For selected times +40, +59, and + 71 min, with correspmmding ranges (apparent heights). of 285, 360, and 510 kn, respectively, the result- ing values are to ® + 44 3/4 min Vv S 16.4 kn/min h & 274 km (3.3) After plotting the resultant cwve (from plus 40 to plus 71 min in Fige 3.19), it appeared that a similar height variation occurred about 15 min later. It was found, in fact, that duplicating the first curve in a position translated just 15 min to the right (later) pro- duced an excellent approximation to the crosses. A further transla- | tim of 15 min again resulted in a good fit, but over a smaller region, as is evident in the Figure. The line approximating the points after plus 85 mJ: was fitted merely by eye, and is a duplication of the corresponding portion of Fig. 3.15 on a different scale. The group of points below 260 km developed into the FI leyer. As may be seen from Fig. 3.19, the first curve, which was ob= tained using the values of Equatio 3.3, agrees well with the trend of the crosses. From this it appears likely that, as hypothesized, thero was a horizontal movement of ionization at a height of about 275 km, traveling at about 16 km/min, and passing overhead at Rongerik about 45 min after Shot 4 was detonated. (The second and third curves, following the first by 15 and 30 min, seem to indicate some sort of periodic motion.) The analysis is, of course, subject to inaccuracies of several types, including these: the actual slant range may have been less than indicated because of retardation of vhe radio wave, the motion may not have been horizontal or of constant velocity, and, furthermore, there is no positive assurance that the sequence of echoes represented a continuous motion, . After an F2=layer trace that appeared neerly normal (lest icnogram of Fig. 3.18) and after a brief interval cf normal F2elayer parameters (see Fig. 3.15 at about plus 1 1/2 hr), a period of over 2 hours ensusd during which the F2-layer height was abnormally great and its critical frequency was sbnormally low. Representative iono~ grams from that period are shorm in cige 2.20. _3e3ehShot The effect on the F2-layer aoove Rongerik took still a differ- ent form after Shot 5. Near shot time and up to about 1/2 hr there. | after, as was the case for the other detonations, there were no returns from the F region, Then, sporadic E, which was wmusually strong on this day, began to be observed; it "blanketed" any possible echoes from above for at least 1/2 hr (for example, see ioogram at + 54 min in Fig. 3.8). Returns from the Fl leyer, (alteit they were extremely "spread" or scattered), were "seen" through the sporadic E starting 47 SECRET