(a) Spacecraft charging by energetic plasma and photoelectric effects is expected to be an important problem for the design and development of SPS which has 50 km^ of surface area. (b) Potentials established on the spacecraft can accelerate and decelerate plasma components to tens of keV, as demonstrated by SCATHA experiments. This would impact the geosynchronous plasma environment. (c) The plasma environment has direct impact on klystron operations by forming electron sheaths in resonant cavities ("multipacting"). This has been demonstrated by SCATHA and other satellites. (d) SCATHA, ISEE, ATS, and GEOS are elements in the coordinated IMS (International Magnetospheric Study)project to define the physics of the geosynchronous plasma. The basis physical understanding gained would be very important in resolving the question of the long-term recycling and energization of argon ions in the magnetosphere. (e) Effects of contaminant from satellite operations such as water, outgassing, and neutrals are studied by the ML-12 experiment on SCATHA. As a result of considering the relevance of SCATHA to the SPS assessment, we recommend that: 1. Coordination should be maintained with SCATHA experiments. 2. Consideration should be given to SCATHA-like instrumentation in conjunction with possible FIREWHEEL-like diagnostic configuration and a high- powered ion engine operation experiment similar to GREYHOUND. (More details of these experiments are given in Section 4.6.3) 3. Consideration of results from joint SCATHA/GEOS II Xe+ beam propagation studies should be included in planning any Ar experiments. 4.6.3 CAMEO, FIREWHEEL and Other Experiments (Chiu) 1. CAMEO. This involved a release of barium from a satellite at L ~ 7-9 at approximately 1000-km altitude. The results indicate that (a) ions are accelerated by natural electric field which may influence the formation of HZE particles from Ar+, and (b) plasma irregularities were observed at very high altitudes (~ 1 V Such releases at high altitudes at the equator would be most relevant for SPS. Other targets of opportunity in this area are a NASA/Max Planck Institute barium release at 6.6 Rg and the BUARO barium jet release by LASL (Koons & Pongratz, 1979, Simons et al. 1979). 2. FIREWHEEL. This experiment consists of barium and lithium releases in the night-side magnetosphere at 7 and 95 Rg by the Max Planck Institute group in March 1980. The unique feature of this experiment, which constitutes
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