Billingham J, Tarter J
NASA Ames Research Center, Moffett Field, CA 94035, USA.
Acta Astronaut. 1992 Mar-Apr;26(3-4):185-8. doi: 10.1016/0094-5765(92)90093-x.
This paper estimates the maximum range at which radar signals from the Earth could be detected by a search system similar to the NASA Search for Extraterrestrial Intelligence Microwave Observing Project (SETI MOP) assumed to be operating out in the galaxy. Figures are calculated for the Targeted Search, and for the Sky Survey parts of the MOP, both operating, as currently planned, in the second half of the decade of the 1990s. Only the most powerful terrestrial transmitters are considered, namely, the planetary radar at Arecibo in Puerto Rico, and the ballistic missile early warning systems (BMEWS). In each case the probabilities of detection over the life of the MOP are also calculated. The calculation assumes that we are only in the eavesdropping mode. Transmissions intended to be detected by SETI systems are likely to be much stronger and would of course be found with higher probability to a greater range. Also, it is assumed that the transmitting civilization is at the same level of technological evolution as ours on Earth. This is very improbable. If we were to detect another technological civilization, it would, on statistical grounds, be much older than we are and might well have much more powerful transmitters. Both factors would make detection by the NASA MOP a much more likely outcome.
本文估算了一个类似于美国国家航空航天局地外文明搜索微波观测项目（SETI MOP）的搜索系统在银河系中运行时，能够探测到来自地球的雷达信号的最大距离。计算了在20世纪90年代后半期按当前计划运行的定向搜索以及MOP的巡天部分的相关数据。仅考虑了地球上最强大的发射源，即位于波多黎各阿雷西博的行星雷达以及弹道导弹预警系统（BMEWS）。在每种情况下，还计算了MOP运行期间的探测概率。该计算假设我们仅处于窃听模式。旨在被SETI系统探测到的传输信号可能要强得多，当然在更大范围内被发现的概率也会更高。此外，假设发射文明的技术发展水平与地球上的我们处于同一水平。这是极不可能的。如果我们要探测到另一个技术文明，从统计学角度来看，它很可能比我们古老得多，而且很可能拥有强大得多的发射源。这两个因素都会使美国国家航空航天局的MOP更有可能探测到信号。
