of the satellite system. In particular, the major optical effects caused by the system are a function of the very existence of the system's structures in orbit and would continue even if the system were turned off. Radio astronomy, however, bears the brunt of the active portion of the system--the intentional transmission of energy to the ground in the form of microwave radiation. In terms of system design, the impacts on both optical and radio astronomy are a result of the fact that SPS is not "perfect". The optical effects arise because the SPS solar blankets will not absorb 100% of the light that strikes them; the radio effects come from the inability to confine all of the transmitted energy either to the narrow cone that connects the orbiting antenna to the rectenna on the ground, or to the assigned portion of the radio spectrum. Another difference between radio and optical astronomy is manifest in their history of dealing with problems such as those presented by the SPS. Radio astronomy is a member of a very large, international community that uses the radio frequency portion of the electromagnetic spectrum. Because these users include both emitters and receivers of radiation that could potentially interfere with each other, the spectrum is managed by the International Telecommunications Union (ITU) which exists by virtue of international treaty. The management process consists of assigning portions of the spectrum to specific classes of users and setting strict standards on the extent to which other users may interfere with certain portions of the spectrum. Radio astronomy has several such bands assigned to it that must be viewed as regions protected by international law. Radio astronomy also has a tradition of vigorous action against those who infringe on these bands. This history of spectrum management has created within radio astronomy a collection of individuals who are specialists in this area. Many of the workshop participants are such specialists and as a result many of the individuals in the radio astronorny working group had served together on similar committees, discussed the effects of satellites on radio astronomy in other contexts, and discussed SPS previously, with some involved in the writing of the NAS/CORF report. The legal basis for protection of radio astronomy and the experience of the radio workshop participants had several effects. The standards on interference in the protected bands that the SPS must meet already exist.
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