the system can be mounted on small or mini satellites.

In response to the demands of light weight, small size, wide field of view (FOV) and real time airborne spectral imaging, a novel spectral imaging system with lightweight and compactness is designed based on fold cascade structure. A concentric cascade spectral imaging system is studied. It mainly consists of two optics, a front fold monocentric objective and an Offner spectral imaging array. The front fold monocentric objective achieves an intermediate curved image with wide FOV, then the Offner spectral imaging array divides the intermediate image into sub-images and obtains spectral sub images through dispersion and reimaging. Based on the first-order theory and aberration characteristics, the cascade spectral imaging system is optimized. The optimized cascade spectral imaging system is with a real time full FOV of 110°, focal length of 110mm, F number of 4.8 and a working wavelength band of 480nm to 760nm. After performance evaluation, both its smile and keystone are well balanced. The spectral resolution is about 0.6nm, the maximum RMS radius on image plane is less than 3μm, and the MTF value is over 0.5@85 lp/mm. The tube length of the optimized system is only 85mm. The obtained cascade spectral imaging system not only achieves a real time spectral imaging in a wide FOV, but also realizes the miniaturization and lightness. It has a great potential application for airborne remote sensing and will make profound theorical value in this field.

Perovskites have been widely used in solar cells manufacturing due to their extraordinary photoelectric characteristics. The crystal quality of perovskite plays an important role in photoelectric conversion. Although conventional crystal quality detection methods, such as scanning electron microscopy(SEM) and atomic force microscope(AFM), have good performance of high spatial resolution, they are usually time-consuming, expensive, and sometimes damage the samples unavoidably. Hyperspectral imaging(HSI) technology has been utilized to monitor material growth process in recent years, due to its advantages of high spectral resolution, non-invasive and fast detection speed. Micro-hyperspectral imaging(MHSI) technology combines both HSI and microscopic technology, enabling it suitable for micro- and nanoscale material analysis. In this work, we have developed a kind of MHSI system. 3D data of perovskite monocrystals were obtained by transmission mode at room temperature. Perovskite mono-crystals were prepared by one-step solution self-assembly method. The experimental results illustrate that the specific absorption wavelength of perovskite is directly proportional to the thickness of mono-crystals. When the thickness increases, the absorption wavelength will shift red. The thickness factor is also verified by white light interference. The composition ratio of perovskite monocrystals has a certain dependence on its absorbance before 540 nm. The higher the proportion of Br atom is, the weaker the light absorption is, and auxiliary verification was carried out by energy dispersive spectrometer(EDS). In conclusion, MHSI technology can effectively monitor and analyze the preparation process and quality evaluation of micro- and nanoscale materials and structure, it shows a wide application prospect in material science and medical fields.

The European Space Agency (ESA), in collaboration with the European Commission (EC) and EUMETSAT, is developing as part of the EC’s Copernicus programme, a space-borne observing system for quantification of anthropogenic carbon dioxide (CO2) emissions. The anthropogenic CO2 monitoring (CO2M) mission will be implemented as a constellation of identical LEO satellites, to be operated over a period > 7 years and measuring CO2 concentration in terms of column-averaged dry air mole fraction (denoted as XCO2). Industrial activities for the phase B2CD have been kicked-off Mid 2020. The demanding requirements necessitate a payload composed of a suite of instruments, which simultaneously perform co-located measurements. A push-broom imaging spectrometer will perform co-located measurements of top-of-atmosphere radiances in the Near Infrared (NIR) and Short-Wave Infrared (SWIR) at high to moderate spectral resolution (NIR: 747- 773nm @0.1nm, SWIR-1: 1595-1675nm @0.3nm, SWIR-2: 1990-2095nm @0.35nm) for retrieving XCO2. These observations are complemented in the same spectrometer by measurements in the visible spectral range (405-490 nm @0.6nm), providing vertical column measurements of nitrogen dioxide (NO2) that serve as a tracer to high temperature combustion of fossil-fuel and related emission plumes (e.g. from coal-fired power plants and cities). High quality retrievals of XCO2 will be ensured even in situations of large aerosol loading, thanks to co-located measurements of aerosol resulting from a Multiple- Angle Polarimeter (MAP). Polarimetric measurements are performed over 40 angular views and in six spectral channels between 410 and 865 nm. Finally, due to the strong sensitivity of the XCO2 retrieval to cloud contamination, a three-band Cloud Imager (CLIM) will provide the required capacity to detect small tropospheric clouds and cirrus cover with an accuracy of 1% to 5% and a sampling better than 400 m.

The presence of peculiarities in terahertz spectra of many organic compounds allows the use of THz imaging and spectroscopy for the detection of various hazardous and explosive substances. This work is devoted to the study of the detection of trace amounts of 1,3,5-Trinitro-1,3,5-triazinane (RDX) in the form of particles localized in millimeter and submillimeter sizes using THz imaging with spectral resolution. As a result of the work, images of trace amounts of RDX in reflected THz radiation were obtained. The contrast in these images made it possible to detect single particles of the powdery substance. The difference in contrast for RDX and polyethylene (PE) in the obtained terahertz images makes it possible to use THz imaging with spectral resolution not only for detection, but also for the identification of chemical compounds.

Precise X-ray Imaging diagnostics to acquire the plasma state and its evolution plays an important role in basic researches such as inertial confinement fusion (ICF), high energy density physics (HEDP), and another ultrafast phenomenon. The plasma signals with the characteristics of small scale, rapid evolution and complex spectrum requires the X-ray diagnostics optics to have high spatial resolution and collection efficiency, as well as certain spectral resolution. The multilayer Kirkpatrick–Baez (KB) microscope is a common X-ray optics to obtain high spatial, collecting efficiency or spectral resolution. Coupling multichannel KB microscope with the framing camera, the temporal evolution behavior of the ultrafast plasma can be recorded. The paper mainly presents our latest research on two-energy sixteen-channel multilayer KB microscope for double-cone ignition (DCI) experiments, including its optical and multilayer design. By high-resolution backlighting and self-emission imaging using two-energy multichannel KB microscope, plasma information related to density and temperature can be realized simultaneously.

The Keck Planet Imager and Characterizer (KPIC) is a novel instrument that combines high-contrast imaging with high-resolution spectroscopy to enable high-dispersion coronagraphy (HDC) techniques that allow us to characterize directly imaged exoplanets at a spectral resolution of R~35,000. At this resolution, individual absorption lines in planetary atmospheres are spectrally resolved, allowing for measurements of molecular abundances to constrain chemical composition, planetary radial velocities to constrain orbital configurations, and planetary spin to constrain angular momentum evolution. I will provide an overview of the instrument, with a focus on its novel fiber injection unit (FIU) and the use of single mode fibers. I will discuss new HDC techniques we are developing that take advantage of the single-mode fibers of KPIC to both spatially and spectrally filter out the bright glare of the host stars to study the faint exoplanets. In particular, we have demonstrated the ability to forward model the high-resolution spectrum of diffracted stellar speckles, allowing us to directly fit our data without the need for cross-correlation functions. I will present some early science observations from KPIC that successfully demonstrate its technical capabilities, with the highlight being the first detection of all four HR 8799 planets at high spectral resolution. I will conclude with future avenues to push the sensitivity of HDC techniques and discuss possible synergies with other exoplanet characterization techniques such as long-baseline interferometry.

The majority of the 4,000 known exoplanets have been detected via transit photometry. Unambiguous characterization of their atmospheres for biosignatures such as H2O, CH4, O3 and O2 can be unlocked with high-resolution spectroscopy from space. To this end, we investigate the feasibility of a high-resolution (R=50,000) spectrograph on a CubeSat. This work compares optical design elements of traditional Echelle grating and a virtually imaged phased array (VIPA) using exposure time calculations. The limited magnitude when varying the spectral resolution and instrument size is reported. VIPAs on a 6U CubeSat is a cost-effective solution for high-resolution spectroscopy from space.

The Nano-satellite Atmospheric Chemistry Hyperspectral Observation System (NACHOS) is a high-throughput (f/2.9), high spectral resolution (~1.3 nm optical resolution, 0.6 nm sampling) Offner-design hyperspectral imager operating in the 300-500 nm spectral region. The 1.5U instrument payload (1U optical system, 0.5U electronics module) is hosted by a 1.5U LANL-designed CubeSat bus to comprise a 3U complete satellite. Spectroscopically similar to NASA’s Ozone Monitoring Instrument (OMI), which provides wide-field global mapping of ozone and other gases at coarse spatial resolution, NACHOS fills the complementary niche of targeted measurements at much higher spatial resolution. With 350 across-track spatial pixels and a 15-degree across-track field of view, NACHOS will provide spectral imaging at roughly 0.4 km per pixel from 500 km altitude. NACHOS incorporates highly streamlined gas-retrieval algorithms for rapid onboard processing, alleviating the need to routinely downlink massive hyperspectral data cubes. We will discuss the instrument design, challenges in achieving mechanical robustness to launch vibration in such a compact instrument, the onboard calibration system, and gas-retrieval data downlink strategy. We will also discuss potential science missions, including monitoring of NO2 as an easily detected proxy for anthropogenic fossil-fuel greenhouse gases, monitoring lowlevel SO2 degassing at pre-eruptive volcanoes, H2CO from wildfires, and characterization of aerosols. The long-term vision is for a many-satellite constellation that could provide both high spatial resolution and frequent revisits for selected targets of interest. As an initial technology demonstration of this vision, the NACHOS project is currently slated to launch two CubeSats in early 2022.

Hyperspectral imaging (HSI) is a novel non-invasive analytical technique based on spectroscopy. It measures the light spectrum from each point of a scene of interest. It generates an accurate digital record for documentation and archiving in art conservation. This information can be used for diagnostics by monitoring changes, degradation or damages to paintings, for supporting in artwork restoration, for artist's material identification and pigment mapping, as well as for discovering the history of a piece of art by e.g. revealing underdrawings and retouchings. HSI measures the continuous spectrum of the light as a function of the wavelength λ for each pixel of the scene at coordinates (x, y) with fine spectral resolution, thus building the so-called 3-dimensional hyperspectral image. This data cube contains an extensive amount of information. Therefore, many numerical methods and algorithms have been developed to enable the extraction of quantitative parameters related to the physicochemical properties of the imaged objects from congested scenes. Here we present HERA, a novel and compact hyperspectral camera by NIREOS. The device, based on the Fourier-transform approach, combines high delay precision, long-term stability, insensitivity to vibrations and broad spectral coverage. It can measure absolute reflectance and fluorescence with very high spectral accuracy and resolution (≈3-nm, comparable to best commercial push-room systems) in the visible and near-infrared. HERA does not require any scanning of the object under analysis. This feature makes it extremely flexible and applicable to the study of works of art of different nature and size. Potential applications range from the on-site study of museum paintings, to the assessment of the conservation status of large monuments and historic buildings, to the documentation of small objects using standard macro photography lenses. In this paper, we will present a series of application examples in the field of conservation science to demonstrate its versatility.

We demonstrate the use of a wide-field, compact and ultra-stable hyperspectral camera, based on the Fourier-transform approach [1], to investigate the photoluminescence emission occurring from different radiative recombination paths in artist materials and paintings. The camera, based on the translating wedge-based identical pulse encoding system (TWINS), is characterized by high spectral resolution, high flexibility and compactness. Thanks to these latter feature we show how the device can be easily adapted for both microscopy measurements and remote time-gated imaging of paintings and we show its use for the identification and mapping of fluorescent species in artworks by also exploiting the potentiality provided by chemometrics methods.

The investigation of artworks of cultural heritage is generally aimed at the characterization of the constituent materials and the evaluation of their state of conservation. Research may shed light on the pigments and their potential deterioration mechanisms, and on the conservation treatments. Laboratory analysis on micro-samples taken from the artwork is still an invaluable practice for a deep understanding of the paint layer composition. In this context, a powerful technique is spectral microscopy, which acquires the spectrum for each point in the image of a sample. To acquire a continuous spectrum, one very efficient method is based on Fourier-transform (FT) spectroscopy as it allows massive parallelization on all the image pixels. Here we introduce a hyperspectral microscope based on an innovative FT spectrometer; the device is compact, robust, with high throughput and broad spectral coverage. In our microscope, light is collected by an infinity-corrected objective, propagates in the innovative spectrometer and is imaged on a silicon monochrome CMOS camera by a tube lens. The typical spectral resolution of the microscope, which can be flexibly adjusted for each measurement, is 3 THz (4 nm at 600 nm). We show very compact implementations of the hyperspectral microscope and their use for wide-field imaging of reflection, fluorescence and, interestingly, fluorescence-free Raman spectra. Thanks to the high throughput, the acquisition time of our microscope is significantly shorter than traditional raster-scanning approaches.

Historical buildings are prone to deterioration due to various reasons including environmental conditions, humidity and structural failures. The main factors of their degradation are moisture and salt activity. Salt weathering affects the appearance of the monuments but also causes chemical and mechanical degradation. The effect of salts in building deterioration is well-known, with several laboratory-based studies focusing on understanding the formation mechanisms. Here, we introduce a new methodology for the non-invasive monitoring and identification of moisture and salts following a complementary remote sensing approach. The study is based on ground-based remote short-wave infrared (SWIR) imaging and remote Raman spectroscopy from standoff distances of 3 to 15m [1]. The remote SWIR spectral imaging system covers the spectral range between 1 and 2.5 μm, with a spectral resolution of 5.5 nm and spatial resolution of 150 μm at a distance of 3m. The in-house developed mobile standoff Raman system operates with a continuous-wave (CW) excitation laser source at 780 nm. The laser beam can be focused at different distances resulting in a spot size of ~1 mm on the target. In our approach, SWIR imaging is used for scanning large wall surfaces. The post-processing of the acquired spectral imaging data using our novel machine learning-based clustering methods highlights the material variations across the wall. The detailed examination of the mean SWIR spectra for each cluster, allows a primary identification of moisture and salts, indicating also variations in volume concentration. The salts identification is then confirmed by remote Raman spectroscopy. The new method is presented through the examination of the historical building in Fort Brockhurst, an English Heritage monument in Portsmouth, UK.

Developed by Airbus Defense and Space under CNES overall responsibility in partnership with Eumetsat, the Infrared Atmospheric Sounding Interferometer New Generation (IASI-NG) is a key payload element of the second generation of European meteorological polar-orbit satellites (METOP-SG). It will continue and improve the IASI mission in the next decades (2020-2040) in the field of operational meteorology, climate monitoring, and characterization of atmospheric composition related to climate, atmospheric chemistry and environment. The main challenge is the performance improvement by a factor two compared to IASI with regard to spectral resolution and radiometric error. The measurement technique is based on wide field Fourier Transform Spectrometer (operating in the 3.5 - 15.5 μm spectral range) with an innovative Mertz compensated interferometer to manage the so-called self-apodisation effect and the associated spectral resolution degradation. End 2019, IASI-NG instrument Critical Design Review has been successful and since nearly all the sub-units of the PFM instrument have been fully characterized and delivered to ADS. Interferometer principle has been partially validated on a Bread Board Model and Interferometer EQM and PFM have completed qualification and performance test. The aim of this paper is first to present the performance budget of the instrument after CDR, based on sub-units consolidation (sub-unit CDR) or measurement (sub-assemblies PFM measurement). We will then focus on the overall instrument development status and the different upcoming milestones until the delivery.

We report the preliminary design of a new small-size remote sensing instrument operating in the Short Wavelength InfraRed (SWIR) domain of the spectrum (1.560µm to 1.700µm) to monitor, detect, and measure atmospheric Carbon Dioxide (CO_2) and Methane (CH_4) concentrations. We highlight the instrument features, technical specifications (including a relatively high spectral resolution of approximately 0.5nm), optical design, and components. The synthetic spectral response of the instrument is also explored using NASA’s Planetary Spectrum Generator (PSG) which is a Line-by-Line radiative transfer code. The instrument is currently under development at the ARC Training Centre for CubeSats, UAVs and Their Applications (CUAVA) and Sydney Astrophotonic Instrumentation Laboratory (SAIL) at the University of Sydney. Once built, it will conduct an atmospheric reconnaissance from an Unmanned Aerial Vehicle (UAV) and will be tested to qualify for future space flights on one of CUAVA’s CubeSats.

Meteosat Third Generation (MTG) is the next challenging mission for accurate observation of the Earth dedicated to meteorology forecast. MTG encompasses two different missions: MTG-I (Imaging) and MTG-S (Sounding). MTG-I optical payload counts the FCI (Flexible Combined Imager), a multi-spectral imager in the continuity of Meteosat Second Generation (MSG) with improved performance and additional spectral bands. MTG-S transports the IRS instrument which is an Infrared Fourier Transform Spectrometer dedicated to the sounding of the atmosphere inspired by the previous IASI mission. Located in a geostationary orbit, the satellites are covering the full hemisphere for imaging (FCI) in less than 10 minutes in 16 different spectral bands from Visible to Very Long Wave IR at a resolution of 0.5-2 km and make a complete IR sounding of the atmosphere (IRS) in less than 1h at a spatial resolution of 4 km and a spectral resolution of 0.625 cm-1. In this article, we describe the detection chains of FCI and IRS instruments which give accurate sight to the remote sensing and afford the capability to reach the objectives of MTG-I and S missions. Some particularities of designs and key performance are presented. MTG on ground tests have provided interesting results which are therefore presented. These results have been obtained after 10 years of intensive research and development at Thales Alenia Space (Prime FCI) and OHB(Prime IRS), with the support and supervision of ESA and EUMETSAT. This research and development work has been performed under an ESA contract.

The European Space Agency (ESA), in collaboration with the European Commission (EC) and EUMETSAT, is developing a space-borne observing system for quantification of anthropogenic carbon dioxide (CO2) emissions. Forming part of the EC's Copernicus programme, the CO2 monitoring (CO2M) mission will be implemented as a constellation of identical satellites, to be operated over a period > 7 years and measuring CO2 concentration in terms of column-averaged mole fraction (denoted as XCO2). Each satellite will continuously image XCO2 along the satellite track on the sun-illuminated part of the orbit, with a swath width of >250 km. Observations will be provided at a spatial resolution < 2 x 2 km2 near the swath center, with high precision (

To obtain the fine characteristics of the atmospheric carbon dioxide absorption spectrum, the imaging spectrometer must have high spectral resolution, but the volume of the instrument will increase simultaneously which is not conducive to remote sensing detection on satellite platforms. To solve this problem, we used a silicon immersion grating as dispersion element that diffraction occurs inside the silicon grating medium, the dispersion and spectral resolution are increased by 3.4 times respect to the conventional grating, and the volume of the spectrometer can be reduced to 1/40 at most. Smile is introduced because of the dispersion difference of light between the non-principal section and the principal section, which affects the spectral fidelity, data retrieval and detection accuracy. We established a model to analyze the smile by the silicon immersion grating and used the distortion of off-axis lens to correct. To miniaturize the instrument, optical system adopted the Littrow structure that the dimension is 410 mm×130 mm×110 mm. The optical system works in the short-wave infrared carbon dioxide weak absorption band 1.594-1.624 μm with a spectral resolution of 0.08 nm, entrance slit length is 16 mm and F number is 2. The optimized MTF is greater than 0.87 at the Nyquist frequency of the detector, the RMS radius of the spot diagram is within the Airy disk, and the maximum smile is less than 0.1 m, which is less than 1% of a single detector pixel. The optical system has excellent imaging performance, meeting the requirements of atmospheric carbon dioxide detection.

Colour diagnosis of traditional Chinese medicine (TCM) is the main content of “looking” inspection in the four-diagnosis methods of "looking, listening, asking and feeling the pulse". The action of light on the face is a very complex process, it is difficult to distinguish reflected light from internally reflected light by human eyes alone. In this paper, we discuss the relationship between TCM facial colour diagnosis and optics, integrate imaging spectroscopy to improve the objectified development of facial colour diagnosis in TCM. A visible band snapshot hyperspectral imaging spectrometer is designed based on a grating dispersion module. This imaging spectrometer is a snapshot system with 34° field of view and a measured spectrum from 400 nm to 680 nm. The spectral resolution reaches 3nm. The total length of the optical system is only 165mm, which can realize the miniaturization of products.

Infrared spectroscopic imaging is an analytical approach that can reveal important molecular information without the need for substantial sample processing. These instruments can provide objective and automated evaluations to aid pathologists improve diagnostic accuracy. The quantum cascade laser, allows for a discrete frequency approach, increasing imaging speeds with superior spatial and spectral resolution. We present our recent progress toward developing new instruments capable of diffraction limited performance at all fingerprint-region wavelengths across the entire field of view. We demonstrate high throughput imaging of tissue sections and tissue microarrays and evaluate the advantages in data quality obtained from a well-corrected system.

Infrared polarimetry is a powerful label-free diagnostic tool to study the molecular alignment and organization in biological tissues and cells. Similar to absorbance images which capture intensity information, polarimetric imaging is essential for capturing the polarization states of the light intensity. Recent advancements in the development of Quantum Cascade Lasers (QCL) sources have opened new avenues in IR imaging with high spatial and spectral resolution while enabling drastic increases in imaging speeds than a corresponding FT-IR approach. We demonstrate improved performance in terms of fast and comprehensive polarimetric image acquisition using a custom-built QCL microscope with point mapping design.

We present a high spectral resolution multiplexing acquisition mode for SRS microscopy based on a dual-beam femtosecond laser. A multi-channel Acousto Optical Tunable Filter (AOTF) generates spectral masks, given by the Hadamard matrix, by turning on and off different subsets of its 8 independent channels, corresponding to different wavelengths available within the broad bandwidth of the “pump” femtosecond laser. The SRS spectrum is retrieved by using the inverse Hadamard matrix. When additive noise is dominating, spectral measurements using the multiplexed method show the same signal to noise ratio of conventional single-wavenumber acquisitions performed with 4 times longer integration time.

Nonlinear interferometers based on non-degenerate spontaneous parametric down-conversion (SPDC) create a link between separate spectral ranges. This allows for measurements in remote spectral regions while detecting light in easily accessible wavelengths. In our work, we use periodically poled lithium niobate to create correlated signal (visible or near-infrared) and idler (mid-infrared) photon pairs. Using a nonlinear interferometer in Michelson geometry, we obtain broadband mid-infrared spectra from light detected with a silicon avalanche photodiode. Combining the nonlinear interferometer with a measurement scheme in close analogy to classical Fourier-transform infrared spectroscopy allows for sub-wavenumber spectral resolution, which opens up possibilities for applications such as precise spectroscopic gas analysis.

We introduce an anamorphic detection paradigm to optimize spatial and spectral resolution in adaptive optics line-scan OCT, wherein an improved light collection efficiency and signal roll-off compared to traditional methods was demonstrated. The benefits for in vivo imaging were exemplified by retrieving nanometer-scale light-induced optical path length dynamics at high speed in individual cones. The high speed, sensitivity and cellular-scale resolution of the resulting adaptive optics line-scan OCT instrument offers a robust and sensitive biomarker for retinal function in health and disease.

We demonstrate a state-of-the-art nanoIR instrument that integrates a broadband mid-IR OPO/DFG system from APE GmbH with a scanning probe system from Bruker. This broadband laser covers an extended wavelength range, and works in both broadband and narrowband modes. The broadband mode covers the range of 670-4000 cm-1 (2.5-15 μm) allowing fast acquisition of s-SNOM spectrum. The narrowband mode covers the range of 670-2200 cm-1 (4.5-15 μm), giving access to key molecular vibrational modes commonly used for chemical identification in the “fingerprint” region. With its higher spectral resolution, the narrowband enables s-SNOM imaging at defined IR wavelength, as well as AFM-IR spectroscopy and imaging. The comprehensive capabilities and performance of this combined system are highlighted by the high quality results obtained from several representative samples including 2D material, polymer film and biological sample.

Reflectance spectroscopy and hyperspectral (or multispectral) imaging that can acquire a matrix of intensity as a function of the position and the wavelength of light (also known as a hypercube) are extensively used to quantify biochemical composition, structure, and vasculature in biological tissue. However, these methods often rely on bulky and costly optical components, which limit the development of compact, rapid, and cost-effective technologies. Fortuitously, several different research communities have demonstrated that it is possible to mathematically reconstruct hyperspectral (with high spectral resolution) or multispectral data from RGB images taken by a conventional camera (three-color sensor). However, these methods, such as compressive (compressed) sensing and deep learning, are often limited for extracting detailed biological spectral profiles and require an extremely large amount of training data. We have recently developed a spectral super-resolution framework that enables us to virtually transform the built-in camera (RGB sensor) of a smartphone into a hyperspectral imager for accurate and precise spectroscopic analyses, without a need for any hardware modifications or accessories. Super-resolution means high-resolution reconstruction of digital images acquired with lowresolution systems. We have extended this concept to the frequency domain for hyperspectral imaging, which has numerous biomedical applications. As an example, our mobile version of spectral super-resolution combines imaging of peripheral tissue and spectroscopic quantification of blood hemoglobin levels in a noninvasive manner. Spectral superresolution spectroscopy can also serve as an example that data-driven technologies can minimize hardware complexity, facilitating the tempo of clinical translation.

Broadband time resolved absorption and dispersion spectroscopy using a conventional Fourier transform spectroscopy is often a challenging task due to very long measurement times. Here, we present time resolved mid-infrared dual-comb absorption and dispersion spectroscopy of methane and ethane under electrical discharge, covering a spectral bandwidth of 2850-3150 cm-1, with spectral resolution of 5 GHz and temporal resolution of 20 µs. This new approach enabled the direct measure of broadband complex refractive index of materials involved in plasma, which is an indication of plasma density.

We present a multi-species trace gas sensor based on a broadband mid-infrared supercontinuum source and a compact home-built Fourier Transform Spectrometer with a balanced detection scheme. The gas sensor provides a spectral resolution of 1 GHz in the wavelength range of 2.4-4.2 µm. Using a global fitting routine, we are able to retrieve the concentrations of different species in complex gas mixtures, achieving detection sensitivities in the order of 100 ppbv.Hz-1/2 (4s measurement time). We used the sensor to measure volatiles from fruit (apples, pears) under storage conditions, demonstrating its potential for monitoring fruit in commercial storage facilities.

Dual-comb coherent anti-Stokes Raman scattering (DC-CARS) spectroscopy is an effective tool for high-speed acquisition of vibrational spectra in the fingerprint region. DC-CARS spectroscopy also provides high spectral resolution by virtue of its ability to cover a large time delay between the pump and probe pulses, from two optical frequency combs with slightly different, fixed pulse repetition rates. However, less than 1% of the incident pulse energy is used to acquire the CARS signal because the repetition interval of the laser pulses (

We introduce a Fourier-transform hyperspectral microscope based on an ultrastable birefringent interferometer. The microscope enables wide field acquisition with broad spectral coverage, tunable spectral resolution, high sensitivity and short acquisition time. We present the prototype of an add-on to a commercial microscope. We provide examples of applications in biology and solid state physics. The microscope is suited for fluorescence and Raman imaging.

As part of its technology demonstration, the Nancy Grace Roman Space Telescope (RST) Coronagraph Instrument (CGI) will demonstrate point source spectroscopy and polarization measurements of disks. The specific implementation of spectroscopy is a zero-deviation Amici prism and a slit to be placed on the planet after high contrast has been achieved by CGI. The polarization optics are a set of Wollaston prisms so that orthogonal polarization states can be measured simultaneously. The CGI spectral characterization mode, being designed and built and Goddard Space Flight Center (GSFC), has a spectral resolution of R50 at its central wavelength and is designed to accommodate a 15% bandpass spanning 610􀀀785nm. In order to recover Stokes information, there are two sets of Wollaston prisms clocked 45 degrees with respect to one another with each measurement taken in series. The Wollaston design and optical elements are a contribution by the Japanese Aerospace Exploration Agency (JAXA), with final alignment and testing being done at GSFC. The spectroscopy mode is designed to target Methane absorption features around 730nm, keeping the spectral resolution as low as possible to improve the signal-to-noise ratio and hence reduce detection time. We highlight the requirements for these modes and address the challenge of on-orbit spectral calibration for a deployable slit in the presence of pointing drifts. Of unique interest is how the observatory error budget couples into good stellar spectrum calibration and subsequent speckle subtraction. We also provide further detail on the optomechanical design, its modeled performance, and operations concept. These performance metrics are simulated to demonstrate how a slit located at an arbitrary field point is homed onto the planet and converted to a calibrated spectrum.

We are developing a high-resolution near-infrared spectrograph for exoplanet searches with telescopes in Suther- land, South Africa; the South Africa Near-infrared Doppler (SAND) instrument. It covers the z- and Y -bands (0.83–1.10 µm) simultaneously with a maximum spectral resolution of 55, 000. This specification enables the precise radial velocity (RV) measurements to search for both giant planets around young stars and habitable planets around nearby M-dwarfs. The SAND is a fiber-fed instrument and, therefore, can be installed into several telescopes at the same site by changing the fiber connection. It will be operated mainly on the PRIME telescope, which is newly developed by Osaka University in Japan. The InfraRed Survey Facility (IRSF) and the Southern African Large Telescope (SALT) are also candidate telescopes for the installation. Inside the SAND spectrograph, a star image ejected from the fiber is sliced half and each sliced image is spectrally dispersed by an echelle grating. As a reference source for the wavelength calibration, light transmitted from a Fabry-Perot Etalon is simultaneously injected into the spectrograph and share the almost identical optical pass. The SAND is expected to realize RV-measurements for targets in large stellar associations at the southern sky, with exclusive and flexible use of the telescope time.

We present the science case, and telescope and instrument designs for our ultra-wide field submillimeter observatory, CCAT-Prime to be sited at a 5600 m elevation site on Cerro Chajnantor in northern Chile. Our science focusses on the study of star and galaxy formation from the epoch of reionization to the present, SZ observations of galaxy clusters, and polarization studies of the CMB and Galactic foregrounds. Our instruments include direct detection polarization-sensitive cameras and spectroscopic imagers, and high spectral resolution heterodyne array receivers. The CCAT-prime telescope is being built by Vertex Antennentechnik GmbH with first light in late 2021.

We are building an image slicer integral field unit (IFU) to go on the IMACS wide-field imaging spectrograph on the Magellan Baade Telescope at Las Campanas Observatory, the Reformatting Optically-Sensitive IMACS Enhancement IFU, or ROSIE IFU. The 50.4" x 53.5" field of view will be pre-sliced into four 12.6" x 53.5" subfields, and then each subfield will be divided into 21 0.6" x 53.5" slices. The four main image slicers will produce four pseudo-slits spaced six arcminutes apart across the IMACS f/2 camera field of view, providing a wavelength coverage of 1800 Angstroms at a spectral resolution of 2000. Optics are in-hand, the first image slicer is being aluminized, mounts are being designed and fabricated, and software is being written. This IFU will enable the efficient mapping of extended objects such as nebulae, galaxies, or outflows, making it a powerful addition to IMACS., 12 pages, 9 figures, 2 tables, submitted to SPIE

MAVIS is a future imaging spectrograph for the VLT in which the spectrograph is fed by an IFU. Imager and IFU are fed by Multi-Conjugate Adaptive Optics for the wavelength range 370 nm to 930 nm. The spectrograph will deliver a spectral resolution of more than 4000. The IFU field has a choice of 2 spaxel sizes. It is 9 arsec2 with 25 mas spaxels and 36 arsec2 with 50 mas. The design follows the proven concept of Advanced Image Slicer (AIS) as for Gemini NIFS and GNIRS, VLT MUSE and KMOS, JWST NIRSpec, and many others. In the present design, the field is first split in 2 and each subfield is imaged on a slicer mirror array made of long thin mirrors that slice the field into 50 images and send them in different directions to be reimaged side by side on the slit by another mirror array. Additional optics on the slit reimage the pupil at the right place in the spectrograph. Three different options are under study for the slit optics. One is a mirror array of considerably lower cost than the standard design in an AIS. At 25 mas, the spaxels are near the diffraction limit of the longest wavelength. This present challenges not present for seeing limited IFUs as focal ratio degradation due to diffraction by the slices. Another challenge comes from the short minimum wavelength. It is difficult to manufacture efficient reflection coatings for the whole wavelength range. Transmissive fore-optics were then also studied. The field splitter which sends half the field to each of the 2 arms was integrated into the fore-optics. This removes 2 air-glass surfaces from each arm.

The Magellan Infrared Multi-object Spectrograph (MIRMOS) is a near-infrared (NIR) multi-object spectrograph (MOS) and integral field unit (IFU) to be deployed at the Magellan 6.5-meter telescopes at Las Campanas Observatory. MIRMOS is designed to address frontier scientific questions in extragalactic, cosmological, and exoplanetary science. These scientific questions led us to spectrograph with an instantaneous wavelength range from 0.89-2.4 µm with a spectral resolution < 3, 700. The spectrograph is fed by a front end that switches between a robotic mechanical slit mask capable of deploying nearly 90 slits over a 13' x 3' field, or by an image slicer IFU with a wide field of 26" × 20". MIRMOS is currently under design at the Carnegie Observatories.

The Fiber Optic Broad-band Optical Spectrometer (FOBOS) is a high-priority spectroscopic facility concept for the W. M. Keck Observatory. Here, we provide an update on the FOBOS conceptual design. FOBOS will deploy 1800 fibers across the 20-arcminute field-of-view of the Keck II Telescope. Starbugs fiber positioners will be used to deploy individual fibers as well as fiber-bundle arrays (integral field units, IFUs). Different combinations of active single fibers or IFUs can be selected to carry light to one of three mounted spectrographs, each with a 600-fiber pseudoslit. Each spectrograph has four wavelength channels, enabling end-to-end instrument sensitivity greater than 30% from 0.31-1.0 µm at a spectral resolution of R ~ 3500. With its high fiber density on a large telescope and modest field-of-view, FOBOS is optimized to obtain deep spectroscopy for large samples. In single- fiber mode, it will deliver premier spectroscopic reference sets for maximizing the information (e.g., photometric redshifts) that can be extracted from panoramic imaging surveys obtained from the forthcoming Rubin and Roman Observatories. Its IFUs will map emission from the circumgalactic interface between forming galaxies and the intergalactic medium at z ~ 2–3, and lay the path for multiplexed resolved spectroscopy of high-z galaxies aided by ground-layer and multi-object adaptive optics. In the nearby universe, its high sampling density and combination of single-fiber and IFU modes will revolutionize our understanding of the M31 disk and bulge via stellar populations and kinematics. Finally, with a robust and intelligent target and program allocation system, FOBOS will be a premier facility for follow-up of rare, faint, and transient sources that can be interleaved into its suite of observing programs. With a commitment to delivering science-ready data products, FOBOS will enable unique and powerful combinations of focused, PI-led programs and community-driven observing campaigns that promise major advances in cosmology, galaxy formation, time-domain astronomy, and stellar evolution.

MANIFEST is a multi-object fibre positioner for the Giant Magellan Telescope that uses ‘Starbug’ robots to accurately position fibre units across the telescope’s focal plane. MANIFEST, when coupled to the telescope’s planned seeing-limited instruments, GMACS and GCLEF, offers access to: larger fields of view; higher multiplex gains; versatile focal plane reformatting of the focal plane via multiple integral-field-units; increased spectral resolution using image-slicers; the capability for simultaneous observations with multiple instruments; the possibility of a gravity-invariant spectrograph mounting; the potential for OH suppression via fiber systems in the near-infrared; and the versatility of adding new instruments in the future. We have now completed the pre-concept phase for MANIFEST. This phase has focused on developing the science case and requirements, further developing high risk aspects of the instrument design, designing the opto-mechanical interfaces to the GMACS and GCLEF instruments, and detailing the interfaces to the GMT.

We present the initial design, performance improvements and science opportunities for an upgrade to the Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS). FIFI-LS efficiently measures fine structure cooling lines, delivering critical constraints of the interstellar medium and starforming environments. SOFIA provides the only FIR observational capability in the world, making FIFI-LS a workhorse for FIR lines, combining optimal spectral resolution and a wide velocity range. Its continuous coverage from 51-203 microns makes FIFI-LS a versatile tool to investigate a multitude of diagnostic lines within our galaxy and in extragalactic environments. The sensitivity and field-of-view (FOV) of FIFI-LS are limited by its 90s-era photoconductor arrays. These limits can be overcome by upgrading the instrument using the latest developments in Kinetic Inductance Detectors (KIDs). KIDs provide sensitivity gains in excess of 1.4 and allow larger arrays, enabling an increase in pixel count by an order of magnitude. This increase allows a wider FOV and instantaneous velocity coverage. The upgrade provides gains in point source observation speed by a factor

BlueMUSE is a blue-optimised, medium spectral resolution, panoramic integral field spectrograph based on the MUSE concept and proposed for the Very Large Telescope. With an optimised transmission down to 350 nm, a larger FoV (1.4 × 1.4 arcmin2) and a higher spectral resolution (λ/Δλ ~ 4000) compared to MUSE, BlueMUSE will open up a new range of galactic and extragalactic science cases allowed by its specific capabilities in the 350-580nm range, beyond those possible with MUSE. In this paper, we present the optomechanical architecture and design of BlueMUSE at pre-phase A level, with a particular attention to some original aspects such as the use of curved detectors.

We present the design and testing of FOURIER, the first generation science beam combiner for the MROI. FOURIER is a three-way, J, H and K band image plane combiner which is designed primarily for observations at faint limiting magnitudes. We outline the main science requirements and discuss how the design of FOURIER contributes to meeting these requirements. We present the first laboratory characterisation of the instrument including validation of the PSF profile, demonstration of high contrast fringes, and the spectral resolution of the instrument, all of which show promising results. We conclude by discussing the path to deployment of FOURIER at the MROI ahead of the first science observation at the array.

The Institute for Astrophysics Gottingen operates a solar observatory that combines a 50 cm siderostat with (1) a vacuum vertical telescope, (2) a very high resolution Fourier Transform Spectrograph (R < 900, 000 at 600 nm), and (3) a Laser Frequency Comb for extremely precise and accurate frequency calibration (< 10 cm/s). We introduce our setup that feeds the spectrograph with either a 32.5” field of view of the solar surface, or with disk-integrated sunlight for Sun-as-a-star observations and explain the necessary computational steps to guide specific positions on the solar surface into the fiber. Our instrument suite can deliver spectroscopic measurements with extremely accurate frequency calibration, which is valid across very large frequency regions (approx. 400-800 nm in wavelength). This allows precision spectroscopy of individual lines in order to study the variability of spectral lines in Sun-as-a-star observations as well as determining the convective blueshift across the solar surface from many spectral lines.

CYRA (CrYogenic solar spectrogRAph) is a facility instrument of the 1.6-meter Goode Solar Telescope (GST) at the Big Bear Solar Observatory (BBSO). CYRA focuses on the study of the near-infrared solar spectrum between 1 and 5 microns, a under explored region which is not only a fertile ground for photospheric magnetic diagnostics, but also allows a unique window into the chromosphere lying atop the photosphere. CYRA is the first ever fully cryogenic spectrograph in any solar observatory with its two predecessors, on the McMath-Pierce and Mees Telescopes, being based on warm optics except for the detectors and order sorting filters. CYRA is used to probe magnetic fields in various solar features and the quiet photosphere. CYRA measurements will allow new and better 3D extrapolations of the solar magnetic field and will provide more accurate boundary conditions for solar activity models. Superior spectral resolution of 150,000 and better allows enhanced observations of the chromosphere in the carbon monoxide (CO) spectral bands and will yield a better understanding of energy transport in the solar atmosphere. CYRA is divided into two optical sub-systems: The Fore-Optics Module and the Spectrograph. The Spectrograph is the heart of the instrument and contains the IR detector, grating, slits, filters, and imaging optics all in a cryogenically cooled Dewar (cryostat). The detector a 2048 by 2048 pixel HAWAII 2 array produced by Teledyne Scientific & Imaging, LLC. The interior of the cryostat and the readout electronics are maintained at 90 Kelvin by helium refrigerant based cryo-coolers, while the IR array is cooled to 30 Kelvin. The Fore-Optics Module de-rotates and stabilizes the solar image, provides scanning capabilities, and transfers the GST image to the Spectrograph. CYRA has been installed and is undergoing its commissioning phase., 11 pages, 9 figures, 2 tables. Prepared for SPIE conference proceedings

International audience; The Maunakea Spectroscopic Explorer (MSE) is a 10m-class, wide-field (1.5 sq. degree) and high-multiplex (< 3000 fibers) spectroscopic facility that will replace the 3.6m Canada-France-Hawaii Telescope. With backend spectrographs operating at low (R ~ 3000), moderate (R ~ 6000) and high (R ~ 20/40 k) spectral resolution across the 0.36 – 1.8 µm range, MSE will be poised to address a variety of science questions among which the nature of dark matter, the origin of the elements in the periodic table, the mass of the neutrino, whilst enabling a new era of rapid-response and time-domain astronomy. This paper is a status report of the MSE Low Moderate Resolution spectrograph design, from the Conceptual Design Review (CoDR) towards the Preliminary Design Phase (PDP).

We will present on the status of a new NUV (3080 A) miniature SHS instrument for detecting the hydroxyl OD/OH isotope ratio remotely in diffused and faint targets such as cometary tails, comae, and planetary exospheres. Developing the SHS instrument has a wide significance to Astrophysics and Planetary science. SHS provides integrated spectra at high R, over a wide FOV in compact designs that offer the ability to make key science measurements for a variety of planetary targets. Many planetary objects that produce UV emissions are angularly extended low brightness targets, i.e., solar wind charge exchange emission, solar system planetary atmospheres and exospheres, mapping atomic emission, comets, and the interplanetary medium. SHS could be implemented on a dedicated SmallSat or ISS that can sit and stare at its target for a long duration of time that cannot be done from the ground or on big missions.