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SSL Satellite Does Not Infringe Under DOE Because of “All Elements” Rule

March 24, 2003
Lombardi, Anthony J.

Decision icon Decision

Last Month at the Federal Circuit - April 2003

Judges: Gajarsa (author), Schall, and Friedman

In Lockheed Martin Corp. v. Space Systems/Loral, Inc., No. 00-1310 (Fed. Cir. Mar. 24, 2003), on remand from the Supreme Court, the Federal Circuit affirmed the district court’s grant of SJ of noninfringement based on new grounds.

Lockheed Martin Corporation (“Lockheed”) is the assignee of U.S. Patent No. 4,084,772 (“the ’772 patent”), which discloses an apparatus and method for steering a satellite. Lockheed’s predecessor, Martin Marietta Corporation, previously brought a patent-infringement action against Space Systems/Loral, Inc. (“SSL”), alleging that certain SSL satellites infringe the ’772 patent.

Typically, a communications satellite orbits the earth in a geosynchronous equatorial orbit, which allows the satellite to maintain the same position relative to fixed points on the earth’s surface. However, while in orbit, a satellite is subject to various destabilizing forces, such as the gravitational effects of the sun and the moon. These forces may cause a satellite to drift out of its equatorial orbit and into an inclined north-south orbit. The system disclosed in the ’772 patent allows a satellite to continue to operate effectively after entering an inclined orbit. It does so by changing the attitude, or pointing direction, of the satellite when the satellite is north and south of the equator so that the satellite remains pointed at the same earth target. This change is accomplished by a momentum wheel, which spins to create angular momentum, much like a gyroscope, to keep the satellite pointed in the proper direction.

The intentional adjustment of the satellite, however, creates a control problem. Prior art satellites use an earth horizon or roll sensor to keep the satellite pointed at the center of the earth during equatorial orbit. If the sensor determines that the satellite is not pointed at the center of the earth, it activates a roll thruster to reorient the satellite. During inclined orbit, however, the satellite is intentionally rotated away from the center of the earth. In addressing this problem, the structure and method disclosed in the ’772 patent causes the sensor to ignore this intentional rotation by generating a signal, which represents the angle of intentional roll, and subtracting it from the signal generated by the sensor.

Claim 1 of the ’772 patent recites, in part, “means for rotating said wheel in accordance with a predetermined rate schedule which varies sinusoidally over the orbit at the orbital frequency of the satellite.” The district court construed the phrase “varies sinusoidally” to mean “a sine-shaped variation that passes through zero.” The Federal Circuit then affirmed the district court’s decision on the ground that its Festo decision barred the application of the DOE because the limitation had been amended. However, following the Supreme Court’s review of Festo, the Supreme Court remanded the case to the Federal Circuit for further consideration.

On remand, Lockheed contended that a factual dispute existed as to whether the SSL satellites met the requirements of the claim language under the DOE. Lockheed argued that the speed of the SSL wheel varies sinusoidally even though it is always spinning faster than a set bias speed. The Federal Circuit, however, considered whether the scope of the DOE was proscribed by the all-elements rule.

The Federal Circuit concluded that it was undisputed that the speed of the SSL wheel does not slow to zero, stop, and reverse direction twice during each orbit of its operation, as is required by the proper construction of the phrase “varies sinusoidally over the orbit at the orbital frequency.” Further, the claim language requires the SSL wheel to vary according to a “predetermined rate schedule.” The SSL satellite, however, does not use a predetermined rate schedule. Because the accused satellite lacks an element that performs these properly construed functions, a finding of infringement under the DOE would entirely vitiate these limitations. Therefore, the Federal Circuit affirmed the district court’s grant of SJ in favor of SSL.