Navigation and Communications Systems Integration

Robert W. Kelly

Abstract:	Commeucmg in the fmt quarter of 1994 Orbital Communications Corporation of Dulles. VA, a wholly owned subsidiary of Orbital Sciences Corporation (OSC). will launch a constellation of satellites into low earth orbit (LEO) for the purpose of establishing a worldwide, low cost, messaging and data communications system with inherent position determination capability. One of the many applications for this system will be to take advantage of its dual capabilities of both communications and position determination. ORBCOMM plans to introduce it to the marine marketplace where it can be used as both a navigational tool and means of sending and receiving record traffic from anywhere on earth at low cost and using low power. The three main components of the ORBCOMM System are the space segment ground segment, and STs (subscriber terminals). For coverage of the U.S., there will be four unmanned Gateway Earth Stations (GES) in the four comers of the U.S., one Network Control Center INCCJ. and a constellation of 26 small satellites. Other countries ‘around me world will have their own NCC and GES (the number of GES being dependent on the size of the country). To date, companies in twenty countries have signed candidate licensee agreements with ORBCOMM to procure ground segments and provide service. The space segment IS comprised of 26 small ~ommurucation satellites m orbit 425 miles (785 la10 above the earth. The satellites relay messages between ORBCOMM Sts and me ground segment LEO satellite systems advantages are: Lower launch costs. Less power required. Integrated position determination. Inexpensive VHF electronics, and omnidirectional VHF amenmu. Excellent overall link availability. The ground segment is comprised of the unmanned GES ‘and the NCC. Each GES has two steerable VHF antennas that track the satellites as they cross the sky. The GE3 and the satellites provide transparent access from the ST to the NCC. The NCC routes messages to the addressee of the message. The conventional STs are full function compact, lightweight devices with long life batteries, s-watt transmitters, antenna, keypad and LCD saeens. Many will have RS-232 data ports and some will be integrated (black box version) with GPS receivers, lap-tops and palm-top computers and other systems. With the system’s inherent position determination capability via doppler shift and enhanced position determination capability with the integration of GPS technology into the ST, the use of the ORBCOMM system is a new generation integrated navigation/communications system is apparent.
Published in:	Proceedings of the 1994 National Technical Meeting of The Institute of Navigation January 24 - 26, 1994 Catamaran Resort Hotel San Diego, CA
Pages:	245 - 250
Cite this article:	Kelly, Robert W., "Navigation and Communications Systems Integration," Proceedings of the 1994 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1994, pp. 245-250.
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