Hanscom Air Force Base Research Articles

Electron and proton beam testing of pixelated solid state detectors

The biasing of guard rings in pixelated ion implanted silicon solid state detectors is often given little analysis as to the potential detrimental effects associated with capacitive coupling of the response of the pixel element to the guard ring and vise versa. This has been demonstrated and illustrates the importance of using beam testing to measure the angular response of particle instruments. We describe herein the development cycle of the Fixed Sensor Head (FSH) instrument, an imaging electron spectrometer that will be flown on the US Air Force's Demonstration and Science eXperiment (DSX) mission. During its construction, the FSH was tested using particle beams many times and each test yielded an important result that contributed to the design of the instrument before being delivered in August 2010.After several lower energy (<30keV) beam calibration tests at Hanscom Air Force Base demonstrated that the FSH was performing very well, a final, higher energy (150keV<E<1MeV) beam test at the Goddard Space Flight Center was almost skipped due to budget and scheduling constraints. This final test illuminated a major problem with the biasing of a detector guard ring that would have been difficult if not impossible to track down on orbit. The problem was easily fixed, but serves to highlight the importance of biasing of guard rings properly, and the necessity of testing instruments across the entire range of possible stimuli that they may encounter.

Comment on “Mount St. Helens: A 30‐Year Legacy of Volcanism”

I read with great interest “Mount St. Helens: A 30‐year legacy of volcanism,” by J. W. Vallance et al., the feature in the 11 May 2010 issue of Eos (91(19), 169–170). This well‐written article is about the volcano itself and ash and aircraft incidents but not about far‐field effects such as traveling ionospheric disturbances (disturbances in the ionosphere that act like traveling waves) that were caused by the explosion.I have a personal interest in the 1980 Mount St. Helens volcanic eruption. At that time I was working as a physicist at the U.S. Air Force Geophysics Laboratory (AFGL) at Hanscom Air Force Base, in Massachusetts. AFGL had a magnetometer array located across the United States, from which I and other scientists at Hanscom observed perturbations in the Earth's magnetic field, which we related directly to the explosion. These perturbations were observed at stations as far away from Mount St. Helens as Mount Clemens, Mich., 3122 kilometers distant. We were able to measure the velocity of the resulting disturbance at about 316 meters per second, in reasonable agreement with velocities of the pressure wave (from 305 to 309 meters per second) that was observed on microbarometers by the Japan Meteorological Agency.

Spacecraft Charging and Mitigation

Satellites and spacecraft materials can become charged to tens or even thousands of volts when ions in the space environment collide with spacecraft. This can sometimes cause electrical discharge of differentially or internally charged spacecraft materials, which can adversely affect satellite operations. Additionally, high-energy ions can penetrate spacecraft materials and deposit their energy within sensitive electronics, causing component damage or failure. To consider various approaches for spacecraft charge mitigation, 150 technologists from around the world representing government, academia, and industry met at the 11th Spacecraft Charging Technology Conference (SCTC) in Albuquerque, N. M., on 20–24 September 2010 (see Figure 1). The conference was held against the backdrop of the apparent charging event of the Galaxy 15 satellite, which some speculate triggered this geosynchronous communications satellite to cease operations, thereby adversely affecting related satellite-reliant communities (see J. Allen, Space Weather, 8, S06008, doi:10.1029/2010SW000588, 2010). Charles P. Pike, formerly of the U.S. Air Force Research Laboratory (AFRL) and past program manager of the AFRL spacecraft charging program, presented a keynote address that recalled the early 1970s, when military satellites in geosynchronous orbit experienced numerous unexpected performance anomalies. Pike then traced how scientists discovered that space weather can have deleterious and sometimes catastrophic effects on spacecraft, satellite operations, and the longevity of space systems. Speakers focused on the ways that energetic charged particles and plasma can adversely affect spacecraft. For example, electrostatic discharge (ESD) of solar cell arrays, on which most spacecraft depend, can destroy the supply of energy to crucial satellite systems. As spacecraft power requirements grow, the current trend toward higher solar panel operating voltages (above 100 volts) increases the environmental susceptibility of spacecraft. Presentations featured ESD mitigation strategies designed and analyzed by researchers from institutions within the United States, Japan, and Europe. Much of the conference focused on the ESD of satellites in geosynchronous orbit, although consideration was also given to other Earth orbits as well as other planetary missions and solar probes. Also discussed were laboratory testing approaches for simulating spacecraft-environment interactions and computer modeling of complex satellite geometries. Many talks at the conference showed how researchers are advancing the science and capabilities of tools, models, material properties, guidelines, and best practices to build robust satellites equipped with spacecraft charging mitigation capabilities. Further, various engineering standards for environmentally tolerant space systems, including those available from NASA (NASA-HDBK-4002A), the International Organization for Standardization (ISO/DIS 11221), and the European Space Agency (ECSS-E-ST-10-04C), are proving useful, meeting participants agreed. Attendees also discussed new technology frontiers for addressing spacecraft charging, which they agreed should focus on better specifications for nonstatic spacecraft materials, advancement of dynamic models of spacecraft-environment interactions, development of novel techniques for spacecraft charge mitigation, and assessing the impacts of new requirements for high-voltage solar panels. Presentations and proceedings of this meeting are available through the National Geophysical Data Center (http://www.ngdc.noaa.gov/stp/satellite/anomaly/2010_sctc/). In addition, a special issue of IEEE Transactions on Plasma Science will be devoted to follow-on and related papers covering spacecraft charging issues. The 12th SCTC is planned for Kitakyushu, Japan, in May 2012. Dale Ferguson is a physicist with the Battlespace Environment Division at AFRL in Albuquerque, N. M. David Cooke is the technical advisor for the AFRL Space Weather Center of Excellence at Hanscom Air Force Base in Bedford, Mass. William Denig is chief of the Solar and Terrestrial Physics Division at NOAA's National Geophysical Data Center in Boulder, Colo. E-mail: william.denig@noaa.gov.

Book Review: The Sun Kings: The Unexpected Tragedy of Richard Carrington and the Tale of How Modern Astronomy Began

Book Review: <i>The Sun Kings: The Unexpected Tragedy of Richard Carrington and the Tale of How Modern Astronomy Began</i>

Space Weather and the Global Positioning System

Space Weather and the Global Positioning System

Analysis of HF signal power observations on two North American circuits

Observations of HF signal powers on two circuits in North America have been compared with the values predicted by two HF propagation programs, Voice of America Coverage Analysis Program (VOACAP) and Advanced Stand Alone Prediction System (ASAPS). Neither program consistently provided the more reliable predicted signal powers. For the longer circuit considered (2820 km WWV Fort Collins to Hanscom Air Force Base), ASAPS was found to be the more accurate program for the lower frequencies (at night), while VOACAP was the more accurate for the higher frequencies (during the day). The RMS errors ranged from a few decibels to 15 dB. For daytime 7.335 MHz propagation on the 490 km CHU Ottawa to Hanscom Air Force Base circuit, the VOACAP RMS errors (∼4 dB) were less than the ASAPS RMS errors (∼8 dB). The errors for the two programs were very similar for 3.330 MHz propagation, peaking at ∼9 dB just after sunrise and just before sunset and ∼3 dB during the night.

Vertical gradient freezing using submerged heater growth with rotation and with weak magnetic and electric fields

Investigations for the melt growth gallium-antimonide (GaSb) semiconductor crystals are underway at the US Air Force Research Laboratory at Hanscom Air Force Base by the vertical gradient freeze (VGF) method utilizing a submerged heater. Electromagnetic stirring can be induced in the gallium-antimonide melt just above the crystal growth interface by applying a weak radial electric current in the melt together with a weak axial magnetic field. A force convection in the melt can be induced by rotating the heater. This paper uses a Chebyshev spectral collocation method and investigates the effects of heater rotation and electromagnetic stirring on the melt motion during the VGF process using a submerged heater. Clockwise and counterclockwise rotations of the heater augment and opposes the flow induced by the electromagnetic stirring, respectively. The radial velocity along the crystal–melt interface is proportional to both the strength of the electromagnetic stirring and the clockwise rotation of the heater. A relatively low rotation rate in the clockwise direction significantly increases this radial velocity.

GPS proxy model for real‐time UHF satellite communications scintillation maps from the Scintillation Network Decision Aid (SCINDA)

In order to provide a more reliable situational awareness of scintillation impacts on users of space‐based communication/navigation systems, L‐band scintillation measurements from GPS satellites are ingested, in real time, to the Scintillation Network Decision Aid (SCINDA) model. SCINDA is a real‐time, data‐driven communication outage forecast and alert system developed by the Air Force Research Laboratory at Hanscom Air Force Base and made operational through a joint effort between the U.S. Air Force and the U.S. Navy. UHF and L‐band scintillation parameters are measured, modeled, and propagated in time to provide a regional specification of the scintillation environment in an effort to mitigate the impacts on the satellite communications (SATCOM) community. In an effort to provide UHF SATCOM users with a more consistent estimation of scintillation impacts on their systems, GPS sensors, measuring S4 at L‐band frequency, are now used as a supplement to the stationary UHF links dramatically increasing the regional coverage at each individual station, particularly those located outside the anomaly crest. Three‐dimensional representations of GPS observed plumes are mapped to the ground from the location of a selected satellite, producing a “scintillation specification map detailing “outage” regions on the globe. In this paper we present results from a validation study of the GPS proxy model and demonstrate its usefulness as an adjunct to the SCINDA model in producing the most accurate and reliable nowcast and forecast scintillation specification products available to UHF SATCOM users.

Vertical gradient freezing of doped gallium–antimonide semiconductor crystals using submerged heater growth and electromagnetic stirring

An investigation of the melt growth of uniformly doped gallium–antimonide (GaSb) semiconductor crystals as well as other III–V alloy crystals with uniform composition are underway at the US Air Force Research Laboratory at Hanscom Air Force Base by the vertical gradient freeze (VGF) method utilizing a submerged heater. Stirring can be induced in the GaSb melt just above the crystal growth interface by applying a small radial electric current in the liquid together with an axial magnetic field. The transport of any dopant and/or alloy component by the stirring can promote better melt homogeneity and allow for more rapid growth rates before the onset of constitutional supercooling. This paper presents a numerical model for the unsteady transport of a dopant during the VGF process by submerged heater growth with a steady axial magnetic field and a steady radial electric current. As the strength of the electromagnetic (EM) stirring increases, the convective dopant transport increases, the dopant transport in the melt reaches a steady state at an earlier time during growth, and the top of the crystal which has solidified after a steady state has been achieved exhibits axial dopant homogeneity. For crystal growth with stronger EM stirring, the crystal exhibits less radial segregation and the axially homogeneous section of the crystal is longer. Dopant distributions in the crystal and in the melt at several different stages during growth are presented.

In situ measurements of subsurface contaminants with a multi-channel laser-induced fluorescence system

A new multi-channel laser-induced fluorescence (LIF) probe with novel optical fiber probe geometry has been designed and integrated into a cone penetrometer testing (CPT) system for in situ contamination detection. The system is capable of collecting excitation and emission matrices (EEMs) of subsurface contaminants as a function of depth in seconds. Compared to our previous multi-channel LIF–CPT system, the new system is faster and more compact, with reduced probe size and sampling area. This article describes the first field demonstration of the system at Hanscom Air Force Base, Massachusetts. One contaminated site within the base was characterized through in situ measurements of 26 LIF–CPT pushes. To validate the LIF results, core samples taken at five locations were analyzed by both on-site LIF measurements and by off-site laboratory analyses with EPA methods. The comparison of the LIF and laboratory results is presented, along with the results of the in situ measurements.

Rapid in situ collection and analysis of semivolatile organics by thermal extraction cone penetrometry gas chromatography/mass spectrometry

A thermal extraction cone penetrometer (TECP) has been developed to detect subsurface contaminants in situ without bringing soil to the surface or into a collection chamber. Coupled with thermal desorption gas chromatography/mass spectrometry (TD-GC/MS) sample collection and analysis can be accomplished in ∼20 min for the full range of U.S. Environmental Protection Agency Target Compounds (EPA). TECP extraction efficiencies of 50 to 100% can be obtained for most EPA Method 8270 compounds. Results of 99 volatile and semivolatile organics analyzed from the same TECP extracted soil in 16 and 40 min are presented. Measurement precision and accuracy were well within the Method 8270 benchmarks required for solvent-extracted soils analyzed by GC/MS. The total ion and reconstructed ion current chromatograms are shown for chlorinated solvents and gasoline constituents extracted from a hazardous waste site located at Hanscom Air Force Base (Bedford, MA). Data compared favorably against traditional purge and trap GC/MS. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 85–92, 2000

Rapid in situ collection and analysis of semivolatile organics by thermal extraction cone penetrometry gas chromatography/mass spectrometry

A thermal extraction cone penetrometer (TECP) has been developed to detect subsurface contaminants in situ without bringing soil to the surface or into a col- lection chamber. Coupled with thermal desorption gas chromatography/mass spectrometry (TD-GC/MS) sample collection and analysis can be accomplished in 20 min for the full range of U.S. Environmental Protection Agency Target Compounds (EPA). TECP extraction effi- ciencies of 50 to 100% can be obtained for most EPA Method 8270 compounds. Results of 99 volatile and semivolatile organics analyzed from the same TECP ex- tracted soil in 16 and 40 min are presented. Measurement precision and accuracy were well within the Method 8270 benchmarks required for solvent-extracted soils ana- lyzed by GC/MS. The total ion and reconstructed ion cur- rent chromatograms are shown for chlorinated solvents and gasoline constituents extracted from a hazardous waste site located at Hanscom Air Force Base (Bedford, MA). Data compared favorably against traditional purge and trap GC/MS. 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 85-92, 2000

Dynamic workplans and field analytics: Metals assessment by inductively coupled plasma/optical emission spectroscopy

Hazardous waste site investigations were carried out at the Marine Corps Air Station (MCAS) in Yuma, Arizona and at Hanscom Air Force Base (HAFB) in Bedford, Massachusetts. The purpose of the first was to determine the location and extent of metals contamination throughout the base. The objective of the second was to evaluate the risk of metals contamination to groundwater from soil at three locations within the airfield. Dynamic workplans were developed and an adaptive sampling and analysis plan carried out with the data produced in the field used to support the goals of each project. An inductively coupled plasma/optical emission spectrometer (ICP/OES) was modified for field operation. A more efficient microwave digestion method and pressurized Teflon filtration system were developed for the HAFB project. Results were comparable to standard Environmental Protection Agency (EPA) methods, which must rely on two digestion procedures to recover EPA-targeted metals within the prescribed recovery range. The MCAS investigation, conducted over a five-month period, advanced the Navy's efforts from 30 months behind schedule to 18 months ahead of schedule, while the data generated at HAFB showed no risk to groundwater from metals.

Fast gas chromatography/mass spectrometry analysis in support of risk‐based decisions

A new data analysis software system (Ion Fingerprint DetectionTM) has been developed to provide fast mass spectral data analysis. Methods have been developed that can provide screening to quantitative gas chromatography/mass spectrometry (GC/MS) data in 30 s to minutes. Compound selectivity is provided through a unique set of algorithms rather than GC separation. The data quality produced for volatile and semivolatile organic contaminants under fast GC/MS conditions during dynamic site investigations carried out at Hanscom Air Force Base (Bedford, MA) and Joliet Army Ammunition Plant (Joliet, IL) are discussed. More than 800 samples were analyzed in each project, with state and federal regulators accepting the data to complete remedial investigation/feasibility (RI/FS) studies. ©1999 John Wiley & Sons, Inc. Field Analyt Chem Technol 3:55–66, 1999

Fast gas chromatography/mass spectrometry analysis in support of risk-based decisions

A new data analysis software system (Ion Fingerprint DetectionTM) has been developed to provide fast mass spectral data analysis. Methods have been developed that can provide screening to quantitative gas chromatography/mass spectrometry (GC/MS) data in 30 s to minutes. Compound selectivity is provided through a unique set of algorithms rather than GC separation. The data quality produced for volatile and semivolatile organic contaminants under fast GC/MS conditions during dynamic site investigations carried out at Hanscom Air Force Base (Bedford, MA) and Joliet Army Ammunition Plant (Joliet, IL) are discussed. More than 800 samples were analyzed in each project, with state and federal regulators accepting the data to complete remedial investigation/feasibility (RI/FS) studies. ©1999 John Wiley & Sons, Inc. Field Analyt Chem Technol 3:55–66, 1999

Comment on “Comparison of atmospheric correction models for thermal bands of the advanced very high resolution radiometer over FIFE” by S. N. Kalluri and R. O. Dubayah

Journal of Geophysical Research: AtmospheresVolume 103, Issue D6 p. 6237-6241 CommentariesFree Access Comment on “Comparison of atmospheric correction models for thermal bands of the advanced very high resolution radiometer over FIFE” by S. N. Kalluri and R. O. Dubayah A. J. Prata, A. J. PrataSearch for more papers by this author A. J. Prata, A. J. PrataSearch for more papers by this author First published: 01 March 1998 https://doi.org/10.1029/96JD03657Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat References Becker, F., The impact of spectral emissivity on the measurement of land surface temperature from a satellite, Int. J. Remote Sens., 8, 1509– 1522, 1987. Becker, F., Z. L. Li, Towards a local split window method over land surfaces, Int. J. Remote Sens., 3, 369– 393, 1990. Coll, C., V. Caselles, J. A. Sobrino, E. Valor, On the atmospheric dependence of the split-window equation for land surface temperature, Int. J. Remote Sens., 151, 105– 122, 1994. Goetz, S. J., R. N. Halthore, F. G. Hall, B. L. Markham, Surface temperature retrieval in a temperate grassland with multiresolution sensors, J. Geophys. Res., 100, 25397– 25410, 1995. Kalluri, S. N. V., R. O. Dubayah, Comparison of atmospheric correction models for thermal bands of the advanced very high resolution radiometer over FIFE, J. Geophys. Res., 100, 25411– 25418, 1995. Kneizys, F. X., et al., Users guide to LOWTRAN-7AFGL Tech. Rep. AFGL-TR-88-0177Opt./Infrared Technol. Div., U. S. Air Force Geophys. Lab., Hanscom Air Force Base, Mass., 1988. Marlatt, W. E., Remote and in situ temperature measurements of land and water surfaces, J. Appl. Meteorol., 6, 272– 279, 1967. McClain, E. P., W. G. Pichel, C. C. Walton, Z. Ahmad, J. Sutton, Multichannel improvements to satellite derived global sea surface temperatures, Adv. Space Res., 2, 43– 47, 1983. McMillin, L. M., D. S. Crosby, Theory and validation of the multiple window sea surface temperature technique, J. Geophys. Res., 89, 3655– 3661, 1984. Prata, A. J., Land surface temperatures derived from the AVHRR and ATSR, 1, Theory, J. Geophys. Res., 98, 16689– 16702, 1993. Prata, A. J., Land surface temperatures derived from AVHRR and ATSR, 2, Experimental results and validation of AVHRR algorithms, J. Geophys. Res., 99, 13025– 13058, 1994. Price, J. C., Land surface temperature measurements from the split window channels of the NOAA-7/AVHRR, J. Geophys. Res., 89, 7231– 7237, 1984. Sobrino, J. A., C. Coll, V. Caselles, Atmospheric correction for land surface temperature using NOAA-11 AVHRR channels 4 and 5, Remote Sens. Environ., 38, 19– 34, 1991. Ulivieri, C., M. M. Castronuovo, R. Franctoni, A. Cardillo, A split-window algorithm for estimating land surface temperature from satellites, Adv. Space. Res., 143, 59– 65, 1994. Citing Literature Volume103, IssueD627 March 1998Pages 6237-6241 ReferencesRelatedInformation

Dynamic work plans and field analytics, the keys to cost-effective hazardous waste site investigations

The rapid assessment of environmental contaminants at hazardous waste sites is of great importance when evaluating the risk to human health or the environment. Traditional site investigations take years or even decades. Rather than dictate the details of the sampling and analysis program, the dynamic work plan focuses on the decision-making structure for sampling and analysis. The framework for conducting an adaptive sampling and analysis program at Hanscom Air Force Base (Bedford, MA) is described. Dynamic site investigation results are presented in the context of the field analytical tools employed, site decisions made, and cost. The data were used to support a soil-to-groundwater risk assessment and to optimize the groundwater/treatment facility operations. © 1998 John Wiley & Sons, Inc. Field Analyt Chem Technol 2:253–265, 1998

Field Evaluation of an Electrochemical Probe for in Situ Screening of Heavy Metals in Groundwater

The use of an electrochemically based probe for in situ determination of heavy metals in groundwater is described. The in situ probe, consisting of a microlithographically fabricated iridium ultramicroelectrode array sensor (UMEA), a custom-built miniaturized potentiostat and microcontroller, is connected to a laptop computer for control and data acquisition. The utility of this probe for rapid on-site screening of heavy metals was shown by conducting a proof-of-concept field demonstration at a metals contaminated landfill site located at Hanscom Air Force Base in Bedford, MA. Using the electroanalytical technique of square wave anodic stripping voltammetry (SWASV), the sensor was used to measure both the labile and total pH <2 forms of copper, lead, cadmium, and zinc at the parts-per-billion level. The on-site and in situ measurements were compared to laboratory-based electroanalytical measurements and to contract laboratory U.S. EPA Method 200.7 ICP analysis. The results indicate that in situ electroana...

Ionospheric radio tomography using maximum entropy: 2. Results of the Russian‐American Tomography Experiment, including the large magnetic storm of November 3–4, 1993

Near the end of the Russian‐American Tomography Experiment, November 3 and 4, 1993, the index of magnetic activity (Kp) climbed rapidly from 0 to 7—in a little under 1 day. The quasi‐logarithmic Kp index ranges from a low of 0 for very calm conditions to 9 for the most intense magnetic storms. During the course of this magnetic storm the ionospheric response was studied using data collected and analyzed in 28 passes. The results of this intensive study, using contour charts of electron density as well as the three important parameters of the average Chapman profile, the maximum density, the altitude of maximum, and the scale height, are presented. We had dual‐frequency receivers set up at four locations on the eastern edge of North America: Block Island, Rhode Island; Hanscom Air Force Base, Massachusetts; Jay, Vermont; and Roberval, Quebec, Canada. Using the dual‐frequency (150 and 400 MHz) beacon on the Navy Navigation Satellite System, with a nominal altitude of 1100 km, a tomography pass would typically last about 20 min from horizon to horizon. From a total of 88 passes, 86 passes possessed sufficiently accurate data and have been analyzed using the maximum entropy method, which determines the average vertical profile in the form of an analytical Chapman profile, as well as a set of electron density contours. The Russian tomography experiment, which utilized the same four locations, as well as the incoherent scatter radar results obtained by the Haystack Observatory group, will be discussed at a later date.

Field demonstration of a multichannel fiber-optic laser-induced fluorescence system in a cone penetrometer vehicle

A laser-induced fluorescence system for in situ detection of soil contamination with cone penetrometer technology, capable of collecting three-dimensional fluorescence fingerprints (excitation–emission matrices, or EEMs) as the probe is advanced vertically, has been developed. In this report, we describe a recent field test at Hanscom Air Force Base, Massachusetts, in which we demonstrated successful operation of the system. The system uses a pair of silica-clad-silica optical fibers for each of its channels (eight of which were used in the work described), one to deliver excitation light from the multiwavelength laser excitation source to the sample, and the other to conduct contaminant fluorescence to a grating spectrograph that utilizes a charge-coupled-device detector to record fluorescence intensity as a function of both excitation and emission wavelength. The matrix-formatted field data are displayed as three-dimensional fingerprints of contamination at given push locations and depths; they are also reduced in dimension by summing over one or both wavelength axes and plotting summed fluorescence versus depth to facilitate visualization of the approximate extent of the contaminant plume. Selected EEMs from each push location are examined for characteristic patterns and compared to standard EEMs of pure compounds and fuels. © 1997 John Wiley & Sons, Inc. Field Analyt Chem Technol 1: 343–355, 1997