<资料来源：[http://www.planetary.org/explore/topics/seti/seti_history_09.html The Planetary Society]>
<资料来源：[https://archive.md/2008.11.15-120433/http://www.planetary.org/explore/topics/seti/seti_history_09.html Ozpa - A Skeptic's Search]>
=='''第9章：Ozpa - 一个怀疑论者的搜索'''==
=='''第9章：Ozpa - 一个怀疑论者的搜索'''==
The lingering questions about how to conduct a search were still very much in evidence in the first post-Ozma SETI project in the United States. So much so that the search leader himself, G. L. Verschuur of the NRAO, expressed serious doubts about the purpose of the enterprise: "It is the author's belief," he wrote in an article describing the project, "that any detection of signal from another civilization will most likely be an accidental one in the sense that we will pick up signals not meant for us. For this reason it is unlikely . . . that a wavelength around 21 cm is the wavelength at which to search." These are indeed serious misgivings, coming from the very person who was to conduct the search.
然而，对搜索项目应该如何开展仍然存留了一些疑问，这在 Ozma 之后美国的第一个 [[SETI]] 项目上面就非常明显。以至于项目的发起人他自己，NRAO 的 G. L. Verchuur，都对这项事业的目的表露出了自己的怀疑。他在一篇描述这个项目的文章中说到：“我（作者）认为，如果我们能探测到任何其它文明的信号，很有可能只是碰巧而已，也就是说那个信号并不是特意发给我们的。因为这个原因，只去探测 21 厘米附近的波长可能并不太合适。”来自项目发起人的这番话，其中确实包含了深深的困惑。
第10行：
第10行：
位于 Gree Bank 的 85 英尺直径射电望远镜，曾被 Ozma 项目所使用，照片是新近拍摄的。图片提供：NRAO/AUI]]
位于 Gree Bank 的 85 英尺直径射电望远镜，曾被 Ozma 项目所使用，照片是新近拍摄的。图片提供：NRAO/AUI]]
Nevertheless, Verschuur went ahead with his program. Conceived as a direct continuation of Drake's 1960 project, it was based, like Ozma, in Green Bank, West Virginia. Whereas Drake had to content himself with the use of an 85-foot radio telescope, Verschuur had the use of a 300-foot dish and a 140-foot dish, as well as far more advanced sensitive equipment. Over the course of 1971 and 1972 Verschuur pointed his instruments at nine nearby stars, including the ones targeted by Ozma, listening at the hydrogen line frequency and correcting for Doppler shifts. In some respects it was an expanded and improved "Ozma," but in other respects it was a much smaller project: whereas Drake's team devoted 150 hours to their observations over three months, Verschuur and his colleagues spent only 13 hours observing over the span of two years. Nevertheless the similarities were such that Verschuur's search became popularly known as "Ozpa."
Ozpa was followed by a larger and more sustained NRAO search designated "Ozma II," which surveyed 674 stars over 500 hours between 1972 and 1976. Over the next three decades, many searches followed. Most of them were small and limited in scope, depending on available telescope time at established observatories, and designed to test a researcher's particular hypothesis. Some, however, were larger and more sustained and a few of those will be mentioned here.
