Abstract: In accordance with one or more aspects of the present disclosure, a method for ranging of a PRN receiver including generating, at a PRN transmitting device that includes a processor and wireless transmitter and is in a line-of-sight position with the PRN receiver, at least two component codes, time shifting, with the processor of the PRN transmitting device, the at least two component codes relative to each other to form time shifted component codes, wirelessly transmitting, with the PRN transmitting device, the time shifted component codes to the PRN receiver with a predetermined modulation, and receiving the time shifted component codes with the PRN receiver that includes a PRN receiver processor, and determining a range estimate of the PRN receiver based on a combination of the time shifted component codes with the PRN receiver processor.

Abstract: In accordance with one or more aspects of the present disclosure, a method for ranging of a PRN receiver including generating, at a PRN transmitting device that includes a processor and wireless transmitter and is in a line-of-sight position with the PRN receiver, at least two component codes, time shifting, with the processor of the PRN transmitting device, the at least two component codes relative to each other to form time shifted component codes, wirelessly transmitting, with the PRN transmitting device, the time shifted component codes to the PRN receiver with a predetermined modulation, and receiving the time shifted component codes with the PRN receiver that includes a PRN receiver processor, and determining a range estimate of the PRN receiver based on a combination of the time shifted component codes with the PRN receiver processor.

Abstract: Methods and apparatus to monitor GPS/GNSS atomic clocks are disclosed. An example method includes establishing a measured difference between an atomic frequency standard (AFS) and a monitoring device. The method also includes modeling an estimated difference model between the AFS and the monitoring device, and computing a residual signal based on the measured difference and the estimated difference model. In addition, the method includes analyzing, by a first detector, the residual signal at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a threshold is exceeded before one or more of a phase jump, a rate jump, or an acceleration error is indicated. Furthermore, the method includes analyzing, by a second detector, a parameter of the estimated difference model at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a drift threshold is exceeded before a drift is indicated.

Abstract: Methods and apparatus to monitor GPS/GNSS atomic clocks are disclosed. An example method includes establishing a measured difference between an atomic frequency standard (AFS) and a monitoring device. The method also includes modeling an estimated difference model between the AFS and the monitoring device, and computing a residual signal based on the measured difference and the estimated difference model. In addition, the method includes analyzing, by a first detector, the residual signal at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a threshold is exceeded before one or more of a phase jump, a rate jump, or an acceleration error is indicated. Furthermore, the method includes analyzing, by a second detector, a parameter of the estimated difference model at multiple thresholds, each of the thresholds having a corresponding persistency defining the number of times a drift threshold is exceeded before a drift is indicated.

Abstract: A system for navigation and tracking may include an inertial navigation system adapted to generate a replica GNSS signal and a global navigation satellite system. The global navigation satellite system may include a module to digitize a GNSS signal received from a constellation of global navigation satellites. A correlator receives the digitized GNSS signal and the replica GNSS signal. The correlator correlates the digitized GNSS signal to the replica GNSS signal to generate a correlated GNSS signal. A coherent integration module coherently integrates the correlated GNSS signal to generate an integrated signal having a predetermined rate. A filter receives the integrated signal and generates a data signal for navigation and tracking. An output device may present the navigation and tracking information based on the data signal, or the navigation and tracking information may be used to provide guidance for a vehicle or may be used to track a target.

Abstract: A system that provides GPS-based navigation/orbit determination capabilities for high-altitude spacecraft. The system uses an existing spacecraft processor and an easy-to-space-qualify minimum-hardware front end to minimize the need for new space-qualified hardware. The system also uses coherent integration to acquire and track the very weak GPS signals at high altitudes. The system also uses diurnal thermal modeling of a spacecraft clock and precision orbit propagation to enable longer coherent integration, a special Kalman filter to allow weak signal tracking by integrated operation of orbit determination and GPS signal tracking, and a segment-by-segment, post-processing, delayed-time approach to allow a low-speed spacecraft processor to provide the software GPS capability.

Abstract: A system that provides GPS-based navigation/orbit determination capabilities for high-altitude spacecraft. The system uses an existing spacecraft processor and an easy-to-space-qualify minimum-hardware front end to minimize the need for new space-qualified hardware. The system also uses coherent integration to acquire and track the very weak GPS signals at high altitudes. The system also uses diurnal thermal modeling of a spacecraft clock and precision orbit propagation to enable longer coherent integration, a special Kalman filter to allow weak signal tracking by integrated operation of orbit determination and GPS signal tracking, and a segment-by-segment, post-processing, delayed-time approach to allow a low-speed spacecraft processor to provide the software GPS capability.

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.