Plasma Line Measurements at Chatanika with High-Speed Correlator and Filter Bank

In the spring and fall of 1978 we made an extensive series of plasma line and correlative observations with the Chatanika incoherent scatter radar. To make these measurements, we greatly modified the radar receiving system. In addition to enlarging the plasma line filter bank the most significant change was the incorporation of a high-speed correlator provided by the French. This was the first use of a correlator in a monostatic radar to obtain the intensity spectra of naturally occurring plasma lines. In this paper we develop the signal-processing theory that we use to obtain the plasma line intensities from these measurements; we also show that these intensities compare well with those obtained from the filter bank. To show the richness of the phenomena and to explore the capabilities of the correlator, we examine a wide variety of spectra that have been enhanced by secondary electrons in the auroral E layer. From the other simultaneous measurements we are able to relate these spectra and their variations to the auroral situation. We also obtained the first measurements in the auroral region of photoelectron-excited plasma lines in the E and F layers. Perhaps most significant, in the plasma line spectra we detected a Doppler shift that we then used to determine the Birkeland current carried by ambient electrons. Although there is a large estimated uncertainty for this first determination, we obtained a downward Birkeland current of 10 μA/m² in the diffuse aurora in what is, most likely, the equatorward portion of the evening sector auroral oval

The design of fluorescence correlation spectroscopy for single molecule techniques

The ribosome is responsible for protein synthesis--a critical process in creating essential proteins for cell survival. Though bulk techniques yield valuable results about the structure of the ribosome, bulk techniques are not ideal in examining ribosomal dynamics and understanding kinetics involved in protein synthesis. On the contrary, the single molecule spectroscopy techniques are ideal in investigating the mechanisms of ribosome dynamics in real-time under equilibrium conditions. The latest advances in single molecule biophysics have opened numerous opportunities in the biological world to study the dynamics of molecules in real-time. Single molecule techniques such as Fluorescence Correlation Spectroscopy (FCS) have opened opportunities to study the ribosome as well as other ribosomal proteins. FCS is used to investigate diffusion coefficients, concentration, and kinetics of biological samples. In this thesis, we address the process of assembling an FCS system, as well as the design of a high-speed correlator. The high-speed correlator allows the software to handle the high data counts that can occur in single molecule experiments. A field-programmable gate arrays (FPGA) dual correlator and a multi-tau correlator are designed to handle the noise and high count rates that can dominate the signal. Also addressed in this thesis are ideal experimental conditions for successfully obtaining and troubleshooting results received from FCS curves.Includes bibliographical reference

A Novel Step for the Enhancement of Security in ARIPORTS Using Optical Ideology

The security systems in airports are very important and the detection of entry of unauthorized person must be in high rate so as to have an improved efficient system. The real time systems in airports are implemented based on CCTV cameras. These CCTV cameras are used to record the events for future references. The high rapidity of correlation must be performed for the improvement of security in airports. Firstly, 4f system is introduced into the real time security system of the airport. The introduction of this optical system improves system performance and high speed of correlation. This optical system is designed in the simulation environment of MATLAB. The CCTV images and database images are compared together in MATLAB for various conditions. These conditions help to define the performance of the projected system and to have a better evaluation of the projected architecture. The projected system can outperform conventional correlator based systems with elevated speed of correlation. The projected system enabled by dynamic Fourier plane correlator system was found to have high speed performance

Interference cancellation detectors in a hardware implementation perspective

To combat interference between users in a DS/CDMA system, several multiuser detection schemes have been proposed. This paper presents a prestudy for a custom DSP implementation of a multi-user detector scheme based on non-decision directed interference cancellation. Two architectural implementation methods for asynchronous detection are suggested and mutually compared. Each of the architectures is shown to have its particular advantages and therefore, a design combining the methods described in this paper is worth future studies

Auroral Plasma Lines: A First Comparison of Theory and Experiment

In this preliminary report on low-energy (0.3 to 3 eV) secondary electrons in the auroral E layer (90 to 150 km), we compare intensities of plasma lines observed with the Chatanika radar to theoretical predictions obtained from a detailed numerical model. The model calculations are initiated with a flux of energetic auroral primary electrons which enter the atmosphere and lose energy to electrons, ions, and neutrals through a combination of elastic and inelastic collisions. This flux is chosen in order that the total calculated ionization rate matches one that is deduced from the radar measurements. From these same calculations the steady state secondary electron flux is deduced as a function of altitude, energy, and pitch angle. This flux is used to calculate plasma line intensities which are then compared with observed intensities. Initial comparisons suggest that the plasma line theory, when applied to low altitudes, must include the effect of electron-neutral collisions. When this is done, the good agreement obtained between theory and experiment indicates the promise of this approach for the study of low-energy auroral electrons

Bandpass filters for unconstrained target recognition and their implementation in coherent optical correlators

An up-dateable correlator is simulated which is based on the non-degenerate four wave mixing (NDFWM) interaction in the photorefractive material bismuth silicon oxide (Bi12SiO20). Specifically, it is shown that variable bandpass filters can be implemented directly in the correlator by adjusting the relative strengths of the signal and reference beams used to write the Fourier transform hologram into the photorefractive. The synthetic discriminant function (SDF) method of grey-level multiplexing is reviewed. A bandpass modification of this technique is used in the design of a multiplexed filter for the recognition of an industrial test component from a limited number of known stable state orientations when viewed from an overhead camera position. Its performance in this task when implemented in the up-dateable correlator is assessed through simulation. The conclusion of this work is that filter multiplexing must be used judiciously for orientation invariant recognition. Only a limited number of images, typically under ten, may be multiplexed into each filter since correlation peak heights and peak-to-sidelobe ratios inevitably progressively deteriorate as images are added to the filter. The effect of severe amplitude disruptions in the frequency plane on correlation peak localisation is examined. In two or higher dimensions simulations show the localisation is very robust to this disruption; an analysis is developed to indicate the reason for this. The effect is exploited by the implementation of an algorithm that locally removes the spatial frequencies that exhibit close phase matching between intra- and inter-class images. The inter-class response can be forced to zero while simultaneously improving the intra-class tolerance to orientation changes. The technique is assessed through simulation with images of two types of motor vehicle, in a variety of orientations, and shown to be effective in improving discrimination and intra-class tolerance for examples in which these were initially very poor. Bandpass filters are experimentally implemented in a joint transform correlator (JTC) based on a NDFWM interaction in Bi12SiO20. The JTC is described and its full bandwidth performance initially assessed. As anticipated from the previous considerations, inter-class discrimination was high but the intra-class tolerance very poor due to the high sensitivity of the filter. The difference of Gaussian approximation to a Laplacian of a Gaussian filter is described and its experimental implementation in the JTC detailed. Experimental results are presented for the orientation independent recognition of a car while maintaining discrimination against another car. An intra-class to inter-class correlation ratio of 7.5 dB was obtained as a best case and 3.6 dB as a worst case, the intra-class variation being at 11 ° increments in orientation at zero elevation angle. The results are extrapolated to estimate that approximately 80 filters would be required for a full 2 steradian orientation coverage. The implementation of the frequency removal technique and the Wiener filter in the JTC is briefly considered in conclusion to this work

Research and technology

As the NASA Center responsible for assembly, checkout, servicing, launch, recovery and operational support of Space Transportation System elements and payloads, Kennedy Space Center is placing emphasis on its research and technology program. In addition to strengthening those areas of engineering and operations technology that contribute to safer, more efficient, and more economical execution of our current mission, we are developing the technological tools needed to execute the Center's mission relative to future programs. The Engineering Development Directorate encompasses most of the laboratories and other Center resources that are key elements of research and technology program implementation, and is responsible for implementation of the majority of the projects in this Kennedy Space Center 1988 Annual Report

A digital spectral analysis technique and its application to radio astronomy

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering, 1963.MICROFICHE COPY AVAILABLE IN ENGINEERING.Vita.Includes bibliographical references (leaves 209-212).by Sander Weinreb.Ph.D