The group felt that the SPS would have an extremely difficult task meeting these standards. Partly as a result of focusing on the protected bands, the effects on radio observations outside the protected bands may not have been treated in as much detail as might be eventually required. This viewpoint was, in fact, probably the most appropriate one for a workshop of this duration. The section in the radio working group report on the "Rusty Bolt Effect" illustrates the fact that all of the ways in which the system could create radio frequency interference in protected bands will not be known until the SPS is actually turned on. Optical astronomy has no such history of enforced protection of observations from interference. Optical astronomers who are interested in faint sources have simply tried to avoid strong sources of light in the planning of their observations and the construction of observatories. They observe at places that are as far removed from large cities as was practical at the time of the construction of the observatory. As with out-of-band radio astronomy, terrain shielding is the method by which optical astronomers attempt to protect their observations from interference. Because of this difference in the history of optical and radio astronomy, existing light pollution standards for optical astronomy are few and have sanction under municipal law only in isolated instances. There are very few light pollution specialists in optical astronomy. As a result, much of the discussion of the optical group centered on setting reasonable standards for light pollution that could be used in this assessment of SPS effects. The concept of "impact thresholds" was developed in this context, and whereas it does not have the quantitative basis that the radio regulations do, the concept should be useful in assessing satellite designs. A final major difference between the optical and radio working group reports can be found in the extensive discussion of the conduct of optical astronomical observations. The optical working group felt that it was necessary to provide sufficient background to allow someone unfamiliar with astronomy to understand the working group report. On the other hand, since the radio working group felt that the discussion of astronomy in the CCIR 224-4 report served the same function for its report, the CCIR report is included here as an appendix to the radio astronomy section.
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