The 2017 Decadal Survey: Thriving on Our Changing Planet, A Decadal Strategy for Earth Observation from Space has called new observations including global coverage Visible to Short Wavelength Infrared (VSWIR) Wide Swath (WS) imaging spectroscopy measurements as part of the Surface Biology and Geology (SBG) Designated Observable. The SBG VSWIR-WS along with the companion SBG Thermal Infrared (TIR) imager is an important element of NASA's larger Earth System Observatory (ESO). To support NASA and the science and applications community, a concept for a technologically mature VSWIR-WS measurement approach has been developed that takes advantage of previous investments, capabilities of industry, and capabilities of other partners. This concept delivers a 185 km cross-track swath with 30-meter spatial sampling measuring spectra from 360 to 2500 nm with contiguous 10 nm spectral sampling. The system uses an optically fast (F/1.8) telescope with a matched pair of high throughput VSWIR Dyson spectrometers, each covering 92.5 km of the swath. State-of-the-art digital-out detector arrays, one in each spectrometer, are used to provide low-noise and high quantum efficiency over the full VSWIR spectral range. Analysis of the concept performance shows that it delivers excellent cross-track spectral uniformity as well as uniformity through the full wavelength range for each spatial sample. This high fidelity performance is needed to spectroscopically derive consistent global maps of the surface properties that are required to address the objectives described in the SBG science and applications traceability matrix (https://sbg.jpl.nasa.gov/satm). The large concave efficiency tuned electron beam lithography fabricated reflection grating is optimized for high signal-to-noise ratio performance across the spectral range, especially in the visible to support the coastal and inland water objectives. With a nominal polar sun-synchronous orbit, this VSWIR-WS concept provides a 16-day revisit with coverage of the global terrestrial surface and designated aquatic regions. This concept takes advantage of key design elements, such as the Dyson spectrometer and digital-out detector array, to control mass, power, and volume. In this paper, we present the performance and design approach for the VSWIS-WS concept that has been refined to support the SBG Designated Observable and address the key research and applications areas of terrestrial and aquatic ecosystems, solid Earth, hydrology, climate, and weather.

Spectroscopic measurements in the millimeter, submillimeter, or THz range, with resolutions exceeding a MHz, provide for highly specific detections of gas-phase absorption and emission by atoms and molecules. Due to relatively low excitation energies involved in the transitions, multiple features are observable in most physical systems, and thus such observations dominate the scientific discovery of molecules in space and contribute significantly to remote sensing of the Earth and planetary bodies. The methods and techniques of THz spectroscopy continue to evolve as capabilities and technologies expand. In this article, we review the genesis of THz spectroscopy in both the laboratory and in space, and follow its development to date, providing background on the challenges, and context for the current developments that promise to extend both remote and in-situ gas composition sensing.

NASA’s Multi-Angle Imager for Aerosols (MAIA) mission, under development at the Jet Propulsion Laboratory, is designed to study the adverse health effects of different types of particulate air pollution. Planned for launch in late 2022 for a 3-year mission, the MAIA satellite instrument will focus on a selected set of metropolitan target areas, where air quality monitors and health data are available. Aerosol concentration and speciation are inferred from multi-angle measurements of backscattered sunlight in 14 spectral bands from 350-2200 nm, with bands near 442, 645 and 1040 nm measuring the degree (DoLP) and angle of linear polarization (AoLP) in addition to radiance. The pushbroom camera has a ~240-km cross-track field of view with a nadir resolution of ~200 m, and is mounted onto a biaxial gimbal to provide along-track view angles within ±60°, to extend the field of regard to ±48°, and to view the instrument’s onboard calibrator (OBC) and dark target. The OBC consists of a sunlit transmissive diffuser, followed by 12 polarizers at different orientations. MAIA’s polarimetry is implemented using miniature wiregrid polarizers on the focal plane array, and dual photoelastic modulators (PEMs) and achromatic quarter-wave plates to rapidly rotate the polarization. The resulting ~26-Hz intensity modulation encodes the linearly polarized and total radiance in each pixel, leaving the DoLP and AoLP insensitive to gain calibration. We report on the polarimetric calibration of the MAIA camera using a vacuum-compatible polarization state generator, consisting of a 1600W Xenon lamp, 12-inch integrating sphere, and rotating high-extinction polarizer. Mueller-matrix-based calibration coefficients for each detector pixel are derived from measurements at multiple polarizer angles, and are used to correct the measurements for instrumental polarization aberrations. Prior to flight, the calibrated MAIA camera is panned across the OBC to characterize its output, using uniform illumination with an irradiance similar to the Sun.

Heterodyne spectroscopic instruments are currently the only practical technical approach for obtaining velocity-resolved spectra in the far infrared. Moreover, to produce the large-scale maps of molecular clouds envisioned for future missions, large-format (100’s pixels) array receivers are required, which is the focus of this whitepaper.

Homochirality is omnipresent in nature on Earth in which life predominately utilizes one handedness of a chiral molecule over another.It is considered a biomarker that can aid in the search for life elsewhere in the solar system on places like Mars, Titan, Europa, and Enceladus.The 2013 planetary science Decadal Survey recommends "a detailed characterization of organics to search for signatures of biological origin, such as molecules with preferred chirality or unusual patterns of molecular weights" as a key future investigation for determining the possibility of life beyond Earth.Mass spectrometers are the primary choice for chemical detection and identification of simple organics for planetary and astrobiology investigations.However, mass spectrometry alone cannot address the challenge of successfully deconvolving mixtures of structurally complex organic molecules of approximately the same molecular weight; this includes lacking the chirality detection capability required for analysis of chiral molecules.ChiralSpec can provide synergetic measurements to mass spectrometers for planetary science and is funded by the NASA Planetary Instrument Concept for the Advancement of Solar System Observations (PICASSO) program.ChiralSpec is a millimeter-wave spectrometer operated in two modes: (1) chirality detection mode, based on a novel three-wave mixing; and (2) survey mode, with the instrument acting as a traditional millimeter-wave spectrometer to characterize chemical composition and quantify abundance of planetary samples.ChiralSpec extends the work done on microwave three-wave mixing into higher frequencies of light where size, weight, and power of many components of the instrument can be reduced.We will report on the current state of this instrument and its future developments.G-band (180-200GHz) and W-band (70-90GHz) excitation channels have been designed, tested, and optimized to show that power requirements are met and that molecular emission can be detected for many two level systems for a test case molecule, propylene oxide.Three-wave mixing experiments are on-going, and we will report our findings.

The abundance of deuterated molecules in a star-forming region is sensitive to the environment in which they are formed. Deuteration fractions therefore provide a powerful tool for studying the physical and chemical evolution of a star-forming system. While local low-mass star-forming regions show very high deuteration ratios, much lower fractions are observed towards Orion and the Galactic Centre. We derive methanol deuteration fractions at a number of locations towards the high-mass star-forming region NGC 6334I, located at a mean distance of 1.3 kpc, and discuss how these can shed light on the conditions prevailing during its formation. We use high sensitivity, high spatial and spectral resolution observations obtained with ALMA to study transitions of the less abundant, optically thin, methanol-isotopologues: (13)CH3OH, CH3(18)OH, CH2DOH and CH3OD, detected towards NGC 6334I. Assuming LTE and excitation temperatures of 120-330 K, we derive column densities for each of the species and use these to infer CH2DOH/CH3OH and CH3OD/CH3OH fractions. Interestingly, the column densities of CH3OD are consistently higher than those of CH2DOH throughout the region. All regions studied in this work show CH2DOH/CH3OH as well as CH2DOH/CH3OD ratios that are considerably lower than those derived towards low-mass star-forming regions and slightly lower than those derived for the high-mass star-forming regions in Orion and the Galactic Centre. The low ratios indicate a grain surface temperature during formation 30 K, for which the efficiency of the formation of deuterated species is significantly reduced.

Variable levels of methane in the martian atmosphere have eluded explanation partly because the measurements are not repeatable in time or location. We report in situ measurements at Gale crater made over a 5-year period by the Tunable Laser Spectrometer on the Curiosity rover. The background levels of methane have a mean value 0.41 ± 0.16 parts per billion by volume (ppbv) (95% confidence interval) and exhibit a strong, repeatable seasonal variation (0.24 to 0.65 ppbv). This variation is greater than that predicted from either ultraviolet degradation of impact-delivered organics on the surface or from the annual surface pressure cycle. The large seasonal variation in the background and occurrences of higher temporary spikes (~7 ppbv) are consistent with small localized sources of methane released from martian surface or subsurface reservoirs.

Airborne particulate matter (PM) is a well-known cause of cardiovascular disease and mortality and has also been associated with respiratory disease, low birth weight, lung cancer, and other adverse health outcomes. However, our understanding of the relative toxicity of specific PM types-mixtures with different proportions of particles of various sizes, shapes, and compositions-is less well understood. Observations from space, in conjunction with data from surface monitors and chemical transport models, offer a practical means of generating frequent, high spatial resolution maps of PM concentrations in major population centers around the world. The Multi-Angle Imager for Aerosols (MAIA) investigation, currently in development, is motivated by the scientific and societal benefits of linking PM types with adverse health outcomes and the value of satellite observations for addressing this objective.

The THz rotational lines of CH+ and its isotopologues have been observed in the range of 0.9-2.6 THz with JPL frequency multiplication chains. They were analyzed together with the known A(1)Pi - X-1 Sigma(+) band system data by using the Dunham formulation and the conventional vibration-rotation energy formula. The A-doubling in in states was reexamined, and the doubling or shifts were found to be different for the e- and f-parity levels. In this investigation, the e- and f-parity states were treated as two separate states. The major molecular constants were determined accurately for these two states separately, and were compared with the values obtained previously. (C) 2018 Elsevier Inc. All rights reserved.

The infrared spectrum of ammonia has proven to be highly problematic for effective Hamiltonian analysis. The most complete previous study of the 3v(2) and v(4)+v(2) bands achieved the accuracy of 0.0069 cm(-1) as reflected by the root-mean-square error of their fit, which is slightly more than 10 times the experimental accuracy. In the present study, we performed a global fit of the existing 2141 literature data involving 3v(2), v(4)+v(2), 3v(2)-v(2) , (v(4)+v(2))-v(2) together with 1281 new data involving 3v(2)-2v(2), 3v(2)-3v(2) and (v(4)+v(2) )-(v(4)+v(2) ) using an effective Hamiltonian together with the Pickett suite of program SPFIT/SPCAT. The new dataset consists of three spectra recorded at the SOLEIL synchrotron facility. The effective Hamiltonian model proposed for 3v(2)/v(4)+v(2) has achieved experimental accuracy. This success combined with our previous success of the 2v(2)/v(4) analysis leads us to believe that the vibrational states higher than 3v(2)/v(2)+v(4) may be analyzed with effective Hamiltonians as well. (C) 2018 Elsevier Inc. All rights reserved.

The infrared spectrum of ammonia has proven to be highly problematic for effective Hamiltonian analysis. The most complete previous study of the 3ν2 and ν4+ν2 bands achieved the accuracy of 0.0069 cm−1 as reflected by the root-mean-square error of their fit, which is slightly more than 10 times the experimental accuracy. In the present study, we performed a global fit of the existing 2141 literature data involving 3ν2, ν4+ν2, 3ν2-ν2, (ν4+ν2)-ν2 together with 1281 new data involving 3ν2-2ν2, 3ν2-3ν2 and (ν4+ν2)-(ν4+ν2) using an effective Hamiltonian together with the Pickett suite of program SPFIT/SPCAT. The new dataset consists of three spectra recorded at the SOLEIL synchrotron facility. The effective Hamiltonian model proposed for 3ν2/ν4+ν2 has achieved experimental accuracy. This success combined with our previous success of the 2ν2/ν4 analysis leads us to believe that the vibrational states higher than 3ν2/ν2+ν4 may be analyzed with effective Hamiltonians as well.

We performed very deep searches for 2 ground-state water transitions in 13 protoplanetary disks with the HIFI instrument on-board the Herschel Space Observatory, with integration times up to 12 hours per line. Two other water transitions that sample warmer gas were also searched for with shallower integrations. The detection rate is low, and the upper limits provided by the observations are generally much lower than predictions of thermo-chemical models with canonical inputs. One ground-state transition is newly detected in the stacked spectrum of AA Tau, DM Tau, LkCa 15, and MWC 480. We run a grid of models to show that the abundance of gas-phase oxygen needs to be reduced by a factor of at least 100 to be consistent with the observational upper limits (and positive detections) if a dust-to-gas mass ratio of 0.01 were to be assumed. As a continuation of previous ideas, we propose that the underlying reason for the depletion of oxygen (hence the low detection rate) is the freeze-out of volatiles such as water and CO onto dust grains followed by grain growth and settling/migration, which permanently removes these gas-phase molecules from the emissive upper layers of the outer disk. Such depletion of volatiles is likely ubiquitous among different disks, though not necessarily to the same degree. The volatiles might be returned back to the gas phase in the inner disk (within about 15 AU), which is consistent with current constraints. Comparison with studies on disk dispersal due to photoevaporation indicates that the timescale for volatile depletion is shorter than that of photoevaporation.

We extended the measurements of the rotational transitions of D2H+ up to 3 THz by using the JPL frequency multiplier chains and a TuFIR system at Toyama. D2H+ was generated in an extended negative glow discharge cell cooled to liquid nitrogen temperature. We observed five new THz lines. All the available rotational transition frequencies together with the combination differences derived from the three fundamental bands were subject to least square analysis to determine the molecular constants. New THz measurements are definitely useful for better characterization of spectroscopic properties. The improved molecular constants provide better predictions of other unobserved rotational transitions.

A Dunham analysis of the AΠ − XΣ band was carried out by Müller, and predictions of the pure rotational transition frequencies were made.a More recently, in submillimeter to THz region, several rotational lines were observed for CH, CH, and CD+.bcd In this investigation, those newly obtained rotational lines are incorporated in the Dunham analysis. The Λ-doubling splittings in Π electronic states have been expressed as (1/2)qJ(J + 1) in most investigations. However, it should be noted that the e-levels of Π state interact with Σ states, while the f -levels with 1Σ− states. For CH, the e-levels of AΠ are pushed upward from the interaction with the ground XΣ state. The 1Σ− states are not known experimentally and they, if any, should lie high over the AΠ state. In this analysis, only the f -levels are included in the least-squares analysis by neglecting the Λ-doubling. The mass independent parameters have been obtained, and the conventional spectroscopic parameters are derived for each isotopologue. These results should be useful for determining the potential energies of this fundamental ion.e

We present results from a comprehensive submillimeter spectral survey toward the source Orion South, based on data obtained with the HIFI instrument aboard the Herschel Space Observatory, covering the frequency range 480 to 1900 GHz. We detect 685 spectral lines with S/N > 3σ, originating from 52 different molecular and atomic species. We model each of the detected species assuming conditions of Local Thermodynamic Equilibrium. This analysis provides an estimate of the physical conditions of Orion South (column density, temperature, source size, & V LSR ). We find evidence for three different cloud components: a cool (T ex ~ 20 - 40 K), spatially extended (> 60″), and quiescent (ΔVFWHM ~ 4 km s -1) component; a warmer (T ex ~ 80 - 100 K), less spatially extended (~ 30″), and dynamic (ΔVFWHM ~ 8 km s -1) component, which is likely affected by embedded outflows; and a kinematically distinct region (T ex > 100 K; V LSR ~ 8 km s -1), dominated by emission from species which trace ultraviolet irradiation, likely at the surface of the cloud. We find little evidence for the existence of a chemically distinct "hot core" component, likely due to the small filling factor of the hot core or hot cores within the Herschel beam. We find that the chemical composition of the gas in the cooler, quiescent component of Orion South more closely resembles that of the quiescent ridge in Orion-KL. The gas in the warmer, dynamic component, however, more closely resembles that of the Compact Ridge and Plateau regions of Orion-KL, suggesting that higher temperatures and shocks also have an influence on the overall chemistry of Orion South.