This paper describes work in modeling the performance of multiwavelength bioaerosol sensors. In particular, results are presented on modeling the performance of the Biological Agent Sensor Testbed (BAST), which employs LED UV sources at 280 and 340 nm. A previously developed catalog of Excitation/Emission Matrix (EEM) data for bioagents and interferents is used to determine fluorescence scattering for a specified particle mixture. These particle mixtures were applied to the model in order to assess discrimination performance. An initial comparison of simulated and measured BAST data is presented. This work was sponsored by DARPA under the Semiconductor Ultraviolet Optical Sources (SUVOS) program.
This paper reports on an investigation into optimal excitation and emission wavelengths for bioaerosol detection. Excitation/Emission Matrix (EEM) fluorescence data were gathered for a variety of materials, including biowarfare (BW) simulants, cell constituents, growth media and known interferents. These data were used to investigate multi-wavelength discrimination algorithms using pattern classification techniques. The results suggest that using two excitation wavelengths and narrower emission bands can improve discrimination between BW agents and interferents.
Models of optically-based biological aerosol sensors may help to predict baseline performance and support efficient sensor optimization. Reducing a sensor’s false positive rate while maintaining sensitivity is an important performance goal that must be optimized. To that end, the capacity to theoretically test environmental backgrounds, in an accelerated fashion, would be valuable. Sensor false positives are presumed to occur as a result of complicated transient fluctuations in the environmental aerosol background. Simulating a sensor’s response to such naturally occurring transients, with an appropriate model, is a mechanism for accelerating sensor characterization. These models complement and reduce the need for experimentally challenging interferant tests. Additionally, validated models include the ability to characterize sensor responses to harmful agents or rare materials while simultaneously adjusting many transient parameters. We describe a model of the Lincoln Laboratory Biological Agent Warning Sensor (BAWS), highlighting our general approach to sensor model architecture. The resulting model was utilized to simulate the sensor’s response to a variety of individual background constituents as well as to time varying backgrounds with multiple constituents. The result of the simulation predicts the sensor’s false positive rate to a simulated indoor and outdoor aerosol background, which can be compared to experimental data. Model applications and improvements will be discussed.
Detect-to-warn defense strategies against airborne contamination are based on providing warning to personnel to take temporary protective actions. The effectiveness of such detect-to-warn active strategies is measured by the reduction in contaminant exposure compared to passive exposure. Effectiveness depends on several factors, including the contaminant release and transport properties, the warning sensor performance and the protective actions taken. In this paper we analyze effectiveness for several specific scenarios where certain reasonable protective actions are assumed and sensor performance is varied. One type of scenario analyzed is the protection of outdoor personnel against an upwind instantaneous point release. Meteorological conditions such as wind speed, turbulence level and heat flux, which result in high exposure levels are assumed. Personnel are warned to temporarily use filter masks based on a warning signal from a sensor placed between them and the release point. Another type of scenario is the protection of personnel inside of a building using active ventilation control. The building air handling properties, such as air exchange and recirculation, degree of leakage and filtration and zone volume, are representative of modern office buildings. Different sensor locations and ventilation control strategies are chosen to defend against outside and inside instantaneous point releases. In each scenario, we evaluate the dependence of effectiveness on sensor sensitivity threshold and response time. In addition, we describe desired values of other sensor attributes, such as false positive sensing rate, size, power consumption, maintenance frequency and procurement cost, to support realistic deployment and operations.
A new high spectral resolution (0.25 cm-1) and high spatial resolution (2.6 km) scanning (46 km swath width) Fourier Transform Spectrometer (FTS) has been built for flight on NASA high altitude (approximately 20 km) aircraft. The instrument, called the NPOESS Aircraft Sounding Testbed- Interferometer (NAST-I), has been flown during several field campaigns to provide experimental observations needed to finalize specifications and to test proposed designs for future satellite instruments; specifically, the Cross-track Infrared Sounder (CrIS) to fly on the National Polar-orbiting Operational Environmental Satellite System (NPOESS). NAST-I provides new and exciting observations of mesoscale structure of the atmosphere, including the fine scale thermodynamic characteristics of hurricanes. The NAST-I instrument is described, its excellent spectral and radiometric performance is demonstrated, and surface and atmospheric remote sensing results obtained during airborne measurement campaigns are presented.
An airborne fourier transform interferometric sounder is being developed to perform atmospheric measurements for the National Polar-orbiting Operational Environmental Satellite System. The interferometer is designed to provide high spectral resolution, low noise data from the NASA ER-2 aircraft suitable for synthesizing and comparing data of potential future satellite-borne sounding instruments, such as AIRS, IMAS, ITS or IASI. The collection and scanning optics provide a 7.5 degree field of view over a cross-track field of regard of +/- 48.2 degrees. The interferometer operates with +/- 2.0 cm optical path difference (OPD) over the spectral range from 3.6-16.1 micrometers . Dynamic alignment is performed using a concentric HeNe laser. Three separate filter/lens/detector assemblies are cooled to 65K using integral rotary stirling coolers. Most of the optical instrumentation is contained within a pressurized N2 enclosure to minimize the effects of descent condensation. The instrument processor/controller is based on a 133 MHz Pentium CPU supporting a dedicated digital signal processor for real-time x16 data decimation. Noise performance referred to a 250 K scene is estimated to be 0.10 K at 14.9 micrometers , 0.15 K at 8.7 micrometers and 0.2 K at 4.7 micrometers .
KEYWORDS: Sensors, Signal processing, Image compression, Imaging systems, Relays, Chromium, Coating, Data compression, Signal to noise ratio, Data communications
An engineering design of an imager upgrade is under consideration for the GOES-N/Q series. The upgrade consist of adding up to three new IR channels at 4 km resolution and doubling the earth coverage rate. The design approach introduces advanced technology as needed to minimize impacts to the sensor optical and mechanical configuration, electronics box layout, data communication links and ground systems. By operating presently redundant portions of detector arrays and developing double rate signal processors, the scanning servo system and electronics modules are largely retained. Bicolor detectors and optical coatings are used to add channels while retaining the present relay optics and radiant cooler layouts. Lossy data compression of visible imagery and lossless data compression of IR imagery are used to preserve the sensor data and precessed data relay communications links. System NEDT and SNR performance and implementation issues for new technologies are addressed.
The present ad hoc method for determining the physical properties of particulate exhaust plumes inverts multiband irradiance data collected over fields-of-view that are highly oblique to the plume axis; it is therefore applicable to the onboard measurement of in-flight aerodynamic effects on plume properties. A simple analytical model that predicts irradiance under these assumptions is presented, together with measurements of Mg/PTFE plumes in vacuum. The first step of the inversion process generates the locus of possible temperatures and velocities consistent with a given irradiance measurement; the second step uses two independent irradiance measurements to ascertain a unique temperature and velocity solution.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.