The electromagnetic spectrum is a vital part of our environment. Measures of radio frequency emissions from natural phenomena enable both practical applications, such as weather predictions and studies of the changing of Earth’s climate here at home, and reveal the physical properties of cosmic sources. For example, radio astronomers study a wide range of subjects, from the era before the first stars formed to the dynamics of our own Sun. Closer to home, our understanding of Earth’s land masses and oceans, its biosphere, the many layers of the atmosphere, and the space around Earth is essential to humanity’s safety and well-being. Some radio-frequency measurements of these natural phenomena have immediate economic benefits, others underlie our view of what we are and of our place in the cosmos. The spectrum is therefore a resource to be used wisely now and to be protected for future generations.
The Panel on Frequency Allocations and Spectrum Protection for Scientific Uses arrived at several key considerations related to scientific use of the spectrum. They are in the areas of scientific impact, sensitivity, stewardship, requirements, and opportunity and challenge:
- Scientific impact—Radio-frequency measurements of natural phenomena provide essential information with broad scientific and economic impacts.
- Sensitivity—Receive-only (“passive”) measurements of weak natural signals in a broad range of frequencies must be made with extreme sensitivity.
- Stewardship—The extreme sensitivity required makes it essential to maintain protected allocations and also to properly manage use of the spectrum near the protected allocations.
- Requirements—Dedicated passive allocations exist only in a limited number of bands. There is need for protection of some bands essential to scientific and societal interests that are not now protected.
- Opportunity and challenge—The receive-only services can sometimes take advantage of uncongested spectrum not allocated to them. Increasing congestion may deny this capability in the future.
By its very nature, research uncovers new and often unexpected pathways for studying our terrestrial environment and the universe. To explore these natural phenomena, the passive scientific services push the limits of receiver technology in order to detect extremely weak signals from both near and distant
sources. However, because the passive scientific services aim to detect radio emission produced by nature, they do not have the option of increasing the signal strength from the source.1 Rather, the signal-to-noise ratio is limited only by the sensitivity of the receiving instruments and the noise in the environment. If the instruments are to achieve their theoretical limit, then the environment must not be contaminated.
This handbook contains practical information regarding the use of the radio spectrum for scientific research. In Chapter 1, the regulatory bodies and issues are described. Chapters 2 and 3 discuss the relevant scientific background necessary to understand the issues with spectrum management for radio astronomy and Earth remote sensing applications, respectively. Chapter 4 discusses issues related to spectrum protection. Chapter 5 lists the science service spectrum allocations in the United States and their uses.
In addition, the report has a number of appendixes. Appendix A offers National Telecommunications and Information Administration definitions concerning interference. Appendix B lists the Institute of Electrical and Electronics Engineers letter designations for radar frequency bands. Appendix C lists important International Astronomical Union (IAU) spectral lines below 300 GHz. Appendix D lists important IAU spectral lines between 300 to 1000 GHz. Appendix E lists important IAU spectral lines above 1 THz. Appendix F examines the use of 0 dBi for sidelobe gain in calculations of interference in radio astronomy. Appendix G presents selected Federal Communications Commission rules and regulations. Appendix H lists selected acronyms from the text.
1 The passive services are those for which the signal is produced by nature and the applications are receive-only.