Integration of Low Earth Orbit Satellite Data Communications Services With Maritime Navigation and Positioning Systems

Robert Kelly

Abstract:	On April 3, 1995, Orbital Communications Corporation of Dulles, VA, at that time a subsidiary of Orbital Sciences Corporation (OSC), launched the first two of a constellation of twenty six 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. Among the many applications for this system will be a number of important, new, capabilities for the maritime industry. ORBCOMM plans to commence commercial service, on an intermittent basis, on February 1, 1996. A variety of services will be offered to both recreational and commercial marine customers; including marine messaging, barge tracking and distress alerting. The three main components of the ORBCOMM System are the space segment, ground segment, and SCs (subscriber communicators). For coverage of the U.S., there are four unmanned Gateway Earth Stations (GES) in the four comers of the U.S., one Network Control Center (NCC), and a constellation of 26 small satellites. Other countries around the 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 communication satellites in orbit 425 miles (785 km) above the earth. The satellites relay messages between ORBCOMM SCs and the ground segment. LEO satellite systems advantages are: Lower launch costs. Less power required. Integrated position determination, Inexpensive VHF electronics, and omnidirectional VHF antennas. 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. ‘Ihe GES and the satellites provide transparent access from the SC to the NCC. The NCC routes messages to the addressee of the message. There will be a number of different SC configurations. Some will be compact, lightweight devices with long life batteries, 5-watt transmitters, antenna, keypad and LCD screens. Many will have RS-232 data ports and some will be integrated with or will interface to 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 SC, the use of the ORBCOMM system as a new generation integrated navigation/communications system is apparent.
Published in:	Proceedings of the 1996 National Technical Meeting of The Institute of Navigation January 22 - 24, 1996 Loews Santa Monica Hotel Santa Monica, CA
Pages:	493 - 499
Cite this article:	Kelly, Robert, "Integration of Low Earth Orbit Satellite Data Communications Services With Maritime Navigation and Positioning Systems," Proceedings of the 1996 National Technical Meeting of The Institute of Navigation, Santa Monica, CA, January 1996, pp. 493-499.
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