Bringing Your Class to the VLA

      Maximizing the Educational Experience

Make a class visit to the VLA an effective, motivational part of your science curriculum. Here are some tips on pre-visit preparation, what to expect during your tour, and how to use the VLA experience to enrich classroom work.

We are pleased that you want to bring your class to the Very Large Array (VLA). The VLA is one of the radio telescopes of the National Radio Astronomy Observatory (NRAO), a facility of the National Science Foundation. As a national research facility, the VLA is open to all scientists. Every year, 600 to 800 scientists use the VLA.

A visit to the VLA can be used in a wide variety of ways to enhance classroom instruction. The educational goals of your visit will depend on the grade level and the background of the students. For younger students, the VLA can serve as an introduction to the idea of scientific research and that such research is an important activity in our state and region. For older students, the VLA can be used as a practical example of concepts in astronomical observation, physics, engineering, mathematics and computer science.

Our Visitor Center and the walking tour were designed to serve as a self-guided educational experience for tourists. We have no staff for the Visitor Center. For educational groups, we provide tour guides as available from among staff members who volunteer for this duty. Because of this, guided tours are much more readily provided during normal weekday working hours. We need at least two weeks' notice to arrange a guided tour.

To make the most effective use of your tour guide's expertise, some basic concepts should be introduced before the visit. You may wish to discuss with the Public Information office or your tour guide some specific topics that you would like to have emphasized during the visit.

This teacher's guide is designed to help you plan your visit and to prepare your students to gain the maximum in new knowledge and inspiration from their exposure to one of the world's premier astronomical research facilities.

Planning and Logistics

The VLA is located 50 miles west of Socorro on U.S. Highway 60. The Visitor Center and walking tour are open from 8:30 a.m. until sunset every day of the year. The Visitor Center has restrooms, water fountains, and a soft-drink machine. No food is available at the VLA site. The nearest restaurants are in Magdalena, to the east, and Datil, to the west. Many restaurants, as well as lodging, are available in Socorro, an hour's drive from the VLA.

The VLA is at an elevation of 7,000 feet. At this elevation, the weather can be considerably colder than that at lower elevations. Snow is possible at the VLA from September through May. Check weather reports before your trip. Advise your students that they will be spending time outdoors during their visit and that they should wear clothing appropriate to cooler weather. During Fall, Winter, and Spring, jackets or coats usually are needed. During the colder months, warm hats and gloves also are advisable.

Allow about 2.5 hours for a guided tour of the VLA. Members of our staff who volunteer to conduct tours vary in their methods of presentation, but a typical tour consists of an introductory lecture in the Visitor Center auditorium, followed by the 20-minute automated slide show, also in the auditorium. After the slide show, the guide usually will take your class on the walking tour, explaining the operation of the VLA at various points along the path. Most guides entertain questions after the slide show and throughout the walking tour.

When you have arranged for a guided tour, please call us as soon as possible if there is any change to your plans. If you are going to be delayed significantly, call (505) 835-7000 and explain that you have a tour guide meeting you at the VLA site and ask the receptionist to relay the message about your delay to your tour guide.

Preparing for the Visit

A modest amount of preparation can make a visit to the VLA much more effective as an educational experience for your students. While the amount of detail and the level of the material you cover will vary with the grade level and the available time, the following topics are useful preparation:

The Scale of the Universe: Students should be introduced to the idea that the universe is an enormous place, with distances that simply cannot be imagined in ordinary, everyday terms. Topics to be covered could include: distances within our solar system; the speed of light; the light-year as a measure of distance; the size of our Milky Way galaxy; and distances to other galaxies.

Components of the Universe: The VLA is used to study a wide variety of objects: planets and moons in our solar system; stars throughout their life cycles; regions of starbirth; supernovae and supernova remnants; galaxies of all types; clusters of galaxies, gravitational lenses; and many more. Students who are aware of what the universe includes will have that knowledge reinforced by visiting an observatory that is regularly studying many of these objects. If your class has studied some particular type of object in depth, you might ask in advance for your tour guide to talk about what the VLA has contributed to our knowledge of those objects.

The Electromagnetic Spectrum: Radio astronomy is part of a modern research effort that uses instruments sensitive to nearly the entire breadth of the electromagnetic spectrum to unlock the secrets of the universe. Students should be aware of the fact that radio waves and light are the same phenomenon. They should learn that electromagnetic waves and sound, though sharing some common principles, are in fact different phenomena. The history of the discovery of radio waves and of the start of radio astronomy makes a fascinating story that will excite students before their visit.

A Local Observatory Visit or Telescope Night: For students just being introduced to astronomy, few experiences match their first look through a telescope. Most large universities and many community colleges have campus observatories where your students would be welcome. In other areas, there probably are local amateur astronomers who would be happy to arrange a "star party" for your class. When you do this, be sure to ask for an explanation of the telescope in use. The VLA dish antennas represent an "optical system" with a direct parallel to reflecting optical telescopes. This connection will be very useful to help your students understand radio astronomy.

The World Wide Web: NRAO and many other observatories have home pages on the World Wide Web. In fact, astronomy is one of the best-represented of the sciences on the Internet. Visit our site at: http://www.nrao.edu. This site includes links to other astronomical institutions, the NSF, NASA and other government agencies. Look at the NRAO press releases here to learn about recent discoveries made by researchers using the VLA.

The VLA in the Classroom

Below are some areas where you could incorporate aspects of the VLA and its research into the curriculum for different academic subjects. Details of these topics may be found in the reference works cited at the end of this guide. These are, of course, only a small number of ideas out of many possible ways to use the VLA as a classroom tool. If you have come up with some useful classroom exercises incorporating the VLA, we'd like to hear about them and possibly include them in future editions of this guide.

Astronomy

· Investigate telescopes and how they work: Use a reflecting telescope as an analog to the VLA antennas.

· Identify the astrophysical processes that produce electromagnetic radiation. Why do celestial objects glow, anyway? What does the radiation tell us about them? How do radio telescopes detect hydrogen gas in space? How do radio observations add to the information available from optical studies?

· Conduct a classroom tour of the solar system. Compare the planets to one another. What landforms and processes does the Earth share with other planets? The VLA is used regularly to study the terrestrial planets as well as comets and asteroids.

· Some VLA solar-system studies are done in conjunction with a giant NASA radar transmitter in Goldstone, CA. Calculate the time it will take for a signal transmitted from this system to reach Mercury, Venus, Mars, or a moon of Jupiter or Saturn and return to Earth. Try this with the planets at different places in their orbits. As an added exercise, calculate how far one of these bodies will travel in its orbit while the signal is enroute to it from Earth.

· Study the life cycles of stars -- protostars to white dwarfs, neutron stars and supernova remnants. Studies of supernovae and supernova remnants have been done for years at the VLA.

· These are just a few suggestions. Ask about possible VLA studies of celestial objects you have covered in class.

Physics

· Study the electromagnetic spectrum. Illustrate the Frequency/Wavelength relationship. Learn about atmospheric "windows" for ground-based observations (What types of electromagnetic radiation do not reach the ground?). Do classroom exercises with prisms and gratings to show the optical spectrum.

· Investigate wave interference (constructive and destructive) -- the basis of interferometry -- the type of radio astronomy done by the VLA. Use a ripple tank to demonstrate this or try pencil-and-paper exercises in wave addition on graph paper.

Mathematics and Computer Science

· Practice Time conversions among different time zones. Discuss sidereal time, the type of time used by observational astronomers. Why is sidereal time useful for astronomical observers?.

· Illustrate coordinate transformation -- Converting Right Ascension and Declination to azimuth and elevation. This process is performed in real time by the VLA's computers.

· Use the VLA's Y-shape and arm distances as an exercise in trigonometry.

· For computer classes, talk about digitization & sampling theory -- turning an analog signal into digital information without loss of information. The analog signals from the VLA antennas must be converted into digital information to be processed into images.

· Study how images are produced on a computer screen, and the various ways that might be chosen to do this.

Engineering and Electronics

· Consider the weight and balance aspects of the VLA's 230-ton antennas. Count the number of wheels on the transporter vehicles, assume the area of contact on the track for each wheel, then compute the pressure placed on the track by each wheel. As the movable dish in each antenna is tilted at different vertical angles, the forces trying to deform that dish will vary. Make drawings illustrating this.

· Illustrate a basic radio receiver by building a crystal radio. Kits are available from a variety of sources, or you can "roll your own" with easily-obtained parts.

· For more advanced classes, study the operation of a superhetrodyne radio receiver. This is the basic type of receiver used in stereos, TV sets, communication systems, and the VLA. (Interestingly, the superhetrodyne receiver was first invented in 1918.)

· The VLA radio receivers are much more sensitive to faint signals than those used in ordinary communication systems. Using the inverse-square law, compare the received signal strength of a very strong source of emission at a great distance (say a few light-years) to that of a moderate to low-power transmitter just a few miles from the VLA.

Where to Learn More

Organizations and Magazines

Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, CA 94112 (415) 337-1100 asp@stars.sfsu.edu This organization has a wide range of educational materials, including Mercury, a bimonthly magazine, classroom exercises, slide sets, books, and a free newsletter on astronomy education for teachers.

Astronomy magazine, Kalmbach Publishing Co, 21027 Crossroads Circle, P.O. Box 1612, Waukesha, WI 53187-1612 (800) 533-6644.

Sky & Telescope magazine, Sky Publishing Co., 49 Bay State Road, Cambridge, MA 02138 (800) 253-0245.

Star Date magazine, 2609 University Ave., Rm. 3.118, The University of Texas at Austin, Austin, TX 78712 (800) STARDATE http://stardate.utexas.edu

American Radio Relay League, 225 Main Street, Newington, CT 06111 http://www.arrl.org; Free information about amateur radio, use of amateur radio in educational programs, and the Shuttle Amateur Radio Experiment (SAREX), a program that uses amateur radio for direct communication between school classrooms and Space Shuttle astronauts during flights.

Project CLEA, Department of Physics, Gettysburg College, Gettysburg, PA 17325 (717) 337-6028 http://www.gettysburg.edu/project/physics/clea/CLEAhome.html; This organization develops laboratory exercises that illustrate modern astronomical techniques using digital data and color images. They are suitable for high school and college classes.

Society of Amateur Radio Astronomers, Hal Braschwitz, 3623 W. 139th St., Cleveland, Ohio 44111 (216) 252-8177 http://www.irsociety.com:80/sara/sara.html

Books

A Field Guide to the Stars and Planets, Donald H. Menzel and Jay M. Pasachoff, Houghton Mifflin Co. (Peterson Field Guide Series).

Modern Astronomy: An Activities Approach, Mary Kay Hemenway and R. Robert Robbins, University of Texas at Austin, 1991, ISBN 0-292-75133-8

Seeing the Sky: 100 Projects, Activities & Explorations in Astronomy, Fred Schaaf, Wiley, 1990, ISBN 0-471-51067-X

StarDate Guide to the Solar System, University of Texas at Austin (see address above).

Eavesdropping on Space, David C. Knight, William Morrow & Co., 1975, ISBN 0-688-22019-3.

The Early Years of Radio Astronomy, W.T. Sullivan, III, Editor, Cambridge, 1984, ISBN 0-521-25485 X.

Radio Astronomy, 2nd Edition, John D. Kraus, Cygnus-Quasar Books, 1986 (Technical treatment).

Understanding Basic Electronics, American Radio Relay League, 1992 ISBN 0-87259-398-3.

Articles

Kenneth I. Kellermann, "Radio Astronomy in the 21st Century," Sky & Telescope, February 1997, pp. 26-33.

Dahlem, M. and Brinks, E:, "The World of Radio Astronomy," Parts 1-4, Mercury, Mar/Apr, May/Jun, Jul/Aug and Sep/Oct 1996.

Gordon, Mark A., "VLBA -- A Continent-Size Radio Telescope," Sky & Telescope, 69:6, pp. 487-490 (June 1985).

Kellermann, K.I. and Thompson, A.R., "The Very Long Baseline Array," Science, 229, pp. 123-130 (12 July 1985).

Kellermann, Kenneth I. and Thompson, A. Richard, "The Very-Long-Baseline Array," Scientific American, 258:1, pp. 54-63 (January 1988).

"Interference and Radioastronomy," A. Richard Thompson, Tomas E. Gergely and Paul A. Vanden Bout, Physics Today, November 1991, pp. 41-49.

Light Pollution, Radio Interference and Space Debris, conf. ser. 17, D.L. Crawford, ed., Astronomical Society of the Pacific, San Francisco, 1991.

This is, of course, only a start. Even a modest library usually has a variety of materials on astronomy and other sciences. Once you start looking, in a library on on the World Wide Web, you'll be amazed at the amount of material available.


Help Us Make This Publication More Useful to You

We hope this brief guide helps you use the VLA and its scientific work as an educational tool. This is an idea book, not a textbook, so many of the suggestions here will require seeking information from libraries or the other resources we've listed at the end. We would appreciate your feedback about the suggestions in this book. We also would appreciate your sharing any ideas you've used to make the VLA an illustrative part of your science curriculum. If you have materials that incorporate aspects of our facility in problems or classroom exercises, please consider submitting them for possible inclusion in later editions, to benefit other educators.

Dave Finley
Public Information Officer

National Radio Astronomy Observatory
P.O. Box O
Socorro, NM 87801
(505) 835-7000
World Wide Web: http://www.nrao.edu

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.