Seamless Handovers in Cobra Teardrop Satellite Arrays
- Paper number
IAC-06-B3.2.02
- Author
Mr. John Draim, United States
- Coauthor
Dr. Paul J. Cefola, Massachussets Institute of Technology (MIT), United States
- Year
2006
- Abstract
Abstract: Satellite systems provide the most efficient and possibly the only means of achieving two-way global communications with mobile systems (ships, aircraft, vehicular traffic). To date, such systems have used only circular orbits, either GEO or LEO. The GEO systems are hampered by their excessive time delay and link margin problems, as well as an inability to provide reliable high-latitude coverage. High inclination LEO satellite systems can and do provide this high-latitude coverage, but due to their low altitude and smaller footprints, they require large numbers of satellites. Medium altitude elliptical constellations, on the other hand, provide an efficient and affordable alternative to these architectures. Users also benefit from their very high average and minimum elevation angles, resulting in minimum signal attenuation due to atmospherics. Carefully designed elliptical arrays can be biased to provide augmented coverage to selected highly populated continental regions, while shifting coverage away from the lower-populated, less profitable, regions. The recently developed Cobra Teardrop array is unique in that it employs time synchronized 8-hour left- and right-leaning elliptical orbits giving mid-latitude observers the illusion of viewing a single satellite continuously orbiting almost directly overhead! In reality, these observers are seeing six different satellites per day, for four hours each (while they are in their active duty cycles). Fortuitously, the satellites are physically in very close proximity at the handover points. The satellite just beginning its active duty cycle is ascending in altitude (towards apogee), while the satellite about to end its active service is descending in altitude (towards perigee). This favorable geometry can be utilized to effect a seamless handover from one satellite to the other (not requiring any electronic buffering). Handover from one satellite to the other is accomplished at the precise instant that the total path length from the transmitting station, through both satellites, to the receiving station, are exactly equal. This is accomplished through synchronization of time hacks that are transmitted simultaneously through each of the paths. In these improved Teardrop arrays, an order of magnitude increase in global communications capacity (equivalent GEO slots) can be realized over earlier Teardrop systems. For decades into the future, these new orbital systems could satisfy a wide range of commercial, government, and military high data rate communications requirements. These would include, but not be limited to, satellite cellular, air traffic control, meteorological, and combat net radio systems. Using standardized elliptical arrays, a much larger number of system operators can be supported, without mutual electronic interference, than would ever be possible with circular orbits.
- Abstract document
- Manuscript document
IAC-06-B3.2.02.pdf (🔒 authorized access only).
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