Analytical Graphics Inc.

James William Woodburn

Douglas John Claffey

James R Wright

David M Holland

Douglas J Claffery

An extended Kalman filter (EKF) is combined with a fixed epoch smoother (FES) to produce a new variable lag smoother (VLS). The fixed epoch lags EKF measurement time-tags with variable time lag. The combination of EKF and FES is referred to herein as a variable lag smoother (VLS).

Nonlinear variable lag smoother

The present invention relates to a method and apparatus for selecting a path between an originating point and a destination point in a communications network comprising a number of objects for a certain time interval. The method comprises constructing a link availability matrix which comprises a start time and an end time for a link between any two objects in the communications network. The start time for all links in the link availability matrix are arranged in a chronological order. A cost matrix is generated for the first start time in the link availability matrix based on selected factors and continuing through the following start times until a connecting path is found between the originating point and destination point using a number of objects in the network. After a connecting path is found, a first disconnect time based on the end times in the link availability matrix for the objects in the connecting path is selected. Steps (c) and (d) are repeated for all subsequent start time in the link availability matrix for the time interval to identify other connecting paths for the origination and destination points. An optimal path is selected for the communication between the origination and destination points based on the selected factors. The invention also relates to the utilization of graphical depictions of the optimal path preferably on a computer showing Earth imagery and the location of the objects in the communication system.

Method and apparatus for determining optimal paths among objects of a communications network

Assessing performance of satellite constellations. For a given constellation of satellites, each having a given number of sensors, a method is disclosed for determining the times of access between each sensor and a plurality of targets located on Earth. Calculation time required for determining access is greatly decreased using pre-computed access calculations as a baseline.

Method and apparatus for calculating access between satellite

Determining suitable launch windows to avoid or minimize close approaches between a launch vehicle and orbiting objects. A method and apparatus is disclosed for minimizing close approaches between spacecraft and other objects in space during the launch and early deployment phase of their lifetime, by defining a launch window, utilizing filters to screen certain objects in space from consideration and identifying launch window blackout times to avoid close approaches with the remaining objects in space under consideration.

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Ardmore, PA, United States of America

James William Woodburn