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Abstracts of Presentations

 

Research Experiences for Undergraduates (REU)
Abstracts of Presentations
August 5, 2010

 

2010 REUs

 

Wideband Radio Tuner for Geospace Science Applications
Presentation (PDF)
Peter Anderson, SUNY Oneonta

 

Much of the research on the Geospace Environment has been done using receivers to examine signals from ground and satellite based beacons. These receivers are often coupled with costly analog components to increase the signal strength and filter out Radio Frequency Interference (RFI). We will describe the production of a generic wideband tuner that could be mass-produced which will in turn cut overall receiver costs. Agilent Genesys RF simulation software allowed us to evaluate several designs and component combinations. After optimization in software we implemented a hardware prototype. We will describe the design of our simulation and hardware prototype and the resulting performance characteristics.

 

Advanced Digital Receiver for Distributed Instrument Arrays
Presentation (PDF)
Ross Daly, Carnegie Mellon University

 

Digital down converters (DDCs) are an essential part of a modern software radio receiver. Recently, Field Programmable Gate Array (FPGA) technology has advanced to the point where it is now possible to create low cost per channel DDCs within a FPGA. Furthermore, Simulink using Xilinx's System Generator for DSP provides a more user-friendly and time efficient way to program the FPGA compared to direct hardware language coding. We created a rate programmable DDC in Simulink and conducted simulations for RF signals up to 160 MHz based on variables such as filter coefficients, gain, bandwidth and input sources. We will describe results using both simulations and hardware co-simulations and will discuss future work needed to process real RF signals in the field.

 

Adaptive GPU-Accelerated Software Satellite Beacon Processing for Geospace Environmental Sensing
Presentation (PDF)
John Grasel, Harvey Mudd College

 

Radio beacons on satellites can be used in conjunction with ground receivers to study the ionosphere. The flexibility of new wideband tuners and digital receiver platforms requires a modular, adaptable software chain to optimally process and interpret beacon overflight data. A python-based system was developed to track the beacon, filter noise, and convert the signal to baseband. The slow but intrinsically parallel nature of the process led to large performance gains when methods were ported to the Graphical Processing Unit (GPU) using a python wrapper of NVIDIA's CUDA programming language. The presentation will discuss methodologies to port algorithms to GPU execution as well as show results for representative VHF/UHF beacon overflights in the Westford, MA vicinity.

 

Relationship between Stratospheric and Ionospheric Disturbances
Presentation (PDF)
Vicki Hsu, University of Colorado at Boulder

 

The ionosphere, located 80 km and above in the Earth's atmosphere, has intrigued and puzzled scientists for years. Ionospheric variability impacts a variety of communication and navigation systems. Although the primary drivers of ionospheric variability are relatively well understood, the effects of the lower atmosphere onto the ionosphere remain elusive. Due to the current deep solar minimum, new studies have shown promising results that shed light on the coupling of the ionosphere to processes from below. This presentation focuses on the sudden stratospheric warming (SSW) event that occurred in January 2010, and presents the results obtained from the Millstone Hill Incoherent Scatter Radar (ISR). Studying the 2010 SSW event will provide more insight into the interactions between the lower and upper atmosphere, and recognizing their connection is essential in understanding and forecasting the geospace environment.

 

Investigating a Type III Solar Burst with the MWA Prototype
Presentation (PDF)
Rachel Kennedy, University of California, Berkeley

 

The Murchison Widefield Array is an ambitious endeavor in remote Western Australia to install a 512-element radio interferometer with unprecedented imaging capabilities at low (80-300 MHz) radio frequencies. The current prototype comprises 32 dipole-antenna tiles which have begun to collect preliminary data on the sun. This talk will focus on a Type III solar burst that was recorded by the array on March 29, 2010, as well as the quiescent periods before and after the burst. In my investigation, I took advantage of the unique spatial, spectral and temporal resolution of the MWA to study the changing profiles of flux, frequency and polarization over time. Finally, I imaged the burst sequentially and concluded that some of the unexpected behavior of the sun at these wavelengths may be the result of a solar active region that has been observed in multiple bands near the center of the disk.

 

Conditioning a Cryogenic Sapphire Oscillator with GPS Reference Presenter
Presentation (PDF)
Tao Mai, Columbia University

 

Hydrogen masers have been widely used as frequency references for Very Long Base-line Interferometry (VLBI). As an alternative, Cryogenic sapphire oscillators (CSO) have stability superior to hydrogen masers on time scales shorter than tens of seconds, which makes them potentially better frequency standards for high frequency VLBI. But CSO's are prone to frequency drifting on longer time scales, and they need to be disciplined by an external time standard. This report discusses improvement of the long term stability of a specific CSO by conditioning it with GPS reference.

 

Mapping Class I Methanol Masers in the DR21 Region
Presentation (PDF)
Talitha Muehlbrad, Texas Lutheran University

 

We present the first interferometric data of methanol masers in the 4-1->30 E transition at 36GHz in DR21OH, DR21W, and DR21N. In the two sources which have other published maps of other methanol maser transitions, our data are in agreement with these other transitions. Masers found in DR21OH match the outflow pattern seen in other transitions, and those found in DR21W are in agreement with the line of masers found in other transitions. DR21N shows a line of bright redshifted masers near a scattering of low-intensity blueshifted masers. A very large magnetic field was detected in DR21W which may be evidence for a different mechanism of maser pumping than commonly assumed for Class I masers.

 

Looking Inwards: Holographic Imaging of Parabolic Antenna Apertures
Presentation (PDF)
Rachel Nancollas, Franklin W. Olin College of Engineering

 

The sensitivity of radio telescopes is strongly dependent on the antenna's near-field characteristics, which can be studied using holographic imaging. Here we discuss a method for producing holographic images of the 5 meter MV3 antenna at Goddard Geophysical and Astronomical Observatory (GGAO) using a data collection system that was developed for the VLBI2010 broadband receiver. Our image processing hinges on the Fourier relationship between the antenna's far-field pattern and the electric-field distribution in the aperture of the primary reflector (i.e. the near-field distribution). The results of our imaging suggest that MV3's subreflector is over-illuminated because we observe significant ripple in the near-field distribution. More importantly, the images generated from MV3 holography collections suggest that our imaging technique can accurately create maps of the antenna surface. In the future, this holography software will be used to image the aperture of the new 12 meter VLBI dish currently under construction at GGAO.

 

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