The telemetered radiation information from the satellite 1958 δ2
(Sputnik III) has been analyzed for sixty-two separate passes recorded
in College, Alaska. The data indicate a dependence of radiation intensity
on altitude in the range 250-500 km. Both the high and low
energy components apparently contribute to the overall increase of
intensity with altitude, but the presence of a continuous afterglow
in the scintillating crystal prevented detailed interpretation of the
results.IGY Project No. 32.42
NSF Grant No. Y/32.42/268Ye

Basler, R. P.

DeWitt, R. N.

Reid, G. C.

English

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RADIATION INFORMATION PROM 1958 62byR. P. Basler, R. N. DeWitt, and’G. C. ReidScientific Report No. 1IGY Project No. 32.42 NSF Grant No. Y/32:4?/268Principal Investigator: C. T. ElveyThe major part of this paper is scheduled for publication in the April 1960 issue of the Journal of Geophysical Research.GEOPHYSICAL INSTITUTEof theUNIVERSITY OF ALASKAScientific Report No. 1 RADIATION INFORMATION FROM 1958 62byR. P. Basler, R. N. DeWitt, and G. C. ReidIGY Project No. 32.42 NSF Grant No. Y/32.42/268Submission Date Principal Investigator:January i960LIST OF FIGURESFig. 1Fig. 2Fig. 3Fig. 4Radiation intensity observed on channels 2 and 3 during a typical passage of 1958 62 over College, Alaska on 5 June 1958. The points for channel 2 represent a 12.3 sec. (10 telemetering cycles) average of the telemetered inten­sities. Closest approach occurred at 20:03:09 Universal Time.Observed dependence of total radiation intensity on alti­tude. The straight line represents a least-squares fit to the data.Observed altitude dependence of the component of the total radiation intensity due to pulses larger than 1-2 MeV.Each point represents the weighted mean of all the obser­vations within a 50 km. height interval. The vertical bars represent the standard deviations.Observed altitude dependence of the component of the total radiation Intensity due to pulses smaller than 1-2 MeV.The straight line represents a least-squares fit to the data.RADIATION INFORMATION FROM 1958 62byR, P. Basler, R. N. DeWitt, and G. C. ReidABSTRACTThe telemetered radiation information from the satellite 1958 62 (Sputnik III) has been analyzed for sixty-two separate passes recorded in College, Alaska. The data indicate a dependence of radiation in­tensity on altitude in the range 250-500 km. Both the high and low energy components apparently contribute to the overall increase of intensity with altitude, but the presence of a continuous afterglow in the scintillating crystal prevented detailed interpretation of the results.INTRODUCTIONThe Geophysical Institute at the University of Alaska has recorded the radio signal from the satellite 1958 62 (Sputnik III) since it was launched on May 15* 1958. The continuously telemetered radiation data from this satellite has been analyzed for sixty-two separate passes recorded in College, Alaska (64° 52’N, 147° 50'W) from May 18 until the partial failure of the telemetering system on June 1J, 1958. This analysis was made on the basis of the information presented at the Rocket and Satellite Symposium during the Fifth Reunion of the Comite Special de 1’ Annexe Geophysique Internationale held in Moscow, July 30- August 9i 1958. Much of the relevant material presented at this sym­posium has since been published elsewhere (Vernov et al. 1959).DATA REDUCTIONThe satellite's 20 Mc/s beacon radio transmission consists of a recurring series of 3 telemetry pulses and a marker pulse, repeating at intervals of 1.23 seconds. The durations of the 2nd and 3**d pulses give a measure of the radiation intensity incident on a sodium iodide crystal as recorded by a photomultiplier. The 2nd pulse changes length in response to the anode current of the photomultiplier and the 3rd pulse changes in response to the current at one of the dinodes. For high energy pulses the relation between these currents is non-linear, so that the difference between the radiation intensities recorded by the two channels at the same time should give a measure of the fraction of the radiation occurring in'the. form of high-energy pulses. For details of the telemetry system, the reader is referred to Vernov et al. (1959).The radio signal strength was recorded on a Sanborn 150 recorder at a chart speed of 10 mm/sec. The individual pulses could readily be identified and their relative durations measured directly from the chart. These durations were tabulated for the entire readable portion of each record and reduced to values of radiation intensity using the published code. A typical graph of this information is shown in Figure 1.The area under each curve represents the total energy released in the sodium iodide scintillating crystal during the recording.The true value of this energy is given by channel 3, the curve for channel 2 being somewhat lower due to the non^-linearity in the later stages of the photomultiplier tube. The oscillations in the two-2-curves are those referred to by Vernov et al. (1959) as due to the satellite's tumbling in the earth’s magnetic field, thus affecting the sensitivity of the photomultiplier.The average radiation intensity values for each of the sixty-two recordings are included in Table 1. These averages were taken from all the available data from any one recording without regard to which portions of the tumbling cycle were sampled, since it was sometimes difficult to determine the position of the crests and troughsof these cycles, especially in a short record. The error introduced by this averaging, however, can not exceed the tumbling modulation which is of the order of 10$.It should be noted that the intensity values recorded are not the actual intensities, but are somewhat higher due to the perpetual afterglow in the scintillating crystal. Since this afterglow is largely due to the high intensity radiation encountered during the north-south crossings of the geomagnetic equator, it will have decayed to near its minimum value when the satellite passes over Alaska. The decay is never completed, partly because the crystal is constantly irradiated, but mostly because the time constant for the afterglow Is comparable to the satellite's period; thus, the crystal Is re-exposed to the high intensity radiation at the magnetic equator before it has had time to recover from its previous exposure. The Intensities recorded on channel 3 can therefore be considered only as upper limits for the actual intensities.-3-ALTITUDE DEPENDENCEThe satellite's position during each of the recordings was de­termined from the orbital information supplied by the Space Track Control Center at the L.G. Hanscora Field in Bedford, Massachusetts.As determined from this information, the height of the satellite at its point of closest approach to College is included In Table 1 for each pass. However, since the recordings were all made during the first weeks following the launching, before the orbit was well established, the heights given are probably not accurate to better than 20 kilometers. Unfortunately, no accurate ephemeris is avail­able for the early months of 1958 62, so at present there is little hope of refining these estimates.Figure 2 shows the average radiation intensity plotted against the closest approach altitude for each satellite passage. The pos­sible height errors, together with the fact that the radiation in­tensity values have been rounded off to the nearest one-tenth BeV/sec, would be expected to produce some scatter in the points. However, the wide scatter, especially at higher altitudes, can not be explained on the basis of inaccurate data.Figure 2 indicates that there is an increase of radiation with altitude, but no definite functional relationship is apparent. How­ever, a straight line seems to be a good first approximation. There seems to be a tendency toward decreasing slope at higher altitudes, but this might be due to the reduced effect of the afterglow during these passes since they are further removed from the magnetic equator.-4-It is interesting to compare Figure 2 with the altitude-intensity curve published by Meredith, Gottlieb, and Van Allen (1955) for Rockoon flight number S.U.I. 20 on JO August 1953- Both were at very nearly the same geomagnetic latitude, and although the Rockoon data are for a much lower altitude (up to about 100 km), both show a nearly linear increase of intensity with altitude.HIGH ENERGY INTENSITY As described above, the telemetering system in 1958 <52 was de- ' signed so that the combined information on channels 2 and 3 would perve to determine the portion of the total energy which is released in the scintillating crystal in the form of pulses whose individual amplitude is greater than 1-2 MeV. The description of this system by Vemov et al. (1959) Is incomplete, but apparently it was intended that the intensity due to pulses greater than 1-2 MeV be given approximately by the difference in the intensities indicated on channel 2 and channel 3. However, the previously mentioned after­glow in the scintillating crystal prevented operation in this fashion by introducing a continuous component in the photomultiplier current which lowered the energy required for a pulse to exceed the linear response range of the anode current. This caused channel 2 to indicate a lower intensity than channel 3> thus indicating a spuriously high intensity of high energy radiation. The values of the high energy intensities as given by the difference between the channel 2 and channel 3 intensities are included in Table 1.If the high-energy pulses are assumed to be entirely due to galactic cosmic rays, their intensity would be expected to be constant and independent of altitude in the range encountered during passages over Alaska. However, the recorded high energy intensity values range up to 40$ of the total intensity, and seem to have an altitude dependence, as shown in Figure 3* The corre­sponding dependence of the low energy intensity on altitude is shown in Figure 4. It can be seen from this information that both the high and low energy components contribute to the previously noted general increase of intensity with altitude, although, as before, the wide scatter of the observed points makes the form of the Increase uncertain. As in Figure 2, the tendency toward decreasing slope at higher altitudes in Figures 3 and 4 might be due to the reduced effect of the afterglow during these passes.The values of intensity in Figures 3 and 4 and the channel 2 and high energy intensities in Table 1 are from all the recordings except those for which the total intensity exceeded the limit of the telemetering system; that is, the relay changing in response to the anode current switched more than once per cycle (1 .2 3 sec.). A more detailed analysis in the manner of Herz et al. (1959)> would probably yield this increased switching rate, but their technique does not seem warranted in our case since it would be necessary in only a few instances and would involve a much more elaborate scaling technique than we used. Also, due to the effect of the afterglow, the information on channel 2 is of questionable value,-6-at least as an indicator of high energy intensity. At best, the difference between channels 2 and 3 can be regarded as the lower limit for the true intensity, the value from channel 3 already having been mentioned as the upper limit.DISCUSSIONSince the inclination of the satellite's orbit (65°) was very close to the latitude of College, Alaska, only a limited latitude range was sampled in all of our observations, so that no systematic intensity variation with latitude could be detected.The intensities sampled ranged from 0.7 to 2.8 BeV/sec, much lower than the average intensity over the complete orbit, reported as 300 BeV/sec (Vernov et al. 1959)» but comparable to what was recorded in the USSR. In all of our recordings the counting circuit was overloaded, indicating that the ionosphere over Alaska from 60 to 65 degrees latitude is also characterized by the permanent low energy (100 KeV) electron flux observed at similar geographic latitudes by Vernov et al. (1959)•Efforts were made to interpret the radiation observations in relation to ionospheric, magnetic, and solar activity, but there was no obvious correlation, and our data were too limited to warrant a statistical approach. However, it should be noted that this was a period of very little activity in any of these fields, and there were no major solar flares, magnetic storms, or radio wave absorp­tion events. It should also be pointed out that the ionosphere over Alaska was constantly sunlit during the period of our recordings.-7-The general Increase of Intensity with altitude, represented in Figure 2, might be due to an increase in the number of geo- magnetically trapped particles at greater heights. This increase would result from the reduced absorption in the less dense higher atmosphere and from an increased sampling of trapped particles, that is a sampling of particles with mirror heights up to and including the altitude of the satellite. The most that can be said about the scatter of points in Figure 2 is that there is an apparent time variation of intensity at any given altitude.-8-ACKNOWLEDGEMENTSThe authors wish to thank the staff members of the Geophysical Institute for their helpful comments and to express their apprecia­tion to Mrs. Catherine Hilandfor her help in scaling the data.This work was supported by the National Science Foundation under Grant No. Y/32:42/268.REFERENCESHerz, A. J., K. W. Ogilvie, J. Olley, and R. B. White; "-Radiation Observations with Satellite 1958 62 over Australia," NATURE Vol. 184, P. 391 (1959).Meredith, L. H., M. B. Gottlieb, and J. A. Van Allen; "Direct Detection of Soft Radiation above 50 Kilometers in the Auroral Zone/1 Physical Review Vol. 97, No. 1, p. 201 (1955).Vernov, S. N., A. E. Chudakov, E. V. Gorchakov, J. L. Logachev, and P. V. Vakulov; "Study of the Cosmic-Ray Soft Component by the 3rd Soviet Earth Satellite," Planetary and Space Science Vol. 1,No. 2, p. 86 (1959).Date195818 May19 May20 May20 May20 May23 May23 May24 May25 May25 May25 May26 May26 May26 May27 May27 May28 May28 May28 May28 May29 May29 May29 May30 May2 June2 June2 June3 June3 June3 June4 June4 June4 June4 June4 June5 June5 June5 June6 June6 June6 June7 June7 JuneTABLE 1.Closest Average Radiation Approach IntensityUT in BeV/sec________ Channel3 Channel 2High Energy Intensity in Bev/sec2325 1 .3 1.1 .22223 1.1 0.9 .20010 1.3 1.1 .20158 1.7 1.5 .22310 1.1 0.9 .22142 0.9 0.7 .22330 1.3 1.1 .22225 1.2 1.0 .20015 1.4 1.2 .22123 1.1 0.9 .22311 1.4 1.1 .30059 2.02206 1.1 0 .8 .32354 1.4 1.1 .32101 1.0 0.8 .22248 1.3 1.1 .20036 1.6 .31955 0.8 0.6 .22143 1.2 1.0 .22331 1.4 1.1 .30119 2.22038 1.0 0.7 .32226 1.2 1.1 .10013 1.8 1.6 .21950 1.0 0.8 .22135 1.3 0.9 .42323 1.6 1.2 .41841 0.9 0.7 .22030 1.3 0.9 .42218 1.5 1.0 .50006 2.21735 0.7 °-§ .21922 1.1 0.8 .32110 1.3 1.1 .22259 2.0l8l4 1.0 0.7 .32002 1.4 1.0 .42151 1.6 1.2 .4I858 1.2 0.8 .42046 1.6 1.1 .52234 2.81940 1.4 0.9 .52125 1.6 1.2 .4Altitude at Closest Approach in km300277338380285263300300344275366300339 271 300 339 258 300 341 412 284 324 375 290 327 390 270 310 354 406 273 326 471 530 299 349 430332395470352432TABLE 1. (cont’d)Date1958ClosestApproachUTAverage Badiation Intensity in Bev/secHigh Energy Intensity in Bev/sec8 June 1829 1 .1 0.7 .48 June 201? 1.5 1 .1 .48 June 2206 1.6 1.1 .59 June 1721 1 .0 0.7 .39 June 1901 1.5 1 .0 .59 June 2057 1.6 1 .1 .510 June 1803 1.1 0 .8 .310 June 2137 1.7 1.4 .311 June 1653 1.1 0 .8 .312 June 1925 1.5 1 .1 .412 June 2109 2.113 June 1625 1.3 0.9 .413 June 1813 1*3 0 .8 .513 June 2000 2.016 June 1636 1.4 0.9 .516 June 2010 2.317 June 1526 1.1 0.7 2i •  <17 June 1901 1.7 1 .2 .517 June 2051 2.4Altitude at Closest Approach in km327400471 299 348 430 327 470 297 394472346429326466295429509U NIVERSAL TI.MEFig. 1. Radiation intensity observed on channels 2 and 3 during a typical passage of 1958 6 2 over College, Alaska on 5 June 1S58. The points for channel 2 represent a 12.3 sec. (10 telemetering cycles) average of the telemetered intensities. Closest approach occurred at 20:03:09 Universal Time.Fig. 2. Observed dependence of total radiation intensity on altitude. The straight line represents a least-squares fit to the data.H E IG H T  ( K M )Fig. 3. Observed altitude dependence of the component of the total radiation intensity due to pulses larger than 1-2 MeV. Each point represents the weighted mean of all the observations within a 50 km height interval. The vertical bars represent the standard deviations.A L T IT U D E  (KM )Fig. 4. Observed altitude dependence of the component of the total radiation intensity due to pulses smaller than 1-2 MeV. The straight line represents a least-squares fit to the data.

Radiation Information from 1958 δ2

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Radiation Information from 1958 δ2

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