The technique of Very Long Baseline Interferometry (VLBI) is used in radio astronomy to observe fine-scale structure in radio sources. Observations are made simultaneously from radio telescopes separated by thousands of miles. The data is recorded on magnetic tapes and sent to a single location to reduce the data. One can thus observe structures one-thousandth of a second of arc in angular separation. This is more than a hundred times better than one can observe with physically connected or single telescopes. The same techniques can be used to measure crustal motions on the Earth. The VLBI observations are important to our understanding of the physical processes taking place in radio sources such as quasars. The Principal Investigator will carry out radio astronomical observations using VLBI techniques. There is support of continued operation of the North Liberty Radio Observatory (NLRO) as part of the U.S. VLBI Network. The NLRO is 1 of 6 institutions in the U.S. which are full members of the U.S. Network. The NLRO is an important participant in VLBI observations (using MkII) recording at frequencies of 5 GHz and below. The NLRO was used for more than 1200 hours for 62 separate experiments during the last 2 years. The use of NLRO for Network VLBI experiments is steadily increasing as the use of global fringe fitting and self calibration techniques (which work best with a large number of telescopes) become more common. The "Iowa" element of the Array should be completed in the next 2 years and will supplant the present telescope. This award will support Dr. Mutel's VLBI research. Observations will be made of structures in the radio source BL Lacertae, whose parts seem to be expanding at speeds exceeding the speed of light. Other observations will be made of selected compact double radio sources. A search will be made for a central component. Radio emissions from certain binary stars will be observed to look for coherent radio bursts. Interstellar scattering of compact radio sources near the galactic plane will be studied. Dr. Mutel is a competent and well-experienced radio astronomer and the results of his research will be important to our understanding of radio sources.
