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We demonstrate a full-cycle breath gas sensor system based on terahertz/millimeter-wave gas spectroscopy. The sensor consists of a transmitter and receiver working around 250 GHz based on SiGe BiCMOS technology. Typical detection thresholds are in the ppm range depending on the respective molecule. The data analysis provides partial pressures of the investigated molecules by fitting of spectra which are measured by wavelength modulation. Beside the spectroscopic measurement and the data analysis, a full cycle of breath analysis includes the sampling and the conditioning of the sample tubes. The full cycle takes about 35 min per sample in average. As the system is compact and easy to operate, it allows for on-site analysis of breath samples in medical laboratories or hospitals.

Introducction JAXA’s MMX (Martian Moons eXploration) mission, to be launched in 2024, will study both Martian satellites, for several years, and will drop a small rover to Phobos, to explore its surface [1]. As part of this rover scientific payload, it will be placed a Raman spectrometer, the RAX Instrument (Raman Spectrometer for MMX). The RAX will be able to analyse the mineral composition of the Phobos regolithe surface with in-situ measurements, complementing the Japanese Sample Return mission, and helping to reveal the nature and distribution of materials on the Martian Moon’s surface, and ultimately its origin and evolution [2]. The RAX instrument [3] has been designed, manufactured, integrated and tested by an international consortium led by DLR (Germany), with significant contributions from JAXA & University of Tokyo (Japan), and INTA-CAB-UVa (Spain). One of the Spanish contributions to RAX, will be the instrument Verification Target, a small piece of PET (polyethylene terephthalate) attached to MMX spacecraft, to be used before launch, and during cruise; for spectral instrument performances verification on-ground and just before the rover release to Phobos. Figure 1. RAX Verification Target design proposed by INTA-CAB-UVa Experimental Thanks to previous expertise of the UVa-INTA group with PET material, used on the Raman Laser Spectrometer (RLS) Calibration Target [4] for ESA’s ExoMars mission; and SuperCam Calibration Target [5] for NASA Mars2020; a newly design-deuterated PET material, decreasing the PET fluorescence background, and adding new Raman bands with respect to ordinary PET [6] has been developed, manufactured, characterized and space-qualified for MMX-RAX mission by INTA-CAB-UVa; so it was proposed as candidate the RAX Verification Target. Figure 2. RAX Verification Target Flight batch for qualification/acceptance Results and discussion During the session, a detailed description of different tests carried out for the space qualification of the deuterated material, will be shown. And how the final performances with respect to other commercial PETs have been improved; and so, how the final verification-calibration of the Raman instrument has been optimized. Acknowledgements INTA’s internal I+D+I project IDMats; and MICINN grants PID2019-107442RB-C32 & PID2019-107442RB-C31 References [1] Michel P. et al. (2022) Earth, Planets and Space 74, 2. [2] Hagelschuer, T. et al. (2019) 70th Int. Astronautical Congress, 2019. [3] Hagelschuer, T. et al. (2022) 73th Int. Astronautical Congress. [4] López-Reyes, G. et al. (2020) Journal of Raman Spectroscopy, 1-13 [5] Manrique, J.A. et al. (2020) Space Sci Rev, 216:138 [6] Mora, J. et al (2020) Acta Astronaut. 167 (2020) 360–373

The results of experimental and theoretical investigations of terahertz-emission-spectrum tuning by means of uniaxial stress of a silicon crystal doped with shallow bismuth donors are presented for the case of intracenter optical excitation. The frequency tuning of two emission lines of the bismuth donor is shown for the case of uniaxial strain along the [001] crystallographic direction. The cross sections of stimulated Raman scattering for uniaxially stressed bismuth-doped silicon are calculated.

Terahertz (THz) quantum-cascade lasers (QCLs) provide powerful, narrow-band, and frequencytunable radiation, which makes them ideal sources for high-resolution molecular spectroscopy. A first application of a THz QCL has been as local oscillator in a heterodyne spectrometer for astronomy on board a Boeing 747. For laboratory spectroscopy, QCLs close the so-called THz gap and enable new research topics.

The Oxygen Spectrometer for Atmospheric Science on a Balloon (OSAS-B) is dedicated to the remote sounding of atomic oxygen in the mesosphere and lower thermosphere (MLT) region of Earth's atmosphere, where atomic oxygen is the dominant species. OSAS-B is a heterodyne receiver for the thermally excited ground state transition of atomic oxygen at 4.75 THz. Due to water absorption, this line can only be observed from high-altitude platforms such as a balloon. A combined Helium/nitrogen dewar comprises the detector of the instrument, a hot-electron bolometer mixer, as well as a quantum-cascade laser, which serves as the local oscillator for heterodyning. A turning mirror allows for measurements at different vertical inclinations and for radiometric calibration against two blackbody sources. The first flight will take place in autumn 2022 within the HEMERA2020 program. We will present the instrument design and results of the laboratory evaluation of the instrument.

We report on the study of phonon properties and electron-phonon coupling in thin NbTiN films, which are intensively exploited in superconducting devices. Studied NbTiN films with thicknesses less than 10~nm are disordered with respect to electron transport, the Ioffe-Regel parameter of $k_F l_e = 2.5-3.0$ ($k_F$ is the Fermi wave vector and $l_e$ is the electron mean free path), and inelastic electron-phonon interaction, the product $q_T l_e \ll 1$ ($q_T$ is the wave vector of a thermal phonon). By means of magnetoconductance and photoresponse techniques, we derived the inelastic electron-phonon scattering rate $1/\tau_{e-ph}$ and determined sound velocities and phonon heat capacities. In the temperature range from 12 to 20~K, the scattering rate varies with temperature as $1/\tau_{e-ph}\propto T^{3.45\pm0.05}$; its value extrapolated to 10~K amounts to approximately 16~ps. Making a comparative analysis of our films and other films used in superconducting devices, such as polycrystalline granular NbN and amorphous WSi, we found a systematic reduction of the sound velocity in all these films by about 50\% as compared to the corresponding bulk crystalline materials. A corresponding increase in the phonon heat capacities in all these films is, however, less than the Debye model predicts. We attribute these findings to reduced film dimensionality and film morphology.

Efficient and compact frequency converters are essential for frequency stabilization of terahertz sources. In this paper, we present a 3.5-THz, x6-harmonic, integrated Schottky diode mixer operating at room temperature. The designed frequency converter is based on a single-ended, planar Schottky diode with a sub-micron anode contact area defined on a suspended 2-$\mu$m ultra-thin GaAs substrate. The dc-grounded anode pad was combined with the radio frequency E-plane probe, which resulted in an electrically compact circuit. At 200 MHz intermediate frequency, a mixer conversion loss of about 59 dB is measured and resulting in a 40 dB signal-to-noise ratio for phase locking 3.5-THz quantum-cascade laser. Using a quasi-static diode model combined with electromagnetic simulations, good agreement with the measured results was obtained. Harmonic frequency converters without the need of cryogenic cooling will help in the realization of highly sensitive space and air-borne heterodyne receivers., Comment: Submitted to IEEE-TST

We present a comparison between THz spectroscopy and gas chromatography-mass spectroscopy (GC-MS), which is considered the gold-standard for sensitive breath detection. For this purpose, we analyzed human breath samples with both methods and discuss key figures as well as advantages and disadvantages for this application. As an example, the detection of isopropanol is presented which was exhaled after hand disinfection of a volunteer. THz spectroscopy provides results consistent with GC-MS and even distinguishes conformers of isopropanol. The sensitivity of the THz spectrometer for isopropanol is roughly 500 times smaller in this case, but can be improved depending on the species and measurement parameters.

High frequency accuracy and stability are important requirements for local oscillators in terahertz heterodyne spectrometers. We report on a phase-locked loop for quantum-cascade lasers (QCLs) operating at 3.5 and 4.7 THz, two very important frequencies in atmospheric science and astronomy. The QCLs are locked to the multiplied output of a frequency synthesizer using a Schottky diode harmonic mixer.

Atomic oxygen governs photochemistry and energy balance of the mesosphere and lower thermosphere of the Earth. Its concentration is extremely difficult to measure with remote sensing techniques since it has only few optically active transitions. Current indirect measurements involve photochemical models and the results are not always in agreement, particularly when obtained with different instruments. In addition, altitudes above 100 km are not covered by these methods. We report on direct measurements of the 4.7-THz fine-structure transition of atomic oxygen at 4.7448 THz using the German Receiver for Astronomy at Terahertz Frequencies on board the Stratospheric Observatory for Infrared Astronomy. Our measurements agree well with atmospheric models and satellite observations below 100 km.

We report high-harmonic generation up to the ninth order from boron-doped Si at room temperature, pumped by intense THz pulses. For comparison with the experiment, we also performed FDTD simulations coupled to a full-band Monte Carlo device model. The simulations predict a significantly stronger flattening of the conversion efficiency with pump power than that observed in the experiments, which points to less pronounced scattering at high fields than expected.

Millimeter-Wave/Terahertz (mmW/THz) spectroscopy affords high precision and specificity, useful for analyzing complex gas mixtures. In conjunction with wavelength modulation spectroscopy (WMS), it stands out as a sensitive technique for trace gas detection. The complex nature of the WMS absorption line shape, however, remains challenging to quantify and interpret. In this work, we propose a practical procedure for processing and analyzing the WMS signal to derive a calibrationfree quantification of the target gas. To validate the method, we compared the results to reference measurements of methanol and water and found a good agreement.

The Raman Spectrometer for MMX (RAX) as part of the JAXAs Martian Moons eXploration (MMX) mission, to be launched in 2024, is designed for in-situ science on the Martian moon Phobos. It is installed on the MMX rover to investigate the Phobos surface mineralogy complementary to the anticipated sample return mission of MMX reaching earth in 2029 [1]. To ensure high Raman signals with the RAX instrument we utilize a volume phase holographic (VPH) grating as diffracting element. The VPH grating diffracts light by refractive index modulations within a thin layer of transmissive gelatin sandwiched between two glass substrates. Optimized VPH grating parameters combined with a small spectral bandwidth lead to peak efficiencies approaching up to 100 % [2]. Due to the rather small Raman scattering efficiency they are particular suitable for space instrumentation, where initial laser intensity is relatively limited [3]. We have designed an optical setup for the characterization of 1st order diffraction efficiency and wave front aberration evaluation. A laser source similar in emission characteristics to the RAX laser (Nd:YAG at 532 nm) is widened to 14.2 mm beam diameter before illuminating the VPH grating. The VPH grating is installed axis-centered on a rotation platform within a second outer rotational platform mounting a camera for optical verification or a laser power meter for the diffraction efficiency measurement. The VPH gratings reach diffraction efficiencies up to 87 % within their specified spectral range with diffraction limited patterns nearly identical to the undisturbed reference beam and dispersed only due to the laser band width.

The optical performance of high-resistivity silicon with a laser-ablated surface was studied in the transmission mode in the frequency range of 0.1–4.7 THz. A reciprocal relationship between the transmission brightness and the surface roughness was observed at discrete THz frequencies. The measured dispersion was reproduced by the THz wave scattering theory using an effective refractive index model. No significant differences between the samples processed either with ps- or ns-duration laser pulses in ambient air or in argon enriched atmosphere were found in the THz regime. It was demonstrated that the majority of optical losses of the silicon with the laser modified surface were due to the scattering of THz waves and not due to the absorption in silicon-compounds formed during the laser ablation.

We report on a compact terahertz (THz) source based on a quantum-cascade laser (QCL). The source is intended for a local oscillator in a THz heterodyne receiver for the detection of the fine structure line of neutral atomic oxygen at 4.7448 THz. The laser is mounted in a mechanical cryocooler. Laser operation is realized in continuous-wave mode in the range from −2.7 to +9.4 GHz around the target frequency. Special care has been taken on the laser design, which employs a GaAs/AlAs active region heterostructure and a resonator with an additional back-facet mirror. At a typical QCL operating point ( I = 200 mA, T = 60 K, ν = 4.75 THz, P opt = 5 mW) close to the target frequency, this system with a mass of only 4 kg requires an electrical input power of less than 130 W for a cooling capacity of up to 4 W. The maximum optical output power of the QCL reaches up to 8 mW with an electrical pump power of less than 1.8 W. The application of such a system in a spaceborne mission appears to be feasible.

The relaxation times of excited states of arsenic dopant in germanium at cryogenic temperatures T < 15 K have been experimentally studied by the optical pump-probe method using radiation of a free-electron laser. Two variants of the excitation of impurity centers have been used in the experiment: (i) from the 1s(A1) ground state of the dopant and (ii) from the 1s(T2) first excited state having a finite thermal population. In the former variant, it has been shown that the decay times of the 2p0 and 3p± states are about 0.8 and 0.6 ns, respectively. In the latter variant, a single measurement can simultaneously provide the relaxation times of two 2p± and 1s(T2) states about 0.6 and no more than 0.16 ns, respectively. The data obtained have indicated the possibility of forming population inversion and the gain of terahertz radiation at the 2p± → 1s(T2) and 2p0 → 1s(T2) transitions at the optical excitation of the mentioned impurity centers.

The terahertz photoluminescence spectra of HgTe/CdHgTe heterostructure with quantum wells under interband optical excitation with a power of 3 to 300 mW have been studied in the temperature range of 30–100 K. The photoluminescence spectrum includes a band corresponding to quantum energies below the width of the band gap. The position of this band does not change with increasing temperature. This property allows attributing it to the capture of holes by acceptor centers. It has been shown that these acceptor centers are singly ionized mercury vacancies, which are double acceptors. A nonmonotonic dependence of the intensity of a signal of a long-wavelength photoluminescence band on the power of an exciting source has been revealed. A short-wavelength photoluminescence band corresponding to interband transitions appears with an increase in the exciting power. It has been shown that this effect is caused by the saturation of the number of partially ionized mercury vacancies with increasing pump intensity.

High-harmonic generation (HHG) is a phenomenon resulting from the strongly nonlinear, non-perturbative interaction between intense electromagnetic pulses and matter. It has been intensively investigated ever since its first observation with optically excited noble-gas atoms in the late 1980s [1] . The HHG effect is not only widely applied in table-top, coherent X-ray sources but is also the key for the generation of intense attosecond pulses [2] . Gases and atom clusters are the most intensively employed materials for HHG. Recently, HHG has also been observed in bulk crystals [3] , which has triggered a surge of research interest in HHG from solids [4] .

In this study, we investigate the characteristics of the LIBS plasma in Martian atmospheric conditions using stationary modeling of the LIBS plasma. LIBS spectra are simulated from a one-dimensional model of the plasma divided into two zones along the line of sight. The simulations are based on local thermal equilibrium and carried out using radiative transfer. The simulated spectra are fitted first to synthetic LIBS spectra to test the implementation and in a second step to time-resolved LIBS data of a carbonate sample obtained in experimentally simulated Martian atmospheric conditions. From the fits to the synthetic LIBS spectra, we confirm that plasmas with spatial gradients in the temperature and densities can be well described in a two-zone plasma model. From the fits to the measured data this observation also holds true. We find that the most of the emission lines are well described in the two-zone model and that the two-zone model is a significant improvement from the one-zone model. Furthermore, we obtain typical values of the plasma properties in the two-zone approximation from 500 ns to 1250 ns after plasma initiation and derive the effect of self-absorption, which is predicted to decrease the strongest pixel intensities by a factor of almost two orders of magnitudes.

In this work transmission and reflection losses in silicon diffractive THz optical components fabricated by direct laser ablation are investigated. One of the possible sources of reflection/transmission losses in laser-fabricated optics is scattering due to the roughness of laser formed surface. Therefore, influence of laser processing parameters on the transmittance of laser processed silicon wafers was investigated in 0.1 –4.7 THz range. Transmittances of silicon samples ablated in ambient air and argon atmospheres were also compared. Using laser ablation technology MPFLs for 0.6 and 4.7 THz frequency radiation were fabricated and their performance was evaluated.

The lunar south pole is of great interest for upcoming lunar exploration endeavors due to the detection of large reservoirs of water ice in the pole’s permanently shadowed regions [1], which could be utilized to reduce the costs of a sustained presence on the Moon [2]. A strong focus of future robotic exploration missions will therefore be on the detection of water and related volatiles. For this purpose, the project Lunar Volatiles Mobile Instrumentation – Extended (LUVMI-X) is developing an initial system design as well as payload and mobility breadboards for a small, lightweight rover [3]. One of the proposed payloads is the Volatiles Identification by Laser Analysis instrument (VOILA), which uses laser-induced breakdown spectroscopy (LIBS) to analyze the elemental composition of the lunar surface with an emphasis on the detection of hydrogen for the inference of the presence of water. VOILA is a joint project by OHB System AG, Laser Zentrum Hannover e.V., and the German Aerospace Center’s Institute of Optical Sensor Systems. It is designed to analyze targets on the lunar surface in front of the LUVMI-X rover at a variable focus between 300 mm to 500 mm, allowing for precise measurements under various measurement conditions. The spectrometer covers the wavelength range from 350 nm to 790 nm, which includes the hydrogen line at 656.3 nm as well as spectral lines of most major rock-forming elements. The breadboard laboratory setup for VOILA was recently completed and first measurements of Moon-relevant samples have been made. Here, we will show the results of these measurements and will discuss their meaning for the further improvement of the instrument design and for its potential use as a volatile-scouting instrument at the lunar south pole.[1] Li S. et al. (2018) PNAS, 36, 8907–8912. [2] Anand M. et al. (2012) Planet. Space Sci., 74, 42–48. [3] Gancet J. et al. (2019) ASTRA 2019. [4] Knight A. K. et al. (2000) Appl. Spectrosc., 54, 331–340. [5] Maurice S. et al. (2012) Space Sci. Rev., 170, 95–166. [6] Wiens R. C. et al. (2012) Space Sci. Rev., 170, 167–227. [7] Wiens R. C. et al. (2017) Spectroscopy, 32. [8] Ren X. et al. (2018) EPSC 2018, Abstract EPSC2018-759. [9] Laxmiprasad A. S. et al. (2013) Adv. Space Res., 52, 332–341. [10] Lasue J. et al. (2012) J. Geophys. Res., 117, E1.

Atomic oxygen is a main component of the mesosphere and lower thermosphere (MLT). The photochemistry and the energy balance of the MLT are governed by atomic oxygen. In addition, it is a tracer for dynamical motions in the MLT. It is difficult to measure with remote sensing techniques. Concentrations can be inferred indirectly from the oxygen air glow or from observations of OH, which is involved in photochemical processes related to atomic oxygen. Such measurements have been performed with several satellite instruments such as SCIAMACHY, SABER, WINDII and OSIRIS. However, the methods are indirect and rely on photochemical models and assumptions such as quenching rates, radiative lifetimes, and reaction coefficients. The results are not always in agreement, particularly when obtained with different instruments.We have explored an alternative approach, namely the observation of the 3P1 → 3P2 fine-structure transition of atomic oxygen at 4.7 THz (63 µm) using the German Receiver for Astronomy at Terahertz Frequencies (GREAT) on board of SOFIA, the Stratospheric Observatory for Infrared Astronomy. GREAT is a heterodyne spectrometer providing high sensitivity and high spectral resolution as low as 76 kHz. This method enables the direct measurement without involving photochemical models to derive the atomic oxygen concentration. The night-time measurements have been performed during a SOFIA flight along the west coast of the US. These are the first measurements which resolve the line shape of the 4.7-THz transition. From the spectra the concentration profiles and radiances of atomic oxygen were derived with a radiative transfer model. The observed radiances range from 1.5 to 2.2 nW cm-2 sr-1 and the the altitude profiles agree within the measurement uncertainty with SABER data and the NRLMSISE-00 model [1].In conclusion, THz heterodyne spectroscopy is a powerful method to measure atomic oxygen in the MLT. With the current progress in THz technology balloon-borne and space-borne 4.7-THz heterodyne spectrometers become feasible [2, 3]. Combining such a THz spectrometer with optical instruments similar to SABER or SCIAMACHY will be even more advantageous for the determination of atomic oxygen in the MLT.[1] H. Richter et al., Direct measurements of atomic oxygen in the mesosphere and lower thermosphere using terahertz heterodyne spectroscopy, accepted for publication in Communications Earth & Environment (2021).[2] M. Wienold et al, A balloon-borne 4.75 THz-heterodyne receiver to probe atomic oxygen in the atmosphere, to appear in: Proceedings of the 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) (Buffalo, NY, 2020).[3] S. P. Rea et al., The low-cost upper-atmosphere sounder (LOCUS), Proceedings of the 26th International Symposium on Space Terahertz Technology (Cambridge, MA, 2015).

The Oxygen Spectrometer for Atmospheric Science on a Balloon (OSAS-B) is dedicated to the remote sounding of atomic oxygen in the mesosphere and lower thermosphere (MLT) region of Earth's atmosphere, where atomic oxygen is the dominant species. Quantitative radiometry of atomic oxygen via its visible and near-infrared transitions has been difficult, due to the complex excitation physics involved. OSAS-B is a heterodyne spectrometer for the thermally excited ground state transition of atomic oxygen at 4.75 THz. It will enable spectrally resolved measurements of the line shape, which in turn enables the determination of the concentration of atomic oxygen in the MLT. Due to water absorption, this line can only be observed from high-altitude platforms such as a high-flying airplanes, balloons or satellites. Recently the first spectrally resolved observation of the 4.75-THz line has been reported using a heterodyne spectrometer on SOFIA, the Stratospheric Observatory for Infrared Astronomy [1]. Compared to SOFIA a balloon-borne instrument has the advantage of not being hampered by atmospheric water vapor absorption. OSAS-B will comprise a hot-electron bolometer mixer and a quantum-cascade laser as local oscillator in a combined helium/nitrogen dewar. A turning mirror will allow for sounding at different vertical inclinations. The first flight of OSAS-B is planned for autumn 2022 in the frame of the European HEMERA project [2].[1] H. Richter et al., Direct measurements of atomic oxygen in the mesosphere and lower thermosphere using terahertz heterodyne spectroscopy, accepted for publication in Communications Earth & Environment (2021).[2] https://www.hemera-h2020.eu/

The analysis of human breath is a very active area of research, driven by the vision of a fast, easy, and non-invasive tool for medical diagnoses at the point of care. Millimeter-wave gas spectroscopy (MMWGS) is a novel, well-suited technique for this application as it provides high sensitivity, specificity and selectivity. Most of all, it offers the perspective of compact low-cost systems to be used in doctors' offices or hospitals. In this work, we demonstrate the analysis of breath samples acquired in a medical environment using MMWGS and evaluate validity, reliability, as well as limitations and perspectives of the method. To this end, we investigated 28 duplicate samples from chronic obstructive lung disease patients and compared the results to gas chromatography-mass spectrometry (GC-MS). The quantification of the data was conducted using a calibration-free fit model, which describes the data precisely and delivers absolute quantities. For ethanol, acetone, and acetonitrile, the results agree well with the GC-MS measurements and are as reliable as GC-MS. The duplicate samples deviate from the mean values by only 6% to 18%. Detection limits of MMWGS depend strongly on the molecular species. For example, acetonitrile can be traced down to 1.8 × 10−12 mol by the MMWGS system, which is comparable to the GC-MS system. We observed correlations of abundances between formaldehyde and acetaldehyde as well as between acetonitrile and acetaldehyde, which demonstrates the potential of MMWGS for breath research. Deutsche Forschungsgemeinschafthttp://dx.doi.org/10.13039/501100001659 Deutsches Zentrum für Lungenforschunghttp://dx.doi.org/10.13039/501100010564

Atomic oxygen is a main component of the mesosphere and lower thermosphere of the Earth, where it governs photochemistry and energy balance and is a tracer for dynamical motions. However, its concentration is extremely difficult to measure with remote sensing techniques since atomic oxygen has few optically active transitions. Current indirect methods involve photochemical models and the results are not always in agreement, particularly when obtained with different instruments. Here we present direct measurements—independent of photochemical models—of the ground state 3P1 → 3P2 fine-structure transition of atomic oxygen at 4.7448 THz using the German Receiver for Astronomy at Terahertz Frequencies (GREAT) on board the Stratospheric Observatory for Infrared Astronomy (SOFIA). We find that our measurements of the concentration of atomic oxygen agree well with atmospheric models informed by satellite observations. We suggest that this direct observation method may be more accurate than existing indirect methods that rely on photochemical models. Atomic oxygen concentrations in the upper atmosphere can be measured directly with an airborne terahertz heterodyne spectrometer. This approach is probably more accurate than indirect estimates from photochemical models, according to a comparison of the two methods.

Mineralogy is the key to understanding the origin of Phobos and its position in the evolution of the Solar System. In situ Raman spectroscopy on Phobos is an important tool to achieve the scientific objectives of the Martian Moons eXploration (MMX) mission, and maximize the scientific merit of the sample return by characterizing the mineral composition and heterogeneity of the surface of Phobos. Conducting in situ Raman spectroscopy in the harsh environment of Phobos requires a very sensitive, compact, lightweight, and robust instrument that can be carried by the compact MMX rover. In this context, the Raman spectrometer for MMX (i.e., RAX) is currently under development via international collaboration between teams from Japan, Germany, and Spain. To demonstrate the capability of a compact Raman system such as RAX, we built an instrument that reproduces the optical performance of the flight model using commercial off-the-shelf parts. Using this performance model, we measured mineral samples relevant to Phobos and Mars, such as anhydrous silicates, carbonates, and hydrous minerals. Our measurements indicate that such minerals can be accurately identified using a RAX-like Raman spectrometer. We demonstrated a spectral resolution of approximately 10 cm−1, high enough to resolve the strongest olivine Raman bands at ~ 820 and ~ 850 cm−1, with highly sensitive Raman peak measurements (e.g., signal-to-noise ratios up to 100). These results strongly suggest that the RAX instrument will be capable of determining the minerals expected on the surface of Phobos, adding valuable information to address the question of the moon’s origin, heterogeneity, and circum-Mars material transport. Graphical Abstract

Verification of thermal-mechanical-optical design for optical instruments in space exploration is highly significant due to large temperature variation and exposure to high shock and vibration levels. Such instruments must be completely robust to these harsh environments, as there are usually no options for realignment. The JAXA Martian Moons eXploration (MMX) Mission is set for launch in 2024 with main objectives to study the Martian moons, Deimos and Phobos. A rover will acquire for the first time Raman spectra of the Phobos surface using the Raman Spectrometer for MMX (RAX) developed at DLR. The Structural-Thermal-Model (STM) of RAX presented an early opportunity to evaluate the robustness of the instrument optical alignment to thermal and mechanical environments. An interferometric method implementing dummy objectives with cross hairs was developed to enable inline six-DOF measurements at critical places within the STM before development model (DM) optics were manufactured.

High-excited discrete states of boron hydrogenlike acceptors in crystalline diamond have been measured by temperature-dependent infrared absorption spectroscopy. We distinguish the boron resonant states in diamond crystals from the localized boron states in the band gap by differentiating the impurity transitions within state continua of the valence light- and heavy-hole subbands on the basis of their relative oscillator strengths, specific selection rules, and temperature dependences. Constraints on the boron binding energy and spin-orbit splitting of the valence band have been derived by analysis of the structure of the infrared absorption spectra of boron-doped diamond, in particular by a comparison with boron spectra in other semiconductors with a diamond lattice.

This paper presents a transmitter (TX) and a receiver (RX) with bowtie-antenna and silicon lens for gas spectroscopy at 222-270 GHz, which are fabricated in IHP’s $0.13~\mu \text{m}$ SiGe BiCMOS technology. The TX and RX use two integrated local oscillators for 222 – 256 GHz and 250 – 270 GHz, which are switched for dual-band operation. Due to its directivity of about 27 dBi, the single integrated bowtie-antenna with silicon lens enables an EIRP of about 25 dBm for the TX, and therefore a considerably higher EIRP for the 2-band TX compared to previously reported systems. The double sideband noise temperature of the RX is 20,000 K (18.5 dB noise figure) as measured by the Y-factor method. Absorption spectroscopy of gaseous methanol is used as a measure for the performance of the gas spectroscopy system with TX- and RX-modules.

Molecular spectroscopy of gases is an important method for various applications on Earth and in space. In the millimeter-wave / terahertz range, many molecules have rotational transitions and are distinguishable by their spectral fingerprint. We analyze the performance of a heterodyne receiver fabricated in SiGe BiCMOS technology, which operates at room temperature and is tunable from 225 GHz to 255 GHz. At 241 GHz, the double sideband noise temperature of the receiver is approximately 20,000 K at 1.5 GHz intermediate frequency and the Allan time is 1 s. First heterodyne measurements of methanol emission lines were successfully performed in laboratory experiments.

1 Introduction The increasing interest in Laser-induced breakdown spectroscopy (LIBS) for space-exploration is confirmed by two more LIBS instruments, SuperCam aboard NASA’s Mars 2020 mission and MarsCoDe as part of China’s Tianwen 1 mission, being launched towards Mars this summer [1, 2]. SuperCam will be the follow-up of the ChemCam instrument, which has been successfully analysing the Martian surface since its landing in 2012 [3]. In 2019, another LIBS instrument has been launched heading for the Moon [4], but did unfortunately not accomplish a soft landing. LIBS is a fast and versatile elemental analysis technique. It is based on laser ablation and needs only optical access to the target. For LIBS, a laser pulse is tightly focused onto the sample, where a small portion of material is ablated and excited into a plasma of neutral atoms, ions and electrons. The plasma emits continuum radiation from bremsstrahlung and electron-ion recombination, together with discrete emission lines from the species in the plasma. The latter allow for identification of the chemical elements contained in the plasma, and therefore in the sample. 2 Challenging elements in LIBS In general, all elements of the periodic table are detectable with LIBS. Some of them, however, have their strongest emission lines outside of the typically observed spectral range from approx. 240 to 800 nm. As the emission intensity of a spectral line strongly depends on, amongst other factors, the population density of the transition’s upper level, transitions between lower energy levels are typically strong. For neutral S, the fundamental ground state transition is located at 180.7 nm, while Cl atoms have their strong ground state transitions between 133 and 138 nm. Both elements are therefore expected to be well detectable in the vacuum-UV (VUV) range below 200 nm. 3 VUV-LIBS VUV-LIBS means the emission of the plasma is detected in the VUV spectral range. In terrestrial environment, this range is obscured due to absorption by O2 and H2O vapour from the atmosphere. VUV absorption in CO2 and CH4 further reduces the applicability of VUV-LIBS on e.g. Mars or Titan. For celestial bodies without a significant atmosphere, however, the predicted high emission intensities in the VUV range for otherwise challenging elements like S and Cl could be exploited to increase the sensitivity for these elements. One drawback of LIBS in a very low pressure environment is the short life time of the plasma and its relatively low intensity. While the reduced atmospheric pressure on Mars in the order of 1 kPa is beneficial for LIBS and produces a large and bright plasma, the low confinement and therefore low probability for collisions of the plasma species at below 10 Pa leads to a short-living and dim plasma [5]. Thus, the sensitivity of LIBS in vacuum is naturally lower, and it could be even more crucial for mission instruments on bodies without atmosphere to make use of the stronger VUV emission lines. VUV-LIBS is readily used in industrial applications, e.g. for S detection in steel [6]. There, laser pulse energies of several hundreds of millijoules, multi-pulse configurations, and purge gas atmospheres are used to compensate for atmospheric absorption and the reduced emissivity of vacuum plasmas, thereby yielding limits of detection in the order of 10-100 ppm. For space exploration, VUV-LIBS has not yet been extensively studied. Radziemski et al. investigated the applicability of VUV-LIBS for use on Mars, using components realistic for a mass-, size- and power-constrained space instrument [7]. They noted significant suppression of the strongest Cl lines in the 130-140 nm range due to the CO2 atmosphere, while at the same time benefiting from the LIBS-favourable pressure. 4 Experimental Details Our set-up is built around a H+P vacuum spectrometer covering the range of 100-300 nm, see Figure 1. The plasma is excited with a pulsed Nd:YAG laser (1064 nm, up to 40 mJ, 6 ns), which is focused vertically onto the sample. The sample is contained in a vacuum chamber, directly flanged to the spectrometer. The radiation emitted by the plasma is coupled into the spectrometer using an off-axis parabolic mirror. The mirror currently limits the spectral range to >120 nm. The whole system is operated at a pressure of ≤1 mPa. The samples analysed in this study are lunar simulants (Exolith LHS-1 and LMS-1 [8]) mixed with different amounts of pure sulfur, different sulfates, or sodium chloride. They have been prepared in-house using mortar and pestle, and a hydraulic press. The resulting atomic fractions of S and Cl range from 0.5 to 4.0 %. 5 Results We successfully detected S in lunar simulant matrices, using the S I emission line at 180.7 nm. Example spectra for Na2SO4 in LHS-1 at 0.5 and 1.6 at% S are shown in Figure 2. Besides Al, Si and O emission lines from the matrix material, the S I emission line is clearly visible already at those low concentrations. Univariate calibration curves suggest a linear relationship between S concentration and emission intensity for low concentrations. The Cl I emission lines around 135 nm spectrally overlap with Si II emission, but a change in their intensity upon changes in the Cl concentration is still recognizable. 6 Summary and Conclusion S and Cl have been detected in lunar simulant matrices at atomic fraction levels in the order of 1 %. For low concentrations of S, we found a linear relationship between S concentration and LIBS signal with a univariate approach. These results are promising for improved detectability of volatiles in space exploration, which are usually hard to detect with conventional LIBS in the spectral range of 240-800 nm. Besides S and Cl, emission lines of Al, Fe, Si and O have been identified. References [1] Wiens et al., Spectroscopy, 32, 5 (2017). [2] Ren et al., EPSC2018, id EPSC2018-759-2 (2018). [3] Maurice et al., J. Anal. At. Spectrom., 31, 863 (2016). [4] Laxmiprasad et al., Advances in Space Research, 52, 332 (2013) [5] Knight et al., Applied Spectroscopy, 54, 331 (2000). [6] Sturm et al., Applied Spectroscopy, 54, 1275 (2000). [7] Radziemski et al., Spectrochim. Acta B, 60, 237 (2005). [8] Britt and Cannon, NESF2019, 82 (2019).