The Magnetic Electron Ion Spectrometer (MagEIS) Instruments Aboard the Radiation Belt Storm Probes (RBSP) Spacecraft

This paper describes the Magnetic Electron Ion Spectrometer (MagEIS) instruments aboard the RBSP spacecraft from an instrumentation and engineering point of view. There are four magnetic spectrometers aboard each of the two spacecraft, one low-energy unit (20–240 keV), two medium-energy units (80–1200 keV), and a high-energy unit (800–4800 keV). The high unit also contains a proton telescope (55 keV–20 MeV). The magnetic spectrometers focus electrons within a selected energy pass band upon a focal plane of several silicon detectors where pulse-height analysis is used to determine if the energy of the incident electron is appropriate for the electron momentum selected by the magnet. Thus each event is a two-parameter analysis, an approach leading to a greatly reduced background. The physics of these instruments are described in detail followed by the engineering implementation. The data outputs are described, and examples of the calibration results and early flight data presented

Validating an integer non-linear program optimization model of a wireless sensor network using agent-based simulation

Deploying wireless sensor networks (WSN) along a barrier line to provide surveillance against illegal intruders is a fundamental sensor-allocation problem. To maximize the detection probability of intruders with a limited number of sensors, we propose an integer non-linear program optimization model which considers multiple types of sensors and targets, probabilistic detection functions and sensor-reliability issues. An agent-based simulation (ABS) model is used to validate the analytic results and evaluate the performance of the WSN under more realistic conditions, such as intruders moving along random paths. Our experiment shows that the results from the optimization model are consistent with the results from the ABS model. This increases our confidence in the ABS model and allows us to conduct a further experiment using moving intruders, which is more realistic, but it is challenging to find an analytic solution. This experiment shows the complementary benefits of using optimization and ABS models

Co-Registration of Optically Sensed Images and Correlation (COSI-Corr): an Operational Methodology for Ground Deformation Measurements

Recent methodological progress, Co-Registration of Optically Sensed Images and Correlation, outlined here, makes it possible to measure horizontal ground deformation from optical images on an operational basis, using the COSI-Corr software package. In particular, its sub-pixel capabilities allow for accurate mapping of surface ruptures and measurement of co-seismic offsets. We retrieved the fault rupture of the 2005 Mw 7.6 Kashmir earthquake from ASTER images, and we also present a dense mapping of the 1992 Mw 7.3 Landers earthquake of California, from the mosaicking of 30 pairs of aerial images

Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice

The CryoSat-2 radar altimeter and ICESat-2 laser altimeter can provide complimentary measurements of the freeboard and thickness of Arctic sea ice. However, both sensors face significant challenges for accurately measuring the ice freeboard when the sea ice is melting in summer months. Here, we used crossover points between CryoSat-2 and ICESat-2 to compare elevation retrievals over summer sea ice between 2018&ndash;2021. We focused on the electromagnetic (EM) bias documented in CryoSat-2 measurements, associated with surface melt ponds over summer sea ice which cause the radar altimeter to underestimate elevation. The laser altimeter of ICESat-2 is not susceptible to this bias, but has other biases associated with melt ponds. So, we compared the elevation difference and reflectance statistics between the two satellites. We found that CryoSat-2 underestimated elevation compared to ICESat-2 by a median difference of 2.4 cm and by a median absolute deviation of 5.3 cm, while the differences between individual ICESat-2 beams and CryoSat-2 ranged between 1&ndash;3.5 cm. Spatial and temporal patterns of the bias were compared to surface roughness information derived from the ICESat-2 elevation data, the ICESat-2 photon rate (surface reflectivity), the CryoSat-2 backscatter and melt pond fraction derived from Seintnel-3 OLCI data. We found good agreement between theoretical predictions of the CryoSat-2 EM melt pond bias and our new observations; however, at typical roughness &lt;0.1 m the experimentally measured bias was larger (5&ndash;10 cm) compared to biases resulting from the theoretical simulations (0&ndash;5 cm). This intercomparison will be valuable for interpreting and improving the summer sea ice freeboard retrievals from both altimeters.</p

Finding and Mending Barrier Gaps in Wireless Sensor Networks

Constructing sensing barriers using wireless sensor networks has important applications in military operations and homeland security. The goal of forming a sensing barrier is to detect intruders attempting to cross the network. Early studies often assume that sensors remain static once deployed. We note that barrier gaps may occur at deployment if sensors are deployed at random. Barrier gaps may also occur in an existing barrier if some sensors used to form the barrier start malfunctioning or run out of power. We present an efficient solution to solve this problem. In particular, we devise an efficient algorithm to find sensing gaps and relocate mobile sensors to form a new barrier while balancing the energy consumption among mobile sensors. We also investigate the related design issues and performance tradeoffs. Simulation results show that our algorithms can effectively improve the barrier coverage of a wireless sensor network under a wide range of deployment parameters. These results provide insights and guidelines to the deployment, design, and performance of mobile wireless sensor networks for barrier coverage

Providing the Third Dimension: High-resolution Multibeam Sonar as a Tool for Archaeological Investigations - An Example from the D-day Beaches of Normandy

In general, marine archaeological investigations begin in the archives, using historic maps, coast surveys, and other materials, to define submerged areas suspected to contain potentially significant historical sites. Following this research phase, a typical archaeological survey uses sidescan sonar and marine magnetometers as initial search tools. Targets are then examined through direct observation by divers, video, or photographs. Magnetometers can demonstrate the presence, absence, and relative susceptibility of ferrous objects but provide little indication of the nature of the target. Sidescan sonar can present a clear image of the overall nature of a target and its surrounding environment, but the sidescan image is often distorted and contains little information about the true 3-D shape of the object. Optical techniques allow precise identification of objects but suffer from very limited range, even in the best of situations. Modern high-resolution multibeam sonar offers an opportunity to cover a relatively large area from a safe distance above the target, while resolving the true three-dimensional (3-D) shape of the object with centimeter-level resolution. A clear demonstration of the applicability of highresolution multibeam sonar to wreck and artifact investigations occurred this summer when the Naval Historical Center (NHC), the Center for Coastal and Ocean Mapping (CCOM) at the University of New Hampshire, and Reson Inc., collaborated to explore the state of preservation and impact on the surrounding environment of a series of wrecks located off the coast of Normandy, France, adjacent to the American landing sectors The survey augmented previously collected magnetometer and high-resolution sidescan sonar data using a Reson 8125 high-resolution focused multibeam sonar with 240, 0.5° (at nadir) beams distributed over a 120° swath. The team investigated 21 areas in water depths ranging from about three -to 30 meters (m); some areas contained individual targets such as landing craft, barges, a destroyer, troop carrier, etc., while others contained multiple smaller targets such as tanks and trucks. Of particular interest were the well-preserved caissons and blockships of the artificial Mulberry Harbor deployed off Omaha Beach. The near-field beam-forming capability of the Reson 8125 combined with 3-D visualization techniques provided an unprecedented level of detail including the ability to recognize individual components of the wrecks (ramps, gun turrets, hatches, etc.), the state of preservation of the wrecks, and the impact of the wrecks on the surrounding seafloor

Enhanced sensing performance of MISiC schottky-diode hydrogen sensor by using HfON as gate insulator

MISiC Schottky-diode hydrogen sensor with HfON gate insulator fabricated by NO nitridation is investigated. The hydrogen-sensing characteristics of this novel sensor are studied by doing steady-state and transient measurements at different temperatures and hydrogen concentrations using a computer-controlled measurement system. Experimental results show that this novel sensor can rapidly respond to hydrogen variation and can give a significant response even at a low H 2 concentration of 48-ppm, e.g., a sensitivity of 81% is achieved at 450°C and 2.5 V, which is two times higher than its HfO 2 counterpart. The enhanced sensitivity of the device should be attributed to a remarkable reduction of the current of the sensor before hydrogen exposure by the NO nitridation because the NO nitridation can passivate the O vacancies in the insulator and facilitate the formation of a SiO 2 interlayer to suppress the leakage current associated with high-k materials. © 2006 IEEE.published_or_final_versio