M.I.T. HAYSTACK OBSERVATORY
Research Experiences for Undergraduates (REU)
Abstracts of Presentations
August 12, 2004
Low-Noise Amplifier Design for 440 MHz
Low-noise amplifiers are one of the most important front-end components in todays receiver technology. For the MISA and Zenith dishes operating at 440 MHz, the front-end LNA must have very low noise figure for high sensitivity, high tolerance to interference, and high gain. These requirements are generally very hard to obtain simultaneously. As in most engineering processes, certain compromises are made along the way to meet the tight requirements. Results from simulations and initial tests of the low-noise amplifier are encouraging. Further improvement of circuit performance is expected in a cryo-cooled environment.
A Multi-Transition Search for Class I Methanol Masers
University of Massachusetts Amherst
Class I methanol masers have been detected in star forming regions, and may be a critical link in detecting very early star formation. These masers are pumped by collisional excitation followed by spontaneous radiative decay and often occur in the outflows of young stars. The Haystack 37-m antenna was used to conduct a search for Class I methanol masers at three transitions towards the known star-forming regions of s255, s235, omc2, and w75 north and west. We have detected masers and mapped the surrounding region. Methanol masers that are coincident in position and velocity between 36 and 44 GHz have been found, as well as emission at 44 GHz with no corresponding emission at 36 GHz. There have been no detections at 25 GHz. A comparison of line widths is also presented. The hope is that these data will facilitate modeling of the pumping mechanism of these masers and the surrounding physical environment.
Empirical Ionospheric Model Based on Arecibo Incoherent Scatter Radar Data
In order to illustrate the properties of the ionosphere and improve prediction capabilities, empirical models of electron density, electron temperature, and ion temperature have previously been created from Millstone Hill incoherent scatter radar data. A new model for the Arecibo radar has now been developed using the software used for the previous models, Saint Santin and MU. The Arecibo Empirical Model operates on data from the years 1970 to 2002, which was gathered through the CEDAR/ Madrigal database. Electron density, electron temperature, ion temperature, and parallel ion velocity variations from 150km to 650km are analyzed with respect to day number, local time, altitude, solar activity (F10.7), and geomagnetic activity (ap). The error estimates for the model parameters, which were not available for the St. Santin Model, are also provided here. Due to the close proximity in geomagnetic latitude, the Arecibo Empirical Model and the Middle and Upper Atmosphere (MU) Model are compared.
43 and 86 GHz VLBI Polarimetry of 3C454.3
Massachusetts Institute of Technology
Very Long Baseline Interferometry (VLBI) is used to study extragalactic radio sources with a greater angular resolution than can be achieved with standard radio or optical telescopes. Observations of the quasar 3C454.3 were made using the Very Long Baseline Array (VLBA); a group of 10 radio telescopes spread across the U.S. that is used for VLBI. Total intensity and linear polarization images of 3C454.3 were made at both 43 and 86 GHz. The 86 GHz linear polarization image of 3C454.3 presented here is the first 86 GHz linear polarization image ever made of this source. 3C454.3 is a blazar; a class of Active Galactic Nuclei (AGNs) that often displays radio jets emanating from a super-massive rotating black hole in the objects core. In an attempt to look for polarization at the center of AGNs, it is better to make measurements at higher frequencies, since Faraday rotation (which can depolarize radiation from the core) decreases with the square of the wavelength.
Meteoroid Properties and Classification Using High Power UHF Radar
Case Western Reserve University
The Millstone Hill 440 MHz High Power UHF Radar is a very useful tool for studying meteors in the Earth's upper atmosphere. In data gathered on July 28, 2003 it was found that some head echo returns showed an anomalous "double streak" seen by no other high power radar system
Two experiments were performed this summer with the intents of gathering general statistics and showing that the double streaks are a real phenomenon, not an artifact of our instrumentation. Six hours of integration provided ample data for analysis of various statistics including altitude, range rate, and duration. For each of these parameters the double and single streaks are separated into two distinct distributions. These results and their possible implications are discussed.
Exploring Solar Capabilities
The low-frequency array being developed by Haystack will allow for astronomical studies in the 80 to 300 MHz frequency range. This array will be used, in part, to address heliospheric science and space weather objectives. To ensure that the telescope will be able to meet our science objectives, it is important to understand the qualities of the solar wind that may drive the array design requirements. The need for such an understanding motivated this project, and can be explored using solar data from several satellites.
Previous studies have shown a relationship between the velocity of the solar wind and the solar rotation cycle, but solar wind density has not been thoroughly studied. Various satellites, including Helios 1 and 2, Pioneer Venus Orbiter and the WIND satellite, provided data for several solar wind parameters at various heliocentric distances. These data were used to construct plots comparing the velocity and density measurements with the solar cycle. A correlation between both the density and velocity of the solar wind and solar rotation cycle was investigated.
Development and Testing of the New SRT Receiver and Modeling the Sun
University of Texas at Austin
The receiver for the Small Radio Telescope (SRT) is being upgraded to a new, digital receiver with the hopes to perform interferometry experiments. Part of our summer work was to test and debug this new receiver. Initial tests were done by observing the Sun using a short baseline of about 50 feet. During the recent high solar activity, the baseline was increased to about 200 feet. To compensate for the deviation from the typical solar behavior, we studied the effects of limb brightening and sunspots on the cross-correlation values. Additional summer work involved the layout and design of the new ground control unit for the SRT.
Last modified: Tue Oct 26 14:02:50 EDT 2004
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