Project Cyclops, A Design... - Department of Earth and Planetary ...

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un about $225/kW. We will assume $300 to allow for buried services. Roughly, then, the total power system capacity and cost will be as given in Table 10-6. The power plant should probably be designed at the outset to handle the ultimate needs, since on-site construction would raise the power consumption during this phase. TABLE 10.6 Power, MW Number of 100-m Equivalent Cost, antennas aperture, km Peak Average $ Million 100 1 4 2.2 2.4 200 1.4 7 3.4 4.2 500 2.2 16 7 10 1000 3.16 31 12 20 2000 4.4 61 25 36 122
11. SIGNAL PROCESSING The Cyclops system as it has been specified in the last three chapters amounts to a very large radio telescope with an effective clear aperture of a few kilometers, capable of simultaneous reception of both orthogonal polarizations of a received signal over a I O0-MHz band. The received band can be quickly tuned anywhere in the low end of the microwave window and, if desired, could be extended to higher frequencies in that window. The system up to this point is a very high resolution, high sensitivity instrument that would find many applications in radio astronomy, radar astronomy, and space probe communications. Each of these applications would require further processing of the signals delivered by the phased outputs of the array. Much of this processing would use standard equipment and techniques peculiar to the application involved. These will not be discussed here. This chapter is primarily concerned with the signal processing techniques and equipment needed to allow the Cyclops system to carry out efficiently its primary mission of detecting signals originated by other intelligent life-spectrally narrow band information-bearing signals. A second concern of this chapter is the techniques and equipment needed to form wide band images of the radio sky, and thereby greatly speed the construction of detailed maps of natural sources. The chapter concludes with a discussion of interfering signals the Cyclops system must contend with and what might be done about these. THE DETECTION OF NARROW BAND SIGNALS We concluded in Chapter 6 that signals of intelligent origin, and particularly signals from intentional beacons, were most likely to contain strong, highly monochromatic components. We saw that these coherent components would probably be best detected using a receiver having a predetection bandwidth on the order of 0.1 to 1 Hz, but that to search sequentially across the spectrum with such a narrow band receiver would result in prohibitively long search times per star. What we are seeking, therefore, is a receiver with some 108 to 109 channels each 1 or 0.1 Hz wide so that we can monitor the entire 100-MHz IF band simultaneously. In this section, we describe such a receiver, but before doing so we will dispose of some alternative methods that have been proposed. Total Power Detection In principle we do not need to divide the spectrum into narrow channels to detect the increase in total power in the IF band produced by a coherent signal in one (or more) channels. All we need to do is to integrate for a long enough time to be able to measure the increase over the noise power alone that is produced by the signal. A little reflection shows that, while possible in principle, such an approach is totally impractical. Suppose there is a coherent signal that doubles the noise power in a 1 Hz band. This produces an increase of 1 part in l0 s in the total noise in a 100 MHz band. To detect such a tiny increase would require integrating 101_ samples of the wide band noise. (See e.g., equations (8) (9) and (10) Chap. 6). This is an integration time of 10 s seconds or roughly 3 years. Even accepting this time, the method fails, for we cannot assume we know the noise bandwidth to this accuracy nor that it is this constant, nor that the system noise temperature is this constant, nor even that the radio sky is this constant. Cross Power Detection Simpson and Omura I have proposed that, instead of a simple noise power measurement, a measurement of =NASA unpublished report, 1970. 123
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(NASA-CR- 11_5) PROJECT CYCLOPS: A
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CR 114445 Available to the public A
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At this very minute, with almost ab
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ACKNOWLEDGMENTS The Cyclops study w
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COMMUNICATION BY ELECTROMAGNETIC WA
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APPENDIX A - Astronomical Data ....
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t _ 2
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of the living beings evolved by the
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Figure2-1. M3I,the great galaxy in
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self.Thus,wecaninterpretFigure2-2as
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magnitude (low brightness) end, the
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Red Giant. The transition from main
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tion, as the central part of the cl
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TABLE 2-4 SELECTED NEARBY STARS WIT
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tideraisingforcesasr--_ where ,v =
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3. Is it possible that living syste
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lawsof natural selection, more like
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starsthroughout the Galaxyhave also
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if the longevity of that life is ty
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The imaginative reader will have no
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Lookingfar ahead,supposewe aresucce
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usuallyterritorial expansion by the
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IOO IO 1 [ [ J [ J I J i [ i I i I
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order with what Morrison has descri
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The quantity gtPt is often called t
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which might result from synchronous
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1. Wewillnothavenough resolving pow
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normalwith the meanat o x/--2. When
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Chapter11 in analyzingthe dataproce
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Therangelimitisthenfoundbyequating_
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TABLE 5-3 PARAMETER Wavelength Tran
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angeanddirectlyasthesquareof antenn
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"_ i i i i i p = STELLAR DENSITY AT
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I-- g u. O >- I--- .d tit (]O 0 0.
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andwidth that will still give near
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acquisitionphasefor otherraces.Supp
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1. They would transmit continuously
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and ¢-Ceti. No signals were detect
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vz .i g)mo PAGE NOr Ir[[,MZ 7. THE
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The price of incomplete sky coverag
Page 83 and 84: modest size.A largedatabaseontapeor
Page 85 and 86: THEAUXILIARYOPTICALSYSTEM Althoughn
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Page 90 and 91: feeds must correct for spherical ab
Page 92 and 93: side of the dish and shade on the o
Page 94 and 95: TABLE 8-1 UNADJUSTED UNIT COST DATA
Page 96 and 97: 7. Using huge specially designed ji
Page 99 and 100: 9. THE RECEIVER SYSTEM The receiver
Page 101 and 102: whereP is the radiated power. Divid
Page 103 and 104: SHADOWED AREA SHADOWED AREA // // /
Page 105 and 106: Corrugatedhornssupportingbalancedhy
Page 107 and 108: o 50 ----- - _ T i 20 _,o 5 ,,,5 09
Page 109 and 110: TABLk ?- I A COMPARISON OF VARIOUS
Page 111 and 112: CENTRAL POINT STATION LSB LINE FREQ
Page 113 and 114: A02 .... + No (25) (i C 1 where No
Page 115 and 116: COAXIAL LINE DIRECTIONALCOUPLER FRE
Page 117 and 118: DeJager, J.T.:IEEETrans.onMicrowave
Page 119 and 120: pR_ING PA6E BLANK HOT FILMF_ 10. TR
Page 121 and 122: o-------------o_ _ o o o o ing of t
Page 123 and 124: addedto theother IF channel. The tw
Page 125 and 126: INPUT MHZ _PF 500 MHZ i : 575 T1 92
Page 127 and 128: azimuth _) has a delay (2a/c)sin 0
Page 129 and 130: stripline. For 2 _< k _< 6, appropr
Page 131 and 132: mation are common to all antennas i
Page 133: A cable pair costs about 20 cents/m
Page 137 and 138: 1.0 T t t I I r .9 -8 asynchronousl
Page 139 and 140: collimated coherent light. A simple
Page 141 and 142: power of the film and associated op
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Page 145 and 146: outputs is assumed. COMPOSITE SIGNA
Page 147 and 148: SPECTRUM I n LINES M n LINES U SPEC
Page 149 and 150: signal andyet have a tolerable fals
Page 151 and 152: i --_- i i i i large values of n. T
Page 153 and 154: plottedin Figure11-15for various va
Page 155 and 156: All the1Fsignalswillarrivein phasei
Page 157 and 158: x:(1 +x) x 2 - _ -- (53) If we wish
Page 159 and 160: 3's = unitcostof signal planelectro
Page 161 and 162: where0ma x is the maximum value of
Page 163 and 164: Roughestimates of the costs of buil
Page 165 and 166: 12. CYCLOPS AS A BEACON Although th
Page 167 and 168: 13. SEARCH STRATEGY The high direct
Page 169 and 170: distantgalaxies (oraninertialrefere
Page 171 and 172: wouldfollowtheuppermost linein Figu
Page 173 and 174: persquaredegreeof fieldwouldberequi
Page 175 and 176: starsfrom/'18 to G5 could support a
Page 177 and 178: 14. CYCLOPS AS A RESEARCH TOOL Thro
Page 179 and 180: Only a few such galaxies have been
Page 181 and 182: 15. CONCLUSIONS AND RECOMMENDATIONS
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APPENDIX A ASTRONOMICAL DATA DISTAN
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PLANETARY Planet ORBITS Semimajor S
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APPENDIX B SUPERCIVILIZATIONS AND C
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ABIOLOGICAL CIVILIZATIONS Many writ
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182
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tqOT APPENDIX C OPTIMUM DETECTION A
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to rmsnoise.Wenotethatthematchedfil
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APPENDIX D SQUARE LAW DETECTION THE
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If the output filter is very wide c
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if B/2 > T we can start instead wit
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Let us now introduce the normalized
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where h-- = expectation count of si
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APPENDIXE RESPONSE OF A GAUSSIAN FI
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APPENDIXF BASE STRUCTURES AZ-EL BAS
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ack,it shouldnotbenecessary to prov
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204
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206 i
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PAGE BLANK NOT APPENDIX H POLARIZAT
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APPENDIX I CASSEGRAINIAN GEOMETRY C
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APPENDIXJ PHASINGOFTHE LOCALOSCILLA
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APPENDIXK EFFECTOF DISPERSION IN CO
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APPENDIX L TUNNEL AND CABLE LENGTHS
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where r = "Ym/'rs- If we let o-_--o
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L-4 we see that the length of IF ca
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APPENDIX M PHASING AND TIME DELAY A
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andobtain V = 2 (Ps [! + _(Ar)] +Pn
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L" D 226
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APPENDIX N SYSTEM CALIBRATION The p
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APPENDIXO THE OPTICAL SPECTRUM ANAL
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232
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APPENDIX P LUMPED CONSTANT DELAY LI
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Thevalueofthefinalcoilonthelineis =
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APPENDIXQ CURVES OF DETECTION STATI
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I I I I LE :E oo
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APPENDIX R RADIO VISIBILITY OF NORM
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io 3 - l rlrllll I I I ]l+,ll_ I _f
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