Patrick J. McNicholl

Polarimetric wavelet phenomenology of space materials

This paper describes new polarimetric wavelet detection principles applied to the backscattering characteristics of space materials in the near infrared. Efficient polarimetric detection techniques are combined with cross-correlation and wavelet analysis for enhanced characterization of space materials. The outcome of this study will support remote characterization of space materials and structures with enhanced discrimination, localization, and high-dynamic range while maintaining uncompromised sensitivity.

Infrared photon discrimination of lung cancer cells

The objective of this study is to explore the polarimetric phenomenology of near infrared light interaction with healthy and lung cancer monolayer cells by using efficient polarimetric transmission detection techniques. Preliminary results indicate that enhanced discrimination between normal and different types of lung cancer cell stages can be achieved based on their transmitted intensities and depolarization properties of the cells. Specifically, the sizes of the nuclei of the cancer cells and the nucleus-to-cytoplasmic ratios appear to have potential impact on the detected polarimetric signatures leading to enhanced discrimination of lung cancer cells.

Polarimetric wavelet fractal remote sensing principles for space materials

A new remote sensing approach based on polarimetric wavelet fractal detection principles is introduced and the Mueller matrix formalism is defined, aimed at enhancing the detection, identification, characterization, and discrimination of unresolved space objects at different aspect angles. The design principles of a multifunctional liquid crystal monostatic polarimetric ladar are introduced and related to operating conditions and system performance metrics. Backscattered polarimetric signal contributions from different space materials were detected using a laboratory ladar testbed, and then analyzed using techniques based on wavelets and fractals. The depolarization, diattenuation, and retardance of the materials were estimated using Mueller matrix decomposition for different aspect angles. The outcome of this study indicates that polarimetric fractal wavelet principles may enhance the capabilities of the ladar to provide characterization and discrimination of unresolved space objects.

An automated ladar polarimetric system for remote characterization of space materials

The calibration, testing, and operational principles of an efficient multifunctional monostatic polarimetric ladar are introduced and related to the system performance metrics. The depolarization, diattenuation, and retardance of the materials were estimated using Mueller matrix (MM) decomposition for different aspect angles. The outcome of this study indicates that polarimetric principles may enhance the capabilities of the ladar to provide adequate characterization and discrimination of unresolved space objects.

Improved correlation determination for intensity interferometers

To image astronomical objects, the Hanbury Brown Twiss (HBT) technique involves measuring intensity correlation for an array of telescopes. The correlation of the intensity fluctuations is a measure of the magnitude of the coherence and can be used to retrieve the intensity distribution of the source using the Van Cittert-Zernike theorem. For low spectral irradiance sources, coincidence counting using modern techniques can drastically reduce data storage/processing requirements as well as allowing for optimization of the effective SNR bandwidth. In counting Intensity Interferometry (II), count fluctuations are measured instead of intensity fluctuations as with an analog II. Those are the two II techniques currently reported in the literature. Since the successful width measurements of bright stars by HBT in the 70s, advances in detectors promise opportunities to apply II to dimmer non-point source objects. To improve SNRs, we propose a new data processing technique for measuring correlation in the low light regime that ensures maximum bandwidth allowed by the reproducibility of photon pulses.

Comparison of CO2 Doppler lidar and GPS rawinsonde wind velocity measurements

A comparison of CO2 Doppler lidar and GPS rawinsonde measurements of horizontal wind velocity was conducted during May 2000 at Hanscom AFB, Massachusetts. Seven days of side-by-side measurements using both lidar and GPS sondes were achieved comparing wind velocity as a function of altitude up to 6 km. The horizontal wind velocity was determined by the CO2 Doppler lidar using the Velocity Azimuth Display (VAD) method. Horizontal winds were also determined simultaneously using a differential GPS-tracked rawinsonde which provides GPS position coordinates once per second. Both lidar VAD wind speed Root Mean Squared Difference (RMS) and lidar vs. GPS sonde RMS were calculated and compared as a function of altitude, time, and stability regime. On average, significant increases in both the lidar VAD RMS and lidar vs. GPS RMS were observed during unstable conditions compared to stable conditions. Analyses of lidar VAD RMS show the smallest typical values average near 0.5 m/s over a single profile.

Statistical bounds and maximum likelihood performance for shot noise limited knife-edge modeled stellar occultation

Applications of stellar occultation by solar system objects have a long history for determining universal time, detecting binary stars, and providing estimates of sizes of asteroids and minor planets. More recently, extension of this last application has been proposed as a technique to provide information (if not complete shadow images) of geosynchronous satellites. Diffraction has long been recognized as a source of distortion for such occultation measurements, and models subsequently developed to compensate for this degradation. Typically these models employ a knife-edge assumption for the obscuring body. In this preliminary study, we report on the fundamental limitations of knife-edge position estimates due to shot noise in an otherwise idealized measurement. In particular, we address the statistical bounds, both Cramér- Rao and Hammersley-Chapman-Robbins, on the uncertainty in the knife-edge position measurement, as well as the performance of the maximum-likelihood estimator. Results are presented as a function of both stellar magnitude and sensor passband; the limiting case of infinite resolving power is also explored.

A Characterization of Cirrus Cloud Properties That Affect Laser Propagation

Abstract Future high-altitude laser systems may be affected by cirrus clouds. Laser transmission models were applied to measured and retrieved cirrus properties to determine cirrus impact on power incident on a target or receiver. A major goal was to see how well radiosondes and geostationary satellite imagery could specify the required properties. Based on the use of ground-based radar and lidar measurements as a reference, errors in cirrus-top and cirrus-base height estimates from radiosonde observations were 20%–25% of geostationary satellite retrieval errors. Radiosondes had a perfect cirrus detection rate as compared with 80% for satellite detection. Ice water path and effective particle size were obtained with a published radar–lidar retrieval algorithm and a documented satellite algorithm. Radar–lidar particle size and ice water path were 1.5 and 3 times the satellite retrievals, respectively. Radar–lidar-based laser extinction coefficients were 55% greater than satellite values. Measured radar–lid...

CO2 doppler lidar measurement of wind velocity and relative backscatter associated with the nocturnal boundary layer

Heterodyne CO2 Doppler lidar measurements of horizontal wind velocity from the surface to 11,000 feet AGL using the Velocity Azimuth Display (VAD) method were made at Holloman AFB, NM from the end of July through mid-August 1998. These data were entered real-time into the space maneuver vehicle descent analysis program to make flight performance predictions needed for test decisions. Daily measurements encompassed the early morning time period associated with the stably-stratified nocturnal boundary layer (NBL). Measurement periods were characterized by growth the decay of wind maxima or jets at different altitudes. Strong vertical shears were often observed in conjunction with these wind maxima. Relative backscatter profiles at the lowest altitudes exhibited periodic oscillations on most mornings. Relative backscatter profiles at the lowest altitudes exhibited periodic oscillations on most mornings. The observed NBL wind profiles were poorly represented by the Ekman model.

Heterodyne CO2 DIAL and its measurements

The Geophysics Directorate of Phillips Laboratory has recently completed redesign of a heterodyne CO2 differential absorption lidar which can simultaneously measure range resolved radial velocity, aerosol backscatter, and differential absorption. The transportable system utilizes two CO2 transversely excited atmospheric (TEA) lasers which can be discretely tuned to many of the rotational lines compromising the 00 degree 1 to 10 degrees 0 vibrational bands of CO2. These lines span a spectral region from about 9.2 to 10.8 micrometers and allow for the DIAL measurement of some minor atmospheric molecular constituents as well as many anthropogenic organic species which have absorption bands in this spectral region. Transmission and reception is coaxial via a single shared 12 inch telescope and hemispherical scanner. Complete spectral processing of the heterodyne signals provides not only backscatter and differential absorption information but also radial wind velocity. Each TEA laser produces a line dependent pulse energy of 20-80 mJ at up to 150 Hz. Presently, the system is processor limited to a net pulse rate of 140 Hz. Results shown will include time-height cross-sections of cirrus backscatter, comparisons of CO2 DIAL-derived water vapor profiles with simultaneous surface and radiosonde in-situ measurements, and wind velocity profiles in the troposphere.