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Although direct measurements of the projected areas of various Geosynchronous Earth Orbit (GEO) satellite facets are impossible without high-resolution imaging, estimates of the albedo-Area (aA) product lead to the possibility of inferring the geometric size of an RSO based on the illuminated area. Such size estimates are an integral part of its identity because satellite mission capabilities can be inferred. We are engaged in parallel development of two methods for calculating aA for the body/communication antennas structures and one method for the solar panels. We have previously reported on the Two Facet Model (2FM) method for body aA, and here we discuss a method based on differences between new observations and a baseline catalog that has been constructed from the GEO Observations with Longitudinal Diversity Simultaneously (GOLDS) data. We report on evaluations of the 2FM and Differential Method (DM) algorithm results. We also discuss a new method of estimating solar panel aA by fitting new data that include specular glints. All of these measurement methods are compared to models and simulations that serve as a proxy for ground truth. Because of the partially directional nature of the composite Bi-directional Reflectivity Distribution Function (BRDF) of all bus-mounted appendages, variance of body aA results is expected to be significant. Short-term and long-term variance of the derived aAs will also be discussed.

We propose a remote-sensing technique to measure temperature in the lower thermosphere with a resonant Raman lidar. A ground-based pulsed laser operating at 630.0304 (636.3776) nm excites 3P2 (3P1) multiplet level of the ground electronic state of atomic oxygen in the atmosphere to the electronically excited 1D2 state and the back-scattered photons at 636.3776 (630.0304) nm, while the atom transitions to 3P1 (3P2), are detected. Using the backscattering Raman cross sections calculated here we show: (1) For the range of altitudes in the lower thermosphere where the fine-structure multiplets of atomic oxygen are in thermodynamic equilibrium with the local translational temperature (LTE) and the electronically excited intermediate state 1D2 remains relaxed primarily by collisions with N2 and O2, the ratio of the backscattered signal can be used to obtain temperature. (2) Higher up, for the range of altitudes where the fine-structure multiplets of atomic oxygen are in LTE and the electronically excited intermediate state 1D2 is relaxed primarily by spontaneous emission of a photon, the Stokes and anti-Stokes backscattered signal can be used to obtain the atomic oxygen density and local temperature. (3) Still higher up, for the range of altitudes where the fine-structure multiplets of atomic oxygen are not in LTE and the electronically excited intermediate state 1D2 is relaxed primarily by spontaneous emission of a photon, the Stokes and anti-Stokes backscattered signal can be used to obtain the density of the 3P2 and 3P1 multiplet levels of the ground electronic state of atomic oxygen. For a ground-based instrument a simulation with 3 km range gate is used to show that the relative error of temperature measurements from 100 to 250 km could be less than 30%. It is pointed out that this technique has the potential of providing unique data that addresses the modeling of satellite drag and the effects of space weather on the upper atmosphere. In addition, this technique may also permit the detection of the thickness of the temperature inversion layers as well as their temperature and density perturbations.

The Raman backscatter cross sections for a 355 nm light source for the three fine-structure components are calculated. The signal-to-noise considerations show that the determination of the densities of the three fine-structure components separately is a feasible experiment. Since these fine-structure components are calculated to be in local thermodynamic equilibrium up to at least 350 km altitude, this experiment also gives atmospheric temperature. It is pointed out that this experiment does not suffer from the drawbacks of the previous efforts to determine atomic oxygen density and should yield reliable results for this density as well as temperature.

We have designed and constructed a photoacoustic (PA) cell to be used for wavelength calibration in a water vapor differential absorption lidar (DIAL) system. This system will be used to remotely determine atmospheric H2O16 concentrations. The accuracy of these measurements depends critically on the ability to tune to and detune from lines in the water vapor spectrum. Specifically, the signal-to-noise ratio of the PA signal must be strong enough to locate the center frequency of an absorption line with accuracy and repeatability better than 0.2 times the Lorentzian half width of the absorption (0.1 cm−1). So, although it represents only a peripheral part of the DIAL experiment, the calibration provided by the PA cell is critical to its overall success. In the environment of a mobile lidar system, problems with mechanical and electronic noise are potentially greater than those in a typical laboratory setting, and the cell is designed to address this situation. The PA cell utilizes a “figure-8” beam tunnel ...

Our Mobile Lidar Trailer (MLT) has been deployed to Cape Canaveral Air Station for the purpose of studying the characteristics of launch vehicle plumes in the stratosphere. In addition to measurements of plume extent and dispersion rates, information on particle species and size can be obtained from the wavelength dependence of the Mie return signal. We measure the backscattering ratio of Mie to Rayleigh return at several wavelengths and compare the results to a model of Mie scattering cross sections for homogeneous spheres of specific refraction index and radius. Of primary interest are the calculations for particles which are present in the exhaust of solid rocket motors (SRM) and are conjectured to be instrumental in the catalysis of halogenic destruction of stratospheric ozone. Our data indicate that these particles, at least within the first half-hour after launch, are small (r < 50 nm as an upper limit). The data also shows a trend of the mean particle radius increasing with time.

Simultaneous observations of the middle atmosphere and lower thermosphere by Na Wind/Temperature (W/T) and Rayleigh/Raman lidar and other ground-based measurements were conducted the night of October 21, during the ALOHA-93 campaign. Rayleigh/Raman lidar measurements provide density from 25 to 90 km and temperature from 25 to 85 km. From the same location, Na W/T lidar measurements were also obtained between ∼83 and 103 km. The combined data provides continuous temperature from 25 to 103 km. Strong perturbations which may be associated with the diurnal tide are observed in the temperature and wind profiles.

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.

Summarization: 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. Παρουσιάστηκε στο: International Conference on Imaging Systems and Techniques (IST), IEEE

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.

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 70's, 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.

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.

The orbital debris environment is of increasing concern to users of space. Models describing this environment depend on accurate and precise measurements of debris for all sizes and altitudes. This paper presents the assessment of an environment model, developed by NASA, and the uncertainties of that model. The uncertainties are shown to be dominated by the lack of knowledge of the debris environment. A Phillips Laboratory (Geophysics Directorate) measurement program is described that will enhance man's understanding of the debris environment. It uses the 2.54 m telescope located at Wright Laboratory (Wright-Patterson AFB, Ohio).

The purpose of this study is to explore novel monostatic ladar detection principles utilizing polarimetric Bidirectional Reflectance Distribution Function (BRDF) and single-pixel detection parameters. The depolarization of backscattered elliptical polarized light beams, from extended area space materials, was studied at different sample orientations. Specifically, the depolarization ratio for both linearly and circularly polarized light waves was estimated under quasimonostatic transceiver geometry. The experimental results indicate that space object materials exhibit distinct depolarization signatures, which provide enhanced discrimination capabilities. The outcome of this study would enhance the monostatic-ladar detection and discrimination capabilities.

This study consists of the exploitation of novel ladar design principles and architectures aimed at the increasing of the superresolution, and imaging capabilities of the space surveillance ladars for efficient detection, discrimination, and monitoring of space objects and man-made materials detection. Ladar interferometric techniques relying on Vertical- Cavity Surface-Emitting Laser (VCSEL) coherent arrays would provide enhanced lightweight imaging solutions, with unsurpassable dynamic range, at low power consumption, remarkable reliability, and reduced cost. The experimental results of this study indicate that the signal-to-noise ratio of backscattered optical signals can be enhanced significantly, by utilizing efficient single-pixel polarimetric techniques; as a result the ladar range accuracy would be improved significantly. In addition, several space materials and man-made materials are shown to exhibit distinct depolarization signatures which can be used to characterize, classify, and identify those materials.

A trailer-based lidar, named Humidity and Aerosol Lidar (HAL), is being built as a remote sensing tool to characterize atmospheric aerosol and water vapor in the line-of-sight. Water vapor and aerosol in the lower atmosphere are critical components affecting the propagation of high-energy laser beams and microwave. The sensor is developed to collect high temporal and vertical resolution data of atmospheric aerosols and water vapor. This ground-based system also serves as a demonstration and an engineering study of a flight-capable sensor for real-time diagnostic of the atmosphere. The lidar, operating on the principles of differential absorption, could measure water vapor to 10 km altitudes. It also measures aerosols and cloud backscatter at altitudes up to 18 km and ranges up to 90 km. Operating with a hemispherical scanner, the sensor could map the 3-dimensional field of aerosols and water vapor and provide vertical as well as horizontal structures. A unidirectional Alexandrite ring laser, operating in single mode near 727.49 nm, is the laser source. The sensor is designed to operate in day and night time. A description of the system, its wavelength calibration unit, the transmitter-receiver system and projected performance will be discussed. Results of the photo-acoustic calibration cell and wavelength selections will be presented. Preliminary results of water vapor and aerosols will be discussed.

Range-resolved co-pointing multiple wavelength lidar backscatter from aerosols is analyzed for a summer day in the northeast United States. Lidar backscatter wavelengths are 355 nm, 532 nm, and 1064 nm and were measured at a vertical range gate of 60 meters. The altitude range of lidar measurement is from the surface to 4 km above ground level and the measurement period spanned five hours from late afternoon through several hours after sunset. Vertical profiles of temperature, relative humidity, and wind velocity, and surface visibility, were also measured to characterize the prevailing air mass. Lidar aerosol backscatter was significant through 3 km and diminished rapidly above. Several aerosol models selected on an a priori basis are used to compute backscatter ratios for wavelength pairs using scattering theory. These are compared with the profiles of measured backscatter ratios in an attempt to infer the type of aerosol present in the lower atmosphere and estimate multiple wavelength extinction. Measured backscatter ratios agreed with the ratios for soot, water-soluble, and haze aerosol models at the lowest altitudes with little agreement above 1 km for any model. Extinction estimates derived from lidar backscatter at 300 m were significantly higher than the corresponding values deduced from surface observations.

The Mobile Lidar Trailer (MLT) was developed and operated to characterize launch vehicle exhaust plume and its effects on the environment. Two recent applications of this facility are discussed in this paper. In the first application, the MLT was used to characterize plumes in the stratosphere up to 45 km in support of the Air Force Space and Missile Center's Rocket Impact on Stratospheric Ozone program. Solid rocket motors used by Titan IV and other heavy launch vehicles release large quantities of gaseous hydrochloric acid in the exhaust and cause concerns about a possible depletion of the ozone layer. The MLT was deployed to Cape Canaveral Air Station since October 1995 to monitor ozone and to investigate plume dynamics and properties. Six campaigns have been conducted and more are planned to provide unique data with the objective of addressing the environmental issues. The plume was observed to disperse rapidly into horizontally extended yet surprisingly thin layer with thickness recorded in over 700 lidar profiles to be less than 250 meters. MLT operates with the laser wavelengths of 532, 355 and 308 nm and a scanning receiving telescope. Data on particle backscattering at the three wavelengths suggest a consistent growth of particle size in the 2-3 hour observation sessions following the launch. In the second type of application, the MLT was used as a remote sensor of nitrogen dioxide, a caustic gaseous by-product of common liquid propellant oxidizer. Two campaigns were conducted at the Sol Se Mete Canyon test site in New Mexico in December 1996 an January 1997 to study the dispersion of nitrogen dioxide and rocket plume.

We review and summarize the measurements and analysis of the atmospheric density data obtained by Rayleigh lidar soundings at Wright Patterson AFB in five campaign periods covering the four seasons of 1989/1990 from summer to spring. The Rayleigh lidar system combined a 14 watts XeF laser with a 2.54 m mirror telescope receiver. A total of 18 nights is included in these measurements with each night series of measurements lasting typically 3 to 5 hours. The altitude coverage for these results extends from 40 to 90 km, and the precision of these results within the middle atmosphere is extraordinarily high. It was of the order of 0.1 % for density and 0.3 K for temperature for data averaged over 30 minutes at 50 to 60 km. The density precision for this data at 90 km for 3 km resolution and 15 minutes averaging was about 5% to 8% depending upon the quality of the seeing at the time of the observations. The large collecting area of the telescope receiver combined with the powerful laser transmitter produces a lidar system of greatly enhanced sensitivity when compared with most other systems in use today.

A combined Raman-Rayleigh Lidar (Light Detection And Ranging) has recently been implemented at the Air Force Geophysics Laboratory's ground-based lidar station to measure neutral density from the lower stratosphere to the upper mesosphere. Rayleigh Lidar reliably measures relative densities in the region above 30 km. In this region, atmospheric extinction can be neglected and backscattering is primarily due to Rayleigh scattering. However, when density measurements are needed for the lower stratosphere two complications arise: the contribution of aerosol (Mie and Rayleigh) scattering to the Rayleigh signal and the effect of aerosol attenuation. Vibrational Raman scattering, being an elastic process for molecules only, can be used to resolve the first ambiguity. The second difficulty requires an inversion technique to help determine the attenuation profile from the Lidar signal and provide a transmission correction of this signal. For the lower stratosphere, the technique adopted in this laboratory is a three-step treatment of data. In step (1) Klett inversion is applied on the elastic scattering signal (Mie and Rayleigh) to obtain a transmission altitude profile. In step (2) the molecular signal from the Raman Lidar is corrected for atmospheric attenuation. In step (3), Raman data for below 25 km is spliced to Rayleigh data for above 25 km to give the entire profile of neutral density. Application of this analysis to experimental data will be shown and discussed.

Raman detection has recently been added to the Air Force Geophysics Laboratory's ground based lidar system (GLEAM) to augment that system's Rayleigh lidar measurements. In this paper we examine the possibilities of using the Raman measurements to self-normalize, and downwardly extend our measurements of stratosphere and lower mesosphere molecular density. By combining inelastic (Raman) and elastic (Rayleigh plus Mie) scatter measurements, one can isolate the Mie component of the scattering using the techniques of Cooney and correct the data to eliminate the effects of atmospheric attenuation. Lidar, Raman lidar.