Satellite communication system

Abstract

A satellite communication system and related method for collecting data in space and transmitting it to a processing center on the earth. The communication system includes at least one satellite orbiting the earth that has a device for collecting the data. The satellite transmits the data to a plurality of receive only terminals on the earth. The terminals process the signals and transmit the data on the communications link to the processing center.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation application of U.S. patent application Ser. No. 09 / 641,654, filed Aug. 18, 2000, titled “Satellite Payload Data Communications and Processing Techniques.BACKGROUND OF THE INVENTION [0002] This invention relates to satellite communication systems, and more specifically relates to such systems in which satellite data is processed by an earth processing center. [0003] Satellite communications are taking on increased importance as evidenced by the following patents issued in the name of one of the inventors of the present invention: U.S. Pat. No. 5,867,530, entitled “Method and Apparatus for Accommodating Signal Blockage in Satellite Mobile Radio Systems,” issued in the name of Keith R. Jenkin, on Feb. 2, 1999 and U.S. Pat. No. 5,940,444, entitled “DARS PSF With No Data Rate Increase,” issued in the name of Keith R. Jenkin and Stephen J. Toner on Aug. 17, 1999. [0004] Prior satellite communication systems ...

AI Technical Summary

Benefits of technology

The present invention is a satellite communication system and method that collects data in space and sends it to a processing center on the earth. The system includes a satellite with a device for collecting data, which is then transmitted to multiple receive-only terminals on the earth. These terminals process the signals and send the data to the processing center. The technical effect of this invention is the ability to collect and transmit data from space to a processing center on the earth using a satellite communication system.

Problems solved by technology

(If the stations were located elsewhere, say near the equator, a prohibitively large number of these expensive facilities and sustaining staff ringing the globe would be needed to avoid blind orbits.)

This results in data already being delayed by up to as much as approximately 100 minutes before it even reaches the ground, which for weather data is highly undesirable.

In remote regions the continuous staffing required over many years becomes a major consideration in program life cycle cost.

In a case like McMurdo (Antarctica) the environment is incredibly adverse, and logistics become a major concern.

Since a downlink to a traditional ground station is a complex operation, a practical limit on the geometrically available contact time is usually imposed.

Since the traditional ground stations are generally located in remote, sparsely populated areas, taking advantage of commercially financed, installed, and maintained fiber optic networks is unlikely since there is no financial motivation for servicing such geographic (polar) areas.

This means communication from traditional ground stations to the processing center (probably in the U.S.) is expensive for the data rates (bandwidth) needed by future weather satellites.

Either dedicated, sole-user fiber is needed, or perhaps a complex, risky, and expensive “hop” from the station to a communications satellite and back to the U.S. is needed.

Or, a slow existing link might be used, but because of limited bandwidth, data will again be delayed awaiting its turn in a rate buffer queue for ground communication.

Since there are, practically speaking, several single point failure opportunities in a traditional ground station system, each point must have incredibly high (i.e. expensive) reliability and sufficient availability.

For instance, if a key station is down for a prolonged period, say due to earthquake damage, or immediately irreparable equipment failure, or staffing problems and so on, critical data will be lost or arrive so late it's essentially useless.

Spacecraft Complexity / Risk of Prior Systems

Since the spacecraft antenna is highly directional (continuously dynamically pointed at the ground station) and since transmit power is limited, only one ground station at a time can be downlinked.

Furthermore, if subsequent contact opportunities arise, a gimbaled spacecraft antenna needs precious time to slew and repoint.

Since several satellites may need servicing by the same station, scheduling is complex amongst disparate systems to avoid usage conflicts.

As more satellites are launched using the same stations, competition for use of the stations increases and scheduling becomes increasingly complex and conflicting.

Adding additional antennas, electronics, and personnel at a traditional ground station facility can help mitigate this situation, but is expensive.

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