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

More documents

Recommendations

Info

and ¢-Ceti. No signals were detected except for a couple of very exciting false alarms. The arguments for using the hydrogen line no longer seem quite so compelling. Many other spectral lines have been discovered. Nevertheless, the concept of a naturally identified frequency is a good one and should not be discarded at this time. Of all the spectral lines, the hydrogen line (1) is the strongest yet found, except for the hydroxyl line in certain regions; (2) is radiated by the most abundant element, which also happens to be element number one; and (3) lies at the low end of the microwave window where we have gravitated for other reasons. There is a real problem, however, with choosing a single natural frequency for transmission and reception. If we do both simultaneously, we jam ourselves. We would have to send half the time, which halves the probability of our being detected, and listen the other half of the time, which doubles the search time. Obviously, we cannot all choose one natural frequency for transmission and another for reception. What then is the best strategy? As we have seen, because of Doppler effects, the choice of an exact transmitted frequency does not eliminate the frequency dimension of the search; it merely reduces it greatly. To eliminate self-jamming what we are seeking is a natural interstellar contact band rather than a single frequency. This band should be many times broader than the Doppler broadening but small enough to permit simultaneous search over at least half the band. The band should contain no strong spectral lines where beacons would interfere with radio astronomy work and where reception would be interfered with by the noise of the spectral lines themselves. (These are good reasons not to choose the hydrogen line itself.) Nor should the band lie below the hydrogen line, since beacons could then interfere strongly with observations of red-shifted hydrogen lines from other galaxies. Furthermore, the unavoidable background noise rises sharply below 1400 MHz. There is one band that seems to fulfill all the requirements. It is the band from the hydrogen line (1420 MHz) to the lowest of the hydroxyl lines (1662 MHz). If we leave 10- or 20-MHz guard bands at either end, we find about 200 MHz of clear band, which is just about what we need for transmission and reception to go on simultaneously. This band is very nearly at the quietest part of our microwave window and would be at the quietest part if the H20 and O2 absorption bands were many times stronger, as they might be on a planet with an atmosphere several times as dense as that of Earth. There may be other such bands that deserve study, but surely the band lying between the resonances of the disassociation products of water is ideally situated and an uncannily poetic place for wate." based life to seek its kind. Where shall we meet? At the water hole, of course! SEMANTICS AND ANTICRYPTOGRAPHY Once a signal (just one!) that is clearly of intelligent origin is detected the acquisition phase is over, at least temporarily. We would immediately suspend the search, lock on to the signal, and apply every means at our disposal to detect and record any modulation that might be present. What form this might take we cannot predict, but only a few likely alternatives exist and it would probably not take long to discover the modulation method. We would then be faced with the problem of determining the meaning or significance of the modulation. Here we can be fairly sure of one thing: the sending race will attempt to make the job of deciphering and understanding the messages as simple and foolproof as possible. The coding will be simple, redundant, and full of clues as to how to reduce the message to clear form. Because this objective is exactly the reverse of what is wanted in cryptography, it has often been called the principle of anticryptography. No optimum method of forcing the proper initial decoding and ensuring the rapid subsequent decipherment of the message content into understandable concepts has been developed. Given the enormous disparity among races as to what might be considered obvious, no single optimum may exist. Sukhotin (ref. 4) has presented an extensive analysis of the problem. Drake 2 and Oliver (ref. 5) have suggested that the initial messages of a sequence might be pictorial, since any intelligent race would very likely have vision. They have suggested sending binary information in repeated sequences having the same length in bits. If this number of bits is the square of a prime number p, the rearrangement of the message into a raster of p lines of length p is strongly suggested, whereupon the received pulses form a picture. If the picture has a "frame," that is, a complete border of pulses, there will be two long rows of pulses representing two opposite sides (such as the top and bottom) and repeated pairs of pulses at the same separation indicating the other two sides. This structure alone would suggest a raster without resorting to prime numbers. Once the receiving race has cracked the code into pictures, the way is cleared for a series of "primer" messages that can convey a great deal of information in 2Private communication to the Order of the Dolphin, Dec. 12, 1961. 64
themselves aswellasdefinesymbolsto beusedlater. Instructionsas to how to respondto the beacon messages wouldalmostcertainlybeincluded.A year's worth of suchmessages wouldprobablyconsistof interspersed primer, intermediate andadvanced messages muchlikeayearspentinaoneroomelementary school withallgrades inoneroom. Thepossibilities areendlessanddifficultto predict. Thetendency to beanthropocentric in thought isvery strongin thisarea.However, theredoesnotseemto be anygreatdifficultyassociated withthesemantics problem.Comparedwiththeacquisitionproblemallelseis easy.Acquisitionof thefirstsignal isthebighurdleand thecentral problemof interstellar communication. REFERENCES 1. Allen,C.W.:Astrophysical Quantities, OxfordUniv. Press, N.Y.,1963. 2. Elvius,T.: Distribution of Common Stars in High Latitudes, in Galactic Structure, S. Blaauw and M. Schmidt, eds., University of Chicago Press, 1965, p. 484. 3. Cocconi, G.; and Morrison, P.: Nature, Sept. 19, 1959, 184, 4690, (844-846). 4. Sukhotin, B.V.: Chapter IV, Extraterrestrial Civilizations, S.A. Kaplan ed., NASA TT F-631, 1971. 5. Oliver, B.M.: Radio Search for Distant Races. Int. Science and Technology, Oct. 1962 (p. 59). 65
Page 1 and 2:
(NASA-CR- 11_5) PROJECT CYCLOPS: A
Page 3 and 4:
CR 114445 Available to the public A
Page 6 and 7:
At this very minute, with almost ab
Page 8 and 9:
ACKNOWLEDGMENTS The Cyclops study w
Page 10 and 11:
COMMUNICATION BY ELECTROMAGNETIC WA
Page 12 and 13:
APPENDIX A - Astronomical Data ....
Page 14 and 15:
t _ 2
Page 16 and 17:
of the living beings evolved by the
Page 18 and 19:
Figure2-1. M3I,the great galaxy in
Page 20 and 21:
self.Thus,wecaninterpretFigure2-2as
Page 22 and 23:
magnitude (low brightness) end, the
Page 24 and 25:
Red Giant. The transition from main
Page 26 and 27: tion, as the central part of the cl
Page 28 and 29: TABLE 2-4 SELECTED NEARBY STARS WIT
Page 30 and 31: tideraisingforcesasr--_ where ,v =
Page 32 and 33: 3. Is it possible that living syste
Page 34 and 35: lawsof natural selection, more like
Page 36 and 37: starsthroughout the Galaxyhave also
Page 38 and 39: if the longevity of that life is ty
Page 40 and 41: The imaginative reader will have no
Page 42 and 43: Lookingfar ahead,supposewe aresucce
Page 44 and 45: usuallyterritorial expansion by the
Page 46 and 47: IOO IO 1 [ [ J [ J I J i [ i I i I
Page 48 and 49: order with what Morrison has descri
Page 50 and 51: The quantity gtPt is often called t
Page 52 and 53: which might result from synchronous
Page 54 and 55: 1. Wewillnothavenough resolving pow
Page 56 and 57: normalwith the meanat o x/--2. When
Page 58 and 59: Chapter11 in analyzingthe dataproce
Page 60 and 61: Therangelimitisthenfoundbyequating_
Page 62 and 63: TABLE 5-3 PARAMETER Wavelength Tran
Page 64 and 65: angeanddirectlyasthesquareof antenn
Page 66 and 67: "_ i i i i i p = STELLAR DENSITY AT
Page 68 and 69: I-- g u. O >- I--- .d tit (]O 0 0.
Page 70 and 71: andwidth that will still give near
Page 72 and 73: acquisitionphasefor otherraces.Supp
Page 74 and 75: 1. They would transmit continuously
Page 79 and 80: vz .i g)mo PAGE NOr Ir[[,MZ 7. THE
Page 81 and 82: The price of incomplete sky coverag
Page 83 and 84: modest size.A largedatabaseontapeor
Page 85 and 86: THEAUXILIARYOPTICALSYSTEM Althoughn
Page 88 and 89: edetectedat 20,000light-years byCyc
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 and 134:
A cable pair costs about 20 cents/m
Page 135 and 136:
11. SIGNAL PROCESSING The Cyclops s
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
Page 143 and 144:
samples simultaneously onto the sam
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
Page 183 and 184:
perhapsdecadesand possiblycenturies
Page 185 and 186:
APPENDIX A ASTRONOMICAL DATA DISTAN
Page 187 and 188:
PLANETARY Planet ORBITS Semimajor S
Page 189 and 190:
APPENDIX B SUPERCIVILIZATIONS AND C
Page 191 and 192:
ABIOLOGICAL CIVILIZATIONS Many writ
Page 193 and 194:
182
Page 195 and 196:
tqOT APPENDIX C OPTIMUM DETECTION A
Page 197 and 198:
to rmsnoise.Wenotethatthematchedfil
Page 199 and 200:
APPENDIX D SQUARE LAW DETECTION THE
Page 201 and 202:
If the output filter is very wide c
Page 203 and 204:
if B/2 > T we can start instead wit
Page 205 and 206:
Let us now introduce the normalized
Page 207 and 208:
where h-- = expectation count of si
Page 209 and 210:
APPENDIXE RESPONSE OF A GAUSSIAN FI
Page 211 and 212:
APPENDIXF BASE STRUCTURES AZ-EL BAS
Page 213 and 214:
ack,it shouldnotbenecessary to prov
Page 215 and 216:
204
Page 217 and 218:
206 i
Page 219 and 220:
PAGE BLANK NOT APPENDIX H POLARIZAT
Page 221 and 222:
APPENDIX I CASSEGRAINIAN GEOMETRY C
Page 223 and 224:
APPENDIXJ PHASINGOFTHE LOCALOSCILLA
Page 225 and 226:
APPENDIXK EFFECTOF DISPERSION IN CO
Page 227 and 228:
APPENDIX L TUNNEL AND CABLE LENGTHS
Page 229 and 230:
where r = "Ym/'rs- If we let o-_--o
Page 231 and 232:
L-4 we see that the length of IF ca
Page 233 and 234:
APPENDIX M PHASING AND TIME DELAY A
Page 235 and 236:
andobtain V = 2 (Ps [! + _(Ar)] +Pn
Page 237 and 238:
L" D 226
Page 239 and 240:
APPENDIX N SYSTEM CALIBRATION The p
Page 241 and 242:
APPENDIXO THE OPTICAL SPECTRUM ANAL
Page 243 and 244:
232
Page 245 and 246:
APPENDIX P LUMPED CONSTANT DELAY LI
Page 247 and 248:
Thevalueofthefinalcoilonthelineis =
Page 249 and 250:
APPENDIXQ CURVES OF DETECTION STATI
Page 251 and 252:
I I I I LE :E oo
Page 253 and 254:
APPENDIX R RADIO VISIBILITY OF NORM
Page 255:
io 3 - l rlrllll I I I ]l+,ll_ I _f
show all

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

Create successful ePaper yourself

Delete template?

Save as template?