“SERENDIP Takes a Great Leap Forward”的版本间差异

2010年8月3日 (二) 20:59的最新版本

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SERENDIP 大跃进之5

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-<big>'''SERENDIP Takes a Great Leap Forward'''</big>
+#redirect [[SERENDIP 大跃进之5]]
-''来自 '''The Planetary Report'''，2009年5月26月''
-'''作者：[[Amir Alexander]]'''
-<资料来源：[http://www.planetary.org/programs/projects/setiathome/setiathome_20090526.html The Planetary Society]>
-[[Image:Arecibo_platform.jpg|right|thumb|220px|'''Arecibo Antenna Platform'''<br>
-'''阿雷西博的天线系统'''<br>
-The Gregorian dome at Arecibo, which houses the the ALFA multi-beam receiver for which SERENDIP will draw its data. Credit: Arecibo Observatory<br>
-阿雷西博的格利高里圆顶，装置着为 SERENDIP 收集数据的 ALFA multi-beam 接收器。来自：阿雷西博天文台]]
-Just when SETI@home is celebrating its [http://planetary.org/news/2009/0521_SETIhome_Celebrates_10_Years_of.html 10th anniversary], its older brother, [http://www.planetary.org/programs/projects/search_for_extraterrestrial_life/seti_radio_searches/facts.html Project SERENDIP], is getting a general makeover. In June of 2009 Dan Werthimer will lead a group of 8 students to the Arecibo Observatory in Puerto Rico to replace the aging SERENDIP IV system which has been idle for the past two years. Once the brand new state-of-the-art SERENDIP V is in place, the project will go back online and return to searching the skies for a signal from an alien civilization.
- 正当 [[SETI@home]] 在[http://planetary.org/news/2009/0521_SETIhome_Celebrates_10_Years_of.html 庆祝10周年之际]，其同胞项目 [http://www.planetary.org/programs/projects/search_for_extraterrestrial_life/seti_radio_searches/facts.html SERENDIP] 也准备大改造。2009年6月 Dan Werthimer 将带领一组8个学生到波多黎各的阿雷西博天文台，更换闲置了两年已经老化的 SERENDIP IV 系统，升级到 SERENDIP V，该项目将恢复运作并继续搜索天空中的外星文明信号。
-If [http://www.planetary.org/programs/projects/setiathome/ SETI@home] is now a respectable 10 years old, Project SERENDIP's roots go back much further. The first SERENDIP was built at U.C. Berkeley in 1979, and collected data from the radio telescope at the Hat creek Observatory in California. Since then the project's hardware has been upgraded repeatedly: In 1992 SERENDIP's 3d generation was installed at the Arecibo radio telescope, the largest and most sensitive in the world. Five years later, with help from The Planetary Society, this system was replaced at Arecibo by SERENDIP IV, which continued in operation for the next 8 years. And now SERENDIP V is set to take over and continue a long and persistent search that began three decades ago.
- 如果说 SETI@home 现在算是有体面的到10岁了，SERENDIP 项目的则可以追溯到更早，最初的 SERENDIP 建于1979年在伯克利分校，收集来源于加利福尼亚州的红帽溪天文台射电望远镜的数据。自那起项目硬件已升级多次：1992年 SREENDIP 第三代安装在世界上最大最灵敏的阿雷西博望远镜上了。5年后，在行星协会的帮助下，这套系统升级到了 SERENDIP IV，服役于之后的8年。现在 SERENDIP V 将接管过来并继续始于30年前的搜索。
-As SERENDIP was upgraded repeatedly over the years, each new generation represented a quantum leap over the capabilities of its predecessor. SERENDIP I, for example, could look at 100 channels at a time, which seemed pretty impressive back in 1979. But its successor, which began operations in 1986, could look at 65,000 channels at a time, and with SERENDIP IV the number was up to 168 million! Such exponential growth is unheard of in most scientific fields, but is not unusual in SETI, which is always on the lookout for new cutting-edge technologies for scanning the skies.
- 这么多年来 SERENDIP 的硬件升级，每次新的继任都比前身的能力有质的飞跃。例如 SERENDIP I，它可以同时观察100个频道，这在1979年是很令人振奋的，而到了1986年它的继任者已经可以同时观察65,000个频道，SERENDIP IV 的能力已经升级到了同时观察 1.68亿个频道！这种指数性的增长在尖端科学领域是从未听到过的，但 SETI@home 并非寻常，因为它一直在寻找最尖端的技术用于扫描天空。
-When Dan Werthimer and David Anderson [http://www.planetary.org/programs/projects/innovative_technologies/setiathome/story_of_setiathome.html launched SETI@home in 1999], SERENDIP had already been in operation for two decades. At Arecibo it had its own dedicated radio feed, used exclusively for SETI purposes. This arrangement suited SETI@home very well, and the new project took full advantage of the infrastructure that was already in place for SERENDIP. For several years the two projects shared the same radio feed and analyzed the same data from space – each in its own distinct way. Finally in 2005 they parted ways, when SETI@home was adapted to the [http://www.planetary.org/programs/projects/innovative_technologies/setiathome/setiathome_20060814.html new multi-beam ALFA receiver] whereas SERENDIP continued to operate with its own dedicated radio feed.
- 当 Dan Werthimer 和 David Anderson 在1999年启动 SETI@home 的时候，SERENDIP 已经运作了20年了。它在阿雷西博有自己专属的无线电数据，专门用于搜寻地位文明。这套装置非常适合 SETI@home，并且充分利用了已经到位的 SERENDIP 基础设施。随之的几年来，这两个项目用它们各自不同的方式从太空中共享并分析着相同的无线电数据。最后在2005年他们分道扬镳了，SETI@home 改进适合了新的 multi-beam ALFA 接收器，而 SERENDIP 则继续使用原有的无线电源。
-SETI@home and SERENDIP are sibling SETI projects, run by the same team from U.C. Berkeley and sharing much of the same history. Conceptually however, they are very different – and complementary. Simply put, whereas SETI@home conducts an exquisitely sensitive search of a relatively narrow band of frequencies, SERENDIP conduct a rougher search of a much broader band.
- SETI@home 和 SERENDIP 同属于 SETI 项目，是由加州伯克利大学分校同一个团队运营而且有着许多相同的历史。然而概念上它们有着很大的不同并互为补充。简而言之，SETI@home 处理相对敏感的窄带频率信号，而 SERENDIP 则进行较为粗糙的更广域的频带。
-As Werthimer likes to put it, every SETI search tries to optimize four factors: Sky coverage, spectrum coverage, sensitivity, and signal types. For three of these parameters, SETI@home is outstanding: the ALFA multi-beam receiver, from which it draws its data, conducts regular and complete surveys of the entire sky visible from Arecibo. Thanks to the unmatched computing power of its world-wide network of personal computers SETI@home is by far the most sensitive search ever attempted, and is capable of scanning the data for a broad range of signal-types. But the last parameter, spectrum coverage, is SETI@home's weak point: All the data, so exquisitely analyzed, is drawn from a band only 2.5 Megahertz wide around the hydrogen line of 1420 Megahertz. If the aliens are transmitting at any frequency outside this band, SETI@home, for all its power and sophistication, will never hear them.
- 用 Werthimer 的话来说，每个 SETI 搜索都试图从这4个方面上进行优化：天空的覆盖范围，频谱范围，灵敏度和信号类型。对于其中的3个方面，SETI@home 做得非常出色，ALFA multi-beam 接收器从阿雷西博对整个可见天空定期的进行全面的测量并汲取数据。同时感谢于全球范围的个人电脑，他们提供了无与伦比的计算能力，使 SETI@home 可以尝试最灵敏的检索，并且能够广阔的范围扫描不同的信号类型。但是，最后1个方面：频谱范围，这是 SETI@home 的薄弱环节，所有如此精确分析的数据都是来自 2.5Mhz 到 1420 Mhz 的全氢线范围。如果地外文明所传输的信号在此范围之外，那么我们将永远不会听到他们的声音。
-[[Image:SERENDIP_5_lg.jpg|center|thumb|512px|'''SERENDIP V'''<br>
-The SERENDIP V SETI spectrometer will be installed at the Arecibo Observatory in June, 2009. Once fully operational it will increase the spectrum coverage of the SERENDIP search by a factor of 6. Credit: Dan Werthimer/U.C. Berkeley<br>
-这套 SERENDIP V SETI 光谱仪将于2009年6月安装到阿雷西博天文台。一旦全面运作将提升 SERENDIP 搜索的频谱覆盖系数至6。来自：Dan Werthimer/U.C.伯克利]]
-Judged by the same standard, SERENDIP appears to be the reverse of SETI@home. The sky-coverage of the two searches is comparable, since in the early years of SETI@home they used the same receiver at Arecibo, and will do so again when the new version is installed in June. But the older project does not have the enormous computing resources of the SETI@home network, and therefore can never hope to equal its sensitivity or its range of signal types. What SERENDIP does offer is excellent spectrum coverage: SERENDIP IV could instantaneously cover a band of 100 Megahertz around the hydrogen, and with SERENDIP V this band will be increased to 300 Megahertz. That is 120 times wider than the band covered by SETI@home.
- 鉴于相同的标准，SERENDIP 似乎相反于 SETI@home。在最初的几年，他们的天空覆盖范围是可比的，都使用阿雷西博相同的接收器，但6月份新设备安装好了，他们将再次如此。但是 SERENDIP 并不具备 SETI@home 网络的巨大计算资源，因此不能希望会达到同样水平的灵敏度和信号类型的范围。那 SERENDIP 提供了什么优良的频谱范围：SERENDIP IV 能即时覆盖氢元素范围100Mhz的波段，而 SERENDIP V 将提升至 300Mhz。这是 SETI@home 所覆盖的波段的120倍。
-To accomplish this, SERENDIP operates very differently from its sibling project. It does not record all the data received in the manner of SETI@home, and then send it on for future analysis. Doing so for such a broad band would require recording hundreds of millions of data points each and every second, which is simply too much data for storage and systematic analysis. Instead, SERENDIP scans the signal from the radio telescope in real time, right when it comes down from the receiver. Most of the data SERENDIP lets pass unrecorded, and it is forever lost. But if the signal strength at a particular frequency stands out sufficiently above the background noise, the system records it and saves it for future analysis. How often this happens depends on the system's sensitivity threshold, which Werthimer and his team set in advance. In practice this comes to about a 100 recorded signals every second and while this may still sound impressive, it is a lot fewer than the hundreds of millions of data points that are discarded at the same time.
- 要做到这一点，SERENDIP 的运作非常不同于其同胞项目。它并不像 SETI@home 那样记录所有接收的数据在未来进行分析。如果这么做，在宽频带上每秒都将需要记录数以亿计的数据点，这实在是需要太多的数据存储和系统分析。相反的，SERENDIP 实时的从射电望远镜扫描信号，当信号失衡的时候从接收器中纠正。SERENDIP 允许绝大部分未录入的数据通过，并且永远抛弃。但是，当信号强度在某一特定频率的背景噪音中足够清晰的凸显出来时，系统将记录并保存这些数据供将来分析。这取决于该系统的灵敏度阀值，如果经常出现这种情况，Wethimer 和他的团队会提高阀值。在实践中，大约每秒会记录100个可能会令人振奋的信号，但于同一时间会有数以百万计的数据被抛弃。
-This, however, is only the beginning of the detection process. The tapes with the recorded signals are then packed up and sent to the SERENDIP team in Berkeley, with an additional copy going to colleagues at Cornell University in Ithaca, New York. Each group then uses complex algorithms to analyze the signals that stood out above the background noise. The algorithms take into account the strength of each signal, the location in the sky that it came from, and whether there is a star, or possibly a known planet, in that direction. Finally they look to see whether a signal had previously been received from the same direction, since a persistent signals is far more promising than a one-time flash in the pan. Any of these features, or a combination of them, could indicate that an innocent looking signal is in fact an intelligent transmission.
- 然而，这仅仅是最初的检测过程。磁带会记录这些信号并递交给伯克利分校的 SERENDIP 团队，同时一个副本会发送给纽约伊萨卡的康奈尔大学团队。每个团队都会对这些在背景噪音中脱颖而出的信号使用复杂的算法进行分析。这些算法会考虑到每个信号的强度，来自于天空中的地点是否伴有一颗恒星，或者是否直接是已知的行星。最后他们希望看到一个信号在同一个方向中是否曾被接收过，因为持续的信号比起昙花一现的信号更有希望。任何一个这些特征或者它们的组合都可能显示出一个无害的信号是来自于一个文明。
-Like every previous generation of the project, SERENDIP V represents a giant step forward over its predecessors. First and foremost, the new system improves on what has always been the project's greatest strength – spectrum coverage. In the first stage, SERENDIP V will cover a band of 200 Megahertz on both sides of the hydrogen line – double the bandwidth of the older system. In reality the improvement is actually fourfold, because the new system will search for a signal in two polarizations, whereas the older system only searched one. At some point in the future the spectrum coverage will be increased to 300 Megahertz at two polarizations, which is six times the older capabilities.
- 如同项目的所有上一代，SERENDIP V 代表着比前任有着一个巨大的进步。首先，新系统进一步提升了项目一直以来最大的优势 - 频谱覆盖。在第一阶段，SERENDIP V 将涵盖氢元素波段 200Mhz 的频率范围 - 这是于旧系统双倍的带宽。而实际中这是提高了4倍。因为新的系统将同时搜寻两个偏振信号，而旧系统只能搜寻一个。在未来的某个时间，频谱范围将增至300Mhz于两个偏振信号，这将是6倍能力的提升。
-[[Image:Alfa installed.jpg|right|thumb|220px|'''The Arecibo Multi-Beam Receiver'''<br>
-'''阿雷西博的 Multi-Beam 接收器'''<br>
-The multi-beam in its place inside the Gregorian dome, 500 feet above the Arecibo dish. Credit: Courtesy of the NAIC - Arecibo Observatory, an NSF facility.<br>
-接收器安装在距阿雷西博碟盘500尺高的格利高里圆顶上。来自：康翠斯全美保险总监协会 - 阿雷西博天文台，美国国家科学基金会设施。]]
-The increased bandwidth will enable SERENDIP V to listen to the entire spectrum of the Arecibo receiver that will be collecting its data. This is the ALFA multi-beam receiver, the very same one used by SETI@home since 2006. ALFA is a modern receiver with excellent sensitivity and a broad spectrum, but it also has this unique feature: Unlike an ordinary receiver, which collects data from one point in the sky at a time, ALFA's seven beams point to seven locations simultaneously, and listening to all of them. This unique feature enables ALFA to cover the sky much faster and more efficiently than traditional receivers, and makes it and ideal instrument for the sky surveys conducted by SERENDIP and SETI@home.
- 提高了带宽将是 SERENDIP V 有足够能力聆听阿雷西博接收器说接收的数据的整个频谱。右边的是 ALFA multi-beam 接收器，这是 SETI@home 自2006年以来所使用的同样的一个。ALFA 是具有优良灵敏度和广域频段的现代接收器，但它也有这样的独特功能：ALFA 的7个束点可以同时对7目标同时进行聆听，这不同于普通的接收器一次只能在一个天空目标进行数据收集。这个独特的功能可以让 ALFA 比传统的接收器更快更有效的对天空进行扫描，并成为 SERENDIP 和 SETI@home 对天空检测的理想手段。
-SERENDIP and SETI@home are sibling projects, representing different but complementary approaches to the search for an alien signal. If, as many SETI researchers believe, a far-away civilization is broadcasting at the magical frequency of the hydrogen line, then their signal will most likely be picked by SETI@home. No other search can approach SETI@home's sensitivity, which is made possible by its global network of computers. But if the aliens, for their own reasons, are broadcasting at a different frequency, then their call is more likely to be heard by SERENDIP, listening to its entire broad band.
- SERENDIP 和 SETI@home 是同胞项目，代表着在搜寻地外文明信号中采用不同但互为补充的方法。如果，如许多 SETI 研究人员认为，一个远离地球的文明是在氢元素频线上进行着广播，那么其信号极有可能被 SETI@home 汲取出来。因为没有其他办法可以达到 SETI@home 的敏感度，这能力来源于全球的计算机网络。但是，如果地外文明由于自身的原因，在其他的频率上进行广播，那么他们更可能被聆听于整个宽域带宽的 SERENDIP 听到。
-Which approach is the right one for SETI? Undoubtedly both: since we have no way of knowing in what form that elusive signal will come, SETI scientists agree that we should cover as many possibilities as possible. Which system is more likely to detect a true signal from aliens? Only time will tell.
- 在 SETI 中哪种做法才是正确呢？毫无疑问他们都是！因为我们没办法知道这些难以触摸的信号会以什么形式出现，SETI 的科学家们认为我们应该涵盖尽可能多的情况。至于哪个系统更可能发现真正的地外文明信号？那只有时间能告诉我们答案。
-==相关链接==
-*[[SETI]]
-*[[SETI@home]]
-*[http://setiathome.ssl.berkeley.edu/ SETI@home 官方网站]
-[[Category:SETI@home 相关文献]][[Category:文献翻译]][[Category:待翻译]]

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