Abstract: Sequential GPS Doppler carrier phase count measurements are used for precision sequential determination of position and velocity of a GPS receiver, such as for orbit determination and geolocation, with minimum throughput time. Real-time orbit determination and geolocation performance is enabled with an optimal sequential filter, and near-real-time performance is enabled with an optimal fixed-lag smoother. Many problems associated with prior art orbit determination are eliminated by addressing the “cycle slip” problem, the unknown initial range problem with RANGECP measurement representations, the problem of serial correlation in the measurements due to reprocessing of overlapping thermal noise. Also, the present invention significantly attenuates the carrier signal phase variation due to rotation of receiver antenna relative to transmitter antenna because the sequential phase count time intervals are sufficiently short.

Abstract: Maximum conjunction probability calculations are refined by addressing rectangular object shapes, even though their orientation may not be known. Object dimensions and relative miss distance, coupled with the aspect ratio of the projected combined covariance, are used to determine the size and orientation of the covariance as well as the object orientation that produces the maximum probability. In treating the objects as rectangles instead of spheres, the probability calculation becomes more realistic by accounting for object shape. In the absence of object attitude information, a footprint is created that completely defines the region where the two objects might touch. This footprint can then be rotated to determine the orientation that produces the largest probability, making it the most conservative estimate for the given conjunction conditions.

Abstract: A system and method for visualization of attitude dependent data is disclosed. An attitude sphere is defined around an object of interest located at the center. Grid points are defined on the surface of the attitude sphere to represent directions. An attitude dependent FOM result is mapped onto the sphere, which is color coded on the associated point to visualize attitude dependency. When used to analyze signals arriving at a receiver, the method accounts for motion of the receiver, the transmitter, and the signal sources. The objects comprise values of figures of merit (FOMs) that are accessible to a user. Additionally, the objects are updated dynamically to reflect the experience of the receiver over time. The receiver orientation may be optimized to minimize interference and jamming and/or to maximize signal strength of a desired signal.

Abstract: Sequential GPS Doppler carrier phase count measurements are used for precision sequential determination of position and velocity of a GPS receiver, such as for orbit determination and geolocation, with minimum throughput time. Real-time orbit determination and geolocation performance is enabled with an optimal sequential filter, and near-real-time performance is enabled with an optimal fixed-lag smoother. Many problems associated with prior art orbit determination are eliminated by addressing the “cycle slip” problem, the unknown initial range problem with RANGECP measurement representations, the problem of serial correlation in the measurements due to reprocessing of overlapping thermal noise. Also, the present invention significantly attenuates the carrier signal phase variation due to rotation of receiver antenna relative to transmitter antenna because the sequential phase count time intervals are sufficiently short.

Abstract: A system and method for orbital planning allows iterative calculations of orbital parameters to be accomplished in an automated way with one parameter solution serving as input to the next parameter's calculation. A software program employs a graphical user interface (GUI) to allow a space mission analyst to set up a series of sub-problems of any desired level of complexity. The program then implements the series automatically and sequentially, incorporating the solution to one sub-problem into the input to the next.

Abstract: The present invention provides a graphical user interface and software architecture that empowers the user to create new vectors, axes, points, coordinate systems, and other elements, and combinations thereof. The explicit means of creating coordinate systems and primitives are carried out via user input, imported data from files, or any other means of supplying numerical data to computer programs. In addition to geometrical relationships, coordinate system definitions can describe rates of change in the primitives, thus providing additional ways to create vectors.

Abstract: The field of view of a sensor mounted on a satellite (or other spacecraft) is obscured by various objects, such as celestial bodies and the satellite's own solar panels. A method is disclosed for visualizing and quantifying, with respect to time, variations in the portions of the sensor's field of view that are obscured. The graphical output of a satellite systems analysis program, which features high-resolution, three-dimensional, animated images of spacecraft, celestial bodies and other objects in the space environment, is utilized. The graphical output is simplified to only a few colors to differentiate only background and irrelevant objects from relevant objects. Differentiation is also made, using different colors, in representation of those portions of the field of view that overlap relevant (obscuring) objects from the remainder of the field of view which is unobscured. By counting pixels of the respective colors, frame-by-frame during animation, the percentage of obscuration over time is quantified.

Abstract: A method and apparatus for estimating the orbits of spacecraft or other objects relative to primary celestial bodies, given applicable measurements. The present invention uses the variation of parameters in universal variables for spacecraft trajectory propagation during operation of its optimal sequential orbit estimation. This method provides a universal capability for all three conics: elliptic, parabolic, and hyperbolic, forward-time and backward-time numerical integration for filtering and smoothing, respectively. A method for determining local and global estimates of atmospheric density is also provided. A method for realistic orbit simulation provides a means for validating an orbit estimate.

Abstract: 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.

Abstract: An method and apparatus and method for determining the position of a satellite overhead by a user using portable computation equipment. The invention uses a portable computational equipment that can be as small as a digital wristwatch or portable computer. Data concerning satellite position is calculated using more robust calculation equipment such as PC and the like. The information on satellite location and timing is downloaded from the PC to the portable calculation equipment for later access in the field by the user. In an alternate embodiment, the orbital determinations can be downloaded to a remote unit for playback in the field.

Abstract: 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.

Abstract: 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.

Abstract: A method for the automatic scaling of radio receiver characteristics. Receiver designs are subject to change based upon the parameters of transmitters and the desired characteristics of communications links in a communications system. The method of the present invention involves automatically scaling the characteristics of a receiver based upon the transmitter proposed and the desired characteristics of a communications link. Auto-scaling calculates the bandwidth necessary for the receiver based upon the transmitter proposed. Information concerning the modulation type and the scaling factor associated with each modulation type are stored in a database for access by the system. Once transmitter characteristics are known, receiver characteristics are automatically calculated. The system allows for multiple designs to be created so that analysts can select the optimal design for the mission.

Abstract: A method and apparatus for modeling the exposure of spacecraft-mounted solar power panels to the sun over a given time interval, such as an orbit period, and a method and apparatus for modeling the drag of spacecraft over a given time interval, such as an orbit period. The result of the exposure modeling can be used to determine varying availability of electrical power for operations to be performed by the spacecraft and on-board apparatus. The results of the drag over time are used to predict orbit decay and fuel requirements for orbit maintenance and station-keeping. The invention uses a graphically based satellite systems analysis program to approximate exposure and drag data through visual projection of the relevant spacecraft elements on a computer display screen.

Abstract: A method and apparatus for modeling the exposure of spacecraft-mounted solar power panels to the sun over a given time interval, such as an orbit period, and a method and apparatus for modeling the drag of spacecraft over a given time interval, such as an orbit period. The result of the exposure modeling can be used to determine varying availability of electrical power for operations to be performed by the spacecraft and on-board apparatus. The results of the drag over time are used to predict orbit decay and fuel requirements for orbit maintenance and station-keeping. The invention uses a graphically based satellite systems analysis program to approximate exposure and drag data through visual projection of the relevant spacecraft elements on a computer display screen.