Basics of Radio Astronomy

Basics of Radio Astronomy


Author:
Diane Fisher Miller
Published in:
Jet Propulsion Laboratory
Release Year: 1998
ISBN:
00000000
Pages: 109
Edition: First Edition
File Size: 1 MB
File Type: pdf
Language: English



Description of Basics of Radio Astronomy


In a collaborative effort, the Science and Technology Center (in Apple Valley, California), the Apple Valley Unified School District, the Jet Propulsion Laboratory, and NASA have converted a 34-meter antenna at NASA's Deep Space Network's Goldstone Complex into a unique interactive research and teaching instrument available to classrooms throughout the United States, via the Internet. The Science and Technology Center is a branch of the Lewis Center for Educational Research.
The Goldstone-Apple Valley Radio Telescope (GAVRT) is located in a remote area of the Mojave Desert, 40 miles north of Barstow, California. The antenna, identified as DSS-12, is a 34-meter diameter dish, 11 times the diameter of a ten-foot microwave dish used for satellite television reception. DSS-12 has been used by NASA to communicate with robotic space probes for more than thirty years. In 1994, when NASA decided to decommission DSS-12 from its operational network, a group of professional scientists, educators, engineers, and several community volunteers envisioned a use for this antenna and began work on what has become the GAVRT Project.
The GAVRT Project is jointly managed by the Science and Technology Center and the DSN Science Office, Telecommunications and Mission Operations Directorate, at the Jet Propulsion Laboratory. Basics of Radio Astronomyworkbook was developed as part of the training of teachers and volunteers who will be operating the telescope. The students plan observations and operate the telescope from the Apple Valley location using Sun workstations. In addition, students and teachers in potentially 10,000 classrooms across the country will be able to register with the center’s Web site and operate the telescope from their own classrooms.

Content of Basics of Radio Astronomy



Introduction 1
Assumptions ....................................................................................................... 1
Disclaimers ......................................................................................................... 1
Learning Strategy ................................................................................................ 1
Help with Abbreviations and Units of Measure .................................................. 2

1. Overview: Discovering an Invisible Universe ................................................... 3
Jansky’s Experiment ................................................................................... 3
Reber’s Prototype Radio Telescope ............................................................ 5
So What’s a Radio Telescope? .................................................................... 5
What’s the GAVRT?.................................................................................... 6

2. The Properties of Electromagnetic Radiation .................................................... 9
What is Electromagnetic Radiation? ........................................................... 9
Frequency and Wavelength ......................................................................... 9
Inverse-Square Law of Propagation .......................................................... 11
The Electromagnetic Spectrum .................................................................. 12
Wave Polarization ...................................................................................... 15

3. The Mechanisms of Electromagnetic Emissions............................................... 19
Thermal Radiation ..................................................................................... 19
Blackbody Characteristics ................................................................... 20
Continuum Emissions from Ionized Gas............................................. 23
Spectral Line Emission from Atoms and Molecules ........................... 23
Non-thermal Mechanisms .......................................................................... 26
Synchrotron Radiation ......................................................................... 26
Masers ................................................................................................. 27

4. Effects of Media ................................................................................................ 29
Atmospheric “Windows” ........................................................................... 29
Absorption and Emission Lines ................................................................. 30
Reflection ................................................................................................... 34
Refraction ................................................................................................... 35
Superposition ............................................................................................... 36
Phase .......................................................................................................... 37
Interference .................................................................................................. 37
Diffraction .................................................................................................... 38
Scintillation ................................................................................................ 40
Faraday Rotation ........................................................................................ 41

5. Effects of Motion and Gravity........................................................................... 43
Doppler Effect............................................................................................. 43
Gravitational Red Shifting .......................................................................... 44
Gravitational Lensing ................................................................................. 45
Superluminal Velocities .............................................................................. 45
Occultations ................................................................................................47

6. Sources of Radio Frequency Emissions ............................................................ 49
Classifying the Source ................................................................................ 49
Star Sources ................................................................................................ 51
Variable Stars........................................................................................ 51
Pulsars .................................................................................................... 52
Our Sun .................................................................................................. 54
Galactic and Extragalactic Sources ...................................................... 56
Quasars ................................................................................................. 57
Planetary Sources and Their Satellites........................................................ 58
The Jupiter System ............................................................................... 58
Sources of Interference ............................................................................... 60

7. Mapping the Sky ............................................................................................... 63
Earth’s Coordinate System.......................................................................... 63
Revolution of Earth .............................................................................. 64
Solar vs. Sidereal Day .......................................................................... 64
Precession of the Earth Axis................................................................. 66
Astronomical Coordinate Systems.............................................................. 66
Horizon Coordinate System ................................................................. 66
Equatorial Coordinate System.............................................................. 68
Ecliptic Coordinate System .................................................................. 71
Galactic Coordinate System ................................................................. 71

8. Our Place in the Universe.................................................................................. 75
The Universe in Six Steps........................................................................... 75
The Search for Extraterrestrial Intelligence ................................................ 79
Appendix:
A. Glossary ........................................................................................................ 81
B. References and Further Reading ................................................................. 89
Books ...................................................................................................... 89
World Wide Web Sites........................................................................... 90
Video ...................................................................................................... 90
Illustration Credits .................................................................................. 91
Index .................................................................................................................... 93
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