DATETIME GROUP 7. LENGTH OF OBSERVATION 10. BRIEF $UMMARY OF SIGHTING PROJECT 10073 RECORD CARD 2. LOCATION 4. TYPE OF OBSERVATION 0 Ground Visual .0 . Ground-Radar 0 Air:-Vi suol 0 Air-Intercept Rodor I. NUMBER OF OBJECTS 9. COURSE 11. COMMENTS 12. CONCLUSIONS 0 Wos Bolloon 0 Probably Balloon 0 Possibly Balloon Wos Aircraft 0 Probably Aircraft Possibly Aircraft D Was Astrononlic:ol ~1eteor cr..: Prol.ably AstronoMical D Possibly AstronoMical 0 Insufficient Data for EYoluation D Unknown ran~v of .';) .. nu.uticc:l m1les & at Probably a meteor. '2 n~ttl.,:11 ai1cs :tt a he1.ght of 6,1 nautit.:n.l utl.H:~. 'l'h0 t~rbet:5 lasted for a Lo~al of 2 2 seconds . ATJC FORM 329 (REV 26 SEP 52) INTERlM LETTER REPORT COI-lrRACT NOt . AF)0(60~)-l7ul t1NIDENTifl!P TARGET OF AN/rrs-l7(xH-2). RADAR MISIoN 164 I. INTRODUCTION .. The AN/FPS-17(XW-2) radar at the Laredo Test Site, Laredo, Texas was 1n operation on 11 October l9S8. The expected target was 1958 the instrumented portion of the third Russian satellite, Sputnik III, A target was observed, but the characteristics or the intercept would.make one believe that the object observe~ was not the one expected, Other possible explanations are discussed below. II. CONCLUSIONS The object observed was most probably& a meteor showing both a head echo type reflection and a specular type reflection from the trail, or (b) two meteors occurring in the same portion or space at ver,r near~ the same time. III. ANALYSIS A. FACTS RELATED TO THE UNIDENTIFIED TARGET The kn~ !acts related to the inter~ept or this unidentified target area (a) the target was observed on ll October 1958 beginning at .07h 21m 44.0s Universal tiroo nnd lasting until 07h 22m l2 .os, an overall duration or 28.0 second g . (b) e target as displayed on film r ecordings of the radar signal consisted of two unusually distinct sections ' The first of these l asted for approximately 0.75 seconds, showing a range change from 454 to 473 nmi. The second portion began lorhere t he first left off and lasted for 27.3 seconds. The ranBe of t his targe t changed from 462 to 467 nmi in that time. Absolute range as indicated here is accurate to within S nmi, but relative to each other they are accurate to 1-rit~in 2 nmi. (c) the target was observed in three or four beams being energized as rollowst Beam l Low Beam 2 Low Beam 1 High Beam 2 High * Ma;y have entered prior to this time, but geam was not energized because of Beam Swi tch1ng o (d) No doppleJ' frequency infomation was available be- cause the range gate was set so that only targets between 504 and 1178 run1 would alarm the Lincoln Coded Pulse doppler system. (e) An intercept of the Russian fjlatellite, 19$8 tl2 had been expected at about 0733Z at a range of 700 to 900 (t) No other targets were observed by the radar between 070lZ and B. POSSIBLE TARGETS A signal such as that received by the radar could, at tiret glance, have been reflected from aqy one ot. the followingl (a) A rocket launched from the vicinity o! the White Sands Proving Grounds (b) A satellite passing through easter~ direction. t he beams in a north- (c) A meteor or meteors, (d) Soma unknovm and unexPected object. C, INTERPRETATION OF THE FACTS A knowledge or the-location and path of the observed object is" desirable if one is to distinguish between the above possibilities. The rapge or about 470 nm1 would position the observed object somewhere in the vicinity of the l-1l1ite Sands Proving Orounds. The observation or the object simultaneously by three of the four beams energized allows us to estimate the angular coordinates more exactly than i! reflections were seen in on~ one beam. If the possibility of side lobe. reflections are neelected, the object observed must have been at an elevation angle between ).$ and h.S degrees and an azimuth an~le from the radar between 312,$ and 313.S degrees, Conversion or these radar coordinates to a more meaningful torm places the observed target probab~ within s nm1 or a point in space defined as follows: Origins at the Air Force Missile Development Conter, Holloman Air Force Base, New Mexico Coord ina tea: West The pat~ (direction and speed) of tHe target cannot be resolved to any great degree of accuracy. The sudden appearance of the signal in three beams indicates that the obj~ct s.uddenly appeared at this position in space and didn't gradual~ move into one beam and then another, The target should be considered as two separate parts, that which l'asted for 0. 7S seconds and the othex:', which had a dlration of 28 seconds. in Beam 2 High, The first target had a range rate of change of about + 2$ nmi per second. The second target had an average range rate of change of 0.2 nmi per second, The accompaqying photographs show'that the signal died out of Beam 1 Hi before it died out of Beam 2 Hi. This could be explained by the passage of the target from one beam into the other, or by a decrease in the strength o the reflected signal. If the target were closer to the center of Beam 2 Hi, we would expect to get the stronger signal in that D. ELIMINATION OF POSSIBLE TARGETS Consideration of the facts available indicates that several or those objects listed as possible targets would not give rise to a signal such as that received. (a) A rocket launched from the White Sands Proving Ground would have been picked up in a low beam about 30 to 40 seconds before it was seen in the high beams, and it normally is seen tor longer than 28 seconds. No such phenomena as that demonstrated by the early portion or the target ass been observed on previous rockets launched at White Sands (b) Only one satellite Has knorm to h~ve bean in tho vicinity a t the time of observation. This one should havo passed throuch t!1e bccrns over 20C runi to the north1-zest about 12 minutes later. The pre- diction bulletina, are subject to some error, btt they are seldom f~r enough off in either position of the orbit or ti:ne of pass ace for this observed object to have been the satellite. All previous observations of satellites on south- to-north passes have s hown similar range rate characteristics. But they have also gratlually moved into Beam 1 and then Beam 2, w~ich is not the case here. No satellites in orbit come so close to the earth as the indicated 64 nmi. rr the.y did, they would soon fall out of orbit or burn up in the at- . mosphere. One should note that there may be several pieces of satellites in orbit which nobody is keeping track oi. These pieces conld, at times, be observed, but the sudden appearance 1n three beams and a rate of chanee of range of 25 nm1 per second are not characteristics of satellite intercepts. (c) The oboerved target height, 64 nmi, is 1n the meteor band. A ve~; sudden appearance of a strong signal is characteristic of meteors. The appearance of the signal suddenly in three beams 1a quite possible 1n the case ot a meteor. Although there is much yet to be learned about meteors, it is known that not all meteors in a beam are detect ed by a radar. There are requirements the orientation of the meteor trail with respect to the radar beam which must be mat. Then, too, the exact height at which a meteor trail becomes debectable varies. Either one or bot}} the orientation of the trail and the ionization formation, could explain why the meteor was not seen until such as it reached a position within the beams. The first portion of the observed trail might well have been an echo from the so-called meteor head thus giving us t.he very hieh rate of change of range t tho meteor head moves rrith the speed o the xmteor itself). Meteor velocities var:r over a t-ride ranee but they m~ be as high aa twice that range rate of change observed.