Mirror Side Research Articles

Developing a Novel Terahertz Fabry-Perot Microcavity Biosensor by Incorporating Porous Film for Yeast Sensing.

We present a novel terahertz (THz) Fabry-Perot (FP) microcavity biosensor that uses a porous polytetrafluoroethylene (PTFE) supporting film to improve microorganism detection. The THz FP microcavity confines and enhances fields in the middle of the cavity, where the target microbial film is placed with the aid of a PTFE film having a dielectric constant close to unity in the THz range. The resonant frequency shift increased linearly with increasing amount of yeasts, without showing saturation behavior under our experimental conditions. These results agree well with finite-difference time-domain (FDTD) simulations. The sensor's sensitivity was 11.7 GHz/μm, close to the optimal condition of 12.5 GHz/μm, when yeast was placed at the cavity's center, but no frequency shift was observed when the yeast was coated on the mirror side. We derived an explicit relation for the frequency shift as a function of the index, amount, and location of the substances that is consistent with the electric field distribution across the cavity. We also produced THz transmission images of yeast-coated PTFE, mapping the frequency shift of the FP resonance and revealing the spatial distribution of yeast.

Optimization study on the influence of rearview mirror and side window glass on interior noise

Based on the LES model, the compressible transient CFD simulation combined with the acoustic finite element method optimizes the effect of the rearview mirror and side window glass on in-vehicle noise from the perspective of sound source and transmission. The primary and secondary orders of the influence of different mirror shape and side window glass geometric parameters on the noise in the car were obtained through the design and analysis of orthogonal experiments, and the results of the flow and sound fields were compared. The following results are presented: acoustic source noise reduction from the rearview mirror is mainly affected by acoustic pressure excitation. The proportion of the mirror body of the rearview mirror, the angle of the lower edge, and the length of the mirror column affect the noise in the car in turn. The noise reduction control with PVB laminated glass as the transmission path is mainly limited by the low frequency turbulent pressure excitation. The inner and outer thicknesses of PVB laminated glass have different influences on the noise in the car under different frequency bands, and the results in the full frequency band are mainly affected by the low frequency band.

Application of Three-Dimensional Arterial Spin Labeling Technique in the Assessment of Cerebral Blood Perfusion in Patients with Middle Cerebral Artery Occlusion: Analysis of Clinical Implications and Prognostic Factors.

Objective To explore the value of three-dimensional- (3D-) arterial spin labeling (ASL) technique in evaluating cerebral perfusion in patients with unilateral middle cerebral artery occlusion (MCAO) and to observe the influencing factors of poor prognosis via long-term follow-up of patients who survived the disease. Methods The clinical data of 60 patients with unilateral middle cerebral artery (MCA) M1 segment occlusion diagnosed by magnetic resonance angiography (MRA) from January 2018 to January 2022 were retrospectively analyzed. All patients were examined by routine MRI, MRA, and 3D-ASL, in which two postlabeling delays (PLDs; 1525 ms and 2525 ms) were used in 3D-ASL. Cerebral blood flow (CBF) in the regions of interest (ROIs) of MCA on the affected side and the mirror side was measured. The clinical data and laboratory indexes of patients were collected and evaluated by clinical scales. With the modified Rankin Score (mRS) as the outcome indicator, patients were assigned to either the poor or the good prognosis group to analyze the factors influencing patient prognosis via univariate and multivariate analyses. Results Among unilateral MCAO patients, there was a significant difference in the CBF of the affected side between the PLD 1525 ms and 2525 ms groups (P < 0.05), but there was no significant difference in the CBF of the mirror side (P > 0.05). Compared with the mirror side, 43 cases (71.7%) of the affected CBF presented with hypoperfusion, 9 cases (15.0%) with normal perfusion, and 8 cases (13.3%) with hyperperfusion. Age, NIHSS score, collateral circulation, and homocysteine (Hcy) were identified by multivariate Logistic regression analysis as independent risk factors for adverse outcomes. Conclusion MCAO can lead to cerebral blood perfusion decline, and 3D-ASL technique can evaluate the post-MCAO cerebral blood perfusion level. Old age, high NIHSS scores, poor collateral circulation, and high Hcy levels are associated with poor clinical outcomes.

Quantitative Analysis of Diffusion-Restricted Lesions in a Differential Diagnosis of Status Epilepticus and Acute Ischemic Stroke.

Background and PurposeDistinction between acute ischemic stroke (AIS) and status epilepticus (SE) on MRI can be challenging as restricted diffusion may occur in both conditions. In this study, we aimed to test a tool, which could help in differentiating AIS from SE when restricted diffusion was present on MRI.Materials and MethodsIn diffusion weighted imaging (DWI) with a b-value of 1,000 and apparent diffusion coefficient (ADC) maps, we compared the ratios of intensities of gray values of diffusion-restricted lesions to the healthy mirror side in patients with AIS and SE. Patients were recruited prospectively between February 2019 and October 2021. All patients underwent MRI and EEG within the first 48 h of symptom onset.ResultsWe identified 26 patients with SE and 164 patients with AIS. All patients had diffusion-restricted lesions with a hyperintensity in DWI and ADC signal decrease. Diffusion restriction was significantly more intense in patients with AIS as compared to patients with SE. The median ratios of intensities of gray values of diffusion-restricted lesions to the healthy mirror side for DWI were 1.42 (interquartile range [IQR] 1.32–1.47) in SE and 1.67 (IQR 1.49–1.90) in AIS (p < 0.001). ADC decrease was more significant in AIS as compared to SE with median ratios of 0.80 (IQR 0.72–0.89) vs. 0.61 (IQR 0.50–0.71), respectively (p < 0.001). A cutoff value for ratios of DWI signal was 1.495 with a sensitivity of 75% and a specificity of 85%. Values lower than 1.495 were more likely to be associated with SE and higher values were with AIS. A cutoff value for ADC ratios was 0.735 with a sensitivity of 73% and a specificity of 84%. Values lower than 0.735 were more likely to be associated with AIS and higher values were with SE.ConclusionDiffusion restriction and ADC decrease were significantly more intense in patients with AIS as compared to SE. Therefore, quantitative analysis of diffusion restriction may be a helpful tool for differentiating between AIS and SE when restricted diffusion is present on MRI.

Numerical Simulation and Experimental Study of Natural Convection Flow in a Test Bench for Solar Air Heaters

This paper is intended to check the thermal convection flow during a new solar air heater (SAH) test bench, which is conducted in the LASEM laboratory. In fact, the applied system includes two-passage heater solar air separated by an absorber. On the other hand, a glass piece is connected to the box prototype via a pipe. Then, the piece of the glass is attached to the front side of this device in which an absorber is inserted. Moreover, two circular holes are made on the same face of the box prototype. The first is an entry hole through which hot air goes inside, and an exit hole through which air is released into the surrounding area. The study was conducted using the Navier-Stokes equations associated with the k–ω turbulence model through the use of the newly released Ansys 17.0 software to characterize the aero-thermal structure of our new system operating in natural convection. In these conditions, it has been observed that the hot zone created on the mirror side receiving the solar radiation generates an ascendant movement. It goes from the bottom to the top and enters the box prototype. The same phenomenon is also created in the box where the airflow coming from the solar heat escapes into the environment. This movement created between the hot zone of the solar heat and the box prototype is also imposed in the cold zone of the solar heat on the heat-insulating side. In these conditions, the air movement is however from the top to the bottom. Indeed, the acceleration of the air velocity at the inlet of the solar heat is due to the change of the section which is more reduced by comparison to the rest of the air circulation duct. Based on our experimental results generated in a two-passage solar air heater connected to the box prototype, the computational approach and the simulation results were validated. By referring to the classic solar air heater with one passage, the energy efficiency measured in the same conditions was enhanced and presented the efficient one with an improvement of about 27%. Finally, the numerical results are compared to our experimental results and those obtained by the authors. The comparison proved a good agreement.

Disentangling 'sciatica' to understand and characterise somatosensory profiles and potential pain mechanisms.

The study aimed to investigate if patients with lumbar radicular pain only and those with combined lumbar radicular pain+radiculopathy differ in their somatosensory profiles and pain experiences. Quantitative sensory testing (QST) was performed in 26 patients (mean age 47±10years, 10 females) with unilateral leg pain in the L5 or S1 distribution in their main pain area (MPA) and contralateral mirror side, in the relevant foot dermatome on the symptomatic side and in the hand dorsum. Pain experience was captured on the painDETECT. Eight patients presented with lumbar radicular pain only and 18 patients with combined radicular pain+radiculopathy. Patients with radicular pain only demonstrated widespread loss of function (mechanical detection) bilaterally in the MPA (p<0.003) and hand (p=0.002), increased heat sensitivity in both legs (p<0.019) and cold/heat sensitivity in the hand (p<0.024). QST measurements in the dermatome did not differ compared to HCs and patients with radiculopathy. Patients with lumbar radiculopathy were characterised by a localised loss of function in the symptomatic leg in the MPA (warm, mechanical, vibration detection, mechanical pain threshold, mechanical pain sensitivity p<0.031) and dermatome (mechanical, vibration detection p<0.001), consistent with a nerve root lesion. Pain descriptors did not differ between the two groups with the exception of numbness (p<0.001). Patients with radicular pain did not report symptoms of numbness, while 78% of patients with radiculopathy did. Distinct differences in somatosensory profiles and pain experiences were demonstrated for each patient group, suggesting differing underlying pain mechanisms.

Venise des deux côtés du miroir : Imaginaire et identité entre l’amour et la mort

"Venice, deeply imaginary and symbolic, is in various cultural documents, like books, paintings, cinema, music, photography and other arts. In this research, we use the literary and the poetic narrative as privileged sources for understanding the imaginary and the identity of this city, closely connected with love and with death too. This investigation uses as a method Gaston Bachelard’s phenomenology defined in The Poetics of Space and the symbolical imaginary described in relation to the material imagination in Water and Dreams. Venice is a city on water and its identity is closely associated with love, as one mirror side, and with death or even hell, as the other mirror side."

Kerr lens effect induced by a super-Gaussian laser beam

Recently, a new type of laser cavity has been proposed. It includes two Diffractive Optical Elements set inside the resonator against the cavity mirrors in order to achieve the structuring of the fundamental mode. The latter is a perfect Gaussian beam (M2 = 1) from the output mirror side, and super-Gaussian in the amplifying medium. Such a special cavity allows for improving the energy extraction, and it should be interesting to mode-lock such a laser cavity by using the KLM technique. For that, we aim to model the Kerr lensing effect, induced by a super-Gaussian beam. An analytical expression for the Kerr focal length has been deduced from a Zernike polynomial development. The obtained results are in a good agreement with a diffraction analysis.

Dictionary for the type II nongeometric flux compactifications

We study the $T$-dual completion of the four-dimensional $\mathcal{N}=1$ type II effective potentials in the presence of (non)geometric fluxes. First, we invoke a cohomology version of the $T$-dual transformations among the various moduli, axions, and fluxes appearing in the type IIA and type IIB effective supergravities. This leads to some useful observations about a significant mixing of the standard NS-NS fluxes with the (non)geometric fluxes on the mirror side. Further, using our $T$-duality rules, we establish an explicit mapping among the $F$ terms, $D$ terms, tadpole conditions, and Bianchi identities of the two theories. Second, we propose what we call a set of ``axionic flux polynomials,'' which depend on all of the axionic moduli and the fluxes. This subsequently helps to present the two scalar potentials in a concise and manifestly $T$-dual form, which can be directly utilized for various phenomenological purposes, as we illustrate in a couple of examples.

Edificio de viviendas en Pelican Island, Florida

El proyecto fue diseñado como prototipo de edificio de viviendas en el perímetro de una ciudad, pero también puede repetirse simétricamente en la misma parcela o a ambos lados de una calle, en emplazamientos urbanos de aproximadamente una hectárea. Este proyecto forma parte de un esfuerzo continuado por mejorar el modelo. Un buen urbanismo es casi imposible de lograr sin buenos ejemplos de vivienda plurifamiliar. Este tipo urbano merece nuestra atención, incluso si los arquitectos, los contratistas y los trabajadores de la construcción rehúyen cada vez más esta opción debido a los litigios.

Diagnostic value of HR-MRI and DCE-MRI in unilateral middle cerebral artery inflammatory stenosis.

PurposeHigh‐resolution magnetic resonance imaging (HR‐MRI) has high spatial resolution and can simultaneously perform wall and lumen imaging. Dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) can evaluate the integrity of the blood–brain barrier. In this paper, the result of 3.0T HR‐MRI and 3.0T DCE‐MRI has been evaluated to explore the application value of unilateral middle cerebral artery inflammatory stenosis and changes in vascular permeability parameters of stroke events.MethodsThirty‐six cases of neurological suspicion of central nervous system vasculitis of our hospital were selected from 20 January 2018 to 1 January 2019, who were diagnosed as unilateral middle cerebral artery M1 stenosis/occlusion by 3D TOF MRA. 3.0T HR‐MRI and 3.0T DCE‐MRI has been applied.ResultsAmong the 36 patients who met the inclusion criteria, 23 patients with central nervous system vasculitis were diagnosed. The 23 patients with HR‐MRI showed diffuse thickening and enhanced stenosis. The K trans value of 10/23 patients with acute–subacute cerebral infarction and 3/23 patients in chronic phase were significantly higher than that of the mirror side, and the K trans value of these patients remeasured in the same region of interest is lower than before after 6 months treatment. The K trans value in the target area of 10 patients without cerebrovascular events was not statistically significant compared with the mirror side. The K trans value of patients with acute–subacute cerebral infarction was significantly higher than that without cerebrovascular events (0.098 ± 0.038 vs. 0.007 ± 0.001, p = .000), and there was no significant difference between K trans in the chronic infarction group and the other two groups (0.098 ± 0.038 vs. 0.044 ± 0.012, p = .058; 0.044 ± 0.012 vs. 0.007 ± 0.001, p = .057).ConclusionHR‐MRI is an accurate direct imaging method and has a high value for the etiological diagnosis of central nervous system vasculitis. DCE‐MRI could be an effective way to evaluate and monitor blood–brain barrier to prevent clinical ischemic stroke.

On-Orbit Calibration of Terra MODIS VIS Bands Using Polarization-Corrected Desert Observations

The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on the Terra spacecraft is completing two decades of successful Earth observations, providing the scientific community with numerous products and supporting applications, such as land surface cover, sea surface temperature, aerosol properties, and vegetation. The 20 reflective solar bands (RSBs) cover a wavelength range from 0.41 to 2.1 $\mu \text{m}$ and are calibrated primarily using a solar diffuser (SD), with lunar measurements and Earth-view (EV) response trends from desert sites used for the response versus scan-angle (RVS) characterization. Prelaunch analysis showed that a few short-wavelength RSBs of Terra MODIS are particularly sensitive to the polarization of the incident light, with on-orbit results further indicating that the polarization sensitivity has experienced changes that are wavelength, mirror side (MS), and scan-angle dependent. Although the primary calibrator, the SD, should provide an unpolarized light, supplemental inputs from the EV response trends used in the RVS characterization are impacted by the Earth scene polarization. The EV trends, uncorrected for polarization, pose a significant challenge in the RVS characterization for the short wavelength bands (3, 8, 9, and 10), therefore impacting the long-term trends and uncertainty characterization. Previous studies from the MODIS Characterization Support Team (MCST) and the National Aeronautics and Space Administration (NASA) Ocean Biology Processing Group (OBPG) have independently estimated the polarization correction to be applied on the calibrated products to mitigate the impacts to some extent. In this article, the RVS is characterized using the EV response trends after correcting for the polarization effects. Results indicate a significant improvement in the long-term trending, reduced uncertainties in the forward prediction, and a more accurate per-pixel uncertainty provided by the uncertainty index (UI) in the MODIS L1B. This enhanced approach will, therefore, be considered for implementation in the future L1B reprocessing efforts. The enhanced approach also vastly simplifies the process of adding long-term trend corrections on top of the MODIS L1B, which should streamline the science data production in the future.

Methodology development for calibration assessment using quasi-deep convective clouds with application to Aqua MODIS TEB.

Deep convective clouds (DCC) are identified by using a combination of brightness temperature (BT) and visible reflectance thresholds. Moreover, it is common practice to use daytime DCC measurements for the calibration assessment of reflective solar and longwave infrared (LWIR) bands. The DCC cold core is suitable for the MODIS Thermal Emissive Bands (TEB) calibration assessment; more specifically, for the offset effect in the quadratic calibration function. However, the reflected solar radiance in the daytime DCC measurements affects the midwave infrared (MWIR) bands. Thus, an assessment over low BT measurements is not applicable to these bands. Because of this, a quasi-DCC (qDCC) technique is developed for the MWIR bands calibration assessment. The feasibility of using nighttime DCC measurements is demonstrated by comparing the DCC and daytime qDCC techniques. A DCC normalization method is also developed to remove the DCC fluctuation impact and enhance the assessment accuracy. The DCC measurements' distribution is asymmetrical for all TEB, and their BT ranges fluctuate around 20 K. An empirical model is developed and applied to normalize the measurements over DCC to a reference temperature. After the normalization, the DCC and qDCC measurements' distributions are close to symmetrical and Gaussian in shape. These improvements are applied to the Aqua MODIS instrument. The calibration stability, noise performance, and consistency are evaluated for all Aqua MODIS TEB. Lastly, the Aqua MODIS formatter reset effect on the calibration offset bias between two mirror sides is analyzed, and a calibration coefficient correction is proposed for future calibration improvements.

Assessment of MODIS thermal emissive bands calibration performance using deep convective clouds

The core of deep convective clouds (DCC) is one of the most consistent Earth targets. When viewed from space, the measurements have minimal impact from water vapor and aerosols and have been used as invariant scenes for calibration assessment for reflectance solar bands. DCC is also one of the coldest targets and can be used for assessing the calibration and product stability for infrared thermal emissive bands (TEB). The stability from the years 2003 to 2019 is analyzed for both Terra and Aqua moderate resolution imaging spectroradiometer (MODIS) long-wave infrared bands. Most bands exhibit very stable long-term trending. Terra band 30 shows the largest rate of change of 0.19 K / year. The Terra–Aqua difference is also analyzed. In general, for both Terra and Aqua, the long-wave infrared bands show good and stable detector uniformity. The impact of response change due to anomalies and events has been analyzed. Since the measurement bias over cold DCC is dominated by the offset term in the calibration equation, an assessment model is developed to estimate the offset bias between the mirror sides. The impact model is also developed to estimate the impact on higher brightness temperature measurements. The offset bias from the assessment modeling in this analysis is used as the input for impact modeling. The measurements over Dome-C, Ocean, and desert scenes are used to verify the impact model. These assessments are very helpful for MODIS TEB calibration and look-up table update procedure improvements.

Newton–Okounkov bodies, cluster duality, and mirror symmetry for Grassmannians

We use cluster structures and mirror symmetry to explicitly describe a natural class of Newton-Okounkov bodies for Grassmannians. We consider the Grassmannian $X=Gr_{n-k}(\mathbb C^n)$, as well as the mirror dual Landau-Ginzburg model $(\check{X}^\circ, W_q:\check{X}^\circ \to \mathbb C)$, where $\check{X}^\circ$ is the complement of a particular anti-canonical divisor in a Langlands dual Grassmannian $\check{X} = Gr_k((\mathbb C^n)^*)$, and the superpotential W_q has a simple expression in terms of Pl\"ucker coordinates. Grassmannians simultaneously have the structure of an $\mathcal{A}$-cluster variety and an $\mathcal{X}$-cluster variety. Given a cluster seed G, we consider two associated coordinate systems: a $\mathcal X$-cluster chart $\Phi_G:(\mathbb C^*)^{k(n-k)}\to X^{\circ}$ and a $\mathcal A$-cluster chart $\Phi_G^{\vee}:(\mathbb C^*)^{k(n-k)}\to \check{X}^\circ$. To each $\mathcal X$-cluster chart $\Phi_G$ and ample `boundary divisor' $D$ in $X\setminus X^{\circ}$, we associate a Newton-Okounkov body $\Delta_G(D)$ in $\mathbb R^{k(n-k)}$, which is defined as the convex hull of rational points. On the other hand using the $\mathcal A$-cluster chart $\Phi_G^{\vee}$ on the mirror side, we obtain a set of rational polytopes, described by inequalities, by writing the superpotential $W_q$ in the $\mathcal A$-cluster coordinates, and then "tropicalising". Our main result is that the Newton-Okounkov bodies $\Delta_G(D)$ and the polytopes obtained by tropicalisation coincide. As an application, we construct degenerations of the Grassmannian to toric varieties corresponding to these Newton-Okounkov bodies. Additionally, when $G$ corresponds to a plabic graph, we give a formula for the lattice points of the Newton-Okounkov bodies, which has an interpretation in terms of quantum Schubert calculus.

Clinical application value of brain CT perfusion imaging in the treatment of acute ischemic stroke thrombolytic therapy.

Clinical application value of CT perfusion (CTP) imaging in the treatment of acute ischemic stroke (AIS) thrombolytic therapy was investigated. Retrospective analysis of 185 suspected AIS patients in Liaocheng Brain Hospital from April 2012 to December 2017 were involved. We observed the non-contrast CT (NCCT) and CTP in the diagnosis of AIS patients, and recorded as well as compared CTP parameters of AIS patients. The National Institute of Health Stroke Scale (NIHSS) rating was conducted, and the correlation between the prognosis of NIHSS scores and CTP parameters was investigated. A total of 177 patients were diagnosed with AIS. The sensitivity levels of CTP examination for diagnosis of AIS patients was significantly higher than that of the NCCT examination (P<0.050). The diagnostic compliance rates of CTP examination was significantly higher than that of the NCCT examination (P<0.050). The cerebral blood volume (CBV) in the abnormal perfusion area was significantly lower than that in the mirror side zone (t=21.160, P<0.001). The prognostic NIHSS score was negatively correlated with CBV in patients with thrombolytic therapy (r=−0.912, P<0.001). The cerebral blood flow (CBF) in the abnormal perfusion zone was significantly lower than that in the mirror side zone (t=19.170, P<0.001). The prognosis of patients with thrombolytic therapy was negatively correlated with CBF (r=−0.915, P<0.001). The mean transit time (MTT) in the abnormal perfusion zone was higher than that in the mirror side zone (t=13.480, P<0.001). NIHSS scores were obtained 3 months after thrombolytic therapy and found that the prognostic NIHSS scores were positively correlated with MTT (r=0.887, P<0.001). The results indicated that brain CTP has a high diagnostic value for intravenous thrombolytic therapy in AIS and there was a significant correlation between the prognosis scores of patients. Thus, it is worthy of being promoted in the clinical diagnosis and treatment of AIS patients.

Determination of response versus scan angle for the NOAA-20 visible infrared imaging radiometer suite thermal emissive bands from emissive radiation measurements during the pitch maneuver

The visible infrared imaging radiometer suite (VIIRS) is a key sensor onboard the newly launched (November 18, 2017) NOAA-20 satellite and the early launched Suomi National Polar-orbiting Partnership (SNPP) satellite. The two VIIRS sensors are nearly identical in design. Its onboard calibration components include a solar diffuser (SD) and a SD stability monitor for the reflective solar bands, a V-grooved blackbody for the thermal emissive bands (TEBs),and a space view port for background subtraction. These onboard calibrators are located at fixed scan angles. The response versus scan angle (RVS) of the VIIRS scan mirror was characterized prelaunch in lab-ambient conditions and is currently used to calibrate the on-orbit response for all scan angles relative to the calibrator's scan angle. A spacecraft-level pitch maneuver was scheduled during the initial intensive calibration and validation testing for both the NOAA-20 and SNPP. The pitch maneuver provided a rare opportunity for VIIRS to make observations of deep space over the entire range of the scan angle, which can be used to characterize the TEBRVS. We analyze the NOAA-20 pitch maneuver data and assess the derived TEB RVS. A comparison between the RVS determined by the pitch maneuver observations and prelaunch lab measurements is conducted for each band, detector, and mirror side of the half-angle mirror.

Design and fabrication of prototype piezoelectric adjustable X-ray mirrors.

Lynx, a next generation X-ray observatory concept currently under study, requires lightweight, high spatial resolution X-ray mirrors. Here we detail the development and fabrication of one of the candidate technologies for Lynx, piezoelectric adjustable X-ray optics. These X-ray mirrors are thin glass shell mirrors with Cr/Ir X-ray reflective coatings on the mirror side and piezoelectric thin film actuators on the actuator side. Magnetron sputtering was used to deposit metal electrodes and metal-oxide piezoelectric layers. The piezoelectric (Pb0.995(Zr0.52Ti0.48)0.99Nb0.01O3) was divided into 112 independent piezoelectric actuators, with 100% yield achieved. We discuss the fabrication procedure, residual thermal stresses and tuning of the Cr/Ir coating stress for the purposes of stress balancing.

Assessment of Terra MODIS On-Orbit Polarization Sensitivity Using Pseudoinvariant Desert Sites

The Moderate Resolution Imaging Spectroradiometer (MODIS) is currently flying on NASA’s Earth Observing System Terra and Aqua satellites, launched in 1999 and 2002, respectively. MODIS reflective solar bands in the visible wavelength range are known to be sensitive to polarized light based on prelaunch polarization sensitivity tests. After about five years of on-orbit operations, it was discovered that the polarization sensitivity at short wavelengths had shown a noticeable increase. In this paper, we examine the impact of polarization on measured top-of-atmosphere (TOA) reflectances based on MODIS Collection-6 L1B over pseudoinvariant desert sites. The standard polarization correction equation is used in combination with simulated at-sensor radiances using the second simulation of a satellite signal in the Solar Spectrum, Vector Radiative Transfer Code (6SV). We ignore the polarization contribution from the surface and a ratio approach is used for both 6SV-derived input parameters and observed TOA reflectances. Results indicate that significant gain corrections up to 25% are required near the end of scan for the 412 and 443 nm bands. The polarization correction reduces the seasonal fluctuations in reflectance trends and mirror side ratios from 30% and 12% to 10% and 5%, respectively, for the two bands. Comparison of the effectiveness of the polarization correction with the results from the NASA Ocean Biology Processing Group shows a good agreement in the corrected reflectance trending results and their seasonal fluctuations.

Optimized calibration methodology of VIIRS day-night band low-gain stage using a solar diffuser.

An enhanced methodology of the standard on-orbit calibration of the day-night band (DNB) of the visible infrared imaging radiometer suite on board the Suomi National Polar-orbiting Partnership satellite is presented, specifically for the low-gain stage. The range of the "sweet spot" for the fully illuminated scans in the calibration events is expanded from 4° to 7.8° in order to increase the number of fully illuminated scans to 72, which then permits a complete calibration of the DNB to be carried out within one orbit for all 36 aggregated modes and the two mirror sides. This improves over the current operational methodology, which is with a more restricted range for the sweet spot that requires multiple orbits to complete a calibration. The expansion necessarily requires the expansion of a key calibration input, the product of the bidirectional reflectance factor of the solar diffuser (SD) with the vignetting function describing the transmission of the attenuation screen in front of the SD port, or BVP for short. The expanded BVP is derived by fitting the function in three separate intervals and joining them smoothly to form a single function. Additional enhancements include the adaptation of the previously improved SD degradation and all other improvements developed for reflective solar bands from the previous work. The time-dependent relative spectral response is also characterized and implemented, and its impact and improvements are studied and discussed. The result shows that the improved DNB calibration coefficients are more stable and smooth, and less noisy.