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Radiative lifetimes of BBr and UV emissions in electron beam excited boron trifluoride gas from phase shift measurements, discussing molecular electronic transition moments
Cs(BBr)6 crystallizes in the trigonal R-3 space group. The structure is two-dimensional and consists of three Cs(BBr)6 sheets oriented in the (0, 0, 1) direction. there are two inequivalent Cs sites. In the first Cs site, Cs is bonded to twelve Br atoms to form distorted edge-sharing CsBr12 cuboctahedra. There are a spread of Cs–Br bond distances ranging from 3.86–4.05 Å. In the second Cs site, Cs is bonded in a 9-coordinate geometry to six Br atoms. There are three shorter (3.80 Å) and three longer (3.86 Å) Cs–Br bond lengths. There are four inequivalent B sites. In the first B site, B is bonded in a distorted single-bond geometry to one Br atom. The B–Br bond length is 1.96 Å. In the second B site, B is bonded in a distorted single-bond geometry to one Br atom. The B–Br bond length is 1.97 Å. In the third B site, B is bonded in a distorted single-bond geometry to one Br atom. The B–Br bond length is 1.96 Å. In the fourth B site, B is bonded in a distorted single-bond geometry to one Br atom. The B–Br bond length is 1.97 Å. There are four inequivalent Br sites. In the first Br site, Br is bonded in a distorted single-bond geometry to two Cs and one B atom. In the second Br site, Br is bonded in a single-bond geometry to two equivalent Cs and one B atom. In the third Br site, Br is bonded in a single-bond geometry to one Cs and one B atom. In the fourth Br site, Br is bonded in a single-bond geometry to one Cs and one B atom.
In order to best detect real changes in the Earth's climate system it is estimated that space based instrumentation measuring the global Earth Radiation Budget (ERB) must remain calibrated with a stability of 0.3% per decade. This level of stability is beyond the specified accuracy of existing ERB programs such as the Clouds and the Earth's Radiant Energy System (CERES, using three broadband radiometric scanning channels: the shortwave (SW 0.3 - 5?m), total (0.3 - >100 micron), and window (8 - 12 micron)). When in low earth orbit, it has been shown that optical response to blue-UV radiance can be reduced significantly (> 3%) due to UV hardened contaminants deposited on the surface of the optics. Evidence suggests that exposure of telescope optics to the forward looking ram direction is the primary cause of this contamination build up. With typical onboard calibration lamps emitting very low energy in the blue-UV region, this darkening is not directly measurable using standard internal calibration techniques. This paper describes a study using a model of ram exposure induced contaminant deposition and darkening, in conjunction standard established in-flight vicarious and internal calibration techniques to derive the spectral shape of the darkening to which a broadband instrument is subjected. The results of the model when applied to the CERES instruments are shown. These findings are of great importance to the EarthCARE project, whose BBR uses one broadband telescope permanently looking forward at 45 degrees, with continual exposure to the ram direction. Specific attention may therefore be needed in the design of BBR optics and on-board calibration in order to prevent or compensate for the spectral darkening seen in the CERES project.
BBr crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of eighteen bromoborane molecules. B is bonded in a distorted single-bond geometry to one Br atom. The B–Br bond length is 1.93 Å. Br is bonded in a single-bond geometry to one B atom. The Br–B bond length is 1.93 Å.
The Visible Infrared Imager Radiometer Suite (VIIRS) instrument onboard the Suomi National Polar‐orbiting Partnership (SNPP) satellite was launched on 28 October 2011. The VIIRS has 5 imagery spectral bands (I-bands), 16 moderate resolution spectral bands (M-bands) and a panchromatic day/night band (DNB). Performance of the VIIRS spatial response and band-to-band co-registration (BBR) was measured through intensive pre-launch tests. These measurements were made in the non-aggregated zones near the start (or end) of scan for the I-bands and M-bands and for a limited number of aggregation modes for the DNB in order to test requirement compliance. This paper presents results based on a recently re-processed pre-launch test data. Sensor (detector) spatial impulse responses in the scan direction are parameterized in terms of ground dynamic field of view (GDFOV), horizontal spatial resolution (HSR), modulation transfer function (MTF), ensquared energy (EE) and integrated out-of-pixel (IOOP) spatial response. Results are presented for the non-aggregation, 2-sample and 3-sample aggregation zones for the I-bands and M-bands, and for a limited number of aggregation modes for the DNB. On-orbit GDFOVs measured for the 5 I-bands in the scan direction using a straight bridge are also presented. Band-to-band co-registration (BBR) is quantified using the prelaunch measured band-to-band offsets. These offsets may be expressed as fractions of horizontal sampling intervals (HSIs), detector spatial response parameters GDFOV or HSR. BBR bases on HSIs in the non-aggregation, 2-sample and 3-sample aggregation zones are presented. BBR matrices based on scan direction GDFOV and HSR are compared to the BBR matrix based on HSI in the non-aggregation zone. We demonstrate that BBR based on GDFOV is a better representation of footprint overlap and so this definition should be used in BBR requirement specifications. We propose that HSR not be used as the primary image quality indicator, since we show that it is neither an adequate representation of the size of sensor spatial response nor an adequate measure of imaging quality.
Spectral bands of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrumentaboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite are spatially co-registered.The accuracy of the band-to-band registration (BBR) is one of the key spatial parameters that must becharacterized. Unlike its predecessor, the Moderate Resolution Imaging Spectroradiometer (MODIS), VIIRS has no on-board calibrator specifically designed to perform on-orbit BBR characterization.To circumvent this problem, a BBR characterization method for VIIRS reflective solar bands (RSB) based on regularly-acquired lunar images has been developed. While its results can satisfactorily demonstrate that the long-term stability of the BBR is well within +/- 0.1 moderate resolution bandpixels, undesired seasonal oscillations have been observed in the trending. The oscillations are most obvious between the visiblenear-infrared bands and short-middle wave infrared bands. This paper investigates the oscillations and identifies their cause as the band spectral dependence of the centroid position and the seasonal rotation of the lunar images over calibration events. Accordingly, an improved algorithm is proposed to quantify the rotation and compensate for its impact. After the correction, the seasonal oscillation in the resulting BBR is reduced from up to 0.05 moderate resolution band pixels to around 0.01 moderate resolution band pixels. After removing this spurious seasonal oscillation, the BBR, as well as its long-term drift are well determined.
This letter presents a novel approach for on-orbit characterization of MODerate resolution Imaging Spectroradiometer (MODIS) band-to-band registration (BBR) using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aboard the Terra spacecraft. The spatial resolution of ASTER spectral bands is much higher than that of MODIS, making it feasible to characterize MODIS on-orbit BBR using their simultaneous observations. The ground target selected for on-orbit MODIS BBR characterization in this letter is a water body, which is a uniform scene with high signal contrast relative to its neighbor areas. A key step of this approach is to accurately localize the measurements of each MODIS band in an ASTER measurement plane coordinate (AMPC). The ASTER measurements are first interpolated and aggregated to simulate the measurements of each MODIS band. The best measurement match between ASTER and each MODIS band is obtained when the measurement difference reaches its weighted minimum. The position of each MODIS band in the AMPC is then used to calculate the BBR. The results are compared with those derived from MODIS onboard Spectro-Radiometric Calibration Assembly. They are in good agreement, generally less than 0.1 MODIS pixel. This approach is useful for other sensors without onboard spatial characterization capability. Index Terms Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), band-to-band registration (BBR), MODerate resolution Imaging Spectroradiometer (MODIS), spatial characterization.
The NASA/NOAA Visible Infrared Imaging Radiometer Suite (VIIRS) is a key instrument in the JPSS missions (SNPP, JPSS-1-4). Being part of the calibration and validation process, JPSS-3 VIIRS prelaunch geometric performance assessment focuses on the sensor’s spatial response, band-to-band co-registration (BBR), and pointing knowledge. In general, JPSS-3 VIIRS’ prelaunch geometric performance is very good, and consistent with SNPP and JPSS-1-2 VIIRS sensors. This paper highlights some specific key findings from the JPSS-3 VIIRS’ prelaunch tests. We first show that with timing adjustments, JPSS-3 VIIRS scan BBR error between VisNIR and S/M/LWIR bands has been reduced from 0.12/0.03 M sampling intervals to 0.005/0.002 M sampling intervals, respectively. Focal Plane Assembly (FPA) rotations have been changed from 0.1 degree to 0.04 degree in VisVIR, from 0.18 degree to 0.09 degree in S/MWIR, and 0.16 degree to 0.08 degree in LWIR. Another finding from the prelaunch test is that JPSS-3 VIIRS has relatively large band-to-band co-registration errors between VisNIR and S/M/LWIR bands in the track direction. This BBR mis-registration increases when aft‐optics assembly (AOA) temperature decreases. The BBR mis-registration is about 0.10 M sampling intervals between VisNIR and S/MWIR bands, and 0.08 M sampling intervals between VisNIR and LWIR bands. By comparison, the track BBR offset in JPSS-2 is less than 0.02 M sampling intervals between VisNIR and S/M/LWIR bands. We also notice that the unsymmetrical Day Night Band (DNB) scan-direction Line Spread Function (LSF) of JPSS-2 VIIRS at different gain stages and aggregation modes have been corrected in J3 VIIRS.
Since launch, lunar observations have been made regularly by both Terra and Aqua MODIS and used for a number of sensor calibration and characterization related applications, including radiometric stability monitoring, spatial characterization, optical leak and electronic cross-talk characterization, and calibration inter-comparison. MODIS has 36 spectral bands with a total of 490 individual detectors. They are located on four focal plane assemblies (FPA). This paper focuses on the use of MODIS lunar observations to characterize its band-to-band registration (BBR). In addition to BBR, the approach developed by the MODIS Characterization Support Team (MCST) can be used to characterize MODIS detector-to-detector registration (DDR). Long-term BBR results developed from this approach are presented and compared with that derived from a unique on-board calibrator (OBC). Results show that on-orbit changes of BBR have been very small for both Terra and Aqua MODIS and this approach can be applied to other remote sensing instruments.
Commercial companies such as Maxar, Planet Labs, and BlackSky have built large archives of high resolution (1-3 m) Earth observing data. The high temporal resolution and global coverage of these satellites makes commercial satellite images ideal for scientists studying rapidly changing processes such as flooding and fires. The high spatial resolution allows scientists to push studies to a fine scale such as monitoring agricultural growth experiments or detecting vehicles for traffic management. Scientists using these data need to know geolocation accuracy, band-to-band registration (BBR), and pixel footprint size to best determine appropriate applications as well as what extra steps they will need to take to use the data. Here, we find those key geometric properties for images from Planet Labs’ SuperDove constellation. Geolocation accuracy is assessed relative to WorldView images at globally distributed cities, band-to-band registration (BBR) is examined for every image we acquired (200+ images), and pixel footprint sizes are calculated from edge responses of the images over Cal/Val sites in China, India, or USA both near launch time and 1+ years after launch. We find that SuperDove geolocation is highly self-consistent with average global offsets among SuperDove images of 3.80 m (1.27 pixels). Despite this self-consistency, relative geolocation accuracy (with WorldView images as reference) varies by location from 3.20 m – 28.09 m mean offset. SuperDove BBR is sub-pixel and varies by band, with a mean radial offset relative to red band varying from 0.39 - 1.13 m. SuperDove image footprint size improves after 1+ years in orbit, with an average footprint size of 3.41 pixels (10.24 m) soon after launch and 3.23 pixels (9.7 m) 1+ years after launch. The BBR and self-consistency offsets are relatively small, given the large footprint sizes. A similarly extensive investigation is in progress for Planet Labs’ Dove-R series.
The Visible Infrared Imaging Radiometer Suite (VIIRS) is a multi-spectral Earth-observing instrument on board the Suomi-NPP (SNPP) and NOAA-20 (N20) spacecraft, with spectral bands ranging in wavelength from 0.41 to 12.2 μm. For the reflective solar bands (RSB), the bands are calibrated on orbit using both solar diffuser (SD) and lunar observations. The lunar observations use near-monthly scheduled spacecraft maneuvers in order to view the Moon within a desired phase angle range. While the primary purpose of the maneuvers is for radiometric calibration, these observations can also be used to characterize the spatial performance of the instrument, including the band-to-band and detector-to-detector registration (BBR/DDR). The Moon can also be observed without spacecraft maneuvers. However, these observations are over a larger phase angle range. While the geometry of these unscheduled observations is more varied, they can still be used to assess the sensor performance. In this work, we will use unscheduled Moon data to analyze the BBR and DDR of the SNPP and N20 VIIRS RSB. For the BBR, we implemented an image cross-correlation approach, which removes the residual oscillations in the trending data when compared to previous methodologies. For the DDR, we developed an edge fitting approach that accounts for the lunar motion across the VIIRS focal plane array on a scan-by-scan basis using lunar and satellite ephemeris data. In our analysis, we find that the BBR and DDR for both VIIRS RSB are stable on orbit.
A throughput profile expressed as a function of the round-trip times of a data transport infrastructure is a critical indicator of its level of optimization, particularly, over dedicated connections. We study the throughput profiles of eleven TCP versions using measurements collected over dedicated hardware-emulated connections with distances spanning round the earth. Among them, BBR has overall higher temporal variations and lower throughput profiles compared to five loss-based TCP versions, and the comparison with other TCP versions is mixed. Using the Poincare map regions of throughput time traces, we show that the richer dynamics of BBR are correlated with its lower throughput profiles. We present basic analytical results that indicate that higher temporal variations of TCP methods lead to lower throughput profiles, thereby establishing the underlying causality. Under external losses, BBR achieves sustained high throughput compared to others as the loss rate is increased. Overall, our results provide insights into the relationship between time dynamics and throughput profiles of TCP versions, in particular, show that limited time traces can be indicative of global properties of throughput profiles.
Ag(BBr)5B5CH6BBr crystallizes in the orthorhombic Pnma space group. The structure is one-dimensional and consists of four bromoborane molecules; four B5CH6 clusters; and two Ag(BBr)5 ribbons oriented in the (1, 0, 0) direction. In each B5CH6 cluster, there are three inequivalent B+0.27+ sites. In the first B+0.27+ site, B+0.27+ is bonded in a bent 120 degrees geometry to one C4- and one H1+ atom. The B–C bond length is 1.70 Å. The B–H bond length is 1.19 Å. In the second B+0.27+ site, B+0.27+ is bonded in a bent 120 degrees geometry to one C4- and one H1+ atom. The B–C bond length is 1.70 Å. The B–H bond length is 1.19 Å. In the third B+0.27+ site, B+0.27+ is bonded in a bent 120 degrees geometry to one C4- and one H1+ atom. The B–C bond length is 1.70 Å. The B–H bond length is 1.19 Å. C4- is bonded in a 1-coordinate geometry to five B+0.27+ and one H1+ atom. The C–H bond length is 1.08 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one B+0.27+ atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one B+0.27+ atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one B+0.27+ atom. In each Ag(BBr)5 ribbon, Ag1+ is bonded to six Br1- atoms to form corner-sharing AgBr6 octahedra. The corner-sharing octahedral tilt angles are 40°. There are a spread of Ag–Br bond distances ranging from 2.83–3.02 Å. There are three inequivalent B+0.27+ sites. In the first B+0.27+ site, B+0.27+ is bonded in a single-bond geometry to one Br1- atom. The B–Br bond length is 1.98 Å. In the second B+0.27+ site, B+0.27+ is bonded in a single-bond geometry to one Br1- atom. The B–Br bond length is 1.97 Å. In the third B+0.27+ site, B+0.27+ is bonded in a single-bond geometry to one Br1- atom. The B–Br bond length is 1.98 Å. There are three inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a distorted single-bond geometry to two equivalent Ag1+ and one B+0.27+ atom. In the second Br1- site, Br1- is bonded in a distorted L-shaped geometry to one Ag1+ and one B+0.27+ atom. In the third Br1- site, Br1- is bonded in a distorted L-shaped geometry to one Ag1+ and one B+0.27+ atom.
Diamond as a templating substrate is largely unexplored, and the unique properties of diamond, including its large bandgap, thermal conductance, and lack of cytotoxicity, makes it versatile in emergent technologies in medicine and quantum sensing. Surface termination of an inert diamond substrate and its chemical reactivity are key in generating new bonds for nucleation and growth of an overlayer material. Oxidized high-pressure high temperature (HPHT) nanodiamonds (NDs) are largely terminated by alcohols that act as nucleophiles to initiate covalent bond formation when an electrophilic reactant is available. In this work, we demonstrate a templated synthesis of ultrathin boron on ND surfaces using trigonal boron compounds. Boron trichloride (BCl 3 ), boron tribromide (BBr 3 ), and borane (BH 3 ) were found to react with ND substrates at room temperature in inert conditions. BBr 3 and BCl 3 were highly reactive with the diamond surface, and sheet-like structures were produced and verified with electron microscopy. Surface-sensitive spectroscopies were used to probe the molecular and atomic structure of the ND constructs’ surface, and quantification showed the boron shell was less than 1 nm thick after 1–24 h reactions. Observation of the reaction supports a self-terminating mechanism, similar to atomic layer deposition growth, and is likely due to the quenching of alcohols on the diamond surface. X-ray absorption spectroscopy revealed that boron-termination generated midgap electronic states that were originally predicted by density functional theory (DFT) several years ago. DFT also predicted a negative electron surface, which has yet to be confirmed experimentally here. The boron-diamond nanostructures were found to aggregate in dichloromethane and were dispersed in various solvents and characterized with dynamic light scattering for future cell imaging or cancer therapy applications using boron neutron capture therapy (BNCT). The unique templating mechanism based on nucleophilic alcohols and electrophilic trigonal precursors allows for covalent bond formation and will be of interest to researchers using diamond for quantum sensing, additive manufacturing, BNCT, and potentially as an electron emitter.
The characteristics of false color imagery produced by instrumentation on earth resource mapping satellites are examined. The spatial fidelity of the imagery is dependent upon the geometric accuracy (GA) and the band-to-band registration (BBR) with which the telescope instrument is assembled. BBR and GA require knowledge of telescope effective focal length (EFL) to one part in 10,000 in order that the next generation of earth mappers be able to carry out their missions. The basis for this level of precision is briefly considered, and a description is given of the means by which such precise EFL measurements have been carried out. Attention is given to accuracy requirements, the technique used to measure effective focal length, possible sources of error in the EFL measurement, approaches for eliminating errors, and the results of the efforts to control measurement errors in EFL determinations.
Visible Infrared Imager Radiometer Suite (VIIRS) instrument on-board the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) satellite is scheduled for launch in October, 2011. It is to provide satellite measured radiance/reflectance data for both weather and climate applications. Along with radiometric calibration, geometric characterization and calibration of Sensor Data Records (SDRs) are crucial to the VIIRS Environmental Data Record (EDR) algorithms and products which are used in numerical weather prediction (NWP). The instrument geometric performance includes: 1) sensor (detector) spatial response, parameterized by the dynamic field of view (DFOV) in the scan direction and instantaneous FOV (IFOV) in the track direction, modulation transfer function (MTF) for the 17 moderate resolution bands (M-bands), and horizontal spatial resolution (HSR) for the five imagery bands (I-bands); 2) matrices of band-to-band co-registration (BBR) from the corresponding detectors in all band pairs; and 3) pointing knowledge and stability characteristics that includes scan plane tilt, scan rate and scan start position variations, and thermally induced variations in pointing with respect to orbital position. They have been calibrated and characterized through ground testing under ambient and thermal vacuum conditions, numerical modeling and analysis. This paper summarizes the results, which are in general compliance with specifications, along with anomaly investigations, and describes paths forward for characterizing on-orbit BBR and spatial response, and for improving instrument on-orbit performance in pointing and geolocation.
Since launch, both Terra and Aqua MODIS instruments have continued to operate and make measurements of the earth's top of atmospheric (TOA) radiances and reflectance. MODIS collects data in 36 spectral bands covering wavelengths from 0.41 to 14.4 microns. These spectral bands and detectors are located on four focal plane assemblies (FPAs). MODIS on-board calibrators (OBC) include a spectro-radiometric calibration assembly (SRCA), which was designed to characterize and monitor sensor spatial and spectral performance, such as on-orbit changes in the band-to-band registration (BBR), modulation transfer function (MTF), spectral band center wavelengths (CW) and bandwidths (BW). In this paper, we provide a status update of MODIS spatial and spectral characterization and performance, following a brief description of SRCA functions and on-orbit calibration activities. Sensor spatial and spectral performance parameters derived from SRCA measurements are introduced and discussed. Results show that on-orbit spatial performance has been very stable for both Terra and Aqua MODIS instruments. The large BBR shifts in Aqua MODIS, an issue identified pre-launch, have remained the same over its entire mission. On-orbit changes in CW and BW are less than 0.5 nm and 1 nm, respectively, for most VIS/NIR spectral bands of both instruments.
For the Moderate Resolution Imaging Spectroradiometer(MODIS) on the Terra and Aqua platforms, regularlyscheduled lunar observations using spacecraft roll maneuvershave been used extensively for sensor characterization. Whilethe primary purpose of these observations is for radiometriccalibration of the reflective solar bands, they have also beenleveraged for a number of other sensor performance assessments,such as the band-to-band (BBR) and detector-to-detector (DDR)spatial registration. The spatial registration calculations arecomplicated by the fact that the Moon does not move in astraight path across the sensor field-of-view (FOV). This path isdetermined by the relative orbital motion between the spacecraftand the Moon and the instrument attitude error that resultsfrom the roll maneuver. In this work, we develop a correctionfor the MODIS lunar spatial characterization measurements bycalculating the predicted path of the Moon across the sensor FOVusing spacecraft and lunar ephemeris data to model the relativeorbital motion between the spacecraft and the Moon along withspacecraft attitude error data acquired during the roll maneuver.The difference between measured and predicted positions of theMoon in the MODIS FOV can be used to calculate the BBRand DDR results. Since the predicted path across the FOV willbe the same for each band, the BBR results will be minimallyaffected. However, we will show that the along-scan spread inthe DDR can be significantly reduced, which results in a muchgreater consistency throughout the full mission for both Aquaand Terra MODIS.