Abstract: Techniques are disclosed for improving daylight performance of a star tracker. A region of interest (ROI) within a field of view of sky is obtained. The region of interest is divided into sub-ROIs. Sub-ROIs including a candidate celestial object are identified. An angular velocity of each candidate celestial object is determined. The known celestial object is a candidate celestial object identified as having a angular velocity, during a time period, that is within a range of angular velocities about a known angular velocity associated with the known celestial object.

Abstract: A method and system for celestial navigation are provided. The method comprises requesting access to a light source on a low earth orbit (LEO) satellite; and sending an uplink message to the LEO satellite to power on the light source, in response to the access request. The method further comprises determining whether the LEO satellite is in view of a camera; capturing a light image, from the light source, on a focal plane location of the camera when the LEO satellite is in view of the camera; and comparing the focal plane location to a predicted location of the LEO satellite. The method updates position information of a user based on an observation error from comparing the focal plane location to the predicted location.

Abstract: This disclosure describes systems and methods for providing antenna steering through GNSS jamming, spoofing, and airplane maneuvers. In certain embodiments, a device includes a GNSS antenna configured to receive GNSS signals transmitted from a plurality of GNSS sources; and a GNSS antenna support structure mounted within a vehicle, wherein the GNSS antenna is mounted to the GNSS antenna support structure, wherein the GNSS antenna support structure is configured to keep directionality of the GNSS antenna pointing up during motion of the vehicle.

Abstract: A post-processed GNSS solution from raw GNSS data acquired from a vehicle and optionally other sources is dynamically calculated at the epoch level without using a Kalman filter. Instead, a plurality of GNSS processing methods is applied to each epoch in either the forward or backward direction and the most accurate solution for each epoch of the forward generated solution and backward generated solution is combined. The combined post-processed GNSS solution is determined based on which of the GNSS processing methods were used to generate an epoch of the forward solution and a corresponding epoch of the backward solution.

Abstract: Systems and methods for static session multipath detection are described herein. In certain embodiments, a system includes one or more global navigation satellite system (GNSS) receivers configured to receive GNSS signals from multiple GNSS satellites, wherein the GNSS receiver provides GNSS measurements. The system also includes one or more processors configured to receive the GNSS measurements.

Abstract: A method of determining three-dimensional attitude is provided. The method includes measuring a carrier phase of each satellite signal received at plurality of spaced antenna. A carrier phase difference between the measured carrier phase for each satellite signal from each satellite received at each antenna is determined. The integrity of the integer ambiguity resolution relating to the carrier phase difference is assured by applying a least-square-error solution using differential carrier phase measurements with applied integer ambiguities between at least two of the plurality of antennas and observing measurement residuals after the least-square-error solution is computed and applying an instantaneous test, an interval test and a solution separation function. Three-dimensional attitude is determined from the carrier phase differences upon completion of the integer ambiguity resolution and the assurance of integrity of the integer ambiguity resolution.

Abstract: A ground map monitor method comprises obtaining positions of communication nodes in a communications network, selecting transmission and reception nodes from the communication nodes, and measuring bistatic signals between the transmission and reception nodes to determine nominal signal performance characteristics for the bistatic signals, including reflected signal time delays, frequency shifts, and power levels. The method further comprises monitoring the bistatic signals for changes to nominal signal performance characteristics. The method uses discriminators between the nominal signal performance characteristics and a current performance level of the bistatic signals, and compares the discriminators against performance thresholds, to determine whether current signal performance characteristics have varied from their nominal levels.

Abstract: Systems and methods for GNSS ambiguity resolution are described herein. In some examples, the systems and methods utilize multiple search engines in parallel to validate potential integer candidates for ambiguity resolution using adaptively adjusted residual thresholds.

Abstract: Techniques for detecting and excluding spoofed Global Navigation Satellite System (GNSS) signals are described. Using position data acquired from inertial sensors, a line of sight (LOS) estimation can be determined to various satellites. This data can be compared with range data provided by a GNSS receiver, for example, by subtracting the LOS estimations with corresponding GNSS ranges. The difference can then be compared to an appropriate threshold to determine whether GNSS spoofing is present. Additionally, the non-spoofed GNSS signals can be used to generate an updated position solution, which is verified by an integrity algorithm. If verified, the updated position solution can be used to calculate the position of the vehicle. However, if not verified, the disclosed techniques can adjust the thresholds used to determine GNSS spoofing and perform additional iterations of integrity monitoring to acquire a verified positioning solution.

Abstract: Systems and methods for GNSS ambiguity resolution are described herein. In some examples, the systems and methods utilize multiple search engines in parallel to validate potential integer candidates for ambiguity resolution using adaptively adjusted residual thresholds.

Abstract: A method of determining three-dimensional attitude is provided. The method includes measuring a carrier phase of each satellite signal received at plurality of spaced antenna. A carrier phase difference between the measured carrier phase for each satellite signal from each satellite received at each antenna is determined. The integrity of the integer ambiguity resolution relating to the carrier phase difference is assured by applying a least-square-error solution using differential carrier phase measurements with applied integer ambiguities between at least two of the plurality of antennas and observing measurement residuals after the least-square-error solution is computed and applying an instantaneous test, an interval test and a solution separation function. Three-dimensional attitude is determined from the carrier phase differences upon completion of the integer ambiguity resolution and the assurance of integrity of the integer ambiguity resolution.

Abstract: Techniques for detecting and excluding spoofed Global Navigation Satellite System (GNSS) signals are described. Using position data acquired from inertial sensors, a line of sight (LOS) estimation can be determined to various satellites. This data can be compared with range data provided by a GNSS receiver, for example, by subtracting the LOS estimations with corresponding GNSS ranges. The difference can then be compared to an appropriate threshold to determine whether GNSS spoofing is present. Additionally, the non-spoofed GNSS signals can be used to generate an updated position solution, which is verified by an integrity algorithm. If verified, the updated position solution can be used to calculate the position of the vehicle. However, if not verified, the disclosed techniques can adjust the thresholds used to determine GNSS spoofing and perform additional iterations of integrity monitoring to acquire a verified positioning solution.

Abstract: An example pointing system includes a sensor that measures change in angular position, a first GNSS antenna, and a second GNSS antenna mounted to a rigid body that is removable from the pointing system after calibration of the sensor. The GNSS antennas have a fixed, known baseline. The pointing system includes at least one GNSS receiver with first and second RF inputs respectively coupled to the GNSS antennas. The at least one GNSS receiver includes respective paths to process GNSS signals received from the first and second RF inputs. The pointing system includes at least one processor, communicatively coupled to the sensor and receiver, configured to: determine initial attitude of the pointing system based on the processed GNSS signals; calibrate the sensor using the determined initial attitude; determine a pointing solution for the pointing system based on measurements from the calibrated sensor without GNSS signals from second GNSS antenna.

Abstract: A method of operating a global positioning receiver is provided. The method includes receiving a plurality of signals from a plurality of satellites. At least a measurement from and location of each satellite is determined based on the received plurality of signals. An approximate vehicle velocity vector is determined based on the received plurality of signals. A dot product between a line of sight between each satellite and a vehicle having the receiver and the determined vehicle velocity vector is determined. Each measurement associated with each determined dot product that is below a minimum dot product threshold is removed to obtain a resultant set of measurements. A position solution based on the resultant set of measurements is then determined.

Abstract: An example pointing system includes a sensor that measures change in angular position, a first GNSS antenna, and a second GNSS antenna mounted to a rigid body that is removable from the pointing system after calibration of the sensor. The GNSS antennas have a fixed, known baseline. The pointing system includes at least one GNSS receiver with first and second RF inputs respectively coupled to the GNSS antennas. The at least one GNSS receiver includes respective paths to process GNSS signals received from the first and second RF inputs. The pointing system includes at least one processor, communicatively coupled to the sensor and receiver, configured to: determine initial attitude of the pointing system based on the processed GNSS signals; calibrate the sensor using the determined initial attitude; determine a pointing solution for the pointing system based on measurements from the calibrated sensor without GNSS signals from second GNSS antenna.

Abstract: A method and apparatus are provided for performing consistency testing for a Bose-Chaudhuri-Hocquenghem (BCH) error corrected first sub-frame of navigation message broadcast from a satellite of a GNSS. Consistency testing is performed by comparing BCH encoded portion(s)s of data symbols with elements of look up table(s) to see if such portions are similar to element(s) of the look up table(s).

Abstract: A method of operating a global positioning receiver is provided. The method includes receiving a plurality of signals from a plurality of satellites. At least a measurement from and location of each satellite is determined based on the received plurality of signals. An approximate vehicle velocity vector is determined based on the received plurality of signals. A dot product between a line of sight between each satellite and a vehicle having the receiver and the determined vehicle velocity vector is determined. Each measurement associated with each determined dot product that is below a minimum dot product threshold is removed to obtain a resultant set of measurements. A position solution based on the resultant set of measurements is then determined.

Abstract: A Global Navigation Satellite System (GNSS) device, such as the Global Positioning System (GPS) device, uses satellite orbital position information from almanac and/or ephemeris data to change a search parameter, such as reducing the number of analyzed frequency bins or setting signal strength threshold, so that satellite signal acquisition times are reduced. An exemplary embodiment estimates an orbital position for at least one GNSS satellite based upon at least one of almanac data and ephemeris data, detects a signal emitted from the at least one GNSS satellite, and based upon the estimated orbital position information for the at least one GNSS satellite that is determined from the almanac data and the ephemeris data, adjusts at least one parameter used in the analysis of the detected signal.

Abstract: A method and a system for providing a substituted timing signal for a missing satellite ephemeris in execution of a RAIM algorithm includes deriving a plurality of position, velocity, and time solutions from a GPS navigation system. The position, velocity and time solutions are derived from a plurality of satellite ephemerides. An atomic clock provides an atomic clock signal. The atomic clock signal is compared to the derived time solutions to arrive at a correction factor. The atomic clock signal is adjusted according to the correction factor to develop an adjusted atomic clock signal. The adjusted atomic clock signal is substituted for a missing satellite ephemeris to execute the RAIM algorithm.

Abstract: A method and a system for providing a substituted timing signal for a missing satellite ephemeris in execution of a RAIM algorithm includes deriving a plurality of position, velocity, and time solutions from a GPS navigation system. The position, velocity and time solutions are derived from a plurality of satellite ephemerides. An atomic clock provides an atomic clock signal. The atomic clock signal is compared to the derived time solutions to arrive at a correction factor. The atomic clock signal is adjusted according to the correction factor to develop an adjusted atomic clock signal. The adjusted atomic clock signal is substituted for a missing satellite ephemeris to execute the RAIM algorithm.