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NASA NTRS2023

Launch Complex 34, SWMU CCO542022 DNAPL Source Zone Operations, Maintenance, and Monitoring, Site-Wide Long-Term Monitoring, and Hot Spot 6 Air Sparge System Annual Performance Monitoring Report Cape Canaveral Space Force Station, Florida

This Annual Performance Monitoring Report (PMR) for the Dense Non-Aqueous Phase Liquid (DNAPL) Source Zone (DSZ), Site-Wide Long-Term Monitoring (LTM), and Hot Spot (HS) 6 Air Sparge (AS) System presents the results of Year 13 operation of the hydraulic containment (HC) Interim Measure (IM), the results of performance monitoring direct-push technology (DPT) sampling and monitoring well sampling conducted in the DSZ, results of the biennial site-wide LTM event, and the results of operations and performance sampling of the HS 6 AS IM at Launch Complex 34 (LC34), located at Cape Canaveral Space Force Station (CCSFS), Florida. This site has been designated Solid Waste Management Unit (SWMU) CC054 under the Kennedy Space Center (KSC) Resource Conservation and Recovery Act (RCRA) Corrective Action Program. For the site-wide biennial LTM event, a total of 55 monitoring wells were sampled for volatile organic compounds (VOCs) in February 2023 and one well was sampled for polychlorinated biphenyls (PCBs) in December 2022. One well planned for VOC sampling was found to be destroyed and could not be sampled (CW0002). The LTM wells are screened in two lithologic zones: Layer 1 (0 to 25 feet below land surface [bls]) and Layer 2 (25 to 30 ft bls), and are located in the outlying areas of LC34 to monitor groundwater conditions within the Low-Concentration Plume (LCP), defined as concentrations exceeding Groundwater Cleanup Target Levels (GCTLs), and the High-Concentration Plume (HCP), defined as concentrations exceeding Natural Attenuation Default Concentrations (NADCs). Results from the biennial sampling event indicated overall plume stability and delineation for the plume, which extends over 300 acres. The operational period for Year 13 of the HCS was from April 1, 2022 to March 31, 2023. Operational runtime for the system was 90 percent during Year 13, with downtime events attributed to planned maintenance, system repairs, and power outages. As of March 31, 2023, a total of 313,673,241 cumulative gallons of groundwater containing 88,337 pounds of VOCs have been removed by the HCS. Influent concentrations of trichloroethene (TCE) have decreased since startup from approximately 280,000 μg/L (January 2010) to 12,000 μg/L (March 2023). During the reporting period, all effluent concentrations from the HCS (aqueous and vapor) were below regulatory reporting limits, indicating the system continues to operate as intended. Performance monitoring was conducted in December 2022 within the DSZ to evaluate TCE contamination. Groundwater samples were collected via DPT at nine locations, consistent with previous events between 2017 and 2021. Full vertical profile sampling was completed at each DPT from 8 to 98 feet bls, at 5-foot intervals. The DPT performance monitoring results are summarized in this PMR. The results revealed TCE remains at concentrations greater than 11,000 μg/L in the DSZ (1-percent solubility, indicative of DNAPL) at eight of the nine DPT locations and at depths ranging from 8 to 98 feet bls. In addition to DPT sampling, groundwater samples were collected from deep monitoring wells in the DSZ area (Layers 7 and 8) in December 2022 to verify vertical delineation. Layer 7/8 monitoring well results were non-detect in December 2022, with exception of three wells (IW0162, IW043D2, and IW044D2), where TCE, cis-1,2-dichloroethene (cDCE), and/or vinyl chloride (VC) were detected above GCTLs. These wells are screened 105 to 115 feet bls, which is below the existing recovery well capture zone. TCE was first detected in IW0162 in December 2021 and has since been sampled at least monthly to monitor TCE concentrations. The maximum TCE concentration during this operational period was 15,000 μg/L at IW0162 in March 2023. Because of the increased TCE concentrations in this well, a new recovery well (RW21D), screened 86 to 106 feet bls, was installed in January 2023 and incorporated into existing HCS operations. The HS 6 AS IM was initiated in 2018 with 160 AS wells, and expanded in 2019 with an additional 140 AS wells. Quarterly performance monitoring was reduced to semi-annual in 2020. The HS 6 AS system remained operational during the reporting period covered under this report. The results of the HS 6 system operation and semi-annual performance monitoring are summarized in this report. Semi-annual monitoring results collected in April and October 2022 show concentrations of contaminants of concern (cDCE, trans-1,2-dichloroethene, and vinyl chloride) are generally decreasing and not impacting the surface water drainage canal, indicating the HS 6 IM is meeting objectives. A Phase Two Expansion of the HS 6 AS IM was recently completed. As of the date of this report, the expansion became operational in August 2023 and the first quarter of monitoring was conducted in November 2023. Details of the construction, start-up, and performance monitoring will be included in a future Annual PMR. Overall, the tasks associated with Year 13 operation of the HC IM, operation of the HS 6 AS IM, and biennial site-wide sampling were performed in accordance with recommendations included in the previous 2021 LC34 (Year 12) annual report. Evaluation of results from the HC IM and HS 6 IM show that these systems are operating as designed and meeting performance objectives. Results from the site-wide biennial LTM program also show that the overall network of monitoring wells is adequate to continue monitoring plume-wide conditions.

Complex 34↗
NASA NTRS1992

Limb observations of the 12.32 micron solar emission line during the 1991 July total eclipse

The limb profile of the Mg I 12.32-micron emission line is determined by occultation in the July 11, 1991 total solar eclipse over Mauna Kea. It is shown that the emission peaks are very close to the 12-micron continuum limb, as predicted by recent theory for this line as a non-LTE photospheric emission. The increase in optical depth for this extreme limb-viewing situation indicates that most of the observed emission arises from above the chromospheric temperature minimum, and it is found that this emission is extended to heights well in excess of the model predictions. The line emission can be observed as high as 2000 km above the 12-micron continuum limb, whereas theory predicts it to remain observable no higher than about 500 km above the continuum limb. The substantial limb extension observed in this line is quantitatively consistent with limb extensions seen in the far-IR continuum, and it is concluded that it is indicative of departures from gravitational hydrostatic equilibrium, or spatial inhomogeneities, in the upper solar atmosphere.

Deming, Drake↗
NASA NTRS2002

Comparison of Aerosol Single Scattering Albedos Derived by Diverse Techniques In Two North Atlantic Experiments

Aerosol single scattering albedo omega (the ratio of scattering to extinction) is important in determining aerosol climatic effects, in explaining relationships between calculated and measured radiative fluxes, and in retrieving aerosol optical depths from satellite radiances. Recently, two experiments in the North Atlantic region, the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2), determined aerosol omega by a variety of techniques. The techniques included fitting of calculated to measured radiative fluxes; retrievals of omega from skylight radiances; best fits of complex refractive index to profiles of backscatter extinction, and size distribution; and in situ measurements of scattering and absorption at the surface and aloft. Both TARFOX and ACE-2 found a fairly wide range of values for omega at midvisable wavelengths approx. 550 nm, with omega(sub midvis) greater than or equal to 0.85 and less than or equal to 0.99 for the marine aerosol impacted by continental pollution. Frequency distributions of omega could usually be approximated by lognormals in omega(sub max) - omega, with some occurrence of bimodality, suggesting the influence of different aerosol sources or processing. In both TARFOX and ACE-2, closure tests between measured and calculated radiative fluxes yielded best-fit values of omega(sub midvis) 0.90 +/- 0.04 for the polluted boundary layer. Although these results have the virtue of describing the column aerosol unperturbed by sampling, they are subject to questions about representativeness and other uncertainties (e.g., thermal offsets, unknown gas absorption) The other techniques gave larger values for omega(sub midvis) for the polluted boundary layer, with a typical result of omega(sub midvis) = 0.95 +/- 0.04. Current uncertainties in omega are large in terms of climate effects More tests are needed of the consistency among different methods and of humidification effects on omega.

Russell, P. B.↗
NASA NTRS1990

Comparison of the ultrastructure of conventionally fixed and high pressure frozen/freeze substituted root tips of Nicotiana and Arabidopsis

To circumvent the limitations of chemical fixation (CF) and to gain more reliable structural information about higher plant tissues, we have cryofixed root tips of Nicotiana and Arabidopsis by high pressure freezing (HPF). Whereas other freezing techniques preserve tissue to a relatively shallow depth, HPF in conjunction with freeze substitution (FS) resulted in excellent preservation of entire root tips. Compared to CF, in tissue prepared by HPF/FS: (1) the plasmalemma and all internal membranes were much smoother and often coated on the cytoplasmic side by a thin layer of stained material, (2) the plasmalemma was appressed to the cell wall, (3) organelle profiles were rounder, (4) the cytoplasmic, mitochondrial, and amyloplast matrices were denser, (5) vacuoles contained electron dense material, (6) microtubules appeared to be more numerous and straighter, with crossbridges observed between them, (7) cisternae of endoplasmic reticulum (ER) were wider and filled with material, (8) Golgi intercisternal elements were more clearly resolved and were observed between both Golgi vesicles and cisternae, and (9) larger vesicles were associated with Golgi stacks. This study demonstrates that HPF/FS can be used to successfully preserve the ultrastructure of relatively large plant tissues without the use of intracellular cryoprotectants.

NASA Program Space Biology↗
NASA NTRS1973

Technique for Obtaining Vertical Profiles of Backscattering and Extinction Cross Sections Using Slant Path Lidar Measurements

A method is presented for solving for vertical profiles of atmospheric particulate extinction and backscattering cross-sections utilizing monostatic lidar slant path measurements. The method is an extension of work by Fernald. It is shown that the number of assumptions necessary for an iterative solution of extinction and backscattering cross sections can be reduced if lidar slant path measurements are used to solve directly for optical depths. The technique is useful only if sufficiently accurate lidar measurements are available. With highly accurate measurements it is also possible to solve directly for extinction cross sections without an iterative solution of a transcendental equation if the proper reduction scheme is used. The required accuracy is discussed and results showing the effect of errors are presented.

Spinhirne, J. D.↗
NASA NTRS2012

Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption in the ASCENDS 2011 Airborne Campaign

We have previously demonstrated an efficient pulsed, wavelength-resolved IPDA lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission. Our team participated in the 2010 ASCENDS airborne campaigns we flew airborne version of the CO2 and O2 lidar on the NASA DC-8. The CO2 lidar measures the atmospheric backscatter profiles and shape of the 1572.33 nm absorption line using 250 mW average laser power, 30 wavelength samples per scan and 300 scans per second. Most flights had 5-6 altitude steps to greater than 12 km, and clear CO2 line shapes were observed at all altitudes. Our post-flight analysis estimated the Iidar range and pulse energies at each wavelength every second. We then solved for the best-fit CO2 absorption line shape, and calculated the Differential Optical Depth (DOD) at the line peak. We compared these to CO2 DODs calculated from spectroscopy based on HITRAN 2008 and the conditions from airborne in-situ readings. Analysis of the 2010 measurements over the Pacific Ocean and Lamont OK shows the expected -linear change of the peak DOD with altitude. For measurements at altitudes greater than 6 km the random errors were approximately 0.3 ppm for 80 sec averaging times. After the 2010 flights we improved the airborne lidar's scan uniformity, calibration and receiver sensitivity. Our team participated in the seven ASCENDS science flights during late July and August 2011. These flights were made over a wide variety of surface and cloud conditions near the US, including over the central valley of California, over several mountain ranges, over both broken and solid stratus cloud deck over the Pacific Ocean, snow patches on mountain tops, over thin and broken clouds above the US Southwest and Iowa, and over forests near the WLEF tower in Wisconsin. Analyses show the retrievals of lidar range and CO2 column absorption, as wen as estimates of CO2 mixing ratio worked well when measuring over topography with rapidly changing height and reflectivity, through thin clouds and to stratus cloud tops. For regions where the CO2 concentration was relatively constant, the measured CO2 absorption profile (averaged for 50 sec) matched the predicted profile to better than 1% RMS error for all flight altitudes. For 1 & 10 second averaging, the scatter in the retrievals was limited by signal shot noise (i.e. the sigual photon count). Analysis to date shows the decrease in CO2 due to vegetation when flying easterward over the Great Plains as well as the increase in CO2 concentration in the vicinity ofthe coal-fired power plant in New Mexico. Examples of these and other results will be presented.

Abshire, James B.↗
NASA NTRS1987

Uranus' (3-0) H2 quadrupole line profiles

Spectra of Uranus' S3(0) and S3(1) H2 quadrupole lines, obtained during the 1978-1980 apparitions, are analyzed, and are found to require the presence of a deep cloud. Modifications of the Baines and Bergstralh (1986) standard model, including an additional haze layer above the 16-km-am H2 level which contains strongly absorbing particles, are needed to fit the observations. For a Rayleigh phase function, such a haze (uniformly mixed with the gas above this level) would have an absorption optical depth of 0.16 and a single scattering particle albedo of 0.30. This modification would imply a fraction of normal H2 equal to 0.25 + or - 0.10, in agreement with the Baines and Bergstralh standard model.

Trafton, L.↗
NASA NTRS1988

The scheduling techniques of ESP2

The Mission Analysis Division of the Systems Analysis and Integration Laboratory at the Marshall Space Flight Center has developed a robust automatic scheduler which can produce detailed schedules for the multi-step activities required for payload operations on the Space Station. This scheduler, a part of the Expert Scheduling Program (ESP2), has five components: the bookkeeper, checker, loader, selector, and explainer. The bookkeeper maintains the usage profiles for nondepletable resources, consumables, equipment, crew, and the times of all the steps for the payload activities for several different schedules simultaneously. The checker searches the data maintained by the bookkeeper and finds times when the constraints of each step of an activity are satisfied. The loader is an expert system that uses the techniques of forward chaining, depth-first searching, and backtracking to manage the workings of the checker so that activities are placed in the schedule without violating constraints (such as crew, resources, and orbit opportunities). The checker searches the data maintained by the bookkeeper and finds times when the constraints of each step of an activity are satisfied. The loader is an expert system which uses the techniques of forward chaining, depth-first searching, and backtracking to manage the workings of the checker so that activities are placed in the schedule without violating the constraints. The selector has several methods of choosing the next activity for the loader to schedule. The explainer shows the user why an activity was or was not scheduled at a certain time; it offers a unique graphical explanation of how the expert system (the loader) works.

Jaap, John P.↗
NASA NTRS2010

Premonsoon Aerosol Characterization and Radiative Effects Over the Indo-Gangetic Plains: Implications for Regional Climate Warming

The Himalayas have a profound effect on the South Asian climate and the regional hydrological cycle, as it forms a barrier for the strong monsoon winds and serves as an elevated heat source, thus controlling the onset and distribution of precipitation during the Indian summer monsoon. Recent studies have suggested that radiative heating by absorbing aerosols, such as dust and black carbon over the Indo-Gangetic Plains (IGP) and slopes of the Himalayas, may significantly accelerate the seasonal warming of the Hindu Kush-Himalayas-Tibetan Plateau (HKHT) and influence the subsequent evolution of the summer monsoon. This paper presents a detailed characterization of aerosols over the IGP and their radiative effects during the premonsoon season (April-May-June) when dust transport constitutes the bulk of the regional aerosol loading, using ground radiometric and spaceborne observations. During the dust-laden period, there is a strong response of surface shortwave flux to aerosol absorption indicated by the diurnally averaged forcing efficiency of -70 W/sq m per unit optical depth. The simulated aerosol single-scattering albedo, constrained by surface flux and aerosol measurements, is estimated to be 0.89+/- 0.01 (at approx.550 nm) with diurnal mean surface and top-of-atmosphere forcing values ranging from -11 to -79.8 W/sq m and +1.4 to +12 W/sq m, respectively, for the premonsoon period. The model-simulated solar heating rate profile peaks in the lower troposphere with enhanced heating penetrating into the middle troposphere (5-6 km), caused by vertically extended aerosols over the IGP with peak altitude of approx.5 km as indicated by spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization observations. On a long-term climate scale, our analysis, on the basis of microwave satellite measurements of tropospheric temperatures from 1979 to 2007, indicates accelerated annual mean warming rates found over the Himalayan-Hindu Kush region (0.21 C/decade+/-0.08 C/decade) and underscores the potential role of enhanced aerosol solar absorption in the maximum warming localized over the western Himalayas (0.26 C/decade f 0.09 C/decade) that significantly exceed the entire HKHT and global warming rates. We believe the accelerated warming rates reported here are critical to both the South Asian summer monsoon and hydro-glaciological resource variability in the Himalayan-Hindu Kush snowpack and therefore to the densely populated downstream regions.

Gautam, Ritesh↗
NASA NTRS2020

Aerosol Layer Height With Enhanced Spectral Coverage Achieved by Synergy Between VIIRS and OMPS-NM Measurements

This study presents a near production-ready algorithm to retrieve the height of biomass burning smoke and mineral dust aerosols as part of NASA’s Deep Blue aerosol data product suite. It utilizes the enhanced spectral coverage achieved by using co-located data from the Visible Infrared Imaging Radiometer Suite (VIIRS) and the Ozone Mapping and Profiler Suite Nadir Mapper (OMPS-NM), both aboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite. Specifically, the 412 nm top-of-atmosphere reflectance from VIIRS and the ultraviolet aerosol index from OMPS-NM are used to determine the height and single-scattering albedo of the absorbing aerosols simultaneously. Constraints on aerosol optical depth at 550 nm and surface reflectance for the 412 nm band are provided by the operational VIIRS Deep Blue aerosol product. Wildfire smoke layer heights obtained from the algorithm over North America, where smoke plumes often stretched thousands of kilometers, are shown to agree with those from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements, with an uncertainty generally within 1-1.5 km. This new height data set will be included in the upcoming Version 2 VIIRS Deep Blue aerosol product.

Aerosol↗
NASA NTRS1992

Wind Profiles Derived from Volume Imaging Lidar Data: Enhancements to the Algorithm and Comparisons with Insitu Observations

This paper presents wind measurements made with the University of Wisconsin Volume Imaging Lidar (VIL) during Aug. 1989 as part of the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE). Enhancements to the algorithm are described. Comparisons of these results to aircraft, balloon, and surface based wind measurements are presented. Observations of the spatial variance of aerosol backscatter are also compared to measurements of the convective boundary layer depth. Measurements are based on two-dimensional cross correlations between horizontal image planes showing the spatial distribution of aerosol scattering observed by the lidar at intervals of approximately 3 minutes. Each image plane covers an area of 500-1000 sq km and the winds calculated represent area averages.

Piironen, A. K.↗
NASA NTRS1982

On the radial structure of planetary rings

Viscous shear stress of a ring of particles in orbit about a planet due to the radial gradient of orbital velocity is discussed. This stress tends to spread the ring with time. At low optical depth (t) and at high t, the shear stress is an increasing function of t. In the intermediate range stress may decrease with increasing t, leading to a diffusive instability which tends to break an initially uniform ring into ringlets of high and low optical depths. According to the shepherd satellite model of narrow ring confinement, the viscous shear stress is opposed by tidal torques from neighboring shepherds, so that radial spreading does not occur. By requiring that the gradient of the viscous shear stress (i.e., angular momentum deposited) be equal to the shepherd satellite torque density at all radii in the rings, equilibrium radial density profiles of a confined ring were constructed. The most noteworthy feature of these profiles is a narrow, high density ringlet surrounded by a low optical density halo of greater width.

Harris, A. W.↗
NASA NTRS2010

In Situ and Lidar Observations of Tropopause Subvisible Cirrus Clouds During TC4

During the Tropical Composition, Clouds, and Climate Coupling (TC4) experiment in July-August 2007, the NASA WB-57F and ER-2 aircraft made coordinated flights through a tropopause subvisible cirrus (SVC) layer off the Pacific Coast of Central America. The ER-2 aircraft was equipped with a remote sensing payload that included the cloud physics lidar (CPL). The WB-57F payload included cloud microphysical and trace gas measurements, and the aircraft made four vertical profiles through the SVC layer shortly after the ER-2 flew over. The in situ and remotely sensed data are used to quantify the meteorological and microphysical properties of the SVC layer, and these data are compared to the limited set of SVC measurements that have previously been made. It is found that the layer encountered was particularly tenuous, with optical depths (tau) between about 10(exp -4) and 10(exp -3). From the in situ and other meteorological data, radiative heating rate perturbations of approx.0.05-0.1 K/day are calculated. These heating rates are smaller than previous estimates for tropopause SVC, consistent with the smaller tau in the present study. Coverage statistics based on CPL data from other TC4 flights indicate that this cloud was not an outlier among the sampled population. SVC with properties similar to the one presented here are below the detection limit of space \based lidars such as CALIPSO, and a comparison with the TC4 statistics suggests that a majority (>50%) of tropopause SVC (with tau < 0.01) could be unaccounted for in studies using CALIPSO data.

Davis, Sean↗
NASA NTRS2012

Characterization of the Morphometry of Impact Craters Hosting Polar Deposits in Mercury's North Polar Region

Earth-based radar images dating back two decades show that the floors of some polar craters on Mercury host radar-bright deposits that have been proposed to consist of frozen volatiles. Several hypotheses have been put forth to explain their source, including volcanic outgassing, chemical sputtering, and deposition of exogenous water ice. Calculations show that volatiles are thermally stable in permanently shadowed areas. An earlier study of the depths of north polar craters determined with photoclinometric techniques applied to Mariner 10 images yielded the conclusion that the mean ratio of crater depth d to rim-crest diameter D for craters hosting polar deposits is two-thirds that of the mean ratio for a comparable population of neighboring craters lacking such deposits. This result could be explained by (though doesn't require) the presence of a thick layer of volatiles within the polar deposit-hosting craters. Here we use altimetric profiles and topographic maps obtained by the Mercury Laser Altimeter (MLA) to revisit this analysis. MLA is an instrument on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, which has been orbiting Mercury since March 2011. MLA transmits a 1064-nm laser pulse at 8 Hz during MESSENGER's trajectory over Mercury s surface. The MLA illuminates surface areas averaging between 15 m and 100 m in diameter, spaced approx 400 m apart along the spacecraft ground track. The radial precision of individual measurements is <1 m, and the current accuracy with respect to Mercury s center of mass is better than 20 m. As of mid-December 2011, MLA coverage had reached to 15 S and has yielded a comprehensive map of the topography of Mercury s northern hemisphere. The MLA data are used here to quantify the shapes of craters in the north polar region and to avoid the shadowing bias of photoclinometric techniques.

Talpe, Matthieu, J.↗
NASA NTRS2024

Launch Complex 34, SWMU CC054 2023 DNAPL Source Zone Operations, Maintenance, and Monitoring, Site-Wide Long-Term Monitoring, and Hot Spot 6 Air Sparge System Annual Performance Monitoring and Phase Two Expansion Construction Completion Report Cape Canaveral Space Force Station, Florida

This Annual Performance Monitoring Report (PMR) for the Dense Non-Aqueous Phase Liquid (DNAPL) Source Zone (DSZ), Site-Wide Long-Term Monitoring (LTM), and Hot Spot 6 (HS 6) Air Sparge (AS) System presents the results of Year 14 operations and performance monitoring of the hydraulic containment (HC) Interim Measure (IM), details associated with construction and implementation of the HS 6 AS system expansion (Phase Two), and the results of operations and performance sampling of the HS 6 AS IM at Launch Complex 34 (LC34), located at Cape Canaveral Space Force Station (CCSFS), Florida. The timeframe for activities documented in this PMR extends from April 1, 2023 to March 31, 2024. LC34 has been designated Solid Waste Management Unit CC054 under the Kennedy Space Center (KSC) Resource Conservation and Recovery Act Corrective Action Program. The objective of the HC IM at LC34 is to contain the shallow and deep DSZ and surrounding dissolved-phase trichloroethene (TCE) high concentration plume via operation of a hydraulic containment system (HCS). The pre-IM design 300 micrograms per liter (μg/L) TCE groundwater contour was used to establish the deep zone capture area for deep recovery wells, and the shallow zone capture area was defined by the DSZ. The system began operating in 2010, and in 2015, the system was expanded to provide HC for areas within the 300 μg/L TCE groundwater isocontours of HS 3 and 4. In 2018 and 2019, an investigation was conducted to recharacterize the DSZ, which included investigating TCE mass in Layer 7. This data was subsequently used to optimize the pumping rates of the HCS and install additional recovery wells in Layer 7 to more adequately capture residual contaminant mass. The operational period for Year 14 of the HCS was from April 1, 2023 to March 31, 2024. Operational runtime for the system was 94 percent during Year 14, with downtime events attributed to planned maintenance, system repairs, and power outages. As of March 31, 2024, a total of 344,849,634 cumulative gallons of groundwater containing 94,656 pounds of chlorinated volatile organic compounds (CVOCs) have been removed by the HCS. During the reporting period covered under this report, the HCS recovered 31,176,393 gallons and approximately 6,319 pounds of CVOC mass. Total combined influent concentrations of TCE have decreased since startup from approximately 280,000 µg/L (January 2010) to 25,000 µg/L (March 2024). During the reporting period, all effluent concentrations from the HCS (aqueous and vapor) were below regulatory reporting limits, indicating the system continues to operate as intended. Performance monitoring was conducted in January 2024 within the DSZ to evaluate TCE contamination. Groundwater samples were collected via DPT at nine locations, consistent with previous events between 2017 and 2022. Full vertical profile sampling was completed at each DPT from 8 to 98 feet below land surface (bls), at 5-foot intervals. The DPT performance monitoring results are summarized in this PMR. The results revealed TCE remains at concentrations greater than 11,000 µg/L in the DSZ (1-percent solubility, indicative of DNAPL) at eight of the nine DPT locations and at depths ranging from 28 to 98 feet bls. An overall decreasing trend of TCE concentrations was observed in DPT samples during this reporting period, which is a reduction from the previous event (December 2022) and the peak event in December 2021, where TCE percentages appeared to increase in all depth zones because several recovery wells were turned off during the AS pilot study in the DSZ. The maximum TCE concentration in January 2024 was 1,600,000 µg/L in the 53 feet bls depth interval at DPT594 (previous maximum result in 2022 was 1,800,000 µg/L in the 48 feet bls depth interval at DPT599). This maximum concentration in the 53 feet bls depth interval is in the deep capture zone. During the January 2024 DPT event, the largest portion of TCE mass was observed in the 48 feet bls interval above/within Layer 4. This trend remains consistent with previous years and appears to indicate continued mass discharge from Layer 4 (fine-grained unit). In addition to DPT sampling, annual groundwater samples were collected from 11 deep monitoring wells in the DSZ area (Layers 7 and 8) in December 2023 to verify vertical and horizontal delineation. Three of the wells were also sampled biweekly to evaluate operations of recovery well RW21D (screened 86 to 106 feet bls), which was installed in January 2023. Of the Layer 7/8 monitoring sampled only annually, results were non-detect or less than groundwater cleanup target levels GCTLs in December 2023, with the exception of one well, IW45D2, which had a cis-1,2-dichloroethene (cDCE), detection greater than the GCTL. Of the three wells sampled biweekly during the operational period, the well located closest to Layer 7 recovery well RW21D (IW44D2, screened 105 to 115 feet bls) had concentrations of TCE, cDCE and vinyl chloride (VC) greater than GCTLs throughout the operational period, but displayed a decreasing trend since the peak concentrations in September 2023. The maximum TCE concentration during this operational period was 190,000 µg/L at IW44D2 in September 2023, but reduced to 700 µg/L in March 2024, indicating the HCS is still effectively removing mass from the source area. Expansion of the HCS and addition of new recovery wells is ongoing and will continue to be evaluated as the groundwater recovery scheme is optimized. Details of the expansion and optimization will be provided in a future PMR. The HS 6 AS IM was initiated in 2018 with 160 AS wells and expanded in 2019 with another 140 AS wells. An additional expansion of the HS 6 AS IM was completed during the reporting period covered under this report and details of the construction implementation and startup of the expansion are detailed in Section III of this report. The new expansion, referred to as Phase Two, was implemented between August 17, 2022 and August 28, 2023, and included the installation of 190 air sparge wells to treat an additional 11.2 acres. The original configuration (referred to as Phase One) operated until Phase Two came online, then all but 52 AS wells were turned off so the components could be moved and utilized in the Phase Two area. The 52 AS wells that remain on are in a barrier configuration preventing contaminated groundwater from impacting the treated area. The HS 6 AS system (both Phase One and Two) operated normally during the reporting period covered under this report. Semi-annual performance monitoring of the Phase One configuration was conducted in April and November 2023, consistent with previous years. For the Phase Two configuration, 21 new monitoring wells were installed and sampled quarterly, with a baseline event in July 2023, and quarterly events in November 2023 and February 2024 summarized in this report. Semi-annual monitoring results collected in April and October 2023 show concentrations of contaminants of concern (cDCE, trans-1,2-dichloroethene, and VC) have decreased to less than GCTLs in nearly all wells and not impacting the surface water drainage canal, indicating the HS 6 IM continues to meet objectives. The baseline and quarterly sampling for the Phase Two configuration indicate generally decreasing concentrations in wells within and around the perimeter of the treatment area. At least two more quarters of monitoring will be conducted and once those results are evaluated a reduced the sampling frequency may be considered. Overall, the tasks associated with Year 14 operation of the HC IM and operation of the HS 6 AS IM were performed in accordance with recommendations included in the previous 2022 LC34 (Year 13) PMR. Evaluation of results from the HC IM and HS 6 IM show that these systems are operating as designed and meeting performance objectives.

groundwater remediation↗
NASA NTRS2012

Evaluating Nighttime CALIOP 0.532 micron Aerosol Optical Depth and Extinction Coefficient Retrievals

NASA Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) Version 3.01 5-km nighttime 0.532 micron aerosol optical depth (AOD) datasets from 2007 are screened, averaged and evaluated at 1 deg X 1 deg resolution versus corresponding/co-incident 0.550 micron AOD derived using the US Navy Aerosol Analysis and Prediction System (NAAPS), featuring two-dimensional variational assimilation of quality-assured NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR) AOD. In the absence of sunlight, since passive radiometric AOD retrievals rely overwhelmingly on scattered radiances, the model represents one of the few practical global estimates available from which to attempt such a validation. Daytime comparisons, though, provide useful context. Regional-mean CALIOP vertical profiles of night/day 0.532 micron extinction coefficient are compared with 0.523/0.532 micron ground-based lidar measurements to investigate representativeness and diurnal variability. In this analysis, mean nighttime CALIOP AOD are mostly lower than daytime (0.121 vs. 0.126 for all aggregated data points, and 0.099 vs. 0.102 when averaged globally per normalised 1 deg. X 1 deg. bin), though the relationship is reversed over land and coastal regions when the data are averaged per normalised bin (0.134/0.108 vs. 0140/0.112, respectively). Offsets assessed within single bins alone approach +/- 20 %. CALIOP AOD, both day and night, are higher than NAAPS over land (0.137 vs. 0.124) and equal over water (0.082 vs. 0.083) when averaged globally per normalised bin. However, for all data points inclusive, NAAPS exceeds CALIOP over land, coast and ocean, both day and night. Again, differences assessed within single bins approach 50% in extreme cases. Correlation between CALIOP and NAAPS AOD is comparable during both day and night. Higher correlation is found nearest the equator, both as a function of sample size and relative signal magnitudes inherent at these latitudes. Root mean square deviation between CALIOP and NAAPS varies between 0.1 and 0.3 globally during both day/night. Averaging of CALIOP along-track AOD data points within a single NAAPS grid bin improves correlation and RMSD, though day/night and land/ocean biases persist and are believed systematic. Vertical profiles of extinction coefficient derived in the Caribbean compare well with ground-based lidar observations, though potentially anomalous selection of a priori lidar ratios for CALIOP retrievals is likely inducing some discrepancies. Mean effective aerosol layer top heights are stable between day and night, indicating consistent layer-identification diurnally, which is noteworthy considering the potential limiting effects of ambient solar noise during day.

aerosol optical depth↗
NASA NTRS1972

Calculation of 5250.216 A line profiles in sunspots.

It is shown that spectral line profiles, used in the calibration and interpretation of magnetograph results, cannot be considered as reliable when they are calculated under the assumption of pure absorption and local thermodynamic equilibrium, frequently employed. Because of this assumption, the line-to-continuous absorption ratio becomes very large at the top of the sunspot model, causing the emergent intensity to originate at a very shallow depth in the sunspot. This is illustrated by calculations of the Fe I 5250.2 A line for three sunspot models.

Dunn, A. R.↗
NASA NTRS1992

Photometry and spectroscopy of Nova Herculis 1991

Observations of Nova Herculis 1991 obtained during the months of 1991 May-September are presented. Spectral observations a few weeks after outburst constrain the distance to Nova Her to between 6 and 12 kpc and show evidence of dust formation in the expanding shell and line profiles with five components having large expansion velocities. Initial photometric observations of the nova in June showed the nova had declined approximately ten magnitudes in the V band from its maximum, and by September, the nova had dimmed by approximately two additional magnitudes. The period derived from these observations agrees with that reported by Leibowitz et al. (1992). Periodic eclipses with a depth of about 0.7 V mag are observed, and the depths of the eclipses are constant over a 2-month period while the overall brightness diminished by one magnitude. The long duration of the eclipses indicates an eclipse of an extended source, likely the accretion disk.

Ingram, Doug↗