Abstract: An improved approach to satellite-based navigation (e.g., GPS) is provided. In one embodiment, a method includes receiving a first set of tracking information. A nominal orbital path for the navigation satellite is determined using the first set of tracking information. Ephemeris data corresponding to the nominal orbital path is computed and uploaded to the navigation satellite. Long-term navigation information corresponding to the nominal orbital path is transmitted to a communication system for broadcast to a plurality of navigation devices. A second set of tracking information is received, an orbital path of the navigation satellite using the second set of tracking information is predicted, and a difference between the predicted orbital path and the nominal orbital path is determined. Commands configured to instruct the navigation satellite to adjust an actual orbital path of the navigation satellite to substantially conform to the nominal orbital path are uploaded to the navigation satellite.

Abstract: An improved approach to satellite-based navigation (e.g., GPS) is provided. In one embodiment, a method includes determining a nominal orbital path of a navigation satellite. The method also includes transmitting ephemeris data corresponding to the nominal orbital path from the navigation satellite to a plurality of navigation devices. The method further includes determining an actual orbital path of the navigation satellite locally at the navigation satellite. In addition, the method includes determining a deviation between the actual orbital path and the nominal orbital path locally at the navigation satellite. The method also includes autonomously adjusting the actual orbital path locally at the navigation satellite to reduce the deviation between the actual orbital path and the nominal orbital path.

Abstract: A multi-constellation GNSS augmentation and assistance system may include a plurality of reference stations. Each reference station may be adapted to receive navigation data from a plurality of different global navigation satellite systems and to monitor integrity and performance data for each different global navigation satellite system. An operation center may receive the integrity and performance data transmitted from each of the plurality of reference stations. A communication network may transmit a message from the operation center to navcom equipment of a user for augmentation and assistance of the navcom equipment.

Abstract: GPS gyro calibration methods and systems are described. In an embodiment, a ground station can receive antenna position data for a spot beam antenna from a global positioning system (GPS) platform where the antenna position data indicates a boresight direction of the spot beam antenna. GPS-enabled receiver(s) can receive scan signals transmitted via the spot beam antenna of the GPS platform, and the GPS-enabled receivers can determine signal power measurements for each of the scan signals. The ground station can receive the signal power measurements from the GPS-enabled receiver(s) and estimate a pointing error of the spot beam antenna based on the signal power measurements and the antenna position data received from the GPS platform. The ground station can then determine gyro calibration parameters from the estimated pointing error and communicate the gyro calibration parameters to the GPS platform to calibrate for gyro drift errors.

Abstract: A GNSS ultra-tight coupling (UTC) receiver architecture applicable to space borne orbit platforms is described. A receiver in accordance with this architecture retains the rotational motion sensors typically found in an inertial measurement unit (IMU) of a conventional UTC receiver, but replaces the IMU accelerometer sensors with precise orbital dynamics models to predict the translational motion of the platform center of gravity (CG). Drag and radiation pressure may be modeled as well. The various models can be implemented in software. The IMU rotational sensors are retained for compensation of the GNSS antenna lever arm effect due to platform rotation.

Abstract: GPS gyro calibration methods and systems are described. In an embodiment, a ground station can receive antenna position data for a spot beam antenna from a global positioning system (GPS) platform where the antenna position data indicates a boresight direction of the spot beam antenna. GPS-enabled receiver(s) can receive scan signals transmitted via the spot beam antenna of the GPS platform, and the GPS-enabled receivers can determine signal power measurements for each of the scan signals. The ground station can receive the signal power measurements from the GPS-enabled receiver(s) and estimate a pointing error of the spot beam antenna based on the signal power measurements and the antenna position data received from the GPS platform. The ground station can then determine gyro calibration parameters from the estimated pointing error and communicate the gyro calibration parameters to the GPS platform to calibrate for gyro drift errors.

Abstract: GPS gyro calibration methods and systems are described. In an embodiment, a ground station can receive antenna position data for a spot beam antenna from a global positioning system (GPS) platform where the antenna position data indicates a boresight direction of the spot beam antenna. GPS-enabled receiver(s) can receive scan signals transmitted via the spot beam antenna of the GPS platform, and the GPS-enabled receivers can determine signal power measurements for each of the scan signals. The ground station can receive the signal power measurements from the GPS-enabled receiver(s) and estimate a pointing error of the spot beam antenna based on the signal power measurements and the antenna position data received from the GPS platform. The ground station can then determine gyro calibration parameters from the estimated pointing error and communicate the gyro calibration parameters to the GPS platform to calibrate for gyro drift errors.

Abstract: User equipment navigation solution with position determination of a navigation signal reflector methods and systems are described. In an embodiment, navigation signals transmitted from global positioning system (GPS) platform(s) can be received at a GPS-enabled receiver as direct navigation signals and reflected navigation signals. The direct navigation signals can then be isolated from the reflected navigation signals. Receiver range measurements can be determined from the direct navigation signals which are received via direct signal paths from the GPS platform(s), and a navigation solution of the GPS-enabled receiver can then be resolved from the receiver range measurements. Similarly, reflector range measurements can be determined from the reflected navigation signals which are received via reflected signal paths from a signal reflector, and a position of the signal reflector can then be resolved from the reflector range measurements at the GPS-enabled receiver.

Abstract: Navigation signal group delay calibration methods and systems are described. In an embodiment, a code signal generated in a navigation system platform can be measured where the code signal includes timing delay(s). An additional code signal generated in the navigation system platform can be measured where the additional code signal is designated as a timing reference signal. A differential group delay between the code signal and the timing reference signal can the be mathematically estimated in the navigation system platform to correct for an inaccurate position estimation that would result from the timing delay(s).

Abstract: An improved approach to satellite-based navigation (e.g., GPS) is provided. In one embodiment, a method includes determining a nominal orbital path of a navigation satellite. The method also includes transmitting ephemeris data corresponding to the nominal orbital path from the navigation satellite to a plurality of navigation devices. The method further includes determining an actual orbital path of the navigation satellite locally at the navigation satellite. In addition, the method includes determining a deviation between the actual orbital path and the nominal orbital path locally at the navigation satellite. The method also includes autonomously adjusting the actual orbital path locally at the navigation satellite to reduce the deviation between the actual orbital path and the nominal orbital path.

Abstract: A system and method for determining the attitude of a platform is provided. The method includes: (a) Searching and scanning for one or more GPS satellite(s) to determine initial platform position; wherein a single directionally steered antenna scans for the GPS/GNSS satellite; (b) pointing and scanning the antenna to GPS/GNSS satellite to determine a first angular measurement of a direction of a GPS/GNSS signal; (c) measuring carrier to noise ratio of the GPS/GNSS satellite; (d) dithering the single directionally steered antenna to obtain an angular measurement relative to an antenna pattern bore-sight reference; (e) repeating steps (b)-(d) to determine a second angular measurement of the direction of a second GPS signal; (f) determining the attitude error of the platform using the first and second angular measurements; (g) updating the platform position and attitude.

Abstract: An improved approach to satellite-based navigation (e.g., GPS) is provided. In one embodiment, a method includes receiving a first set of tracking information. A nominal orbital path for the navigation satellite is determined using the first set of tracking information. Ephemeris data corresponding to the nominal orbital path is computed and uploaded to the navigation satellite. Long-term navigation information corresponding to the nominal orbital path is transmitted to a communication system for broadcast to a plurality of navigation devices. A second set of tracking information is received, an orbital path of the navigation satellite using the second set of tracking information is predicted, and a difference between the predicted orbital path and the nominal orbital path is determined. Commands configured to instruct the navigation satellite to adjust an actual orbital path of the navigation satellite to substantially conform to the nominal orbital path are uploaded to the navigation satellite.

Abstract: A GNSS ultra-tight coupling (UTC) receiver architecture applicable to space borne orbit platforms is described. A receiver in accordance with this architecture retains the rotational motion sensors typically found in an inertial measurement unit (IMU) of a conventional UTC receiver, but replaces the IMU accelerometer sensors with precise orbital dynamics models to predict the translational motion of the platform center of gravity (CG). Drag and radiation pressure may be modeled as well. The various models can be implemented in software. The IMU rotational sensors are retained for compensation of the GNSS antenna lever arm effect due to platform rotation.

Abstract: User equipment navigation solution with position determination of a navigation signal reflector methods and systems are described. In an embodiment, navigation signals transmitted from global positioning system (GPS) platform(s) can be received at a GPS-enabled receiver as direct navigation signals and reflected navigation signals. The direct navigation signals can then be isolated from the reflected navigation signals. Receiver range measurements can be determined from the direct navigation signals which are received via direct signal paths from the GPS platform(s), and a navigation solution of the GPS-enabled receiver can then be resolved from the receiver range measurements. Similarly, reflector range measurements can be determined from the reflected navigation signals which are received via reflected signal paths from a signal reflector, and a position of the signal reflector can then be resolved from the reflector range measurements at the GPS-enabled receiver.

Abstract: A system and method for determining the attitude of a platform is provided. The method includes: (a) Searching and scanning for one or more GPS satellite(s) to determine initial platform position; wherein a single directionally steered antenna scans for the GPS/GNSS satellite; (b) pointing and scanning the antenna to GPS/GNSS satellite to determine a first angular measurement of a direction of a GPS/GNSS signal; (c) measuring carrier to noise ratio of the GPS/GNSS satellite; (d) dithering the single directionally steered antenna to obtain an angular measurement relative to an antenna pattern bore-sight reference; (e) repeating steps (b)-(d) to determine a second angular measurement of the direction of a second GPS signal; (f) determining the attitude error of the platform using the first and second angular measurements; (g) updating the platform position and attitude.

Abstract: Navigation signal group delay calibration methods and systems are described. In an embodiment, a code signal generated in a navigation system platform can be measured where the code signal includes timing delay(s). An additional code signal generated in the navigation system platform can be measured where the additional code signal is designated as a timing reference signal. A differential group delay between the code signal and the timing reference signal can the be mathematically estimated in the navigation system platform to correct for an inaccurate position estimation that would result from the timing delay(s).

Abstract: A method and apparatus for calibrating such a spot beam antenna by use of scanned spot beam signal characteristics measured by a plurality of ground based navigation receivers is disclosed.

Abstract: A method and apparatus for estimating a lever arm correction between the wide beam antenna and the spot beam antenna in a navigational satellite system is disclosed. A prescribed satellite maneuver is used to increase the accuracy of the predicted satellite attitude in determining the lever arm, and lever arm corrections are provided to navigation receivers using curve fit coefficients to permit long range estimates and to minimize data transmission requirements.

Abstract: A method and apparatus for estimating a lever arm correction between the wide beam antenna and the spot beam antenna in a navigational satellite system is disclosed. A prescribed satellite maneuver is used to increase the accuracy of the predicted satellite attitude in determining the lever arm, and lever arm corrections are provided from a ground segment to navigation receivers using curve fit coefficients to permit long range estimates and to minimize data transmission requirements.

Abstract: A method and apparatus for estimating a lever arm correction between the wide beam antenna and the spot beam antenna in a navigational satellite system is disclosed. A prescribed satellite maneuver is used to increase the accuracy of the predicted satellite attitude in determining the lever arm, and lever arm corrections are provided from a ground segment to navigation receivers using curve fit coefficients to permit long range estimates and to minimize data transmission requirements.