Interactive Applets and JAVA programs for Teaching Principles of Radio Astronomy J. M. Marr and K. Durkota We have developed a set of JAVA files which can be used in undergraduate physics and astronomy classes as interactive demonstrations of some of the principles of radio astronomy. We will demonstrate: ● an applet to help students become familiar with the Fourier Transforms of basic functions; ● an applet in which the user inputs any number of virtual sources of any size in any location in the sky and the resulting visibility function is instantly displayed; ● a package of JAVA programs, designed primarily to analyze data from the Haystack VSRT Interferometer, but also useful without equipment to demonstrate the beam pattern, fringe function, and visibility function and how they depend on the wavelength, antenna size, antenna separation, and source structure.

1. Tool for Interactive Fourier Transforms (Applet) Fixes Needed: 1.Label of lower title 2.Save File Exercises: 1.Spike  Cosine wave. 2.X-value of Spike  frequency of cosine 3.Two neighboring spikes  beat signal 4.Spike at x=0  constant function 5.Gaussian  Gaussian 6.Widths of Gaussians -One-dimensional -real functions only  Cosine transform (not full FFT) -immediate response Instructions page at:

2.Very Small Radio Telescope Interferometer_Plotter (VSRTI_Plotter) (Java package) Fixes Needed: 1.Create Model Curve in Plot Visibilities 2.Save File 3.X-axis label in Plot Visibilities 4.Label of input buttons “  Baseline” in Visibilities, “Baseline” in Fringe Pattern Exercises: 1.Beam shape vs. D and 2.Fringe pattern vs. b and 3.Visibility pattern for: - one source - two sources Designed for analyzing data in labs using the Haystack VSRT Interferometer, but also useful without data see “instructions”

3. Visibility Function of Virtual Radio Sources (Applet—not w/ Internet Explorer, but Mozilla OK) Fixes Needed: -Currently, only shows even Visibility functions!! -Need to get working with all browsers.