Reply policy and signal type: assumptions drawn from minimal source information

A scenario is developed under which a discovery of extraterrestrial technology is made by one of the World’s search for exterrestial intelligence (SETI) programs. The nature of the signal received gives an absolute minimum of information as to the nature of the senders. Current SETI detection and reply policy is examined under these assumptions. Current policy calls for prompt and public release of signal information and stellar coordinates upon announcement of a discovery. The SETI protocol calls for no reply until authorized by international consultations. It is argued that changes are needed in these policies to guard against the possibility of unauthorized replies that could severely complicate long-term interstellar communication.     

Museums, seti and community awareness

Commentators on the social implications of detecting an extraterrestrial civilisation have stressed the need for community education and awareness during the SETI search, and for public sources of accurate, authoritative information if and when a signal is detected. Museums have a role in community education and are recognised by the community as authoritative sources of expert information. They are, therefore, well placed to be important conduits through which information on the progress of SETI programs and any signal detection can be channelled to the public. Via both exhibitions and in-house educational activities, museums are able to provide long-term community education and awareness programs and can respond quickly with detailed and accurate information in the event of a detection. This paper will consider the role of museums in educating the public about SETI. It will present suggestions for ways in which SETI researchers can develop mutually profitable relationships with museums, and also consider some of the reasons why museums might choose not to become involved with SETI, because of the wildly sensationalised and often mis-informed controversy which has surrounded it.     

Detection of antipodal signalling and its application to wideband SETI

The SETI community is becoming increasingly interested in extending its searches to include wideband signals, such as information-bearing beacons. However, prior to discovery of a target signal, a SETI receiver has no knowledge of the signal parameters (bandwidth, carrier frequency, modulation type, etc.) and so detection can be very challenging, especially at low signal-to-noise ratios. However, this paper shows by example that there exist signal classes and corresponding detection methods that permit straightforward discovery of wideband signals of unknown structure. The example given is a form of binary antipodal signalling that utilises spread-spectrum modulation, which offers benefits to the receiver in terms of immunity to noise/interference and ease of detection. The proposed detection method is a ‘symbol-wise’ autocorrelation process that takes advantage of the cyclostationarity property of modulated signals. Detection sensitivity is suboptimal in comparison with what is possible if the target signal structure is known. However, this deficit can be overcome by processing longer timespans of signal, providing scope for detection at extremely low signal-to-noise ratios. It is postulated that antipodal signalling represents an attractive option for interstellar beacons because it is both power efficient and there exists a simple complementary detection method not requiring explicit coordination between the transmitter and receiver. This in turn suggests there is a case for extending future SETI searches to include this class of signal.     

Analysis of a crossed Bragg cell acousto-optical spectrometer for SETI

The search for radio signals from extraterrestrial intelligent beings (SETI) requires the use of large instantaneous bandwidth (500 MHz) and high resolution (20 Hz) spectrometers. Digital systems with a high degree of modularity can be used to provide this capability, and this method has been widely discussed. Another technique for meeting the SETI requirement is to use a crossed Bragg cell spectrometer as described by Psaltis and Casasent. This technique makes use of the Folded Spectrum concept, introduced by Thomas. The Folded Spectrum is a 2-D Fourier Transform of a raster scanned 1-D signal. It is directly related to the long 1-D spectrum of the original signal and is ideally suited for optical signal processing. The folded spectrum technique has received little attention to date, primarily because early systems made use of photographic film which are unsuitable for the real time data analysis and voluminous data requirements of SETI. An analysis of the crossed Bragg cell spectrometer is presented as a method to achieve the spectral processing requirements for SETI. Systematic noise contributions unique to the Bragg cell system will be discussed.     

Frequency management and SETI: threats to SETI observations in the 1–3 GHz band

The nature of a SETI search makes observations uniquely vulnerable to radio frequency interference because the frequency of a possible ETI signal is unknown. Sensitive radio telescopes, sophisticated software and enhanced signal detection equipment are employed to detect faint signals in the 1–3 GHz frequency range. Frequency management at SETI occurs within a policy environment of the ITU spectrum allocation process. Increased demand by commercial satellite services for access to spectrum adjacent to bandwidth allocated to radio astronomy creates severe international and domestic pressures on SETI observations. Strategies for addressing the RFI problem at the international level will be discussed that include a contingency ITU allocation plan for exclusive use of a particular frequency range by SETI in the event a signal is detected. The lunar farside is, by international agreement, a radio quiet zone for use by radio astronomers. Protected from most human-generated emissions, a SETI radio telescope array on the lunar farside would provide reliable data with minimum interference.     

A new 6 MHz 128.000 channel spectrum analyzer

We present an FFT-based digital spectrometer designed for SETI and Radioastronomy applications. In the typical configuration, the system is capable of supplying the spectrum of the received signal every 28.8 ms, for a maximum 128 K (131,072) frequency bins at an input bandwidth of 6 MHz.     

Security considerations in signal detection

This paper maintains that international security considerations are likely to present major problems to the community of scientists who first confirm the existence of an extraterrestrial technology. The discussion focuses on those activities that will affect the SETI community should a detection be made. It is probable that security agencies will require official debriefings, signal monitoring, some forms of information management, and a voice in science policy with regard to reply. The SETI community has, in the past, underestimated the constraints that are likely to be placed upon them in the post-detection environment. Such constraints present major problems for the scientific community. Response to these constraints should be discussed prior to detection.     

ILD智能交通流量测试仪

介绍一种交通流量测试仪，它具有高灵敏度、高信噪比、传输距离远，可以准确地测量机动车、自行车流量，且成本低。由于该仪器设置了驱动变送器，采用了一种新的传输结构，引入了微机技术，模式识别等技术，从而研制出性能稳定、操作方便、实用性强且具有国际先进水平的道路交通流量测试装置。     

A search for narrow band signals with SERENDIP II: a progress report

Commensal programs for the Search for Extraterrestrial Intelligence (SETI), carried out concurrently with conventional radio astronomical observing programs, can be an attractive and cost-effective means of exploring the large multidimensional search space intrinsic to this effort. Our automated commensal system, SERENDIP II, is a high resolution 131,072 channel spectrometer. It searches for 0.49 Hz signals in sequential 64,700 Hz bands of the IF signal from a radio telescope being used for an astronomical observation. Upon detection of a narrow band signal with power above a preset threshold, the frequency, power, time, and telescope direction are recorded for later study. The system has been tested at the Hat Creek Radio Astronomy Observatory 85 ft telescope and the NASA-JPL Deep Space Station (DSS 14) 64 m telescope. It is currently collecting data at the National Radio Astronomy Observatory 300 ft telescope.     

Positive consequences of SETI before detection

Even before a signal is detected, six positive consequences will result from the scientific search for extraterrestrial intelligence, usually called SETI. (1) Humanity’s self-image: SETI has enlarged our view of ourselves and enhanced our sense of meaning. Increasingly, we feel a kinship with the civilizations whose signals we are trying to detect. (2) A fresh perspective: SETI forces us to think about how extraterrestrials might perceive us. This gives us a fresh perspective on our society’s values, priorities, laws and foibles. (3) Questions: SETI is stimulating thought and discussion about several fundamental questions. (4) Education: some broad-gage educational programs have already been centered around SETI. (5) Tangible spin-offs: in addition to providing jobs for some people, SETI provides various spin-offs, such as search methods, computer software, data, and international scientific cooperation. (6) Future scenarios: SETI will increasingly stimulate us to think carefully about possible detection scenarios and their consequences, about our reply, and generally about the role of extraterrestrial communication in our long-term future. Such thinking leads, in turn, to fresh perspectives on the SETI enterprise itself.     

A SETI metapolicy: New directions towards comprehensive policies concerning the detection of extraterrestrial intelligence

At present we have only one agreed public policy for handling the detection of an extraterrestrial intelligence (ETI), the ‘First SETI Protocol’ of 1989, which guides action in the immediate aftermath of detection, even though SETI (the Search for Extraterrestrial Intelligence) constitutes an active search for such a detection. The purpose of this paper is to set out areas in which policies might fruitfully be developed, including reviewing the rationale and investment in SETI, handling ETI artefacts, and approaches to direct contact. ‘Negative’ possibilities will be examined, for example, whether an ETI artefact or data should be purposefully destroyed.     

Short-pulse SETI

While most optical SETI experiments are configured to detect nanosecond pulses, the majority of their counterpart radio searches integrate for seconds to minutes, looking for unchanging narrow-band carriers or slowly pulsed modulation. The former approach is suggested as an effective way to stand out against stellar photon noise, while the latter approach is dictated by the dispersive effects of the interstellar medium as well as the high visibility of narrow-band signal components.In this paper, we consider effective signal strategies for those that produce, rather than simply search for, optical and radio beacons—signals that are designed to elicit responses from technological civilizations. By considering the communication problem from the point of view of the transmitters, rather than the receivers, we deduce some likely signal characteristics for beacons, and concommitant new strategies for SETI.     

The art and science of interstellar message composition: a report on international workshops to encourage multidisciplinary discussion

Throughout the history of the Search for Extraterrestrial Intelligence (SETI), there has been widespread recognition of the profound societal implications of detecting intelligence beyond Earth. At the SETI Institute, interstellar message construction serves as the focus of a multidisciplinary attempt to prepare for the cultural impact of signal detection and the critical events that would follow. Interstellar message construction at the SETI Institute builds upon the recommendations of the 1991–1992 Workshops on the Cultural Aspects of SETI, while also exploring opportunities for multidisciplinary contributions on new topics. Through a series of international workshops in Toulouse, Paris, Zagreb, Washington, and Bremen, the SETI Institute and partner organizations have fostered broad-based discussion about some of the most important decisions that would follow detection of extraterrestrial intelligence, including “should we reply?” and if so, “what should we say, and how might we say it?”. Several of the themes addressed at these workshops will be highlighted, including the relationship between art and science in designing messages, the value of interactive messages, and the importance of better understanding the nature of language.     

Studies of radio frequency interference at Parkes Observatory

During 16 weeks of continuous SETI observing at the Parkes Observatory in New South Wales, Australia, a set of time-averaged data with 643 Hz resolution were recorded and returned to the SETI Institute for post-processing. These data are the 14 second (10 frame) average powers in each of 15,552 “subband” channels covering 10 MHz of the spectrum in both right and left circular polarizations that were used by the signal detection hardware to baseline and threshold the 1 Hz high resolution SETI spectra. The observations covered frequencies from 1.2 to 3 GHz, tracking 209 stellar targets across the sky. The data at each frequency were averaged over all directions and then interrogated to attempt to determine the prevalence of radio frequency interference (RFI). Estimates were made for the probability of encountering RFI at a particular frequency. Particular attention has been paid to those portions of the spectrum that are allocated as primary use status, or footnote protection for radioastronomy. This sixteen-week snapshot of the RFI situation at Parkes is by now out of date. Unfortunately, a year later, the situation has undoubtedly worsened.     

基于Spartan-6的微结构探测器APV25数字化系统设计

为满足微结构气体探测器多通道信号高速读出的需求,文章基于现场可编程门阵列(FPGA)Spartan-6设计了128通道前置放大芯片APV25的数字化系统。该系统中,APV25输出的串行模拟信号经模/数转换芯片ADS5242进行模/数转换,由Spartan-6接收、解串、缓冲和打包后,经千兆以太网传送至计算机进行存储和分析。经测试,该系统可实现APV25的最大采样速率280 k Hz,基线噪声低至716 e-。输入电荷量低于75 000 e-时,电荷响应线性良好。由于APV25的抗辐射特性,该系统有望用于空间多通道辐射探测系统。     

Who are the SETI sceptics?

Search for ExtraTerrestrial Intelligence (SETI) is now more than half a century old and has provoked enough discussion on technical, philosophical, and popular level, much of it critical. Historically, the criticism of SETI has been strong enough to heavily influence the course of research, so that there is a significant interest in discerning the nuances and fine points of critical argumentation. In this paper, I outline the two major forms of SETI scepticism, “fundamentalist” and “instrumentalist,” which are often conflated in the published literature, both technical and popular. Precise delineation between these two types of scepticism is important for future research as a part of a wider taxonomic project, the build-up of SETI theory, as well as for smooth joining of SETI with the ongoing astrobiological revolution. Resolving the confusion in this respect is likely to lead to an improved atmosphere and heightened public image of future SETI searches and related activities.     

SAR高速实时信号处理系统设计

合成孔径雷达回波数据速率一般高达3GSPS,如何采集、存储、压缩、传输如此高速率的数据成为一个难点。文章在分析了SAR回波数据特点的基础上,设计并实现了一个SAR高速实时信号处理系统。该系统以FP-GA为核心处理器、ADC08D1500为高性能的AD采集芯片、DDR_SDRAM为数据存储器、TLK2711为数据传输芯片。实验结果表明：本文设计的高速实时信号处理系统性能良好,能够很好地实时处理高速率的SAR回波数据。同时该系统易于实现,具有较强的实用性。     

基于TM1300的AC-3定点解码算法的设计与优化

TM1300 是专为处理高质量的视频、音频数据而开发的高效多媒体处理器.本文主要介绍了AC-3音频解码算法在TM1300上的设计及优化.     

基于TM1300的AC-3定点解码算法的设计与优化

TM1300是专为处理高质量的视频、音频数据而开发的高效多媒体处理器。本文主要介绍了AC-3音频解码算法在TM1300上的设计及优化。