M.I.T. HAYSTACK OBSERVATORY
Research Experiences for Undergraduates (REU)
Abstracts of Presentations
August 7, 2003
Data Mining for Meteor Echoes Using High Power UHF Rada
Upgrades to the Millstone Hill Incoherent Scatter Radar and MIDAS data acquisition system allow raw receiver data to be gathered with each radar pulse during normal experiment operations. This raw data may have an abundance of micrometeor data that is overlooked or thrown out as noise during the investigation of other atmospheric parameters. This paper discusses the development of a new data analysis scheme designed to run in the background of MIDAS-W during raw data acquisition that will tag and store meteor echo data for later analysis. Various success levels using different radar pulse wave forms are discussed as well as examples of successfully tagged and analyzed meteor head echoes. Also discussed are current applications of meteor head echoes to determine velocity, deceleration, mass and altitude of incoming meteoric material as well as future applications of using meteor echo data to determine orbital properties and sporadic meteor origins.
On Performing Interferometry on the Sun utilizing a Yagi-Uda Array and an
SRT at MIT Haystack Observatory
Interferometry, VLBI , and now eVLBI are now the cutting edge of radio astronomy. Utilizing more than one antenna, the system can create large apertures allowing for greater resolution of objects than ever before. However, due to the complexity and cost of maintaining correlating supercomputers, large dishes, and vast quantities of personnel, these experiments are usually out of the reach of students in throughout grade school and even during undergraduate years. Our goal is to bridge the gap between full scale observations with equipment like the Haystack 37 m telescope and what is available to those with less funding. To this end we took the first step by attempting basic interferometry utilizing a Yagi-Uda Antenna and an SRT in order to begin work towards the ultimate goal of VLBI experiments run with SRTs at different institutions across the country.
Pushing VLBI Polarimetry to High Frequencies
Nicole E. Gugliucci
A certain subclass of active galactic nuclei (AGNs) called blazars emit synchrotron radiation almost directly along our line of sight, showing a relatively strong and featureless continuum. These may be variable on a scale of days and show significant movement of material along jets over time scales as short as a few months. The radiation from such sources is usually not observed to be strongly polarized near the core, an optically thick region. Faraday screens may depolarize the emission before it reaches the observer, but this effect drops off with a decrease in ?2. By observing at higher frequencies, polarization may be seen in or near the cores of AGNs. In previous studies at 43 and 86 GHz, this has not been the case. Determining the polarization of the source is crucial to understanding the nature and behavior of magnetic fields in and around these extragalactic powerhouses. Very Long Baseline Interferometry (VLBI) is necessary to get the proper angular resolution these sources demand at these frequencies. The sources 3C273 and J1337-12 were imaged in both total intensity and polarization with data taken in January 2003. 3C273 was compared with data taken previously at these frequencies in April 2000 and May 2002. J1337-12 was imaged for the first time at 86 GHz.
Understanding the Statistical Properties of LOFAR Skies
In the continuing effort to improve the LOFAR simulation and calibration software, it is important to generate skies as realistic as possible for the calibrator to image and analyze. However, there is currently no model for the statistical distribution of source shapes and flux densities at LOFAR's low frequencies and high resolution. To build such a model, two wide-field images centered on the extragalactic AGN 3C249.1 were created from VLA observations of the source, each with an approximate 3.5 degree radius. A source catalog was compiled from the images with identification by eye and subsequent use of routines in the AIPS environment to extract source properties. The first image, at 328-MHz, provides valuable information about the distribution of source flux densities and angular sizes, important in attempting to understand the distribution of unresolved, potential calibrator sources for LOFAR. The second image, at 74-MHz, provides a check for the above source list as well as spectral index information useful for extrapolating to LOFAR frequencies.
The Implementation of RTP Framing for e-VLBI
University of Arizona
For the past 30 years Very-Long-Baseline Interferometry (VLBI) has provided astronomers with the most accurate measurements to date of both distant radio sources as well as the tectonic plates. The resolutions attainable through VLBI are orders of magnitude better than other instruments. In order to transmit radio signals collected at different sites to a correlator for processing the VLBI data was stored on magnetic tapes, and then the magnetic tapes were whipped through the mail to the central processing site. This was not only arduous and inefficient, it was also costly. Now this means of shipment can be replaced by global high speed networks. This means of transmission is called e-VLBI. New protocols must be developed so e-VLBI can become a proficient high bandwidth background user. The protocol agreed upon uses a Real-time Transport Protocol (RTP) framework to preserve timing information and synchronization. The RTP is then transported using the Internet User Datagram Protocol (UDP) with RTP Control Protocol (RTCP) monitoring the networks performance. When this protocol is fully functional astronomers will be able to observe all over the world and receive results in real time.
Digital Transmit Waveform Generator for Incoherent Scatter Radar
Embry-Riddle Aeronautical University
The Millstone Hill Incoherent Scatter Radar facility currently uses an analog waveform generator to transmit a 440 MHz pulsed sine wave. It is totally functional, however there are many benefits to the use of a digital waveform generator. This paper discusses the creation and testing of a digital transmit waveform generator for the Millstone Hill Incoherent Scatter Radar. It includes the process of testing the prototype direct digital synthesizer and analog components; choosing the proper elements to create the final product; the design of the circuit boards; and the testing of the final product.
LOFAR Simulator and Array Development
The Low Frequency Array (LOFAR) and Square Kilometer Array (SKA), both still in development, are members of next-generation radio interferometer arrays. The new design is intended expand the lower range of radio frequencies available for observation and to provide scientists with a highly flexible, sensitive and robust observational tool. Since both arrays differ substantially from the design of current radio telescopes, effects that can be ignored in current instruments become critically important in the performance of the new arrays. The Haystack group has developed a simulator to model the roles these effects have on telescope performance. Recently, tests were conducted on a variety of LOFAR and SKA array designs, including layouts tailored specifically to the terrain of potential LOFAR sites. In addition, phase errors due to ionospheric effects were introduced into the simulations. This talk focuses on how the results of these tests contribute to the understanding of design tradeoffs and optimizations for these telescopes.
Observations of the April 2002 Storm Event by the Global Incoherent Scatter Radar Network
University of Colorado (Colorado Springs)
In this paper, the results of the April 2002 world-day campaign are reviewed. Initiated by the Haystack Observatory, this campaign unites the efforts of eight incoherent scatter radars (ISR) to collect ionospheric data during a major solar storm event beginning on April 17, 2002. Because of the sparse ionospheric data available, this collected data-set provides a major source of information for atmospheric studies. In addition, the participating IS radars are generally located along longitudinal and latitudinal sectors, an occurrence that makes this campaign unique and invaluable for studying spatial and temporal effects of ionospheric storms. Emphasis is given to describing pre-storm electron density depletions, correlations between electron density and kinetic temperatures, and comparisons between IS radar empirical data and ASPEN, a first principle physical model.
Empirical Ionospheric Model Based on Saint Santin Incoherent Scatter Radar Data
University of Illinois at Urbana Champaign
Recently, several empirical models of ionospheric electron density, ion temperature, and electron temperature were made from Millstone Hill incoherent scatter radar data. Using the software developed for this model, another empirical model was constructed using data from the incoherent scatter radar at St. Santin, France. The St. Santin Empirical Model uses data for the years 1966 through 1987 obtained from the CEDAR/Madrigal database and produces variations of electron density, ion temperature, and electron temperature in the E and F region ionosphere with day number, local time, altitude, and solar activity as represented by the solar 10.7 cm flux index. Here St. Santin radar data distributions and statistics are discussed for modeling purposes. St. Santin Empirical Model outputs are analyzed, and comparisons are made between the measured data and the model data in addition to comparisons between predictions of the Millstone Hill Empirical Model and the St. Santin Empirical Model.
Analysis of LOFAR High Band Antenna Design
The Cooper Union for the Advancement of Science & Art
The current design of the LOFAR high band antenna (120-240 MHz), consisting of a 4x4 square array of dipoles, is analyzed using both electromagnetic computer simulations and prototype testing. The prototype beamformer circuit boards, which control the steering of the array's beam, are individually tested with a network analyzer to ensure that the delay and amplification characteristics meet design specifications. Among the aspects investigated across the parameters of frequency, polarization, element spacing, and dipole geometry are the resulting steered radiation patterns, impedance, and mutual coupling.
Last modified: Mon Nov 10 16:32:04 EST 2003
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