Memorandum for Dr. Don Rote, Argonne National Laboratory Subject SPS Ionospheric Impact Date 12 July 1979 Following our workshop on "Upper Atmospheric Research In Support of the*SPS Environmental Assessment" at La Jolla, CA I briefed a U.S.Navy Communications group at Naval Ocean Systems Center, San Diego (J.H.Richter, D.Sailors, W.Moler, Messrs. Argo and Ferguson) on the project and on our study on 3 July. One prediction which concerned these Navy communications experts very much came from a morphology subgroup chaired by J. redder of NRL, and calls for a region in which the ionization Is depleted by roughly a factor of two, extending globally at the latitude of Injection, several thousand kilometers in width and extending upward from approximately 160 km. Ilie ionization is depleted because l^O and H? molecules from the rocket exhaust (HLLV second stage, circularization and deorbit burns, POTV and COTV) react with the ambient atomic (0+) ions to form molecular ions, 0H+ and H20+, which recombine very much faster with electrons than do the atomic ions, thus reducing the effective ionization. The effect of this on global HF long-haul (sky wave) communications is extremely serious as the band (3-30 MHz) is extremely crowded, and indeed at an International Conference of CCIR next year the USA expects to lose some frequency allocations to developing nations which depend on (cheap and simple) HF Com rather than use higher frequency satellite communications. Dr. Sailors (714-225*7400) explained that reducing the electron density by a factor 2 reduces the maximum usable frequency (which Is reflected from the ionosphere) by •fP , thus reducing the band limit of 30 MHz to 21 MHz. For long-range communications the upper portion of the band, say 15"3O MHz is optimal. This would be cut to the range 15-21 MHz, or to 6 MHz from 15 MHz, which is Indeed a drastic reduction in a crowded band. (The numbers are all illustrative only). I discussed the matter later with Dr. Gabriel Frenkel at IDA (another CCIR participant) and he confirmed Dr. Sailors' statements , the pressure on the band, and the problems of the International negotiations. This problem is one of which Dr. Charles Rush should take cognisance, as he is in the CCIR community. I got the impression that this effect is so serious that it might prove to be a "program stopper" for SPS because of the international implications. Let me stress that the estimate of the depleted ionospheric region is not based on detailed calculations but just on educated guesses. Computing the morphology of the disturbed ionospheric region presents a significant and high priority aspect of the SPS Upper Atmospheric Environmental Assessment. Explicitly the "factor 2" represents just an initial estimate which must be improved upon. Ernest Bauer, 8109 Fenway Rd.,Bethesda,MD 20034. (301)469-6726 Ernest Bauer.
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