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Abstracts of Presentations


Research Experiences for Undergraduates (REU)
Abstracts of Presentations
August 9, 2007


2007 REUs and RETs


Development of an Integrated Beacon Receiver
Presentation (PDF)
William Harmon, Rochester Institute of Technology


Software radio reception and processing of satellite-based radio beacon and SATCOM signals can provide useful data for scientists to examine properties of the ionosphere. In particular, radio wave amplitude, phase scintillation, and total electron content variations can be studied. In this project, a digitally controlled hardware tuner was developed to interface with a turnstile antenna and down-convert three beacon signals and one SATCOM signal to a 126MHz intermediate frequency usable by the MIDAS-M software radio platform. An up-down conversion architecture was designed and simulated using Eagleware based on estimated signal strengths and component S2P files. The final design was then put into schematic form and PCB layout was planned using Altium Designer. The boards are fully fabricated and ready for testing and integration with the MIDAS-M system.


Beacon Signal Acquisition and Processing Using Software Radio
Presentation (PDF)
Harendra Guturu, University of California, Berkeley


The software radio receiver implements beacon signal acquisition and processing using general purpose computing elements on a modern software radio platform. Use of regular computers and standard programming languages allows the receiver to be more flexible, portable, and easier to maintain. It also affords the ability of optimizing processing parameters in software rather than having to design and fabricate new hardware. Python is used as the programming language of choice due to its clean structured nature, free scientific libraries similar to those found in MATLAB, and fast development time. After a received signal is down converted by the tuner and sampled, the data is passed on to Python scripts that handle the filtering of the data, tracking the signal center frequency, shifting the signal to baseband and down-converting it to a final bandwidth of 100 Hz from an initial 100 kHz bandwidth. The filtering lowers the noise in the signal to allow more accurate tracking of the signal center frequency. Once the frequency is known the signal is modulated to baseband since all the scientific calculations are performed on a zero frequency signal. The down conversion stage is used since a high bandwidth data rate is not necessary to store a baseband signal. The low bandwidth, baseband signal is then passed on in HDF5 format for scientific analysis, visualization and loading into the Madrigal database.


Receiver Data Processing, Visualization and Management Using Madrigal
Presentation (PDF)
Damian Ancukiewicz, Columbia University


The software beacon receiver is designed to use software radio to process satellite beacon signals in order to detect and record scintillations, which are rapid fluctuations in signal power and phase caused by ionospheric irregularities. This project involved the implementation of the final parts of the signal chain in the beacon receiver: the calculation of ionospheric parameters from the processed signal voltages, the loading of these parameters into the Madrigal scientific database, and the visualization of these parameters. The high-level processing software calculates the S4 (normalized standard deviation of signal power) and sigma-phi (standard deviation of signal phase) from the tracked and down-converted voltage samples. Both of these parameters are used by scientists to gauge the severity of ionospheric scintillation. Additionally, total electron content (TEC) of the atmosphere can be calculated, which helps understand the ionospheric structure at the time of a satellite overpass. The ionospheric parameters are then used to create a new, final, HDF5 format file. This file is then used to load the parameters into the Madrigal scientific database so that they can be accessed over the Web. Additionally, visualizations are inserted into Madrigal, including simple time-series plots, satellite azimuth/elevation plots and map plots.


Analysis of long-term temperature trends in the upper atmosphere
Presentation (PDF)
James M. Kurdzo, Millersville University of Pennsylvania

Climate change, be it in the troposphere or the upper atmosphere, is one of the most critically pressing issues in our society today. Meteorologists and climate scientists have long since demonstrated the alarming rates of warming in the lower atmosphere, but the space weather community is yet to grab the spotlight. For the first time, a large enough database of observations is readily available for extensive analysis of temperature trends in the ionosphere. Data acquired from 1978 to 2007 by the Millstone Hill incoherent scatter radar (42.6°N, 288.5°E) has been analyzed in order to provide a direct estimate of temperature trends between 250 and 550 kilometers. These long-term trends indicate significant daytime hour cooling, varying between approximately -3.5 K/Year to -8.0 K/Year depending on height and time. These measurements are accurate both for ion temperatures (Ti) and neutral temperatures (Tn) with daytime standard deviations as low as 0.8 K/Year, showing that these are very reliable results that are considerably larger than theoretical predictions based solely on increasing concentrations of greenhouse gases in the lower atmosphere.


Characterization of E-region Neutral Wind Dynamics at Sondrestrom
Presentation (PDF)
Ryo Saotome, Trinity College


Data obtained by the Sondrestrom incoherent scatter radar, located at 67°N, 309°E, from campaigns during September 1-30 2005 and March 6 - April 6 2006 were analyzed to characterize neutral wind dynamics in the lower thermosphere. Lomb-Scargle spectral analysis revealed several significant waves in the data from both campaigns including 8-hour, semidiurnal and diurnal tides, as well as quasi-8 to 10-day planetary waves. Various harmonic components derived from the spectral analysis were then fit to the data over a range of altitudes in order to extract the amplitude and phase of the tidal components. For the zonal equinox winds in both the fall and spring, the amplitude of the semi-diurnal tide is shown to be stronger than the diurnal component at altitudes below 108 km, while the opposite is shown to be true for higher altitudes. This is in disagreement with the GSWM model, which predicts a larger semi-diurnal component at all altitudes. Daily variations in the mean winds and amplitudes for both the diurnal and semi-diurnal components are also observed. The presence and phase progression of an 8-hour wave, also not predicted by theoretical models, is discussed as well.


Radio Interferometric Observations of the Sun with High Time and Frequency Resolution
Presentation (PDF)
John Garzone, Columbus State University


A Small Radio Telescope (SRT) three-element interferometer was used to examine solar emission at 1415 MHz in high frequency and time resolution using the VLBI mode of the SRT. Solar observations in high frequency and time resolution are an insufficiently explored area of investigation, because the required technology has only recently become available. Unfortunately, the given period of observation occurred during a solar minimum, therefore low solar activity resulted in a lack of interesting data. Due to this lack of data, project goals shifted towards the development of a data analysis pipeline for the examination of archived data taken with the three-element SRT interferometer from June through August of 2006. This analysis pipeline was designed with the purpose of locating instances of solar activity based upon statistical data analysis. The results of this data analysis will be presented. Finally, the analysis pipeline will also serve as a testbed for a similar application in the MWA 32T project later in 2007.


Algorithms for Transient Detection
Presentation (PDF)
John Gilling, Boston University


One of the key science areas of the Mileura Wide-Field Array (MWA) will be to scan the sky for transient radio emissions, originating from sources in the sky ranging from large Jupiter-like planets to active galactic nuclei. A central element of the transient detection software collaboration is the All Sky Monitor (ASM), which will make continuous comparisons in real-time between the observed images and the reference sky model, appropriately modified to account for the array characteristics. This process consists of convolving the sky with an array beam pattern, in order to find the response of the array to the sky, and distinguishing RFI signals from astronomically notable transients. I have written a series of programs that calculate a beam pattern for a single tile, for a 32-tile prototype array, and for a 496-tile sample array, as well as programs that convolve a given reference sky with the calculated beam pattern and plot the brightness distribution. This software has been used to evaluate different approaches to the convolution and detection tasks, and will eventually be incorporated into the operational ASM software.


Development of a Solar Imaging Array of Very Small Radio Telescopes
Presentation (PDF)
Theodoros Tsiligaridis, University of Washington, Seattle


A 3-element interferometer built using very small radio telescopes (VSRT's) was used for observing the Sun at a frequency band of 35 MHz wide centered at 12.086 GHz daily. The signals from the LNBF's are processed with a USB 2.0 video grabber and other inexpensive consumer electronics. The baselines used were based on a reference between the two adjacent dishes and thus, the baselines of the first two dishes are the same; 0.2699 meters, and the distance from that center point to the third dish is 2.9464 meters. Data from the Sun was collected over a two month period and software was used to calculate the fringe visibility amplitudes and closure phase. Modeling programs were developed to imitate the Sun's chromospheric behavior and a comparison of the closure phase between the VSRT data and the model's curves was achieved via least-squares analysis and construction of surface plots to display the sensitivity of the model as different parameters varied, which would yield solutions to the least squares problem. Various approaches were taken to examine the sunspot activity. The software was developed in two languages; Matlab and Python, and the motivation for using Python was to make the software system accessible to community colleges and introduce radio interferometry, since it's freely downloadable. The cardinal factors that contribute to the visibility of the model include the uniform Sun component, a linear brightness gradient applied to simulate dish mispointing, limb brightening and a changeable sunspot of varying intensity. We found that the more sophisticated limb brightening (adding many rings) tended to fit the actual data a lot better than the previous limb brightening profile did (only one outer ring). Although dish mispointing made it difficult to infer information about the Sun at times and the sun was not showing much activity during the summer, we were not only successfully able to detect sunspot activity using the 3-element VSRT system, but also observed a decaying trend of the sunspot's intensity over a period of six days. The hardware of the 3-element VSRT system was also documented in detail.


Hydrogen Line Observations using a 3-element Small Radio Telescope Interferometer
Presentation (PDF)
Joshua Suresh, Massachusetts Institute of Technology


A small-baseline three-element SRT array was used to examine the feasibility of observing compact HI structures in our Galaxy. The presentation will examine the sensitivity limits for the detection of HI sources with baselines varying from roughly 2 to 70 meters. Single-SRT HI observations were also conducted, and software was developed to normalize spectral data and plot it against galactic coordinates. While mapping galactic hydrogen was largely successful, the inherently low brightness of HI sources and manmade RFI sources made SRT interferometry difficult.




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