IONOSPHERIC OBSERVATIONS: ARCHIVED DATA AND THE HEAO-C LAUNCH Michael Mendillo and C. C. Chacko Astronomy Department - Boston University Boston, Massachusetts 02215 Sustained, large-scale rocket launch campaigns of the kind envisioned for the proposed Satellite Power System will affect the Earth's environment to an unprecedented degree. The problem of evaluating the consequences of such a campaign is a complex one due to the very large number of chemical, mechanical and electromagnetic processes operating in the Earth's atmosphere, ionosphere and magnetosphere. We have undertaken a two-fold course of study of ionospheric observations with a view towards documenting some of these effects without need of resorting to costly new experiments. Our first approach centered on a search for ionospheric depletions (''holes”) that may have been detected during routine observations of the ionosphere from stations close to NASA launch sites. Using a list of over 400 rocket launches carried out by NASA between November 1958 and August 1978, the vast archives of ionosonde records stored at the World Data Center in Boulder, Colorado, were examined for rocket-induced ionospheric changes. Most of NASA's larger rockets were launched from the Kennedy Space Center, and thus the ionograms from Cape Canaveral, Grand Bahama Island, San Salvador, Cuba and Jamaica were the prime ones examined in our search for ''retroactive experiments.” During the years 1959 to 1971, a total of 156 major rocket launches occurred from KSC. Of these, only 5 cases of relatively clear rocket-associated effects were found. With the closing of the Grand Bahama Island station in 1971, the last ionosonde capable of monitoring KSC launches disappeared. Data from Cuba, Jamaica, KSC, Grand Bahama Island and San Salvador are being reduced to describe the spatial and temporal extent of the resultant disturbance. A more promising avenue of study concerns the transformation of a scheduled rocket launch into an ''experiment of opportunity” by establishing a temporary network of observing sites in regions close to the rocket trajectory. The launch of NASA's HEAO-C satellite on 20 September 1979 provided an extraordinary opportunity to mount such a campaign. The event was monitored by a network of 12 satellite radio beacon observatories, 2 incoherent scatter radars, an airborne optical observatory, 3 ground-based air-glow systems, and over 150 radio propagation monitoring sites using both professional and radio amateur facilities. The ionospheric depletion caused by the rocket exhaust cloud spanned a region of approximately 2 million sq. km. The total electron content depletions near the rocket trajectory showed more than an 80% reduction from ambient conditions. The extensive network of diagnostic systems assembled for the event provided the most complete description yet obtained for a large-scale, rocket-induced ionospheric hole.
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