The Michelson Interferometer for Global High-resolution imaging of the Thermosphere and Ionosphere (MIGHTI) instrument was built for launch and operation on the NASA Ionospheric Connection Explorer (ICON) mission. The instrument was designed to measure thermospheric horizontal wind velocity profiles and thermospheric temperature in altitude regions between 90km and 300km, during day and night. For the wind measurements it uses two perpendicular fields of view pointed at the Earth's limb, observing the Doppler shift of the atomic oxygen red and green lines at 630.0nm and 557.7nm wavelength. The wavelength shift is measured using field-widened, temperature compensated Doppler Asymmetric Spatial Heterodyne (DASH) spectrometers, employing low order échelle gratings operating at two different orders for the different atmospheric lines. The temperature measurement is accomplished by a multichannel photometric measurement of the spectral shape of the molecular oxygen A-band around 762nm wavelength. For each field of view, the signals of the two oxygen lines and the A-band are detected on different regions of a single, cooled, frame transfer charge coupled device (CCD) detector. On-board calibration sources are used to periodically quantify thermal drifts, simultaneously with observing the atmosphere. The MIGHTI requirements, the resulting instrument design and the calibration are described.
Fluorescence and thermal imaging were used to examine the dynamics of stomatal patches for a single surface of Xanthium strumarium L. leaves following a decrease in ambient humidity. Patches were not observed in all experiments, and in many experiments the patches were shortlived. In some experiments, however, patches persisted for many hours and showed complex temporal and spatial patterns. Rapidly sampled fluorescence images showed that the measurable variations of these patches were sufficiently slow to be captured by fluorescence images taken at 3-min intervals using a saturating flash of light. Stomatal patchiness with saturating flashes of light was not demonstrably different from that without saturating flashes of light, suggesting that the regular flashes of light did not directly cause the phenomenon. Comparison of simultaneous fluorescence and thermal images showed that the fluorescence patterns were largely the result of stomatal conductance patterns, and both thermal and fluorescence images showed patches of stomatal conductance that propagated coherently across the leaf surface. These nondispersing patches often crossed a given region of the leaf repeatedly at regular intervals, resulting in oscillations in stomatal conductance for that region. The existence of these coherently propagating structures has implications for the mechanisms that cause patchy stomatal behaviour as well as for the physiological ramifications of this phenomenon.
A global spectral irradiance intercomparison using spectroradiometers was organized by the National Renewable Energy Laboratory's (NREL's) Solar Radiation Research Laboratory. The intercomparison was performed both indoors and outdoors on September 17, 2013. Five laboratories participated in the intercomparison using 10 spectroradiometers. A coordinated measurement setup and a common platform were employed to compare spectral irradiances under both indoor and outdoor conditions. The intercomparison was aimed at understanding the performance of the different spectroradiometers and sharing knowledge in making spectral irradiance measurements. At NREL's Optical Metrology Laboratory, the intercomparison is part of an internal performance-based quality-control check to monitor the legitimacy of a measurement and calibration undertaken by a laboratory to demonstrate compliance with International Standards Organization/International Electrotechnical Commission (ISO/IEC) 17025 accreditation requirements.The indoor performance comparison showed that all of the participating spectroradiometers had satisfactory statistical results (±1) compared to the NREL reference instrument. However, each laboratory's instruments behaves differently with respect to the statistical limit, and such differences could be related to various reasons-for example, differing calibration setups from one laboratory to another, differing environmental conditions inside laboratories, whether a primary or secondary spectral irradiance calibration lamp was used for the calibration, instrument age, and the amount of time since the last calibration.The outdoor intercomparison showed up to ±10% deviation relative to the average spectral irradiance measured by the participating spectroradiometers. Differing scan rates, sizes of the entrance optics, or fast-changing atmospheric conditions could be reasons for such deviations. Mean bias error (MBE) and root mean square error (RMSE) were calculated representing average differences from the three outdoor runs and results from the aggregation of hundredwavelength bins. Almost all instruments were within +10% MBE and 10% RMSE.Simulations using the Simple Model of the Atmospheric Radiative Transfer of Sunshine (SMARTS) were applied to the outdoor intercomparison as an explanatory tool and to understand how well the SMARTS-modeled spectra compare to various types of spectroradiometers considering the model's spectral resolution compared to the spectroradiometers under scrutiny. Running the smoothing postprocessor of the SMARTS model was therefore necessary to downgrade the resolution of its spectra and make them match that of any specific instrument based on the shape of its passband (e.g., Gaussian), its width (as measured by the full width at half maximum), and its wavelength step (e.g., 5 nm). The SMARTS model in the outdoor intercomparison provides relevant information when predicting clear-sky solar spectral irradiance under varying atmospheric conditions. The output from the model compared well to the outdoo...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.