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- 21 - SPACE SCIENCES The space sciences program at the ONR has had a long and distin- guished history, some of which laid the foundations for the field prior to launch of the first artificial satellites. It is evident from the FY 1986 report that a baseline research program continues to support important research in this area, which is becoming more significant to the Navy's mission as many essential assets are located in near-earth space and must operate under a variety of environmental conditions, both natural and raanmade. Evidence has accumulated in recent years, however, that active modification of the near-earth space environment is likely to assume a very important role, both as a means of enhancing and controlling com- munications and of interfering with similar activities by potential adversaries. There exists, therefore, a need to pursue a program of experimental and simulation studies that will provide basic under- standing of the plasma physical processes operating in the near-earth environment. Such understanding will then lead to potential opera- tional systems in the next decade and beyond. SECOND GENERATION IONOSPHERIC MODIFICATION FACILITY Backgound: Over the past two decades, ground-based ionospheric heating facilities utilizing powerful HF transmitters have been developed in the United States, the Soviet Union, and Europe. These facilities, with effective radiated powers of 50-400 MW, have produced a variety of interesting and potentially useful effects resulting from the interaction of intense HF radio waves with the ionosphere. Among these are direct ionospheric generation of ultralow frequency (ULF), extremely low frequency (ELF), and very low frequency (VLF) waves, formation of ionospheric structures, and direct heating of the iono- spheric plasma. In addition, it has been demonstrated that intense radio wave signals stimulate plasma instability processes in the ionosphere. -A direct consequence of this stimulation is strong absorption of the incident radio frequency energy. Although the ONR funded work in this area through the HIPAS facil- ity, the power generated was not adequate to achieve significant effects. With the conclusion of the HIPAS program, it is necessary to consider a second-generation facility that could be used as a research tool into the early 1990s and could well have important operational utility in that time frame. The principal objective would be to develop a high-power, ground-based, ionospheric heating facility for communications and surveillance. Relevance to Navy Requirements: The wide-ranging effects induced by ground-based heaters lead to considerations of (a) the potential applications that these facilities might have in the fields of communi- cations and surveillance, and (b) the form that advanced second-gener- ation heating facilities might have. Calculations have indicated that more powerful heating installations should be capable of producing enhanced ionization layers in the ionosphere. These layers would be
- 22 - capable of supporting controllable long-range communication links and over-the-horizon (OTH) radar coverage. Other researchers have dem- onstrated that more powerful ionospheric heaters would be capable of direct generation of strong VLF and ELF signals within the ionosphere. These low-frequency signals could also be utilized for communication purposes. Finally, an advanced ionospheric heating facility could produce controllable perturbations of the ionosphere. These pertur- bations could be imposed along the path of satellite-to-ground and ground-to-ground communication systems to test their operational capabilities under disturbed conditions. Research Program: An advanced ionospheric heating facility would need to have an effective radiated power ranging from 1-2 gigawatts to produce the anticipated effects. This is approximately an order of magnitude greater than the power capabilities of existing U.S. heating facilities; furthermore, an advanced facility would need frequency ability within the HF band, and it would need beam steering so that the heated ionospheric volume might be formed in an overhead or oblique direction. The contemplated facility could utilize a large two-dimen- sional phased array of medium powered (1-10 kW) solid state trans- mitters and cross-polarized log periodic antennas.
- 23 - APPENDIX A Naval Studies Board Electronics Panel National Academy of Sciences Washington, D.C. June 30 - July 1, 1987 Agenda Tuesday. June 30 - NAS 280 0830-0900 INTRODUCTION Drs. Kostoff/Moss, ONR 0900-0930 OVERVIEW - SEM Dr. Borsuk, CRP 0930-1040 ELECTRONICS Dr. Borsuk, NRL 1040-1150 ELECTRONICS Dr. Davis, CRP 1150-1230 ELECTRONICS Dr. Whiting, ARP 1230-1300 Open Discussion 1300-1400 Lunch 1400-1430 Open Discussion 1430-1800 Executive Session 1800 Adjourn Wednesday, July 1 - JH 451 0830-1200 Executive Session 1200-1300 Lunch 1300-1800 Executive Session 1800 Adjourn
